Sorbents: Properties, Materials and Applications : Properties, Materials and Applications [1 ed.] 9781616683085, 9781607418511

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Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved. Sorbents: Properties, Materials and Applications : Properties, Materials and Applications, Nova Science Publishers, Incorporated, 2009. ProQuest Ebook Central,

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved. Sorbents: Properties, Materials and Applications : Properties, Materials and Applications, Nova Science Publishers, Incorporated, 2009. ProQuest Ebook Central,

Environmental Research Advances Series

SORBENTS: PROPERTIES, MATERIALS AND APPLICATIONS

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

No part of this digital document may be reproduced, stored in a retrieval system or transmitted in any form or by any means. The publisher has taken reasonable care in the preparation of this digital document, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained herein. This digital document is sold with the clear understanding that the publisher is not engaged in rendering legal, medical or any other professional services.

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ENVIRONMENTAL RESEARCH ADVANCES SERIES Environmental Research Advances. Volume 1 Harold J. Benson (Editor) 2008 ISBN 978-1-60456-314-6 Bioengineering for Pollution Prevention Dianne Ahmann and John R. Dorgan (Editors) 2009 ISBN: 978-1-60692-900-1 Estimating Future Recreational Demand Peter T. Yao (Editor) 2009. ISBN 978-1-60692-472-3 Handbook on Environmental Quality Evan K. Drury and Tylor S. Pridgen (Editors) 2009. ISBN: 978-1-60741-420-9

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Sorbents: Properties, Materials and Applications Thomas P. Willis (Editor) 2009. ISBN: 978-1-60741-851-1

Sorbents: Properties, Materials and Applications : Properties, Materials and Applications, Nova Science Publishers, Incorporated, 2009. ProQuest Ebook Central,

Environmental Research Advances Series

SORBENTS: PROPERTIES, MATERIALS AND APPLICATIONS

THOMAS P. WILLIS

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

EDITOR

Nova Science Publishers, Inc. New York

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Copyright © 2009 by Nova Science Publishers, Inc. All rights reserved. No part of this book may be reproduced, stored in a retrieval system or transmitted in any form or by any means: electronic, electrostatic, magnetic, tape, mechanical photocopying, recording or otherwise without the written permission of the Publisher. For permission to use material from this book please contact us: Telephone 631-231-7269; Fax 631-231-8175 Web Site: http://www.novapublishers.com NOTICE TO THE READER The Publisher has taken reasonable care in the preparation of this book, but makes no expressed or implied warranty of any kind and assumes no responsibility for any errors or omissions. No liability is assumed for incidental or consequential damages in connection with or arising out of information contained in this book. The Publisher shall not be liable for any special, consequential, or exemplary damages resulting, in whole or in part, from the readers’ use of, or reliance upon, this material. Any parts of this book based on government reports are so indicated and copyright is claimed for those parts to the extent applicable to compilations of such works. Independent verification should be sought for any data, advice or recommendations contained in this book. In addition, no responsibility is assumed by the publisher for any injury and/or damage to persons or property arising from any methods, products, instructions, ideas or otherwise contained in this publication. This publication is designed to provide accurate and authoritative information with regard to the subject matter covered herein. It is sold with the clear understanding that the Publisher is not engaged in rendering legal or any other professional services. If legal or any other expert assistance is required, the services of a competent person should be sought. FROM A DECLARATION OF PARTICIPANTS JOINTLY ADOPTED BY A COMMITTEE OF THE AMERICAN BAR ASSOCIATION AND A COMMITTEE OF PUBLISHERS.

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LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Willis, Thomas P. Sorbents properties, materials and applications / Thomas P. Willis. p. cm. Includes index. ISBN 978-1-61668-308-5 (E-Book) 1. Sorbents. I. Title. TP159.S6W55 2009 660'.284235--dc22 2009021050

Published by Nova Science Publishers, Inc. Ô New York

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CONTENTS Preface Chapter 1

The Use of Sorbents for the Analysis of Emerging Pollutants in Indoor Air Carmen Garcia-Jares, Ruth Barro, Jorge Regueiro and María Llompart

Chapter 2

Use of Sorbents in Air Quality Control Systems E. Gallego, F.J. Roca, J.F. Perales and X. Guardino

Chapter 3

Nanocomposites (Salt inside Porous Matrix) for Methanol Sorption: Design of Phase Composition and Sorption Properties, Practical Applications Larisa G. Gordeeva and Yuriy I. Aristov

Chapter 4

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vii

A Novel Use of Sorbents for Photochemical Studies: Photo-SolidPhase Microextraction (Photo-SPME) Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez, Carmen García-Jares and Marta Lores

1

71

109

139

Chapter 5

Dye Wastewaters, Alternative Physiochemical Treatment Reagent F.N. Emengo, J.K. Nduka, C.N. Anodebe and P.A.C Okoye

Chapter 6

Utilization of Phlogopite-Rich Mine Tailings in Abatement of Phosphorus Loading to Watercourses Salla Venäläinen

201

Nanostructural Carbon Sorbents for Different Functional Application Z.A. Mansurov and M.K. Gilmanov

217

Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules Mustafa Yilmaz and Shahabuddin Memon

285

Chapter 7

Chapter 8

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vi

Contents

Chapter 9

The Magnetic Sorbents Used for Detoxification of Blood N. P. Glukhoedov, M. V. Kutushov, M. A. Pluzan, G. V. Stepanov, L. Kh. Komissarova, V. I. Filippov, L. A. Goncharov and F. S. Bayburtskiy

335

Chapter 10

Surface Controlled Reaction Kinetics on Calcium-Based Sorbents Jinsheng Wang and Siauw H. Ng

341

Chapter 11

Non-Conventional Sorbents for the Dye Removal from Waters: Mechanisms and Selected Applications Pavel Janoš

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Index

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PREFACE Sorbents are insoluble materials or mixtures of materials used to recover liquids through the mechanism of absorption, or adsorption, or both. Absorbents are materials that pick up and retain liquid distributed throughout its molecular structure causing the solid to swell. The absorbent must be at least 70 percent insoluble in excess fluid. Adsorbents are insoluble materials that are coated by a liquid on its surface, including pores and capillaries, without the solid swelling more than 50 percent in excess liquid. To be useful in combating oil spills, sorbents need to be both oleophilic (oil-attracting) and hydrophobic (water-repellent). Although they may be used as the sole cleanup method in small spills, sorbents are most often used to remove final traces of oil, or in areas that cannot be reached by skimmers. Any oil that is removed from sorbent materials must also be properly disposed of or recycled. This new book gathers the latest research in this field from around the world. Chapter 1 - This chapter reviews and discuses recent literature related to methodological developments for the analysis of pollutants in indoor air, focusing the attention on emergent contaminants and biocides, which their environmental and health concern are increasing and are extensively found in indoor air. Some of them are suspected to behave as priority organic pollutants and/or endocrine disrupting compounds, and can be found both in the air gas phase and also associated to the suspended particulate matter and settled dust. The high comfort achieved in developed countries, increased the demand and the widespread consumption of biocides and fragranced household products. In addition, people in developed countries spend up to 90% of their time indoors. Inadequate ventilation coupled with the slow indoor degradation processes may increase indoor pollution levels. High temperature and humidity levels can also increase concentrations of some pollutants. Hence, inhalation of indoor air is potentially the most important exposure pathway to many pollutants. The chemicals that are extensively found in indoor environments include compounds that are suspected to behave as priority organic pollutants and endocrine disrupting compounds such as phthalate esters, polybrominated and phosphate flame retardants, fragrances, pesticides, biocides, and other organic compounds such as organotin and perfluorinated alkyl compounds that are of increasing concern as indoor pollutants. This chapter reports analytical developments and applications regarding the considered contaminants in the indoor environment, paying main attention to the sampling and analysis of the gas phase indoors. Available sorbents for sample collection, as well as analyte

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Thomas P. Willis

desorption techniques, clean-up procedures, determination techniques, and method performance evaluation will be summarized and discussed. Chapter 2 - Environmental analysis means in many cases the analysis of pollutants in trace and ultra-trace quantities (Ras 2008). Hence, sensitive, selective, fast and reliable methodologies are needed to detect pollutants in ambient air, and concentration techniques have often to be applied prior to the analysis (Camel & Caude 1995, Begerow et al. 1996, Dewulf & Van Langenhove 1999, Uhde 1999, Harper 2000, Dettmer & Engewald 2002, Desauziers 2004, Michulec et al. 2005, Demeestere et al. 2007, Ulman & Chilmonczyk 2007). When an analytical methodology is developed to study air pollution several terms have to be taken into account such as the pollutant state (gaseous or particulate matter), compound type or family, compound concentration, period of measurement (short- or long-term, e.g. instantaneous, 24-hour, monthly or yearly concentrations), the measurement site (in situ or in the laboratory) and the principal aim of the study (qualitative, estimation of a emission, punctual or long-term concentrations, main, minor or trace components study) (Michuelec et al. 2005). Thus, the application of solid sorbents to pollution and air quality control is an essential parameter to determine exactly the type and kind of compounds that are present in the atmosphere (Dettmer & Engewald 2003). The sampling enriches the analytes in the adsorbent, removing selectively form the matrix the target compounds by adsorption or reaction with the sorbent surface (Harper 2000). Target compounds are further analyzed using generally chromatographic techniques (Camel & Caude, 1995), as the single component analysis of the constituents of the atmosphere is preferred to the sum of pollutants in the case of volatile organic compounds (VOC) (Dettmer & Engewald 2002, Ras 2008). The interest in determining atmospheric pollutants has increased over the last several decades, as several act as precursors of photochemical smog formation, others represent a threat to human health (irritation of mucous membranes, psychological stress and long-term toxic reactions) (ECAIAQ 1997, Desauziers 2004, Hutter et al. 2006, Liang and Liao 2007, Ulman & Chimonczyk 2007) and comfort, as they are related to bad odors (Wolkolff and Nielsen 2001, Zuraimi et al. 2006). In the same way, some of them contribute to global change, by depleting the stratospheric ozone layer and by the radiative forcing of the earth (Dewulf & Van Langenhove 1999, Michulec et al. 2005). The complexity of pollutants occurrence in the atmosphere, in terms of composition (polar to non-polar compounds, very volatile and semivolatile compounds) and abundance (below detection limit (ppbv to pptv) to over detectors saturation limit), points out the necessity to develop versatile analytical methods (Desauziers 2004, Ribes et al. 2007). Chapter 3 - In this communication we suggest and discuss a new approach to targetorientated design of methanol sorbents “a salt in a porous matrix” for various applications. In the frame of this approach the demands of particular application are formulated and the composite adsorbent with properties meeting these demands is synthesised. Practical tools available to tailor such optimal sorbent, are suggested and discussed: the chemical nature of confined salt, the porous structure of the host matrix and additives forming solid solution with a basic confined salt. All these tools can be used to adjust the properties of real composite adsorbent to those of the optimal one. Finally the intent synthesis of composite adsorbents of methanol for two practical applications, namely increase in conversion of the catalytic methanol synthesis and the adsorption cooling, is described. Chapter 4 - Photo-SPME has recently been developed in our laboratory as a useful technique in elucidating the photodegradation mechanisms of a variety of environmental

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pollutants, permitting the simultaneous analysis of both primary compounds and photoproducts. This technique, in which a SPME fibre is used as support for photochemical studies, can be considered as an important innovation among SPME developments. Main kinetic parameters, the identity and photochemical behaviour of photoproducts, as well as the photodegradation pathways have been obtained for emergent pollutants or wellestablished substances of environmental concern (polycyclic and nitro musks, triclosan, PCBs, PBDEs, PAHs, pesticides). In addition to the successful results obtained with model solutions and controlled UV-irradiation conditions, photo-SPME has also demonstrated to be useful when extended to environmental conditions using real water samples and simulated solar irradiation. Comparison between photo-SPME with aqueous photodegradation followed by normal or classical SPME has been performed, underlining the advantageous use of photoSPME in environmental photodegradation studies. It is worth noting the novelty of many of the applications, such as musks, PBDEs, triclosan and pyrethroid insecticides for which the data of photochemical degradation were scarce or nonexistent. In summary, in this chapter, the state-of-the-art and the advantages of using solid-phase microextraction (SPME) fibres as a support for photochemical studies are reviewed and fully discussed. Trends and applications of photo-SPME to fields different of environmental are also explored. Chapter 5 - The adsorptivity of a basic dye-methylene Blue and an acidic dye - Eosin B, on wood was studied by monitoring colour reduction. The reaction was found to be feasible for methylene blue and negative for Eosin B, with respect to the various process variables investigated. It was found that the rate of reaction for methylene blue with the surface sites on the exterior of the wood particle controls the overall sorption during the early portion of the time course, though some mass transfer resistant due to boundary layer effect was apparent. The activation energies for the adsorption of methylene blue on the woods-obeche and Iroko were 31.125kg Mol-1 and 31.114kg Mol-1 'respectively. This variation in activation energy may be attributed to differed densities of the wood. In this work, the effect of stirring rate and particle sizes of adsorbent, effect of temperature on the rate processes and regressional analysis for computation of activation energy of adsorbents were determined. The data generated from the study suggest the implementation of wastewater treatment facility that is not for adsorptive properties alone but for either modified or combined properties that have been precisely determined and yet economical. Chapter 6 - Phosphorus (P) from domestic sewage waters and other diffuse sources of pollution is a threat to natural water systems. Households in sparsely populated areas that are commonly outside a sewer network thus need an easily maintained purification technique to remove P from their wastewaters. Furthermore, the P load from other sources of loading, such as agricultural land, requires counteracting measures. In a given agricultural region, a major part of P loading to surface waters may originate from some critical source areas, such as feeding and queuing areas on pasture soils or in fields receiving repeated loading of manure from chicken houses or fur ranches. Environmentally sound measures are needed to amend this type of hotspot to reduce the mobility of P enriched in the surface soil layers. The present study was undertaken to unravel the P retention ability of phlogopite-rich mine tailings produced in the enrichment process of apatite ore and its utilization as an adsorbent in wastewater treatment and in remediation of soil in critical areas. Due to its chemical and mineralogical properties, the material can be assumed to be suitable for P retention. The sorption of P was studied both in the solution phase to unravel the retention

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mechanisms as well as in more versatile soil environments. Sorption-desorption isotherms and various chemical extractions were employed to elucidate the P sorption reactions and retention components and capacity of the tailings. The contribution of artificial weathering of the material, as well as the reaction time and particle size, on P retention were also examined. In general, the results showed that phlogopite-rich mine tailings retain P efficiently. The isotherm determined for the untreated material was tortuous in shape, suggesting that several mechanisms and components, such as amorphous Al and Fe oxides and accessory calcite, are involved in P sorption. Artificial weathering, extended reaction time and decrease in particle size increased P retention. An incubation experiment with soil revealed that the tailings significantly improved the P sorption capacity of the soil, the artificially weathered material in particular. The untreated tailings did not affect the distribution of the sorbed P among various chemical pools while the acid-treated tailings decreased labile P and increased the amount of P retained by Fe oxides. Chapter 7 - Physico-chemical parameters of the synthesis of carbonized sorbents based on plant raw material are investigated along with the properties of these sorbents. The data of FTIR, ESR spectroscopy & BET- method, as well as electron microscopy are reported. It is stated that carbonized sorbents possess high specific surface area and porosity. Carboxylic, carbonyl, hydroxyl groups are detected on the surface of the synthesized sorbents. It is assumed that high sorption ability with respect to Co, Ni, Pb, Cd, Cu ions is connected with the formation of chelate complexes. It was shown that carbonized nanostructured sorbents are able to: adsorb cesium-137 (137Cs), strontium-90 (90Sr) & lead-210 (210Pb) successfully; reduce ions of gold (III) on the surface selectively; separate fusicoccine and similar biostimulators effectively; remove LPS-endotoxines from blood plasma selectively. They may be used as carriers to introduce probiotics into intestine thanks to formation of stable colonies on their developed surface. A method of preparation of honeycomb monoliths from carbonized rice husk with developed mesoporous structure via modification of the porous structure by silica leaching has been developed. Chapter 8 - Sorption of ions as well as organic molecules from aqueous media by calixarene based materials has been a widely developing area in material science and technology since last few decades. Mostly, it is achieved by the immobilization (physically or chemically) of modified calixarenes onto various supports such as polymers, silica, and resins. The calixarene macrocycles due to their bowl-shaped geometry are indeed used as hosts allowing organic and inorganic guests to coordinate/sorb onto their cavity. The possibility of designing versatile organic, coordination and organometallic architectures at the lower (narrow) and upper (wide) rims of the calixarenes are also very appealing for extending the cavity, or to take advantage of the proximity to promote substituent interactions. Thus, novel calixarene derivatives are continue to being synthesized and appended in polymeric materials in order to obtain regenerable resins for the recovery of various elements (metals/metalloids/non-metals) and neutral molecules. The calixarene based sorbents are generally applied in various fields such as catalyst recovery, power plant, agriculture, metals finishing, microelectronics, biotechnology processes, rare earths speciation, and potable water. Besides this, they find applications in the area of selective ion extractions, receptors, catalysis, optical devices, chemical sensor devices, the stationary phase for capillary chromatography, ion transport membranes, biomimetics, and luminescence probes etc. This survey is focused to have an overview of calixarene based sorbents for the extraction of ions

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and neutral molecules. The article does not, however, attempt to cover all of the different approaches to extraction processes. Chapter 9 - In given article use of magnetic sorbents for detoxification of blood has been investigated. Restored-iron, iron-carbon and iron-silica do not cause changes in erythrocyte's osmotic resistance and possess high sorption efficiency for substances of different molecular mass. These magnetic carriers can be recommended for extracorporeal blood detoxification of low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances. Chapter 10 - CaO based sorbents are widely used in the electric power industry to capture sulphur released from fuels, such as in coal gasifiers, fluidized bed combustors, and flue gas desulphurization units. In recent years, using CaO based sorbents for capturing CO2 from coal combustors has also been actively studied. The capturing of the pollutants is a process of reactive sorption, and the effectiveness of the sorbents depends on the reactivity of CaO with the species to be sorbed. Despite the importance of the applications, the detailed reaction mechanisms are not well understood and the interpretations of the kinetic behavior are controversial. In the present study effort is made to seek some generalizations for the different reaction systems, with focus on the effects of physical and chemical changes of the sorbent surface on the reactivity and the observed kinetic behavior. Simplified mathematical models are developed to describe the sorption kinetics, and a simple method for data analysis and performance prediction is demonstrated. Chapter 11 - Synthetic dyes that are extensively used in various industrial branches represent a serious environmental problem when they are emitted into the effluents as they are hardly biodegradable in conventional wastewater treatment plants. Therefore, alternative methods for decolouration of the wastewaters are developed, among them adsorption on solid sorbents is one of the most effective ones. Because the conventional sorbents such as activated carbon are rather expensive for large-scale applications, various low-cost materials have been tested as alternative non-conventional sorbents for the dye removal from waters. Numerous natural materials (zeolites, clays), industrial wastes (fly ash, iron slag), agrowastes or biosorbents exhibit a sufficient ability to retain various kinds of dyes from aqueous solutions and are available (locally and sometimes also globally) in great quantities and at low prices, and thus they can be used potentially for the treatment of the dye-containing effluents. A brief review of the non-conventional sorbents for the dye removal is given in this article together with selected applications. It should be emphasized that the dye sorption onto nonconventional sorbents is a rather complex process in which several mechanisms may be effective simultaneously. Effects of principal operational parameters on the dye sorption are discussed in the article, such as an effect of pH (governing both the dissociation/protonation of the active groups on the sorbent surface as well as side equilibria in solution), the presence of inorganic salts or surfactants. Basic equations describing the sorption equilibria (sorption isotherms) are presented. The results of kinetic measurements that allowed (in some cases) to identify a rate-limiting step of the overall sorption process are also mentioned in this chapter.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 © 2009 Nova Science Publishers, Inc.

Chapter 1

THE USE OF SORBENTS FOR THE ANALYSIS OF EMERGING POLLUTANTS IN INDOOR AIR Carmen Garcia-Jares1*, Ruth Barro2, Jorge Regueiro1 and María Llompart1 1

Departamento de Quimica Analitica, Nutricion y Bromatologia, Instituto de Investigacion y Analisis Alimentarios, Universidad de Santiago de Compostela, Santiago de Compostela 15782, Spain 2 CIEMAT (Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas), Ministerio de Ciencia e Innovacion, CEDER, Autovía de Navarra A-15, Salida 56, Lubia 42290, Soria, Spain

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ABSTRACT This chapter reviews and discuses recent literature related to methodological developments for the analysis of pollutants in indoor air, focusing the attention on emergent contaminants and biocides, which their environmental and health concern are increasing and are extensively found in indoor air. Some of them are suspected to behave as priority organic pollutants and/or endocrine disrupting compounds, and can be found both in the air gas phase and also associated to the suspended particulate matter and settled dust. The high comfort achieved in developed countries, increased the demand and the widespread consumption of biocides and fragranced household products. In addition, people in developed countries spend up to 90% of their time indoors. Inadequate ventilation coupled with the slow indoor degradation processes may increase indoor pollution levels. High temperature and humidity levels can also increase concentrations of some pollutants. Hence, inhalation of indoor air is potentially the most important exposure pathway to many pollutants. The chemicals that are extensively found in indoor environments include compounds that are suspected to behave as priority organic pollutants and endocrine disrupting *

Corresponding author. Phone: +34-981563100, ext. 14394, fax: +34-981595012; E-mail address: [email protected]

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Carmen Garcia-Jares, Ruth Barro, Jorge Regueiro et al. compounds such as phthalate esters, polybrominated and phosphate flame retardants, fragrances, pesticides, biocides, and other organic compounds such as organotin and perfluorinated alkyl compounds that are of increasing concern as indoor pollutants. This chapter reports analytical developments and applications regarding the considered contaminants in the indoor environment, paying main attention to the sampling and analysis of the gas phase indoors. Available sorbents for sample collection, as well as analyte desorption techniques, clean-up procedures, determination techniques, and method performance evaluation will be summarized and discussed.

GENERAL ABBREVIATIONS

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BTV ETS FES HS I.D. I/O IS K-D LDPE LOD LOQ MESCO MESI m/z NTD PISCES PUF QA/QC SIF S/N SPMDs SWCNTs TWA

breakthrough volume environmental tobacco smoke fullerenes-extracted soot head-space internal diameter indoor/outdoor ratios internal standard Kuderma-Danish low-density polyethylene limit of detection limit of quantification membrane-enclosed sorptive coating sampler membrane extraction with solid interface mass to charge ratio needle trap device passive in situ concentration/extraction samplers polyurethane foam quality assurance / quality control sorbent-impregnated filters signal to noise ratio semipermeable membrane devices single-walled carbon nanotubes time-weighted average

Organizations ASTM CEN IARC IUPAC NBS NIOSH OSHA US EPA

American Society for Testing and Materials European Committee for Standardization International Agency for Research on Cancer International Union of Pure and Applied Chemistry National Bureau of Standards National Institute for Occupational Safety and Health Occupational Safety and Health Administration United States Environmental Protection Agency

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The Use of Sorbents for the Analysis of Emerging Pollutants in Indoor Air

Techniques AED APCI ECD ESI FPD GC GPC HPLC IC ITD MAE MIMS MS PCI PID PSE PTV SE SPDE SPE SPME SPTD SRM TD TSD

atomic electron detection/detector atmospheric pressure ionization electron capture detection/detector electrospray ionization flame photoionization detection/detector gas chromatography gel permeation chromatography high-pressure liquid chromatography ion chromatography on trap detector microwave assisted extraction membrane introduction mass spectrometry mass spectrometry positive chemical ionization photoionization detector pressurize solvent extraction programmable temperature vaporizing solvent extraction solid-phase dynamic extraction solid phase extraction solid-phase microextraction short-path thermal desorption selected reaction monitoring thermal desorption thermoionic specific detection/detector

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Fibres CAR CW DVB PA PDMS TR

carboxen carbowax divinylbenzene polyacrilate polydimethylsiloxane template resin

Compounds ADBI AHMI AHTN ATII BBP

celestolide (4-acetyl-1,1-dimethyl-6-tert-butylindane) phantolide (6-acetyl-1,1,2,3,3,5-hexamethyl-indane) tonalide (7-acetyl-1,1,3,4,4,6-hexamethyl-tetraline) traseolide, (5-acetyl-1,1,2,6-tetramethyl-3-iso-propyldihydroindane) butylbenzyl phthalate

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Carmen Garcia-Jares, Ruth Barro, Jorge Regueiro et al. BECDIP 1-bromo-3-ethoxycarbonyloxy-1,2-diiodo-1-propene BFRs brominated flame retardants BTBPE bis-(2,4,6-tribromophenoxy)ethane BTEX mixture of benzene, toluene, ethylbenzene and xylenes CPIP 1-(4-chlorophenyl)-3-iodopropargylformal DBP dibutyl phthalate DDT dichloro-diphenyl-trichloroethane DeBDethane decabromodiphenyl ethane DEHP bis-(2-ethylhexyl) phthalate DEP diethyl phthalate DIBP diisobutyl phthalate DIDP diisodecyl phthalate DINP diisononyl phthalate DMP dimethyl phthalate DPMI Cashmeran (6,7-dihydro-1,1,2,3,3-pentamethyl-4(5H)indanone) EDCs endocrine disrupting compounds EtFOSE perfluorooctane sulfonamidoethanol HAPs hazardous air pollutants HBCD hexabromocyclododecane HCHs hexachlorocyclohexanes HHCB galaxolide (1,3,4,6,7,8-hexahydro-4,6,6,7,8,8-hexamethylcyclopenta-(g)-2benzopyrane FTOHs fluorotelomer alcohols IPBC 3-iodo-2-propynyl-N-butylcarbamate MeFOSE perfluorooctane sulfonamidoethanol MK musk ketone (4-tert-butyl-3,5-dinitro-2,6-dimethylacetophenone) MM musk moskene (4,6-dinitro-1,1,3,3,5-pentamethylindane) MTBE methyl tert-buthyl ether MX musk xylene (1-tert-butyl-3,5-dimethyl-2,4,6-trinitrobenzene) OPPs organic priority pollutants Ops organophosphate esters PAHs polycyclic aromatic hydrocarbons PBBs polybrominated biphenyls PBDEs polybrominated diphenyl ethers PCBs polychlorinated biphenyls PCDDs polychlorodibenzodioxins PCDFs polychlorodibenzofurans POPs priority organic pollutants PVC polyvynylchloride PFASs perfluoralkyl sulfonamides PFCs perfluorinated compounds PFOA perfluorooctanoate PFOS perfluorooctane sulfonate POPs priority organic pollutants SVOCs semivolatile organic compounds TBBPA tetrabromobisphenol-A

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The Use of Sorbents for the Analysis of Emerging Pollutants in Indoor Air TBP TBT TCEP TCMTB TCPP TDCT THMs TPeP TPhP TPP TPTC VOCs

5

tri-n-butyl phosphate tributyl tin tris(2-chloroethyl) phosphate 2-(thiocyanomethylthio)benzothiazole tris(2-chloropropyl) phosphate thermal desorption cold trap trihalomethanes tripentyl phosphate triphenyl phosphate tripropyl phosphate triphenyltin chloride volatile organic compounds

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1. INTRODUCTION The concern about pollutants present in indoor environments has increased in the last few years. Chemicals that building occupants are exposed to today are substantially different from those that occupants experienced years ago [1]. The markedly growing consumption of chemical products as cosmetics, air fresheners, house-cleaners, biocides, appliances and electronic equipment, building materials e.g. carpeting, paints, furnishings, etc. may turn our homes, schools, offices and workplaces into harmful microenvironments. People in developed countries spend up to about 90% of their time indoors [2, 3], and hence the exposure to household pollutants has dangerously increased. Thus, and taking into account that each person inhales about 22 m3 air per day [4], inhalation of indoor air has potentially become the most important exposure pathway to many pollutants and can be more relevant to human exposure assessment than ambient concentrations. Concerning infants and most vulnerable people, although outdoor air pollution first brought the issue of air pollution health effects to public attention, it is now indoor air pollution that likely has the greatest impact e.g. on children´s health [5]. As a first approach to evaluate the relationship between indoor air pollution and human exposure to pollutants, the AIRMEX project started in 2003. Personal exposures were conducted with employers and/or teachers working in different occupational environments such as public buildings, schools and kindergartens. Preliminary results indicate that personal exposure concentrations are higher than the indoor/outdoor concentrations [6]. Air is considered a very difficult environmental matrix to handle. It is a heterogeneous system of gases, aerosols and solid particles and its composition evolves, leading to a continuous movement, diffusion and reaction of the pollutants [7]. The concentration of an indoor pollutant depends not only on its indoor emission rate, but also on the rate at which it is being transported from outdoors to indoors, adsorbed by indoor surfaces, degraded by a slower indoor chemistry and removed by ventilation. Moreover, high temperature and humidity levels can increase concentrations of some pollutants. For example, it is well known that semivolatile organic compounds (SVOCs) are redistributed from their original sources to all indoor surfaces [8]. Vehicle garages can also be a pollution source as they often contain high concentrations of volatile organic compounds (VOCs) that may migrate into adjoining

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residences [9]. Surprisingly, some studies have identified indoor sources as the predominant factor influencing outdoor ambient air concentrations in densely populated areas [10]. Compounds that can be found indoors are flame retardants as polybrominated diphenyl ethers (PBDEs) and biphenyls, organophosphates, plasticizers such as phthalates or organotin compounds, fragrances, pesticides like organophosphate compounds, pyrethroids, among many others. Some of them are suspected to be POPs and/or EDCs, and can be found in the gaseous phase and/or associated to the suspended particulate matter and settled dust. A recent review summarizes available information on emission rates and indoor concentrations of various pollutants, such as VOCs, ozone, particulate matter and SVOCs (phthalate esters, brominated flame retardants –BFRs-, organophosphate flame retardants and polycyclic aromatic hydrocarbons -PAHs) that are related to electronic office equipment e.g. computers, printers, and photocopy machines [11]. An important finding is that personal exposures may be significantly larger than those estimated through average pollutant indoor concentrations, due to proximity of users to the sources over extended periods of time. At this time, exposure levels to these chemicals are largely un-documented as a result of a gap in the regulatory requirements, and data of major exposure sources and pathways is extremely limited yet. Measurement of organic pollutants in air is often a hard task to overcome, in part because of the large number of diverse compounds of potential concern, the variety of available techniques for sampling and analysis, and the lack of standardized methods. Consequently, the growing demand on environmental monitoring by the society, and the appearance on stage of new chemicals have encouraged the development of new, more rapid and sensitive, easy of use, and less expensive methods for the analysis of emerging pollutants in indoor air. International agencies have published analytical methods for air monitoring, which are available for all users on their respective webpages. But, standardization is a long process, and for that reason, in many cases, the proposed methods are long and tedious conventional methods, not upgraded to the upcoming and novel techniques. On the other hand, they constitute a very useful and valuable resource for routine analysis or for laboratories that perform air analysis occasionally. U. S. Environmental Protection Agency (US EPA) has published a compendium of methods for the determination of toxic organic compounds in ambient air [12]. Table 1 summarizes the methods for the analysis of pollutants of concern in air, involving the utilization of sorbents. On the part of the National Institute for Occupational Safety and Health (NIOSH), individual analytical methods have been listed by chemical name or method number [13]. In addition, about 100 standards which address analysis of workplace air samples have been developed by American Society for Testing and Materials (ASTM), and are available after payment [14]. Regarding the European Union, the Technical Committee CEN/TC 264 “Air Quality” of the European Committee for Standardization (CEN) has also published several European Standards for air analysis [15]. In this chapter, the role of sorbent materials in the analytical developments and applications, regarding emerging contaminants in the indoor environment are reported. Available sorbents for sample collection, as well as analyte desorption techniques, clean-up procedures, determination systems, and method performance evaluation are summarized and discussed.

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Table 1. Brief description of EPA methods for air analysis involving the use of sorbents (from ref. 12) Method no.

Applicable compounds

Sampling device

TO-1

VOCs

Active sampling on a Tenax cartridge

TO-2

VOCs

Carbon molecular sieve

TO-3

VOCs

Cryogenic preconcentration in a stainless steel trap packed with silanized glass beads

TO-4A

Pesticides, PCBs

Active sampling using a filter and a PUF trap

Method no.

Applicable compounds

Sampling device

TO-7

Anilines (NNitrosodimet hylamine)

TO-9A

Dioxins

TO-10A

Pesticides, PCBs

Active sampling using a low-volume sampler through a PUF plug

TO-11A

Aldehydes, ketones

Active sampling with a coated DNPH-cartridge

TO-13A

PAHs

TO-17

VOCs

Active sampling through a cartridge containing Thermosorb/N adsorbent Active sampling using a high-volume sampler through a glass fiber filter and a PUF adsorbent cartridge

Active sampling using a high-volume sampler through a glass fiber filter and a PUF or XAD-2 cartridge Active sampling through a multi-bed sorbent tube e.g. TenaxGR/Carbopack B, Carbopack B/Carbosieve SIII, Carbopack B/Carboxen 1000, Carbopack C/Carbopack B/Carbosieve SIII, Carbopack C/Carbopack B/Carboxen 1000, etc.

Desorption technique Thermal desorption Thermal desorption

GC/MS, GC/FID

Cryofocusing

GC/FID, GC/ECD

Solvent extraction with 10% diethyl ether/hexane Desorption technique

Chromatographic technique

GC/MS, GC/FID

GC/FID-ECD, GC/MS Chromatographic technique

Solvent extraction with dichloromethane

GC/MS

Solvent extraction with toluene

HRGC/HRMS

Solvent extraction with 5% diethyl ether/hexane Solvent extraction with acetonitrile

GC coupled to multi-detectors (ECD, PID, FID, etc.) HPLC/UV

Solvent extraction using 10% diethyl ether

GC/MS

Thermal desorption

GC/MS, GC/FID, etc.

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2. SAMPLING TECHNIQUES AND SORBENT MATERIALS A proper sampling device should fulfil the requirement of providing a representative air sample. Enrichment into solid sorbents is by far, the most widely used technique for sampling pollutants in air, although nowadays, other more recent techniques, such as solid-phase microextraction (SPME) or the use of membranes play an ever-increasing role. Organic pollutants can be sampled in indoor air by whole, active, or passive sampling techniques. Major advantages and drawbacks of each sampling technique are summarized in table 2. The simplest way to collect air samples is the whole air sampling, also called grab sampling, using polymer badges, glass containers or stainless-steel canisters. Total air sample is collected, avoiding breakthrough problems. Once the samples are collected, an aliquot can be introduced in a chromatographic system, either by direct injection, or using a preconcentration step, such as a cold trap or a cryofocusing device, which enhances the sensitivity of the method. Thus, some advantages derived from this procedure are that multiple aliquots of the sample can be re-injected into the system, and that very low blank levels are usually obtained. In addition, samples can be stored for several weeks without changes in their composition. However, these vessels may add a potential source of contamination, so they must be carefully pre-treated and pre-conditioned in order to avoid contamination or losses. The sample may contain a significant amount of water, which should be removed before analysis, resulting in evaporative losses of the less volatile compounds [16]. Table 2. Advantages and disadvantages of air sampling methods Type of sampling

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Whole sampling

Passive sampling

Active sampling

Advantages

Disadvantages

Simple Total sampling No breakthrough No degradation No moisture effect Low blank levels Long storage

Need a preconcentration step to achieve acceptable detection limits Contamination by the inner surfaces of the vessel Possible irreversible losses due to wall adsorption Possible losses while water removing before analysis Need pretreatment and preconditioning Severe clean-up procedures between samples Expensive to transport: heavy bottles Expensive devices: inner bottle surface and the clean-up step of shut-off valves Unstable flow-rates Influenced by meteorological conditions Long sampling times Difficult calibration

Simple Cheap Long-term exposures Simultaneous deployment in several locations Short-term exposures Suitable for a wide volatility range of analytes Easy calibration Re-utilization of sorbents

Careful sorbent selection Measure the breakthrough volumes Need pumps Expensive Possible degradations Interferences with moisture

The use of passive air samplers for indoor and workplace air is not as common as active sampling. Passive air samplers are increasingly employed for monitoring POPs due to their

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ideal applicability for long-term on site monitoring providing TWA estimations. The currently available passive sampling devices are either based on permeation or diffusion. Because of their simplicity, low prize and their ease of use, diffusive sampling devices became very popular the last few years. Nevertheless, their low sampling rates require long sampling times, from days to even several weeks at low concentrations, but it is low cost facilitates simultaneous deployment in a large number of locations. The most relevant drawback for this type of sampling is that environmental conditions such as temperature, humidity, wind, and air velocity influence the quantification significantly. A further problem is the accumulation of artefacts in stored samples. Current calibration methods that exist for passive sampling, including equilibrium extraction, linear uptake, and kinetic calibration, are presented in the review written by Ouyang and Pawliszyn [17]. Passive samplers usually consist of the sampling medium (adsorbent layer), a diffusion path, and a diffusion barrier (permeable membrane) [18]. The receiving phase of a passive sampler can be solvent, polymer resin, chemical reagent or porous adsorbent [17]. Passive samplers include solvent-filled devices, semi-permeable membrane devices (SPMDs), (MESCO), passive in situ membrane-enclosed sorptive coating sampler concentration/extraction samplers (PISCES), sorbent-filled devices, polyurethane foam (PUF) disks and SPME devices [17]. Some of the most common passive sampling devices commercially available for air sampling are Radiello (patented by an Italian foundation), Analyst, ORSA-5 (Drägerwerk, Germany) and OVM (3 M, Germany) [19], all containing an adsorbing cartridge of activated charcoal. Empore disks (Waters), with an octadecyl (C18) resin as the absorption material is another passive sampler which can be used for air analysis, and it is recommended for applications where high-pressure liquid chromatography (HPLC) is utilized for subsequent analysis. SPMDs filled with triolein have become the most popular passive system for hydrophobic compounds. A problem is the time-consuming sample-treatment procedure by dialysis, necessary when SPMD is used [20]. SPMDs have been lately used e.g. for the determination of organophosphorus pesticides in the air of a research laboratory [21]. In this work, the analytes were quantitatively recovered by using a shorter extraction procedure using microwaves instead of the conventional process by dialysis. As they have been increasingly in use for passive sampling, it is worth a mention the widely used PUF disks, applied e.g. for the collection of brominated flame retardants [22, 23], perfluorinated compounds (PFCs) [24], or polychlorinated byphenyls (PCBs) and organochlorine pesticides [25]. Last year, a comprehensive study was published on the subject [26]. PUF disks are generally mounted inside two stainless steel bowls to buffer the air flow to the disk and to shield it from precipitation and light [27]. Semivolatile compounds such as PCBs, PAHs, PBDEs, and organochlorine pesticides such as DDTs, HCHs, and chlordanes were passively sampled using PUF disks in cities of 3 countries (Mexico, Sweden and United Kingdom). Ratios between indoor and outdoor air concentrations (I/O ratios) were estimated because they may be a good tool to indicate whether there are indoor sources (I/O>1) or outdoor sources (I/O 98

0.3-20 pg m-3

2006

202

TetraHexaBDEs

PUF (300 m3 flow 0.60.8 m3 min-1)

GC/EI-MS (SIM)

54-104

1 pg m-3

2007

207

Tri-HexaBDEs

PUF disk (21 days, uptake rate 2.5 m3 day1 : 50 m3) previous addition of surrogates (BDE-3, d6-γ-HCH, PCB-107, PCB-198) PUF disk (28 days, uptake rate 1.1-1.9 m3 day-1: 31-53 m3), previous addition of surrogates (PCB19, PCB147)

Soxhlet with petroleum eter/acetone (1:1). Concentration to 1 mL, solvent exchange to isooctane, addition of 13C-labeled surrogates, clean-up on a multilayer (basic, neutral, acidic, neutral) silica column and elution with 60 mL dichloromethane/hexane (1:1). Clean-up on alumina, elution with 60 mL dichloromethane/hexane (1:1), concentration to < 10 mL and addition of 13 C-labeled IS Soxhlet with dichloromethane/hexane (1:1), previous addition of 13C-labeled surrogates. Treatment with H2SO4(c), clean-up on acidic silica, elution with hexane, clean-up on florisil, concentration and solvent exchange to nonane Soxhlet with petroleum eter, previous addition of surrogates (BDE-2, BDE-35). Concentration to 0.5 mL, solvent exchange to isooctane and addition of IS (Mirex)

GC/NCI-MS (SIM)

110-116

1.2-18 pg m-3

2007

79

Soxhlet with hexane, previous addition of 13 C-labeled surrogates. Concentration to 2 mL, treatment with 2 mL H2SO4(c), liquid extraction with dimethylsulfoxide, cleanup on florisil, elution with 20 mL hexane. Concentration and solvent exchange to 20 µL nonane and addition of IS (PCB-29, PCB-129) PSE extraction with petroleum eter, previous addition of 13C-labeled surrogates. Concentration to 0.2 mL and filtration through glass wool

GC/EI-MS (SIM)

45-67

0.1 pg m-3

2007

82

GC/NCI-MS (SIM)

NR

NR

2007

22

TriHexaPBDEs

Tri-DecaBDE

PUF (9 m3, 2 L min-1)

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Table 8. (Continued) Analytes

Sampling sorbent

Desorption and sample treatment

Determination

Recovery (%)

LOD

Year

Ref.

HCDBCO

PUF disk (21 days, uptake rate 2.5 m3 day1 : 52.5 m3) XAD-2 (6-26 m3, flow 13-18 L min-1)

Soxhlet with petroleum eter. Concentration to 0.5 mL and solvent exchange to isooctane Soxhlet with dichloromethane. Concentration to a small volume, cleanup on silica, elution with 50 mL dichloromethane, concentration to 0.3-0.5 mL, solvent exchange to isooctane and addition of IS Ultrasound extraction with 5 mL dichloromethane, previous addition of 13 C-labeled surrogates. Concentration to 1 mL, solvent exchange to hexane, concentration to 1 mL, clean-up on a Isolute NH2 cartridge

GC/NCI-MS (SIM)

NR

1.3 pg m-3

2007

144

GC/NCI-MS (SIM)

64-90

NR

2008

80

GC/NICI-MS (SIM)

NR

NR

2008

23

Ultrasound extraction with 5 mL dichlorometane, previous addition of surrogate (TPP). Filtration through glass wool, concentration to a small volume and addition of IS (ABP) Ultrasound extraction with 5 mL dichlorometane previous addition of surrogate (MDPP). Concentration to 0.1 mL

GC/NPD

>95

0.1 ng m-3

2000

215

GC/NPD

> 95

NR

2001

141

GC/EI-MS (SIM)

NR

1 ng m-3 (LOQ)

2001

135

Tri-DecaBDE

MonoDecaBDE

PUF (2 m3, flow 3 L min-1)

TiBP, TBP, TCEP, TCPP, TPhP, TBEP, TEHP

PUF (2.1 m3, flow 3.0 L min-1)

TPhP, IPPDPP, PPDPP, TBPDPP, TBP, TCEP, TCPP, TBEP TCEP, TCPP

PUF (1.5 m3, 3 L min-1 and (3.6 m3, 9 L min-1)

PUF (1 m3, 5 L min1 )

Soxhlet with hexane/acetone (4:1). Concentration to small volume

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Analytes

Sampling sorbent

Desorption and sample treatment

Determination

Recovery (%)

LOD

Year

Ref.

TBP, TCEP, TPhP, TBEP, TEHP, TCrP, TCPP, TDCPP TEP, TPP, TiPP, TiBP, TCEP, TCPP

PUF (1.4-3.4 m3,flow 4 L min-1)

Ultrasound extraction with 37 mL dichlorometane, previous addition of surrogate (TPP). Solvent exchange to hexane, concentration to 0.1 mL and addition of IS (Phenanthrene-d10) Thermal desorption (2 min, 250 ºC)

GC/EI-MS

62-100

0.073-0.41 ng m-3

2004

212

GC/NPD

NR

~2 ng m-3

2004

218

Thermal desorption (2 min, 250 ºC)

GC/NPD

NR

7 µm PDMS 0.1 ng m-3 100 µm PDMS 0.01 ng m-3

2004

219

Ultrasound extraction with dichloromethane. Concentration to a small volume

GC/PCI-MSMS

NR

0.1-1.4 ng m-3

2004

140

Ultrasound extraction with 8 mL acetone, and shaking. Centrifugation, decantation of 5 mL supernatant, addition of IS (fluoranthene-d10) and concentration to 0.3 mL

GC/EI MS (SIM)

94-112

0.1-0.6 ng m-3

2004

137

TEP, TPP, TiBP, TBP, TCEP, TCPP

TMP, TEP, TPP, TiPP, TiBP, TBP, TCEP, TCPP, TPhP, TTP TCrP, TEP, TPhP, TPP, TBEP, TCEP, TDCPP, TEHP

Non-equilibrium SPME (100 µm PDMS, 60 min) with controlled linear airflow (7cm s-1) Equilibrium SPME (7 µm PDMS 12 h or 100 µm PDMS 24 h)with controlled linear airflow (10 cm s-1) Cellulose filter (1.4 m3, flow 3 L min-1) previous addition of surrogate (MDPhP) Empore C18 (7.2 m3, flow 5 L min-1)

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Table 8. (Continued) Analytes

Sampling sorbent

Desorption and sample treatment

Determination

Recovery (%)

LOD

Year

Ref.

TMP, TPP, TBP, TCPP, TCEP, TDCPP, TPhP, TBEP, TEHP, DOPP, TEEdP, CLP1 TEP, TPP, TiBP, TCEP, TCPP

Isolute NH2 (1.0-2.7 m3, flow 2.5 L min1 )

Elution with 10 mL dichloromethane, previous addition of surrogate (TPeP). Concentration to dryness, dissolution in dichloroethane and concentration to 0.1 mL

GC/NPD

82-110 (34–58 TEEdP, TMP, TPhP)

0.1-3.9 ng m-3

2005

216

Non-equilibrium SPME (100 µm PDMS, 40-90 min) or equilibrium SPME (30 µm PDMS, >18 h) with controlled linear airflow (10-35 cm s-1: flow 1.1-3.8 L min-1) Isolute NH2 (1.5 m3, flow 2.5-3.3 L min1 )

Thermal desorption (2 min, 250 ºC)

GC/NPD

NR

NR

2005

220

Elution with 5 mL methyl-tert-butyl eter, previous addition of SS (THP). Addition of IS (TPeP)

GC/NPD

~ 100 %

0.1-0.3 ng m-3

2005

217

Empore C18 (14.4 m3, flow 10 L min-1)

Ultrasound extraction with 10 mL acetone. Concentration of 5 mL of extract to 0.5 mL and addition of IS (tris(1H,1H,5H-octafluoropentyl) phosphate)

GC/FPD

90-100

0.24-3.5 ng m-

2007

207

TEP, TiPP, TPP, TBP, TCEP, TCPP, TDCPP, TBEP, TPhP, DPEHP, TEHP, TTP TMP, TEP, TPP, TBP, TCPP, TCEP, TEHP, TBEP, TDCPP, TPhP, TCrP

3

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Passive air samplers based on polyurethane foam disks are being increasingly employed for sampling of brominated compounds in indoor air [22, 23, 203-205]. They are particularly attractive because of their facility to obtain time-integrated samples in indoor locations, where active samplers would not be practical over long time periods. In passive sampling, conversion of contaminant masses per sample into concentrations in air requires knowledge of the air uptake rate of the disk samplers and their deployment time. Wilford et al [203] estimated an average uptake rate of 2.5 m3 per day for tri- to hexaBDES. Sampling time usually ranges between 20 and 50 days, which approximately yields to air volumes from 50 to 100 m3. Another approach is the use of organic films from window surfaces as timeintegrated passive samplers for PBDEs [206]. These organic films are formed by condensation of gas phase species and organic aerosols as well as by deposition of particulate-associated compounds. With knowledge of the uptake rate and film-air partition coefficient (KFA), it is possible to estimate gas-phase air concentrations assuming that compounds in film and the gas-phase in air are at equilibrium. Brominated flame retardants are commonly extracted from sorbents by Soxhlet extraction which, despite its drawbacks, is still widely used due to its general robustness and high extraction efficiency. In this way, recoveries higher than 98 % for tetra- to heptaBDEs after Soxhlet extraction with dichloromethane and petroleum ether/acetone (1:1) have been reported [84]. Ultrasound-assisted extraction can be advantageous for the extraction of PBDEs and other brominated compounds [141, 143, 199, 202, 207] since this technique allows shorten extraction times and uses smaller solvent volumes. Very recently, a pressurized solvent extraction (PSE)-based procedure was applied by Allen et al [79] for the analysis of tri- to decaBDE in residential indoor air. Glass fibre filters and polyurethane foam plugs were extracted separately with dichloromethane and petroleum ether respectively. Extractions were completed in 5 min and, although higher costs were initially involved compared to Soxhlet extraction, the reduced extraction time and lower solvent consumption decreased the long-term cost and made the PSE more environmentally friendly. After extraction, a variety of clean-up procedures on silica gel, alumina, florisil or combinations of these sorbents are commonly used to improve the sensitivity for further analysis [22, 201, 204]. A complete procedure is described by Karlsson et al [81], who pre-cleaned Soxhlet extracts on a KOH/H2SO4-treated silica column followed by a clean-up on a gel permeation chromatography (GPC) system before analysis with GC/MS. Recoveries, evaluated by addition of 13C-labeled surrogate standards, were in the range from 12 to 97% for tri- to decaBDE with LODs lower than 0.2 ng m-3. Separation of brominated flame retardants is generally performed by means of GC/MS. Nevertheless, thermal degradation during their chromatographic separation has been reported for highly substituted PBDEs, mainly BDE-209. Degradation of these compounds leads to low repeatability in their analysis [198] and thus, special attention must be paid to ensure a proper GC analysis. Residence time in the column has been shown to be critical. If the residence time is too long, thermal degradation of highly substituted congeners, especially BDE-209, is substantial. Shorter standard columns were initially used for the analysis of decaBDE and so, the analysis of PBDEs, both the low and the high brominated congeners, required the use of two columns of different length. Although this approach is still in use in many laboratories, the development of narrow bore columns has allowed a proper determination of all congeners using only one column [208]. Narrow bore columns, with maximum length 8–10 m, small internal diameter (0.10 mm), and a thin film coating (0.10 µm), achieve comparable resolution in shorter analysis

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times [208, 209]. A comprehensive study on the influence of main GC parameters on the determination of decaBDE has been performed by Bjorklund et al [210]. According to these authors, the on-column injector is the most suitable injector for clean samples analysis, whereas programmable temperature vaporizing (PTV) injector provides a good compromise between robustness and yields for more complex samples. A further optimization of GC analysis of the highly substituted PBDEs has recently been described by Regueiro et al [144]. This study has been focused not only on decaBDE separation but also on the octa- and nona-brominated ethers, obtaining satisfactory results in terms of yield, accuracy and precision using a narrow bore column and a split/splitless injector operated at 320 ºC. Mass spectrometry is the most widely used detection system for analyzing brominated flame retardants in indoor air samples, specially operating in the negative chemical ionization mode (NCI) [23, 80-82, 141-143, 195, 199 ,200, 203, 205]. This technique provides a very high sensitivity and selectivity for brominated compounds, especially with selected ion monitoring of the most abundant fragment, Br− (m/z= 79/81). However, there may be problems with identification and co-elution of other brominated compounds, and it is not possible the use of 13C-labelled compounds as internal surrogate standards (SSs) [202]. Using GC/NCI-MS, Gevao et al [205] determined tri- to heptaBDEs in indoor air reaching LODs from 0.2 to 0.5 pg m-3. Mass spectrometry in the EI (SIM) mode has also been employed for quantification of this kind of compounds in indoor air [22, 84, 96, 201, 204, 206], reporting LODs in the range 0.3-20 pg m-3 for the analysis of tetra- to hexaBDEs [84]. The presence of Br atoms in the molecules of the compounds allows the use of gas chromatography with an atomic emission detector (AED). In this way, a wavelength of 827 nm was selected for Br detection and LODs in the low ng m-3 were obtained for most compounds in indoor air. [207]. Analysis of TBBPA and 2,4,6-tribromophenol —used as BFR and also the major breakdown product of TBBPA— by GC requires a previous derivatization step. In this way, acetylation was carried out with diazomethane [141, 195]. The use of LC/MS in the determination of TBBPA is an alternative that provides several different detection modes and eliminates the need of derivatization. For the determination of TBBPA in air, Tollback et al [202] developed a LC/MS method using electrospray ionization (ESI) in the negative ionization mode with SIM. This kind of ionization was compared to atmospheric pressure ionization (APCI), achieving LODs between 30-fold and 40-fold lower.

Concentration in Indoor Air Several studies have reported concentration levels of brominated flame retardants in air from electronics recycling facilities [96, 141]. Sjodin et al [141] investigated the presence of several of these compounds in an electronics recycling plant and other indoor work environments in Sweden. The highest concentrations of all the identified brominated flame retardants were found in the recycling facility. For the rest of sampling sites, the corresponding concentrations in air were, in general, several orders of magnitude lower. Most abundant compounds in the recycling plant were BDE183, BDE209, BTBPE, and TBBPA with mean values in the range 19-36 ng m-3. On the other hand, BDE-47 was the most abundant PBDE congener in a computer teaching hall and a circuit board assembly plant with a mean concentration of 0.76 and 0.35 ng m-3, respectively. Indoor air concentrations of tri- to hexaBDEs have been measured in homes in Canada, detecting up to 1600 pg m-3 [203]. These values were higher than those reported

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in indoor air in Kuwait, with an average concentration in homes of 15 pg m-3 [205]. Shoeib et al [84] determined concentrations in homes ranging between 76 pg m-3 and 2088 pg m-3 for tri- to heptaBDEs, whereas those reported by Chen et al [80] were in the range 0.3-1710 pg m-3. In figure 2, the levels found in several homes and one office in different countries are depicted. Harrad et al [201] reported levels of tetra- to hexaBDEs in outdoor and indoor air from different microenvironments including offices and homes. Concentrations of the tetra- and pentaBDEs in indoor air were always higher than those detected in outdoor air. Values for all studied compounds ranged from 100 ng m-3 have been reported [154, 174].

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Concentration in Indoor Air Phthalate indoor concentrations highly depend on the building materials and the type of furniture at each sampling emplacement. Hence, a broad range of values have been reported for the analyzed compounds (see figure 4). Results on the monitoring of phthalate esters in 125 homes in California (USA), showed a clear predominance of DBP and DEP in indoor air, with mean values of 410 and 350 ng m-3, respectively [233]. In this study, DEHP (110 ng m-3) and BBP (35 ng m-3) were also found. Higher concentrations of total phthalates (>1000 ng m-3) have been quantified in apartments and homes [77, 154, 174], which demonstrates that DBP predominates in the gas phase of domestic indoor environments. Fromme et al [77] extended the study of the indoor occurrence of phthalates and musk compounds to kindergartens, finding mainly DMP and DBP at similar mean concentrations (1100-1200 ng m-3). DBP and DEHP have also been quantified in office rooms, finding concentrations in the broad range found in homes [154]. The indoor exposure to EDCs was studied by Rudel et al [96], reporting that phthalates were the most abundant of the 89 organic chemicals considered in the 120 homes surveyed; total concentrations of DEP, DBP, DEHP, and BBP ranged from 85

0.1-2.0 ng m-3 (7.2 m3)

2004

137

GC/EI-MS (SIM)

82-91

0.018-0.140 ng (gas phase)

2004

68

GC/EI-MS (ITD, SIM)

NR

0.03-76.7 µg m-3

2004

183

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Analyte

Sampling

Desorption and sample treatment

Determination

Recovery (%) NR

LOD

Year

Ref

8 pesticides: malathion, chlorpyrifos, diazinon, etc 38 pesticides: herbicides, pyrethroids, organophosphate and organochlorine insecticides, fungicides Insecticides (pyrethroids)

PUF (30-40 L min-1, 24 h)

Extraction with 2 mL toluene/acetone (9:1) (NIOSH 5600)

GC/MS (SIM)

0.001-0.002 µg m-3

2004

69

PUF (24 h, 5 L min-1, 7.1 m3)

Soxhlet with 150 mL dichloromethane. Concentration to 100 µL followed by dilution in 2 mL acetone

GC/ECD, GC/TSD, HPLC/UV (DAD)

73.1-120.2

LOQs = 0.1-562 ng m-3

2006

67

SPMDs suspended about 2 m height from floor (48 h)

Microwave-assisted extraction with hexane/acetone (1:1). Concentration, reconstitution in 5 mL hexane, and extraction with acetonitrile. Clean-up with alumina-C18 and elution with 10 mL acetonitrile. Evaporation to dryness. Addition of IS in isooctane Extraction by shaking with acetone or ethyl acetate. Centrifugation

GC/EI-MS-MS

61-103 (after 2nd extraction)

0.3-0.9 ng per SPMD

2006

139

4 fungicides, 1 insecticide and 1 acaricide 11 pyrethroids, 1 synergist, 1 fungicide, 1 carbamate 10 pyrethroids, 1 synergist, 1 fungicide, 1 carbamate Pentachlorophenol, bisphenol- A and nonylphenol Disinfectants: Quaternary Ammonium Compounds (QACs)

Supelpak or C18

GC/NPD, HPLC/UV

LOQ=0.2-20 µg m-3 (60 L)

2006

105

Tenax (100 L min-1, 1 m3)

Ultrasound extraction with 1 mL ethyl acetate

GC/MS (ITD), GC/μECD

79-102 (Supelpak), 84-106 (C18) 81-114

0.03-4.1 ng m-3 (μECD), 1.4-9.1 ng m-3 (MS)

2006

44

Florisil (100 L min-1, 1 m3)

Addition of 100 µL acetone followed by HS-SPME (PA fiber, 30 min, 100ºC)

GC/MS (ITD), GC/μECD

76-119

0.001-2.1 ng m-3 (μECD), 0.0467.1 ng m-3 (MS)

2006

53

XAD-2 (48 h, 4 L min-1)

Soxhlet with dichloromethane. Concentration, SPE with florisil and concentration. Addition of surrogates Ultrasound extraction with 5 mL acetonitrile

GC/MS

55-120

0.09 ng m-3

2007

256

IC (Cationic preconcentration column), LC/MSMS

99.83-101.00

28 µg m-3 (100 L, IC), 5 ng m-3 (100 L, LC/MSMS)

2007

257

XAD-2 (1 Lmin-1, 100 L)

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two different sandwich combinations; PUF/XAD-2/PUF and PUF/XAD-4/PUF for trapping currently used pesticides in the gaseous phase using high volume (hi-vol) samplers [264]. The sandwiches were only slightly more efficient than XAD-2 and XAD4 resins, followed by PUFs, and taking into account that losses of pumping efficiency were found using the sandwich designs, XAD-2 was the adsorbent recommended. Tsiropoulos et al investigated the trapping efficiency of XAD-2, XAD-4, Supelpak-2, Florisil and C18 for five pesticides [105]. Supelpak-2 and C18 were selected as the best adsorbents, based on their performance characteristics, such as sufficient trapping efficiency, no dependence on the relative humidity, extended range of concentration levels, good recoveries and storage stability. As it was previously mentioned in section 5 of this chapter, the use of quartz filters and Empore disks was tried to determine 92 SVOCs, including insecticides, synergists and fungicides [137]. Among them, 20 pesticides including fenthion, piperonyl butoxide, allethrin or tetramethrin, could not be sufficiently collected by the disks due to low retention efficiencies; while other pesticides, such as fenitrothion, pentachlorophenol or deltamethrin, could not be accurately quantified since their calibration curves were not linear. Elflein et al also underlined recovery problems when sampling household insecticides by means of a glass filter and two polyurethane foam cartridges [170], assuming a decomposition mechanism on the filter during the spiking experiment for four pyrethroids. In addition, these authors sentenced that polyurethane foam contributes to the “matrix-induced chromatographic response enhancement”. As it was previously described in this chapter, when adsorbents are used for sampling, calibration is usually performed by direct spiking of adsorbents with solutions of known concentrations of the target analytes. Another procedure to calibrate, in this case, trifluralin and triallate, was introduced by Cessna and Kerr [147]. A polytetrafluoroethylene (PTFE) U-tube is fortified with a solution of pesticides in hexane and immersed in a water bath at 50 ºC. Then, air is continuously drawn through an U-tube at 0.1 L min-1 towards two mini-tubes packed with Tenax TA arranged in series. In this way, an easy and realistic calibration was feasible, simulating different concentrations of air samples. Due to their possible workplace implications, some papers regarding outdoor air analysis should be pointed out. Cartridges with Florisil were used to estimate the leaf-air transfer of pesticides in vegetables [145, 146] or to measure atrazine and alachlor concentrations in agricultural areas [263]. Egea Gonzalez and co-workers developed a screening method to analyze more than 70 pesticides in air of urban locations surrounded by greenhouses [265]. These authors tested three different adsorbents (Tenax TA, Chromosorb 106 and Supelpak) obtaining the poorest recoveries with Supelpak. Several authors have reviewed the passive sampling of pesticides, among other organic pollutants, in ambient air [266-268]. However, the number of passive sampling studies for collecting pesticides in indoor air is scarce. Esteve-Turrillas and co-workers sampled pyrethroid insecticides with SPMDs [139]. The membranes were suspended about 2 m height for a total time of 48 h in a dark and closed room treated with different insecticide sprays. Dai et al sampled chlorpyrifos (a termiticide) for one month in indoor air in houses using a passive sampler consisting of a porous PTFE tube filled with 0.75 g of Supelpak adsorbent resins [255]. Ramesh and Vijayalakshmi collected three pyrethroids in air of rooms treated with insecticides using an airtight syringe and then dissolved them in acetone [253]. The exposition of a SPME fiber to the contaminated atmosphere constitutes an alternative for sampling pesticides in indoor air. In this way, Ferrari et al published a

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multiresidue method using SPME for the determination of 11 pesticides in confined atmospheres [183]. Compounds belonged to different chemical families with a large range of saturated vapour pressures. A PDMS fiber was immersed for 40 min in a 250mL flask through which air samples were dynamically pumped from the analysed atmosphere. As a field application, the proposed method was applied for the determination of procymidone concentrations as a function of time in a greenhouse. The use of SPME fibres completely avoids the use of solvents and can be applied to determine pesticide concentrations in workplace environments, like in the breathing zone of workers in greenhouses. Paschke et al compared the applicability of SPME and SPMDs for semi-volatile chlorinated organic compounds in a landfill, where large amounts of lindane by-products were deposited in the past, together with other hazardous chemical residues [269]. Both samplers yielded to comparable TWA air concentrations of lindane and its isomers and of dichloro-diphenyl-trichloroethane with its metabolites. Cisper and Hemberger developed a method for the on-line detection of SVOCs, including pesticides, using membrane introduction mass spectrometry (MIMS) [131], clearly expanding the practical limits of MIMS analysis. The method used a composite membrane made by plasma deposition of a thin PDMS layer on a microporous polypropylene support fiber. Air sample flowed over the outside of the fibres counter current to the helium flow. Concentrations were found in the pptv range. When analytes were retained on an adsorbent, an appropriate solvent is required, usually at high volumes, to quantitatively elute them. In addition to the time-consuming steps for concentration and clean up of the organic extracts, including the risk of analyte losses, the possible photodecomposition of some pesticides has been reported [137, 165, 170], showing that the determination of certain pesticides in air might require performing a rapid and careful trapping-extraction process. Classical extraction processes such as Soxhlet has extensively been used [67, 72, 74,96, 103, 254, 256], as well as solvent extraction with acetone [56, 57, 105], methanol [263, 270], acetonitrile [259], ethyl acetate [105, 252], hexane and dichloromethane [68], toluene [255], or mixtures of solvents [69], usually followed by shaking for several minutes. As a consequence of the large volumes of solvents used in this kind of extractions, a further concentration step may be required, as well as drying with anhydrous sodium sulphate [145]. Filtration through silanized glass wool [57, 73], HPLC fractionation [252], or cleaning procedures are also generally needed [68, 74, 139, 145, 256, 260]. Besides the conventional solvent extraction procedures, other techniques have been proposed for the extraction of pesticides from the trapping sorbents. Extraction of analytes is sometimes helped by sonication, usually over a period of no more than 15 minutes [44, 73, 137, 146, 170, 257, 258, 265]. Reduction in the amount of trapping sorbent would allow the reduction in solvent volumes. In this way, a recent paper describes the use of only 25 mg Tenax as trapping sorbent as part of a method to determine several pesticides in indoor air based on US-assisted extraction with a volume of ethyl acetate as low as 1 mL [44]. Detection limits for this simple and fast method ranged from 0.03 to 4.1 ng m-3 (1 m3), with no need of concentration or further treatment of the extracts. Another approach based on the use of SPMDs was described for the determination of insecticides in air, requiring solvent re-extractions with 30 mL of a mixture of hexane-acetone and microwave extraction for 20 min [139]. In this procedure, concentration, reconstitution of the extracts, and different clean up steps derived from the matrix effect of SPMDs, were needed to achieve good recoveries, whereas detection limits ranged from 0.3 to 0.9 ng per membrane.

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Thermal desorption is an alternative if a thermally desorbable adsorbent has been used for trapping pesticides. Some authors extracted chlordanes [58], two herbicides (trifluralin and triallate) [147], or 10 pesticides including triazines, carbamates and organochlorides, from Tenax by thermal desorption [271]. Baroja et al determined fenothrion and its main metabolites in forestry air by sampling on Tenax and using a thermal desorption cold trap [272]. The use of headspace (HS)-SPME has been proposed as an alternative to solvent and direct thermal desorption of pesticides, enhancing the selectivity and the sensitivity of the analysis. In such a way, Barro et al optimized a method for determining several pesticides in indoor air after their retention on 25 mg of Florisil [53]. After the addition of 100 µL acetone to the sorbent, a SPME was carried out by exposing a polyacrilate fiber to the HS of the vial. The fiber was then thermally desorbed in the injection port of a gas chromatograph. Using μECD detection, method detection limits as low as 0.001 ng m-3 were achieved for most insecticides. The techniques of choice for the determination of pesticides in air are GC/ECD [44, 53, 56, 73, 103, 145-147, 252, 253, 260] and GC/MS [57, 58, 69, 74, 103, 170, 254, 256, 258, 260, 263, 272], although other less common detectors such as thermoionic specific detector (TSD) [67], or NPD [56, 105] have also been used with GC. When higher sensitivity is required, GC/MS-MS [72] can also be used. Egea Gonzalez et al determined 70 pesticides by GC/MS-MS using a large volume injection technique [265]. Injecting a higher volume of sample extract (10 µL) the sensitivity was enhanced, achieving LOQ values ranging from 0.2 for chlorothalonil to 27 ng m-3 for cypermethrin, based on a 1.44 m3 air sampled. In addition, the use of HPLC/UV [67, 73, 105, 259] has also been reported. Vincent et al determined quaternary ammonium biocide compounds by ion chromatography (IC) and LC/MS-MS [257]. In this particular case, IC appears to be a good alternative since it is not expensive and its use is very simple compared to LC/MS-MS. Moreover, the limit of detection could be reduced by a factor of 100 with an injection volume of 50 μL.

Concentration in Indoor Air Pesticide control indoors is getting increasing attention. Concentrations of common household pesticides are generally higher indoors than outdoors [273]. Class and Kintrup determined household insecticides in commercial formulations, residues, surfaces, and in air during and after indoor application [165]. The concentrations of insecticides in air and their deposits on surfaces (up to 1000 µg m-3) revealed possible exposure of humans by inhalation or skin adsorption. Electrically heated evaporators cause allethrin concentrations in air of 2-5 µg m-3 during application; much higher concentrations (300 µg m-3 and more) were observed when pyrethroids and other insecticides were sprayed as aerosols into a room. The insecticides laid on surfaces and some readily formed transformation products persisted for 60 h or longer. Berger-Preiss et al monitored the concentrations of two pyrethroids, pyrethrum and the synergist piperonyl butoxide in a model house over a period of two years after simulated pest control against cockroaches [73]. Only the pyrethrins decreased rapidly, mainly by photodecomposition. Deltamethrin and permethrin levels in the gas phase were 1.5 and 8 ng m-3 respectively, when a normal dose was applied. Roinestad et al identified 34 pesticides in household air ranging from 5.7 to 254.7 ng m-3 [57]. Comparison of dichlorvos, o-phenylphenol and propoxur levels in a home were also carried out immediately after spraying (354.7, 63.0 and 434.3 ng m-3 respectively), and 8 weeks after application (not detected, 35.8 and 5.8 ng m-3). In other study, concentrations of aldrin, dieldrin, four chlordanes, pentachloroanisole and

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hexachlorocyclohexanes were measured in the living area of a home and outdoors [74]. All compounds except the hexachlorocyclohexanes showed higher indoor than outdoor air concentrations, implying that their sources were in the home. Ramesh and Vijayalakshmi deployed two different mosquito coils, an aerosol sample, and two different mosquito mats containing pyrethroids in a close room [253]. Air samples were collected at different intervals ranging from 15 min to 8 h from three different positions in the room (top, middle and bottom). The concentrations of pyrethroids were initially high at the top of the room, followed by a steady decline on moving towards the floor. At the end of a 6 h period, most of the residues were below 0.1 ppb. Rudel and co-workers determined pesticides, among other EDCs in 120 homes [96]. The 90th percentile concentrations for pesticides ranged from 10 to 19 ng m-3 in air. The indoor prevalence of pesticides that have been banned or restricted for many years, such as DDT, chlordane, heptachlor, methoxychlor, dieldrin and pentachlorophenol, suggested that indoor degradation is negligible. Whyatt et al measured 8 pesticides in 48-h breathed out air samples collected from more than 200 mothers during pregnancy [254]. A significant correlation was observed between the levels of chlorpyrifos, diazinon and propoxur in the breathed out air and the levels of these insecticides or their metabolites in plasma samples (maternal and/or cord). The fungicide o-phenylphenol was also detected in all air samples, but it was not measured in plasma. Other studies measured pesticides in indoor air of homes, i.g. chlordanes [68], chlorpyrifos [103, 255], phenols [256], or organophosphorus pesticides [69]. Moreover, biocides as DDT, lindane, methoxychlor, among others were identified in different locations of museums [261]. The inhalational exposure to pesticides in greenhouses is considered more critical than outdoors, because greenhouse walls restrict their rapid distribution and dilution via airflow [56]. Cruz Márquez et al developed a method for assessing both likelihood and exposure of farmers to spray applications of malathion in greenhouses [72]. The malathion concentration in the breathing area during the application was found between 69.4-85.9 µg m-3. Insecticides and fungicides were monitored in greenhouses for 3-4 days after application of plant protection products by manual sprayers on different types of crops (flowers and vegetables) [56]. The maximum concentration found was 28 µg m-3 for parathion, and after a dissipation period of several hours, the levels were greatly influenced by ventilation and temperature. The objective of Bouvier et al [67] was to assess the residential pesticide exposure of non-occupationally exposed adults, and to compare it with occupational exposure of subjects working indoors. The study involved 20 exposed persons, 38 insecticides, and the sampling of 19 residences, two greenhouses, three florist shops and three veterinary departments. Indoor air concentrations were often low, but could reach 200-300 ng m-3 for atrazine and propoxur in residences. As expected, gardeners were exposed to pesticides sprayed in greenhouses, although florists and veterinary workers were also indirectly exposed due to the former pest control operations. Pesticide measurements were up to 220 ng m-3 for methidathion in greenhouses, 28.6 ng m-3 for lindane in florist shops, and 52.9 ng m-3 for diazinon in veterinary departments. Other authors monitored the concentrations of widely used plant protecting agents during and after application, as well as their spatial and temporal distribution in agricultural areas [55, 260, 271, 274, 275].

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6.5. Perfluorinated Alkyl Compounds Perfluorinated alkyl compounds (PFAs) are a group of organic chemicals used in a variety of consumer products for water and oil resistance, including surface treatments for fabric, upholstery, carpet, paper, and leather, in fire-fighting foams, and as insecticides [276]. Many of them combine bioaccumulative potential, toxic effects and extreme persistence; thus, they are considered as candidates for the Stockholm Convention list of persistent organic pollutants (POPs) and are regarded as a new and emerging class of environmental contaminants. Perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA) and related compounds such as perfluoralkyl sulfonamides (PFASs) and fluorotelomer alcohols (FTOHs) figure among the most widespread PFAs [24, 277]. Up to now, there are only very few available data on indoor air concentrations of PFCs, but concentrations of volatile polyfluorinated compounds appear to be considerably higher in indoor than in outdoor air. Perfluoroalkyl sulfonamides have been collected in indoor air by both active and passive procedures (see table 12). Active sampling has been carried out using SPE cartridges [277] or a glass filter followed by polyurethane foam plugs [84], and air volumes between 20 and 200 m3. These compounds have also been collected by means of polyurethane foam disk passive air samplers [24]. Very recently, Shoeib et al [278] have developed a novel type of polyurethane foam disk impregnated with XAD-4 powder, which provides a higher sorptive capacity for organic and polar chemicals, such as the FTOHs and PFASs. Uptake rates for this sorbent-impregnated polyurethane foam disks from 1.4 to 4.6 m3 day-1 were estimated for the studied compounds. Extraction of fluorinated compounds has been mainly performed by Soxhlet [24, 84, 278] with no further clean-up after volume concentration. Analysis is usually carried out by GC/MS operated in the EI mode with SIM [24, 84] or in the PCI mode [277, 278]. Separation of PFASs can be performed with common stationary phases 5 % phenyl substituted methylpolysiloxane [24, 84], although more polar capillary columns are required for FTOHs [277, 278]. Shoeib et al [24] determined PFAS in indoor air with recoveries ranging from 64 to 89 %, relative standard deviation (RSD) values lower than 8 %, and LODs between 0.01 and 7.1 pg m-3. Shoeib et al [84] determined concentrations of PFAS in indoor air from homes and laboratories. N-methyl perfluorooctane sulfonamidoethanol (MeFOSE), widely used as a stain repellent on carpets, was the most abundant in both indoor and outdoor air, followed by N-ethyl perfluorooctane sulfonamidoethanol (EtFOSE) (see Table 2). Mean indoor concentrations of MeFOSE and EtFOSE were 2589 and 772 pg m-3, respectively. These concentrations were approximately 100 times higher than their outdoor values. PFAs in indoor air from office were evaluated by Jahnke et al [277], obtaining values for MeFOSE and EtFOSE of 727 and 305 pg m-3, respectively.

6.6. Environmental Tobacco Smoke Environmental tobacco smoke (ETS) contains thousands of compounds, many of which are demonstrated carcinogens [279], such as benzene and 1, 3-butadiene. In addition, other ingredients of ETS classified as possible carcinogens according to IARC are naphthalene, styrene, ethyl benzene, and isoprene. The risk of cancer can be higher in child since they are most affected by household exposure [280]. ETS also contains

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Table 12. Analytical procedures for the determination of perfluorinated alkyl compounds in indoor air Analytes

Sampling

Desorption and sample treatment

Determination

MeFOSE, EtFOSE, EtFOSA, MeFOSEA FTOHs, MeFOSA, EtFOSA, MeFOSE, EtFOSE MeFOSE, EtFOSE, MeFOSEA

PUF disks (21 days, uptake rate 2.5 m3 day-1: 52.5 m3)

Soxhlet with petroleum eter, concentration to 0.5 mL, and addition of IS (Mirex)

Isolute ENV+ (20100 m3, 1.1 m3 h-1)

PUF (100-200 m3, 400 L min-1)

FTOHs, MeFOSE, MeFOSA, EtFOSE, EtFOSA, MeFOSEA

PUF disk impregnated with XAD-4 powder (83 days, uptake rate 1.44.6 m3 day-1, 116-382 m3)

LOD

Year

Ref.

GC/EI-MS (SIM)

Recovery (%) 64-89

0.01-7.1 pg m-3

2005

24

Elution with 34 mL ethyl acetate, concentration, cahange to isooctane, concentration to 0.2 mL, and addition of IS (TCN)

GC/PCI-MS (SIM)

17-400

3-300 pg m-3

2007

277

Soxhlet with petroleum ether/acetone (1:1). Concentration to 1 mL, solvent exchange to ethyl acetate, and addition of IS (Mirex) Soxhlet with petroleum ether/acetone (1:1), previous addition of 13C-labeled and deuterated surrogates. Concentration to 0.5 mL, centrifugation and addition of IS (N,N-Me2FOSA)

GC/EI-MS (SIM)

47-60

0.3-20 pg m-3

2004

84

GC/PCI-MS (SIM)

86-126

NR

2008

278

58

Carmen Garcia-Jares, Ruth Barro, Jorge Regueiro et al.

pyridine, toluene, limonene, phenol, and other chemicals that are considered possible harmful for humans. A recent study conducted by Vainiotalo et al [37] focused on the measurement of 16 ETS components in Finnish restaurants. They used several samplers, of which a 3M (OVM 3500) diffusive one was for 3-ethenylpyridine and nicotine (sampling rate, 24 mL min-1). These both compounds were also collected in charcoal tubes using a pump at a rate of 100 or 200 mL min-1. Volatiles such as toluene, limonene, and pyridine, among others, were collected in Tenax; and 1,3-butadiene and isoprene, were retained in Carbopack X. The analysis of 3-ethenylpyridine and nicotine required desorption of the samplers with a toluene/pyridine solution, whereas the Tenax and the Carbopack X tubes were thermally desorbed. In all cases, a GC/MS analysis was performed. In the above commented study concentrations of ETS-specific VOCs were similar to those detected in restaurants elsewhere [91, 281], whereas those of BTEX were found to be lower. The study indicated that ETS significantly increases the levels of several toxic impurities and that it is a source of 1,3-butadiene.

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CONCLUSION The consumption of chemical products associated to the growing demand of higher comfort is not expected to decrease in the next years. Although controls on production, distribution, and utilization, are becoming stricter, new chemicals are entering our lives, which may turn our homes, schools, offices and workplaces into harmful microenvironments. Hence, continuous research on exposure to those chemicals and on their toxic effects on humans and environment is required. The so-called emerging pollutants that can be found indoors cover compounds such as flame retardants (polybrominated diphenyl ethers, polybrominated biphenyls, or organophosphates), plasticizers (i.g. phthalates, organotin compounds), fragrances, perfluorinated alkyl compounds, together with other compounds, such as pesticides, biocides, insecticides, or the environmental tobacco smoke. For most of them ecotoxicological data are still scarce and therefore, it is difficult to predict their health effects. The growing demand on environmental monitoring by the society, and the appearance on stage of new chemicals have encouraged the development of new, more rapid and sensitive, easy of use, and less expensive methods for the analysis of these pollutants in indoor air. The role of sorbent materials in these analytical developments and, as a consequence, in the application of the aforementioned methods in the indoor environment has been reported, and the available sorbents for sample collection, extraction/desorption techniques, clean-up procedures, determination systems, and method performance evaluation have been summarized and discussed. Development of new and better sorbents for air sampling is on-going. Fullerenesextracted soot (FES) can be used as low cost adsorbents for VOCs collection. Applicability of tire powder for VOCs collection has also been well demonstrated by a linear-partitioning model. Single-walled carbon nanotubes (SWCNTs), very useful in other scientist fields have been recently proposed as a novel adsorbent for collecting VOCs in air. Their large surface area and high adsorption and desorption efficiencies makes them suitable sorbents, particularly for compounds with low boiling points and strong volatility. New multi-layer sorbents are being developed as well, because they afford the opportunity to collect compounds of a wide volatility range combining

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different sorbents into a single multi-layer one, diminishing the effect of water on the analysis, and improving the reproducibility, and the adsorption-desorption efficiencies. Among desorption techniques, extractions based on ultrasounds or microwave radiations are attracting great attention. Another possibility is the combination of solid sorbents with a whole air sampling technique, for example the collection of an air sample into Tedlar bags or canisters, followed by the adsorption of the target analytes onto single sorbent tubes, or into a multilayer adsorbent bed. To enhance the sensitivity of the analytical method, SPME may also act as a sample pre-concentrator after sampling using conventional methods. Thus, sampling could be carried out by whole, passive, or active methods, and then, the analytes collected during sampling could be extracted by exposing a SPME fiber. SDPE has been recently applied for air monitoring, and it has become a fast alternative to conventional methods. The use of membranes for air analysis is also growing, and must be taken into account as another new possibility, e.g. MESI on-line systems, devices based on LDPE membranes, or MIMS determination systems.

REFERENCES [1] [2]

[3] [4]

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[5] [6] [7] [8] [9] [10] [11] [12]

[13]

[14] [15]

Weschler, C. J. Atmos. Environ. 2009, 43, 153-169. Molhave, L; Clausen, G.; Berglund, B.; De Ceaurriz, J.; Kettrup, A.; Lindvall, T.; Maroni, M.; Pickering, A. C.; Risse, U.; Rothweiler, H.; Seifert, B.; Younes, M. Indoor Air. 1997, 7, 225-240. Brown, S. K.; Sim, M. R.; Abramson, M. J.; Gray, C. N. Indoor Air. 1994, 4, 123134. World Health Organization (WHO), Environmental Health Criteria 128 (Hexachlorobenzene), International Programme on Chemical Safety, 1991, Geneva. Etzel, R. A. Int. J. Hyg. Environ. Health. 2007, 210, 611-616. Kotzias, D. Exp. Toxicol. Pathol. 2005, 57, 5-7. Camel, V.; Caude, M. J. Chromatogr. A 1995, 710, 3-19. Weschler, C. J.; Nazaroff, W. W. Atmos. Environ. 2008, 42, 9018-9040. Batterman, S. ; Jia, C.; Hatzivasilis, G. Environ. Res. 2007, 104, 224-240. Rudel, R. A.; Perovich, L. J. Atmos. Environ. 2009, 43, 170-181. Destaillats, H.; Maddalena, R. L.; Singer, B. C.; Hodgson, A. T.; McKone, T. E. Atmos. Environ. 2008, 42, 1371-1388. U. S. Environmental Protection Agency (US EPA), Air Toxic Methods, Technology Transfer Network, Ambient Monitoring Technology Information Center, http://www.epa.gov/ttn/amtic/ airtox.html (available February 2009). National Institute for Occupational Safety and Health (NIOSH), Manual of Analytical Methods (NMAM), http://www. cdc.gov/ niosh/nmam/ (available February 2009). American Society for Testing and Materials (ASTM), Standards, http://www.astm. org/Standard/ index.shtml (available February 2009). European Committee for Standardization (CEN), CEN/TC 264 “Air Quality”, Standards, http://www.cen.eu/CENORM/Sectors/TechnicalCommitteesWorkshops/CENTechn icalCommittees/Standards.asp?param=6245&title=CEN%2FTC+264 (available February 2009).

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60

Carmen Garcia-Jares, Ruth Barro, Jorge Regueiro et al.

[16] Tolnai, B.; Hlavay, J.; Möller, D.; Prümke, H. J.; Becker, H.; Dostler, M. Microchem. J. 2000, 67, 163-169. [17] Ouyang, G.; Pawliszyn, J. J. Chromatogr. A 2007, 1168, 226-235. [18] Dettmer, K.; Engewald, W. Chromatographia. 2003, 57, S339-S347. [19] Gokhale, S.; Kohajda, T.; Schlink, U. Sci. Total Environ. 2008, 407, 122-138. [20] Namiesnik, J.; Zabiegala, B.; Kot-Wasik, A.; Partyka, M.; Wasik, A. Anal. Bioanal. Chem. 2005, 381, 279-301. [21] Esteve-Turrillas, F. A.; Pastor, A.; de la Guardia, M. Anal. Chim. Acta. 2008, 626, 21-27. [22] Hazrati, S.; Harrad, S. Chemosphere. 2007, 67, 448-455. [23] Zhu, J.; Hou, Y.; Feng, Y.; Shoeib, M.; Harner, T. Environ. Sci. Technol. 2008, 42, 386-391. [24] Shoeib, M.; Harner, T.; Wilford, B. H.; Jones, K. C.; Zhu, J. Environ. Sci. Technol. 2005, 39, 6599-6606. [25] Mikes, I.; Cupr, P.; Trapp, S.; Klanova, J. Environ. Pollut. 2009, 157, 488-496. [26] Bohlin, P.; Jones, K. C.; Tovalin, H.; Strandberg, B. Atmos. Environ. 2008, 42, 7234-7241. [27] Chaemfa, C.; Barber, J. L.; Gocht, T.; Harner, T.; Holoubek, I.; Klanova, J.; Jones, K. C. Environ. Pollut. 2008, 156, 1290-1297. [28] Zhu, X.; Pfister, G.; Henkelmann, B.; Kotalik, J.; Fiedler, S.; Schramm, K. W. Chemosphere. 2007, 68, 1623-1629. [29] Zhu, X.; Pfister, G.; Henkelmann, B.; Kotalik, J.; Bernhöft, S.; Fiedler, S.; Schramm, K. W. Environ. Pollut. 2008, 156, 461-466. [30] Meredith, M. L.; Hites, R. A. Environ. Sci. Technol. 1987, 21, 709-712. [31] Hermanson, M. H.; Hites, R. A. Environ. Sci. Technol. 1990, 24, 666-671. [32] Zhao, Y.; Yang, L.; Wang, Q. Environ. Sci. Technol. 2008, 42, 6046-6050. [33] Orecchio, S.; Gianguzza, A.; Culotta, L. Environ. Res. 2008, 107, 371-379. [34] Gong, Y.; Eom, I. Y.; Lou, D. W.; Hein, D.; Pawliszyn, J. Anal. Chem. 2008, 80, 7275-7282. [35] Harper, M. J. Chromatogr. A 2000, 885, 129-151. [36] Dettmer, K.; Engewald, W. Anal. Bioanal. Chem. 2002, 373, 490-500. [37] Vainiotalo, S.; Väänänen, V.; Vaaranrinta, R. Environ. Res. 2008, 108, 280-288. [38] Greally, B. R.; Nickless, G.; Simmonds, P. G. J. Chromatogr. A 2006, 1133, 49-57. [39] Kongtip, P.; Tangprakorn, B.; Yoosook, W.; Chantanakul, S. J. Occup. Health. 2008, 50, 122-129. [40] Stanetzek, I.; Giese, U.; Schuster, R. H.; Wünsch, G. Am. Ind. Hyg. Assoc. J. 1996, 57, 128-133. [41] Trabue, S. L.; Scoggin, K. D.; Li, H.; Burns, R.; Xin, H. Environ. Sci. Technol. 2008, 42, 3745-3750. [42] Caro, J.; Gallego, M. Talanta. 2008, 76, 847-853. [43] Van Netten, C. Sci. Total Environ. 2009, 407, 1206-1210. [44] Barro, R.; Garcia-Jares, C.; Llompart, M.; Bollain, M.H.; Cela, R. J. Chromatogr. A 2006, 1111, 1-10. [45] Fernández-Martínez, G.; López-Mahía, P.; Muniategui-Lorenzo, S.; PradaRodríguez, D.; Fernández-Fernández, E. Water Air Soil Pollut. 2001, 129, 267-288. [46] Lee, C. W.; Dai, Y. T.; Chien, C. H.; Hsu, D. J. Environ. Res. 2006, 100, 139-149. [47] Singer, B. C.; Hodgson, A. T.; Hotchi, T.; Ming, K. Y.; Sextro, R. G.; Wood, E. E.; Brown, N. J. Atmos. Environ. 2007, 41, 3251-3265.

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61

[48] Schripp, T.; Nachtwey, B.; Toelke, J.; Salthammer, T.; Uhde, E.; Wensing, M.; Bahadir, M. Anal. Bioanal. Chem. 2007, 387, 1907-1919. [49] Parra, M. A.; Elustondo, D.; Bermejo, R.; Santamaría, J. M. Atmos. Environ. 2008, 42, 6647-6654. [50] Regueiro, J.; Garcia-Jares, C.; Llompart, M.; Lamas, J. P.; Cela, R. J. Chromatogr. A 2009, doi: 10.1016/j.chroma.2008.09.062 (in press). [51] Li, J.; Feng, Y. L.; Xie, C. J.; Huang, J.; Yu, J. Z.; Feng, J. L.; Sheng, G. Y.; Fu, J. M.: Wu, M. H. Anal. Chim. Acta 2009, 635, 84-93. [52] Barro, R.; Ares, S.; Garcia-Jares, C. Llompart, M.; Cela, R. Anal. Bioanal. Chem. 2005, 381, 255-260. [53] Barro, R.; Ares, S.; Garcia-Jares, C. Llompart, M.; Cela, R. J. Chromatogr. A 2005, 1072, 99-106. [54] Barro, R.; Garcia-Jares, C.; Llompart, M.; Cela, R. J. Chromatogr. Sci. 2006, 44, 430-437. [55] Demel, J.; Buchberger, W.; Malissa Jr., H. J. Chromatogr. A 2001, 931, 107-117. [56] Siebers, J.; Mattusch, P. Chemosphere. 1996, 33, 1597-1607. [57] Roinestad, K. S.; Louis, J. B.; Rosen, J. D. J. AOAC Int. 1993, 76, 1121-1126. [58] Haraguchi, K.; Kitamura, E.; Yamashita, T.; Kido, A. Atmos. Environ. 1994, 28, 1319-1325. [59] Berezkin, V.G.; Drugov, Y.S. Gas Chromatography in Air Pollution Analysis; Elsevier, Amsterdam, 1991. [60] Rothweiler, H.; Wager, P. A.; Schlatter, C. Atmos. Environ. 1991, 25 B, 231-235. [61] Ciccioli, P.; Cecinato, A.; Brancaleoni, E.; Frattoni, M. J. High Resolut. Chromatogr. 1992, 15, 75-84. [62] Helmig, D.; Greenberg, J. P. J. Chromatogr. A 1994, 677, 123-132. [63] Pellizzari, E. D. ; Demian, B. ; Krost, K. J. Anal. Chem. 1984, 56, 793-798. [64] Helmig, D. Atmos. Environ. 1997, 31, 3635-3651. [65] McClenny, W. A.; Oliver, K. D.; Jacumin Jr., H. H.; Hunter Daughtrey Jr., E. J. Environ. Monit. 2002, 4, 695-705. [66] Ashworth, D. J.; Zheng, W.; Yates, S. R. Atmos. Environ. 2008, 42, 5483-5488. [67] Bouvier, G.; Blanchard, O.; Momas, I.; Seta, N. Sci. Total Environ. 2006, 366, 7491. [68] Offenberg, J. H.; Naumova, Y. Y.; Turpin, B. J.; Eisenreich, S. J.; Morandi, M. T.; Stock, T.; Colome, S. D.; Winer, A. M.; Spektor, D. M.; Zhang, J.; Weisel, C. P. Environ. Sci. Technol. 2004, 38, 2760-2768. [69] Lu, C.; Kedan, G.; Fisker-Andersen, J.; Kissel, J. C.; Fenske, R. A. Environ. Res. 2004, 96, 283-289. [70] Elflein, L.; Berger-Preiss, E.; Levsen, K.; Wünsch, G. J. Chromatogr. A 2003, 985, 147-157. [71] Hoepner, A.; Garfinkel, R.; Hazi, Y.; Reyes, A.; Ramirez, J.; Cosme, Y.; Perera, P. Environ. Health. Perspect. 2003, 111, 749-756. [72] Cruz Márquez, M.; Arrebola, F. J.; Egea González, F. J.; Castro Cano, M. L.; Martínez Vidal, J. L. J. Chromatogr. A 2001, 939, 79-89. [73] Berger-Preiss, E.; Preiss, A.; Sielaff, K.; Raabe, M.; Ilgen, B.; Levsen, K. Indoor Air. 1997, 7, 248-261. [74] Wallace, J. C.; Brzuzy, L. P.; Simonich, S. L.; Visscher, S. M.; Hites, R. A. Environ. Sci. Technol. 1996, 30, 2715-2718.

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62

Carmen Garcia-Jares, Ruth Barro, Jorge Regueiro et al.

[75] Alegria, H. A.; Wong, F.; Jantunen, L. M.; Bidleman, T. F.; Salvador-Figueroa, M.; Gold-Bouchot, G.; Ceja-Moreno, V.; Waliszewski, S. M.; Infanzon, R. Atmos. Environ. 2008, 42, 8810-8818. [76] Mari, M.; Nadal, M.; Schuhmacher, M.; Domingo, J. L. Chemosphere. 2008, 73, 990-998. [77] Fromme, H.; Lahrz, T.; Piloty, M.; Gebhart, H.; Oddoy, A.; Rüden, H. Indoor Air. 2004, 14, 188-195. [78] Fromme, H.; Albrecht, M.; Drexler, H.; Gruber, L.; Schlummer, M.; Parlar, H.; Körner, W.; Wanner, A.; Heitmann, D.; Roscher, E.; Bolte, G. Int. J. Hyg. Environ. Health. 2007, 210, 345-349. [79] Allen, J. G.; McClean, M. D.; Stapleton, H. M.; Nelson, J. W.; Webster, T. F. Environ. Sci. Technol. 2007, 41, 4574-4579. [80] Chen, L.; Mai, B.; Xu, Z.; Peng, X.; Han, J.; Ran, Y.; Sheng, G.; Fu, J. Atmos. Environ. 2008, 42, 78-86. [81] Karlsson, M.; Julander, A.; Van Bavel, B.; Hardell, L. Environ. Int. 2007, 33, 6269. [82] Cahill, T. M.; Groskova, D.; Charles, M. J.; Sanborn, J. R.; Denison, M. S.; Baker, L. Environ. Sci. Technol. 2007, 41, 6370-6377. [83] Quintana, J.B.; Rodil, R.; Reemtsmad, T.; García-López, M. Rodríguez, I. TrAC Trends in Analytical Chemistry. 2008, 27, 904-915. [84] Shoeib, M.; Harner, T.; Ikonomou, M.; Kannan, K. Environ. Sci. Technol. 2004, 38, 1313-1320. [85] U. S. Environmental Protection Agency (U. S. EPA), Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, Office of Research and Development, National Risk Management Research Laboratory, Center for Environmental Research Information, 2nd Ed, Cincinnati, 1999. [86] Weng, M.; Zhu, L.; Yang, K.; Chen, S. J. Hazard. Mater. 2009 doi: 10.1016/j.jhazmat.2008.08.094 (in press). [87] Kazos, E. A.; Nanos, C. G.; Stalikas, C. D.; Konidari, C. N. Chemosphere. 2008, 72, 1413-1419. [88] U. S. Environmental Protection Agency (U. S. EPA), Compendium Method TO-17. Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling Onto Sorbent Tubes, Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, Office of Research and Development, National Risk Management Research Laboratory, Center for Environmental Research Information, 2nd Ed, Cincinnati, 1999. [89] Su, H. J.; Chao, C. J.; Chang, H. Y.; Wu, P. C. Atmos. Environ. 2007, 41, 12301236. [90] Kuntasal, O. O.; Karman, D.; Wang, D.; Tuncel, S. G.; Tuncel, G. J. Chromatogr. A 2005, 1099, 43-54. [91] Kim, Y. M.; Harrad, S.; Harrison, R. M. Environ. Sci. Technol. 2001, 35, 997-1004. [92] Davis, M. E.; Blicharz, A. P.; Hart, J. E.; Laden, F.; Garshick, E.; Smith, T. J. Environ. Sci. Technol. 2007, 41, 7152-7158. [93] Sapkota, A.; Williams, D. A.; Buckley, T. J. Environ. Sci. Technol. 2005, 39, 29362943. [94] Wu, C. H.; Lin, M. N.; Feng, C. T.; Yang, K. L.; Lo, Y. S.; Lo, J. G. J. Chromatogr. A 2003, 996, 225-231. [95] Baek, S. O.; Jenkins, R. A. Atmos. Environ. 2004, 38, 6583-6599.

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[96] Rudel, R. A.; Camann, D. E.; Spengler, J. D.; Korn, L. R.; Brody, J. G. Environ. Sci. Technol. 2003, 37, 4543-4553. [97] Li, A.; Schoonover, T. M.; Zou, Q.; Norlock, F.; Conroy, L. M.; Scheff, P.A.; Wadden, R. A. Atmos. Environ. 2005, 39, 3491-3499. [98] Norlock, F.; Jang, J. K.; Zou, Q.; Schoonover, T. M.; Li, A. J. Air Waste Manage Assoc. 2002, 52, 19-22. [99] Rudel, R. A.; Brody, J. G.; Spengler, J. D.; Vallarino, J.; Geno, P. W.; Yau, A. J. Air Waste Manage Assoc. 2001, 51, 499-512. [100] Iavicoli, I. ; Chiarotti, M.; Bergamaschi, A.; Marsili, R.; Carelli, G. J. Chromatogr. A 2007, 1150, 226-235. [101] Xie, Z.; Ebinghaus, R.; Temme, C.; Lohmann, R.; Caba, A.; Ruck, W. Environ. Sci. Technol. 2007, 41, 4555-4560. [102] Julander, A.; Westbergb, H.; Engwall, M. ; Van Bavel, B. Sci. Total Environ. 2005, 350, 151-160. [103] Stout II, D. M.; Mason, M. A. Atmos. Environ. 2003, 37, 5539-5549. [104] Ribes, A.; Carrera, G.; Gallego, E.; Roca, X.; Berenguer, M. J.; Guardino, X. J. Chromatogr. A 2007, 1140, 44-55. [105] Tsiropoulos, N. G.; Bakeas, E. B.; Raptis, V.; Batistatou, S. S. Anal. Chim. Acta. 2006, 573-574, 209-215. [106] Herrington, J. S.; Zhang, J. J. Atmos. Environ. 2008, 42, 2429-2436. [107] Bechara, J.; Borbon, A.; Jambert, C.; Perros, P. E. Anal. Bioanal. Chem. 2008, 392, 865-876. [108] J. Wang, L. Tuduri, M. Mercury, M. Millet, O. Briand, M. Montury, Environ. Pollut. 157 (2009) 365-370. [109] Nicolle, J. ; Desauziers, V.; Mocho, P. J. Chromatogr. A 2008, 1208, 10-15. [110] Scheppers-Wercinski, S. A.; Pawliszyn, J. Solid Phase Microextraction; Dekker, New York (N. Y), 1999, pp 1-26. [111] Ai, J. Anal. Chem. 1997, 69, 1230-1236. [112] Gorecki, T. In Applications of Solid Phase Microextraction; Pawliszyn, J. Ed.; RSC Chromatography Monographs. The Royal Society of Chemistry, Cambridge, 1999, pp 92-108. [113] Namiesnik, J.; Jastrzebska, A.; Zygmunt, B. J. Chromatogr. A 2003, 1016, 1-9. [114] Wei, L.; Ou, Q.; Li, J.; Liang, B. Chromatographia. 2004, 59, 601-606. [115] Luo, F.; Wu, Z.; Tao, P.; Cong, Y. Anal. Chim. Acta. 2009, 631, 62-68. [116] Saba, A. ; Cuzzola, A.; Raffaelli, A.; Pucci, S.; Salvadori, P. Rapid Commun. Mass Spectrom. 2001, 15, 2404-2408. [117] Saba, A. ; Raffaelli, A.; Pucci, S.; Salvadori, P. Rapid Commun. Mass Spectrom. 1999, 13, 1899-1902. [118] Elke, K.; Jermann, E.; Begerow, J.; Dunemann, L. J. Chromatogr. A 1998, 826, 317-324. [119] Chai, M.; Pawliszyn, J. Environ. Sci. Technol. 1995, 29, 693-701. [120] Lestremau, F.; Andersson, F. A. T.; Desauziers, V.; Fanlo, J. L. Anal. Chem. 2003, 75, 2626-2632. [121] Lee, J. H.; Hwang, S. M.; Lee, D. W.; Heo, G. S. Bull. Korean Chem. Soc. 2002, 23, 488-496. [122] Chai, M.; Tang, Y. Z. Int. J. Environ. Anal. Chem. 1998, 72, 77-82. [123] Kim, K. H.; Kim, D. Microchem. J. 2009, 91, 16-20. [124] Ras, M. R.; Marcé, R. M.; Borrull, F. Talanta. 2008, 77, 774778. [125] Lipinski, J. Fresenius J. Anal. Chem. 2001, 369, 57-62.

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[126] Van Durme, J.; Demeestere, K.; Dewulf, J.; Ronsse, F.; Braeckman, L.; Pieters, J.; Van Langenhove, H. J. Chromatogr. A 2007, 1175, 145-153. [127] Wang, L.; Lord, H.; Morehead, R.; Dorman, F.; Pawliszyn, J. J. Agric. Food Chem. 2002, 50, 6281-6286. [128] Yang, M. J.; Harms, S.; Luo, Y. Z.; Pawliszyn, J. Anal. Chem. 1994, 66, 13391346. [129] Wennrich, L.; Popp, P.; Hafner, C. J. Environ. Monit. 2002, 4, 371-376. [130] Paschke, H.; Popp, P. Chemosphere. 2005, 58, 855-863. [131] Cisper, M. E.; Hemberger, P. H. Rapid Commun. Mass Spectrom. 1997, 11, 14491453. [132] Hong, J.; Maguhn, J.; Freitag, D.; Kettrup, A. Fresenius J. Anal. Chem. 2001, 371, 961-965. [133] Wei, M. C.; Jen, J. F. J. Chromatogr. A 2003, 1012, 111-120. [134] Wei, M. C.; Chang, W. T.; Jen, J. F. Anal. Bioanal. Chem. 2007, 387, 999-1005. [135] Ingerowski, G.; Friedle, A.; Thumulla, J. Indoor Air. 2001, 11, 145-149. [136] Kallenborn, R.; Gatermann, R. In The Handbook of Environmental Chemistry; Rimkus, G. G. Ed.; Vol. 3, Part X, Springer, Berlin, 2004; pp 85-104. [137] Yoshida, T.; Matsunaga, I.; Oda, H. J. Chromatogr. A 2004, 1023, 255-269. [138] Arrebola, F.J.; Martinez Vidal, J.L.; Fernández-Gutiérrez, A. J. Chromatogr. Sci. 2001, 39, 177-182. [139] Esteve-Turrillas, F.A.; Pastor, A.; De la Guardia, M. Anal. Chim. Acta. 2006, 560, 118-127. [140] Bjorklund, J.; Isetun, S.; Nilsson, U. Rapid Commun. Mass Spectrom. 2004, 18, 3079-3083. [141] Sjödin, A.; Carlsson, H.; Thuresson, K.; Sjölin, S.; Bergman, A.; Östman, C. Environ. Sci. Technol. 2001, 35, 448-454. [142] Santos, F. J.; Galceran, M. T. TrAC Trends in Analytical Chemistry. 2002, 21, 672685 [143] Kierkegaard, A.; Bjorklund, J.; Friden, U. Environ. Sci. Technol. 2004, 38, 32473253. [144] Regueiro, J.; Llompart, M.; Garcia-Jares, C.; Cela, R. Anal. Bioanal. Chem. 2007, 388, 1095-1107. [145] Yang, X.; Jiang, X.; Yu, G.; Yao, F.; Bian, Y.; Wang, F. Environ. Pollut. 2007, 148, 555-561. [146] Castro, J.; Pérez, R.A.; Miguel, E.; Sánchez-Brunete, C.; Tadeo, J.L. J. Chromatogr. A 2002, 947, 119-127. [147] Cessna, A. J.; Kerr, L. A. J. Chromatogr. 1993, 642, 417-423. [148] Polo, M.; Garcia-Jares, C. M.; Llompart, M.; Cela, R. Anal. Bioanal. Chem. 2007, 388, 1789-1799. [149] Pradhan, M.; Aziz, M. S. I.; Grilli, R.; Orr-Ewing, A. J. Environ. Sci. Technol. 2008, 42, 7354-7359. [150] Moliner-Martínez, Y.; Campíns-Falcó, P.; Herráez-Hernández, R. J. Chromatogr. A 2004, 1059, 17-24. [151] U. S. Environmental Protection Agency (U. S. EPA), Compendium Method TO11A. Determination of formaldehyde in Ambient Air Using Adsorbent Cartridge Followed by High Performance Liquid Chromatography (HPLC). Active Sampling Methodology, Compendium of Methods for the Determination of Toxic Organic Compounds in Ambient Air, Office of Research and Development, National Risk

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The Use of Sorbents for the Analysis of Emerging Pollutants in Indoor Air

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Management Research Laboratory, Center for Environmental Research Information, 2nd Ed, Cincinnati, 1999. [152] E. R. Kennedy, T. J. Fischbach, R. Song, P. M. Eller, S. A. Shulman, Guidelines for Air Sampling and Analytical Method Development and Evaluation, National Institute for Occupational Safety and Health (NIOSH), U. S. Department of Health and Human Services, Public Health Service, Center for Disease Control and Prevention, Cincinnati, 1995. [153] McClenny, W. A.; Oliver, K. D.; Jacumin Jr., H. H.; Hunter Daughtrey Jr., E.; Whitaker, D. A. J. Environ. Monit. 2005, 7, 248-256. [154] Toda, H.; Sako, K.; Yagome, Y.; Nakamura, T. Anal. Chim. Acta. 2004, 519, 213218. [155] Kallenborn, R.; Gatermann, R.; Planting, S.; Rimkus, G.G.; Lund, M.; Schlabach, M.; Burkow, I.C. J. Chromatogr. A. 1999, 846, 295-306. [156] Figge, K.; Rabel, W.; Wiek, A. Fresenius Z. Anal. Chem. 1987, 327, 261-278. [157] Baya, M. P.; Siskos, P. A. Analyst. 1996, 121, 303-307. [158] Peters, R. J. B.; Bakkeren, H. A. Analyst. 1994, 119, 71-74. [159] Harper, M. Ann. Occup. Hyg. 1993, 37, 65-88. [160] Sydor, R.; Pietrzyk, D. J. Anal. Chem. 1978, 50, 1842-1847. [161] Pierini, E.; Sampaolo, L.; Mastrogiacomo, A. R. J. Chromatogr. A 1999, 855, 593600. [162] Prado, C.; Alcaraz, M. J.; Fuentes, A.; Garrido, J.; Periago, J. F. J. Chromatogr. A 2006, 1129, 82-87. [163] Liu, J. M.; Lin, L.; Fan, H. L.; Ning, Z. W.; Zhao, P. Chin. J. Anal. Chem. 2007, 35, 830-838. [164] Strömvall, A. M.; Petersson, G. J. Chromatogr. A 1992, 589, 385-401. [165] Class, T. J.; Kintrup, J. Fresenius J. Anal. Chem. 1991, 340, 446-453. [166] Class, T. J. Fresenius J. Anal. Chem. 1992, 342, 805-808. [167] Fernandez-Alvarez, M.; Sanchez-Prado, L.; Lores, M.; Llompart, M.; Garcıa-Jares, C.; Cela, R. J. Chromatogr. A, 2007, 1152, 156-167. [168] Zanella, R.; Schilling, M.; Klockow, D. J. Environ. Monit., 1999, 1, 441–443. [169] Pellizzari, E. D.; Krost, K. J. Anal. Chem. 1984, 56, 1813-1819. [170] International Union of Pure and Applied Chemistry (IUPAC); The Gold Book. Compendium of Chemical Terminology, 2nd Ed., Blackwell Scientific Publications, Oxford, 1997, http://goldbook.iupac.org/ (available February 2009). [171] Lodge jr, J. P. Methods of air sampling and analysis. Intersociety Committee, CRC Press, Taylor and Francis, London, 1988. [172] Desauziers, V. Trends Anal. Chem. 2004, 23, 252-260. [173] Barro, R.; Ares, S.; Garcia-Jares, C.; Llompart, M.; Cela, R. J. Chromatogr. A 2004, 1045, 189-196. [174] Otaka, T.; Yoshinaga, J.; Yanagisawa, Y. Environ. Sci. Technol. 2001, 35, 30993102. [175] Tumbiolo, S.; Gal, J. F.; Maria, P. C.; Zerbinati, O. Anal. Bioanal. Chem. 2004, 380, 824-830. [176] Chen, Y.; Koziel, J. A.; Pawliszyn, J. Anal. Chem. 2003, 75, 6485-6493. [177] Tuduri, L.; Desauziers, V.; Fanlo, J. L. Microcol. Sep. 2000, 12, 550-557. [178] Bartelt, R. J.; Zilkowski, B. W. Anal. Chem. 1999, 71, 92-101. [179] Bartelt, R. J.; Zilkowski, B. W. Anal. Chem. 2000, 72, 3949-3955. [180] Bartelt, R. J. Anal. Chem. 1997, 69, 364-372. [181] Gorlo, D.; Wolska, L.; Zygmunt, B.; Namiesnik, J. Talanta. 1997, 44, 1543-1550.

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[182] Mangani, F.; Cenciarini, R. Chromatographia. 1995, 41, 678-684. [183] Ferrari, F.; Sanusi, A.; Millet, M.; Montury, M. Anal. Bioanal. Chem. 2004, 379, 476-483. [184] Barro, R.; Regueiro, J.; LLompart, M.; Garcia-Jares, C. J. Chromatogr. A 2009, 1216, 540-566. [185] Garcia-Jares, C.; Regueiro, J.; Barro, R.; Dagnac, T.; LLompart, M. J. Chromatogr. A 2009, 1216, 567-597. [186] Mandalakis, M.; Atsarou, V. ; Stephanou, E. G. Environ. Pollut. 2008, 155, 375382. [187] Covaci, A. ; Voorspoels, S. ; De Boer, J. Environ. Inter. 2003, 29, 735-756. [188] De Wit, C. Chemosphere, 2002, 46, 583-624. [189] Sjödin, A.; Päpke, O.; McGahee, E.; Jones, R.; Focant, J.F.; Pless-Mulloli, T.; Toms, L.M.; Wang, R.; Zhang, Y.; Needham, L.; Herrmann, T.; Patterson, D. Organohal. Comp. 2004, 66, 3770-3775. [190] Harrad, S.; Diamond, M. Atmos. Environ. 2006, 40, 1187-1188. [191] Jones-Otazo, H.A.; Clarke, J.P.; Diamond, M.L.; Archbold, J.A.; Ferguson, G.; Harner, T.; Richardson, G.M.; Ryan, J.J.; Wilford, B. Environ. Sci. Technol. 2005, 39, 5121-5130. [192] Currado, G.M.; Harrad, S. Environ. Sci. Technol. 2000, 34, 78-82. [193] Päpke, O.; Fürst, P.; Herrmann, T. Talanta. 2004, 63, 1203-1211. [194] Covaci, A.; Voorspoels, S.; Ramos, L.; Neels, H.; Blust, R. J. Chromatogr. A 2007, 1153, 145-171. [195] Thomsen, C.; Leknes, H.; Lundanes, E.; Becher, G. J. Chromatogr. A 2001, 923, 299-304. [196] Herrmann, T.; Schilling, B.; Päpke, O. Organohalogen Compd. 2003, 63, 361-364. [197] De Boer, J.; Wells, D.E. Trends Anal. Chem. 2006, 25, 364-372. [198] De Boer, J.; Cofino, W.P. Chemosphere, 2002, 46, 625-633. [199] Bjorklund, J.; Tollback, P.; Ostman, C. J. Sep. Sci. 2003, 26, 1104-1110. [200] Pettersson-Julander, A.; Van Bavel, B.; Engwall, M.; Westberg, H. J. Environ. Monit. 2004, 6, 874-880. [201] Harrad, S.; Wijesekera, R.; Hunter, S.; Halliwell, C.; Baker, R. Environ. Sci. Technol. 2004, 38, 2345-2350. [202] Tollbäck, J.; Creszenci, C.; Dyremark, E. J. Chromatogr. A. 2006, 1104, 106-112. [203] Wilford, B.H.; Harner, T.; Zhu, J.; Shoeib, M.; Jones, K.C. Environ. Sci. Technol. 2004, 38, 5312-5318. [204] Harrad, S.; Hazrati, S.; Ibarra, C. Environ. Sci. Technol. 2006, 40, 4633-4638. [205] Gevao, B.; Al-Bahloul, M.; Al-Ghadban, A.N.; Ali, L.; Al-Omair, A.; Helaleh, M.; Al-Matrouk, K.; Zafar, J. Atmos. Environ. 2006, 40, 1419-1426. [206] Butt, C.M.; Diamond, M.L.; Truong, J.; Ikonomou, M.G.; Ter Schure, A.F.H. Environ. Sci. Technol. 2004, 38, 724-731. [207] Saito, I.; Onuki, A.; Seto, H. Indoor Air. 2007, 17, 28-36. [208] Björklund, J. Gas chromatography and mass spectrometry of polybrominated diphenyl ethers. Ph. D. Thesis, Department of Analytical Chemistry, Stockholm University, Stockholm, Sweden, 2003. [209] Covaci, A. ; De Boer, J. ; Ryan, J.J. ; Voorspoels, S.; Schepens, P. Anal. Chem. 2002, 74, 790-798. [210] Björklund, J.; Tollbäck, P.; Hiärne, C.; Dyremark, E.; Östman, C. J. Chromatogr. A 2004, 1041, 201-210. [211] Carlsson, H. ; Nilsson, U. ; Östman, C. Environ. Sci. Technol. 2000, 34, 3885-3889.

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[212] Hartmann, P.C.; Burgi, D.; Giger, W. Chemosphere. 2004, 57, 781-787. [213] WHO, Environmental Health Criteria 112 (Tri-n-butyl phosphate) International Programme on Chemical Safety, WHO, Geneva, 1991. [214] WHO, Environmental Health Criteria 209 (Flame retardants: tris(chloropropyl) phosphate and tris(2-chloroethyl) phosphate). International Programme on Chemical Safety, WHO, Geneva, 1998. [215] Carlsson, H.; Nilsson, U. ; Becker, G. ; Östman, C. Environ. Sci. Technol. 1997, 31, 2931-2936. [216] Marklund, A.; Andersson, B.; Haglund, P. J. Environ. Monit. 2005, 7, 814-819. [217] Staaf, T.; Östman, C. J. Environ. Monit. 2005, 7, 344-348. [218] Isetun, S.; Nilsson, U.; Colmsjö, A.; Johansson, R. Anal. Bioanal. Chem. 2004, 378, 1847-1853. [219] Isetun, S.; Nilsson, U.; Colmsjö, A. Anal. Bioanal. Chem. 2004, 380, 319-324. [220] Isetun, S.; Nilsson, U. Analyst. 2005, 130, 94-98. [221] Sanchez, C. ; Ericsson, M.; Carlsson, H. ; Colmsjö, A. J. Chromatogr. A 2003, 993, 103-110. [222] Frankhauser, A.; Grob, K. Anal. Chim. Acta. 2007, 582, 353-360. [223] Gomez-Hens, M.; Aguilar-Ceballos, M.P. Trends Anal. Chem. 2003, 22, 847-857. [224] Tienpont,B.; David, D.; Sandra, P.; Vanwalleghem, F. J. Microcol. Sep. 2000, 12, 194-203 [225] Llompart, M.; García-Jares, C.; Landín, P. In Chromatographic Analysis of the Environment; Nollet, L.M.L. Ed.; 3rd Ed, CRC Press, Boca Raton, FL, 2007, pp 1103-1154. [226] Kang, Y.; Den, W.; Bai, H.; Ko, F.H. J. Chromatogr. A 2005, 1070, 137-145. [227] Kawata, K.; Minagawa, M.; Fujieda, Y. J. Chromatogr. 1993, 653, 369-373. [228] Xie, Z.; Selzer, J.; Ebinghaus, R.; Caba, A.; Ruck, W. Anal. Chim. Acta. 2006, 546, 198-207. [229] Peijnenburg, W.J.G.M., Struijs, J. Ecotoxicol. Environ. Safety. 2006, 63, 204-215. [230] Wang, X.K. Chin. Chem. Lett. 2002, 13, 557-560. [231] Thuren, A.; Larsson, P. Environ. Sci. Technol. 1990, 24, 554-559. [232] Helmig, D. J. Chromatogr. A 1999, 843, 129-146. [233] Sheldon, L.; Clayton, A.; Keever, J.; Perritt, R.; Whitaker, D. PTEAM: Monitoring of Phthalates and PAHs in Indoor and Outdoor Air Samples in Riverside, California: Final Report, Volume II, California Air Resources Board, Research Division, Contract No. A933-144, Sacramento, CA, December 1992. [234] Cooke, G.M. Toxicol. Lett. 2002, 126, 121-130. [235] Kallenborn, R.; Gatermann, R.; Rimkus, G.G. J. Environ. Monit. 1999, 1, 70N-74N. [236] US EPA, High production volume (HPV) Chemical List database June 8, 2003 (http:/www.epa.gov/chemrtk/opptsrch.htm). [237] Peck, A.M.; Hornbuckle, K.C. Environ. Sci. Technol. 2004, 38, 367-372. [238] Bridges, B. Flavour Fragr. J. 2002, 17, 361-371. [239] Chen, D.; Zeng, X.; Sheng, Y.; Bi, X.; Gui, H.; Sheng, G.; Fu, J. Chemosphere. 2007, 66, 252-258. [240] Buerge, I.J. ; Buser, H.R. ; Muller, M.D. ; Poiger, T. Environ. Sci. Technol. 2003, 37, 5636-5644. [241] Dorr, G.; Noller, B.; Woods, N.; Hewitt, A.; Hanan, J.; Adkins, S.; Ricci, P.F. Rational Environmental Management of Agrochemicals; ACS Symposium Series, vol. 966, 2007, pp 53-65.

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[242] Ritter, L.; Goushleff, N. C. I.; Arbuckle, T.; Cole, D.; Donald; D; Raizenne, M. J. Toxicol. Env. Health, Part B: Critical Reviews 2006, 9, 441-456. [243] Tariq, M.I.; Afzal, S. ; Hussain, I. Environ. Int. 2004, 30, 471-479. [244] Fernandez-Alvarez, M.; Llompart, M.; Lamas, J.P.; Lores, M.; Garcia-Jares, C.; Cela, R.; Dagnac, T. J. Chromatogr. A 2008, 1188, 154-163. [245] Xue, N.; Xu, X.; Jin, Z. Chemosphere. 2005, 61, 1594-1606. [246] Harner, T.; Shoeib, M.; Kozma, M.; Gobas, F.A.; Li, S.M. Environ. Sci. Technol. 2005, 39, 724-731. [247] Jeannot, R.; Dagnac, T. In: Chromatographic Analysis of the Environment; L.M.L. Nollet Ed.; Chromatographic Science Series, vol. 93, Taylor & Francis, Boca Raton, Florida, USA, 2006, pp 841-888. [248] Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological Profile for pyrethrins and pyrethroids, U.S. Department of Health and Human Services, Public Health Service, 2003. [249] World Health Organization (WHO). Environmental Health Criteria Nos. 64, 82, 87, 94, 96-99 and 142, The International Programme on Chemical Safety, United Nations Environment Programme, International Labour Organisation and World Health Organization, Geneva, pp1986-1992. [250] Clark, J. R.; Goodman, L. R.; Borthwick, P. W.; Jr. Patrick, J. M.; Cripe, G. M. ; Moody, P. M. Environ. Toxicol. Chem. 1989, 8, 393-401. [251] Cotas, J. R.; Symonik, D. M.; Bradbury, S. P.; Dyer, S. D.; Timson, L. K.; Atchison, G. J. Environ. Toxicol. Chem. 1989, 8, 671-679. [252] Seiber, J.N.; Glotfelty, D.E; Lucas, A.D.; McChesney, M.M.; Sagebiel, J.C.; Wehner, T.A. Arch. Environ. Contam. Toxicol. 1990, 19, 583-592. [253] Ramesh, A.; Vijayalakshmi, A. J. Environ. Monit. 2001, 191-193. [254] Whyatt, R.M. ; Barr, D.B. ; Carmann, D.E. ; Kinney, P.L. ; Barr, J.R. ; Andrews, H.F. ; Hoepner, L.A. ; Garfinkel, R. ; Hazi, Y. ; Reyes, A. ; Ramirez, J. ; Cosme, Y. ; Perera, P. Environ. Health. Perspect. 2003, 111, 749-756. [255] Dai, H. ; Asakawa, F. ; Suna, S. ; Hirao, T. ; Karita, T. ; Fukunaga, I. ; Jitsunari, F. Environ. Health Prev. Med. 2003, 8, 139-145. [256] Wilson, N.K. ; Chuang, J.C. ; Morgan, M.K. ; Lordo, R.A. ; Sheldon, L.S. Environ. Res. 2007, 103, 9-20. [257] Vincent, G. ; Kopferschmitt-Kubler, M.C. ; Mirabel, P.; Pauli, G.; Millet, M. Environ. Monit. Assess. 2007, 133, 25-30. [258] Berger-Preiss, E. ; Elflein, L. Methods Biotechnol. 2006, 19, 179-190. [259] Kennedy, E.R. ; Lin, J.J. ; Reynolds, J.M. ; Perkins, J.B. Am. Ind. Hyg. Assoc. J. 1997, 58, 720-725. [260] Yao, Y. ; Tuduri, L. ; Harner, T. ; Blanchard, P. ; Waite, D. ; Poissant, L. ; Murphy, C. ; Belzer, W. ; Aulagnier, F. ; Li, Y.F. ; Sverko, E. Atmos. Environ. 2006, 40, 4339-4351. [261] Schieweck, A. ; Delius, W. ; Siwinski, N. ; Vogtenrath, W. ; Genning, C. ; Salthammer, T. Atmos. Environ. 2007, 41, 3266-3275. [262] Watanabe, T. Bull. Environ. Contam. Toxicol. 1998, 60, 669-676. [263] Roach, C. E.; Anderson, L. G.; Foreman, W. T. In Proceedings of the AWMA Annual Meeting, 90th, 1997, Paper No. 97-RA122.03. [264] Dobson, R.; Scheyer, A.; Rizet, A.L.; Mirabel, P.; Millet, M. Anal. Bioanal. Chem. 2006, 386, 1781-1789. [265] Egea-Gonzalez, F.J.; Mena-Granero, A.; Glass, C.R.; Garrido-Frenich, A.; Martinez Vidal, J.L. Rapid Commun. Mass Spectrom. 2004, 18, 537-543.

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[266] Bohlin, P.; Jones, K.C. ; Strandberg, B. J. Environ. Monit. 2007, 9, 501-509. [267] Esteve-Turrillas, F.A.; Yusá, V.; Pastor, A.; De la Guardia, M. Talanta. 2008, 74, 443-457. [268] Partyka, M.; Zabiegala, B.; Namiesnik, J. Crit. Rev. Anal. Chem. 2007, 37, 51-78. [269] Paschke, A.; Vrana, B.; Popp, P.; Schürmann, G. Environ. Pollut. 2006, 144, 414422. [270] Oepkemeier, S.; Schreiber, S.; Breuer, D.; Key, G.; Kleiböhmer, W. Anal. Chim. Acta. 1999, 393, 103-108. [271] Briand, O.; Millet, M.; Bertrand, F. ; Clément, M.; Seux, R. Anal. Bioanal. Chem. 2002, 374, 848-857. [272] Baroja, O. ; Unceta, N. ; Sampedro, M.C. ; Goicolea, M.A. ; Barrio, R.J. J. Chromatogr. A 2004, 1059, 165-170. [273] Mukerjee, S.; Ellenson, W.D.; Lewis, R.G.; Stevens, R.K.; Somerville, M.C.; Shadwick, D.S.; Willis, R.D. Environ. Int. 1997, 23, 657-673. [274] Baraud, L.; Tessier, D.; Aaron, J.J.; Quisefit, J.P.; Pinart, J. Anal. Bioanal. Chem. 2003, 377, 1148-1152. [275] Sanusi, A.; Millet, M.; Mirabel, P.; Wortham, H. Sci. Total Environ. 2000, 263, 263-277. [276] Giesy, J.P.; Kannan, K. Environ. Sci. Technol. 2002, 36, 146A-152A. [277] Jahnke, A.; Huber, S.; Temme, C.; Kylin, H.; Berger, U. J. Chromatogr. A 2007, 1164, 1-9. [278] Shoeib, M.; Harner, T.; Lee, S.C.; Lane, D.; Zhu, J. Anal. Chem. 2008, 80, 675. [279] IARC, IARC Monographs on the Evaluation of the carcinogenic risks to humans. Tobacco smoke and involuntary smoking, vol. 83, Lyon, 2004, pp 1012-1070. [280] Irigaray, P. ; Newby, J. A.; Clapp, R.; Hardell, L.; Howard, V.; Montagnier, L.; Epstein, S.; Belpomme, D. Biomed. Pharmacotherapy. 2007, 61, 640-658. [281] Higgins, C. E.; Thompson, C. V.; Jigner, R. H.; Jenkins, R. A.; Guerin, M. R. Determination of vapor phase hydrocarbons and nitrogen-containing constituents in environmental tobacco smoke. Internal Progress Report. Analytical Chemistry Division, Oak Ridge National Laboratory, Oak Ridge, 1990.

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In: Sorbents: Properties, Materials and Applications ISBN: 978-1-60741-851-1 Editor: Thomas P. Willis © 2009 Nova Science Publishers, Inc.

Chapter 2

USE OF SORBENTS IN AIR QUALITY CONTROL SYSTEMS E.Gallego*1, F.J. Roca1, J.F. Perales1 and X.Guardino†2 1

Laboratori del Centre de Medi Ambient. Universitat Politècnica de Catalunya (LCMA-UPC). Avda. Diagonal, 647. E-08028 Barcelona 2 Centro Nacional de Condiciones de Trabajo. INSHT. Dulcet 2-10. E 08034 Barcelona

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INTRODUCTION Environmental analysis means in many cases the analysis of pollutants in trace and ultra-trace quantities (Ras 2008). Hence, sensitive, selective, fast and reliable methodologies are needed to detect pollutants in ambient air, and concentration techniques have often to be applied prior to the analysis (Camel & Caude 1995, Begerow et al. 1996, Dewulf & Van Langenhove 1999, Uhde 1999, Harper 2000, Dettmer & Engewald 2002, Desauziers 2004, Michulec et al. 2005, Demeestere et al. 2007, Ulman & Chilmonczyk 2007). When an analytical methodology is developed to study air pollution several terms have to be taken into account such as the pollutant state (gaseous or particulate matter), compound type or family, compound concentration, period of measurement (short- or long-term, e.g. instantaneous, 24-hour, monthly or yearly concentrations), the measurement site (in situ or in the laboratory) and the principal aim of the study (qualitative, estimation of a emission, punctual or long-term concentrations, main, minor or trace components study) (Michuelec et al. 2005). Thus, the application of solid sorbents to pollution and air quality control is an essential parameter to determine exactly the type and kind of compounds that are present in the atmosphere (Dettmer & Engewald 2003). The sampling enriches the analytes in the adsorbent, removing selectively form the matrix the target compounds by adsorption or reaction with the sorbent surface (Harper 2000). Target compounds are further analyzed using generally chromatographic techniques (Camel & Caude, 1995), as the single component analysis of the constituents of the atmosphere is preferred to the sum of pollutants in the case of volatile organic compounds (VOC) (Dettmer & Engewald 2002, Ras 2008). The interest * †

e-mail: [email protected] e-mail: [email protected]

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in determining atmospheric pollutants has increased over the last several decades, as several act as precursors of photochemical smog formation, others represent a threat to human health (irritation of mucous membranes, psychological stress and long-term toxic reactions) (ECA-IAQ 1997, Desauziers 2004, Hutter et al. 2006, Liang and Liao 2007, Ulman & Chimonczyk 2007) and comfort, as they are related to bad odors (Wolkolff and Nielsen 2001, Zuraimi et al. 2006). In the same way, some of them contribute to global change, by depleting the stratospheric ozone layer and by the radiative forcing of the earth (Dewulf & Van Langenhove 1999, Michulec et al. 2005). The complexity of pollutants occurrence in the atmosphere, in terms of composition (polar to non-polar compounds, very volatile and semi- volatile compounds) and abundance (below detection limit (ppbv to pptv) to over detectors saturation limit), points out the necessity to develop versatile analytical methods (Desauziers 2004, Ribes et al. 2007). Sorbent based methods have been successfully used in the collection of air samples to determine air quality (Uchiyama et al. 1999, Dettmer & Engewald 2003, Donaldson et al. 2003, Kuntasal et al. 2005, Ribes et al. 2007, Ras 2008). However, several precautions should be taken to avoid negative effects derived from factors such as flow rate sampling, sample concentration, ambient humidity and temperature, breakthrough and analyte stability (Wu et al. 2004). Sorbents have variable selectivity towards different types of compounds; hence, according to the characteristics of the sampled components, different combinations of sorbents are utilized in single-bed or multi-bed arrangements (combination of various sorbents) to achieve the determination of a wide range of target trace compounds present in air samples (Camel & Caude 1995, Matisová & Škrabáková 1995, Dewulf & Van Langenhove 1999, Dettmer et al. 2000, Donaldson et al. 2003, Demeestere et al. 2007, Barro et al. 2009). However, collection efficiency will vary depending on several variables, such as nature and strength of the adsorptive forces, ambient air concentrations and sampling environmental conditions (Harper 1993). Different air sampling strategies have been described in the literature (Godish 1997, D¹browski 2001, Kim et al. 2004), however, sorbent based methods permit a high sampling versatility (compatible with both apolar and semi-volatile compounds, active and passive sampling), high concentration power, easy portability, low cost and easy storage of sorbent tubes (Volden et al. 2005, Prado et al. 2006, Ribes et al. 2007).

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1. TYPES OF SORBENTS During the past two decades, new classes of solid sorbents have been developed, including activated carbon fibers and carbon molecular sieves, fullereness and heterofullereness, microporus glasses and nanoporus materials, being both carbonaceous and inorganic (Hrouzková et al. 1998). A classification in three categories of sorbents could be done: inorganic materials (e.g. silica gel), carbon based adsorbents (e.g. graphitized carbon blacks, carbon molecular sieves, activated charcoal) and organic polymers (e.g. Tenax, XAD resins) (Table 1) (Uhde 1999, Dettmer & Engewald 2002). Carbonaceous sorbents, with a matrix mainly consisting in carbon, have high chemical inertness and thermal stability, and their use is not limited by pH, such as other organic polymer sorbents. In addition to that, they are also prepared to support higher temperatures (Matisová & Škrabáková 1995, Sunesson 2007).

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Table 1. Characteristics of the most commonly used adsorbents in preconcentration of pollutants in ambient air samplings Sorbent

Characteristics

Graphitized Carbon Blacks (GCBs) Almost nonCarbotrap B porous carbon Almost nonCarbopack B porous carbon Carbotrap C

Non-porous carbon

T limit

Surface water affinity

Mesh size

Pore diameter (Å)

350ºC

Hydrophobic

20/40

225ºC

Hydrophobic

Very weak

350ºC

Hydrophobic

Strength

Mediumweak Mediumweak

Pore volume (ml g-1) Microporous

Total

Surface area (m2 g-1)

Analytes

80-300

0.0

0.58

95-100

C2-C5 C5-C12

60/80

>40

-

0.14

100

C5-C12

20/40

-

0.0

0.02

9-12

C2-C5 C5-C10 C12-C20

-

-

-

10-12

C12-C20

100

0.0

0.62-0.63

240-260

C3-C5

100

-

0.62

240-250

C3-C5

Very weak

500ºC

Hydrophobic

Carbotrap X

Non-porous carbon Porous carbon

Medium

225ºC

Hydrophobic

Carbopack X

Porous carbon

Medium

500ºC

Hydrophobic

350ºC

Hydrophobic

20/40

-

0.003

0.12

24-34

C12-C20

500ºC

Hydrophobic

40/6060/80

-

-

-

24-25

C12-C20

500ºC

Hydrophobic

60/80

255

0.0

1.73

220

C3-C9

20/45

-

0.20

0.59

495-510

C2-C5

20/45

-

0.19

0.50

400-460

C2-C5

20/45

5-8

0.07-0.20

0.39-0.44

387-485

C2-C5

Carbopack C

Almost nonporous Almost nonCarbopack Y porous Non-porous Carbopack Z carbon Carbon Molecular Sieves (CMSs) Carbon skeletal Carboxen 563 framework Carbon skeletal Carboxen 564 framework Carbon skeletal Carboxen 569 framework Carbotrap Y

Weakmedium Weakmedium Weakmedium Strong

>400ºC

Strong

>400ºC

Strong

>400ºC

Highly hydrophobic Highly hydrophobic Highly hydrophobic

60/8080/100 20/40 40/6060/80

Carboxen 1000

Carbon skeletal framework

Very strong

>400ºC

Highly hydrophobic

40/6060/8080/100

10-12

0.42-0.44

0.85

915-1200

C2-C3

Carboxen 1003

Carbon skeletal framework

Strong

>400ºC

Highly hydrophobic

40/60

5-8

0.38-0.48

0.80-0.92

1000-1045

C2-C5

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Table 1. Continued Sorbent Carboxen 1016 Carbosieve S-II Carbosieve S-III Carbosieve G

Characteristics Carbon skeletal framework Carbon skeletal framework Carbon skeletal framework Carbon skeletal framework

Strength

T limit

Surface water affinity

Mesh size

Pore diameter (Å)

Strong

>400ºC

Highly hydrophobic

60/80

Strong

>400ºC

Hydrophobic

Very strong

>400ºC

Strong

Pore volume (ml g-1) Microporous

Total

Surface area (m2 g-1)

Analytes

-

0.0

0.34

75

C2-C5

60/80

-

-

-

1000

C1-C2

Hydrophobic

60/80

4-16

0.35-0.38

0.39

820-1000

C2-C5 C5-C10

225

Hydrophobic

45/6060/80

6-15

0.51

0.49

910-1160

C1-C3

Polymeric Adsorbents XAD-2

Styrenedivinylbenzene

Medium

200

Very Hydorphobic

20/50

90

-

0.65

300

>C12

Tenax TA

2,6-diphenylene oxide polymer

Weak

350

Very Hydrophobic

60/8080/100

-

0.002

0.05

20-35

C5-C10 C6-C14 C7-C26

Weak

350-400

Hydrophobic

20/3535/60

-

0.002

0.05

21-35

C5-C10

Medium

225-250

Hydorphobic

60/8080/100

-

0.09

1.33

700-800

C2-C3 Small molecules

Medium

190

Hydrophobic Polar

50/80 80/100

-

-

-

250-300

C2-C8 Ammonia Acetylene

Strong

180

Hydrophilic

35/60

-

-

-

750

C2-C5

Very strong

220-400

Hydrophilic

20/40

-

0.50

0.54

500-1500

C2-C5

70% Tenax TA+ 30% graphite carbon StyreneChromosorb 106 divinylbenzene polymer Divinylbenzeneethyleneglycol Porapak N dimethylacrylate polymer General purpose adsorbents Effective for Silica gel polar compounds Activated Highly porous charcoal material Tenax GR

Source: Camel & Caude 1995, Knobloch & Engewald 1995, Matisová & Škrabáková 1995, Hrouzková et al 1998, Gawlowski et al. 1999, Dettmer & Engewald 2002, Dettmer & Engewald 2003, Michulec et al. 2005, Pennequin-Cardinal et al. 2005, Ras 2008 and www.sigma-aldrich.com/supelco.

Use of Sorbents in Air Quality Control Systems

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The development of adsorption techniques is parallel to the development of technology of manufacture of adsorbents. These sorbents can take a broad range of chemical forms and different geometrical surface structures (Dąbrowski 2001), varying in adsorptive properties and kinetics (Sircar 2008). In addition to that, the physico-chemical properties of these recently developed materials are superior compared to the sorbent materials previously used for air-sampling of airborne compounds. Pore size and shape, surface area, total volume of porosity, particle size functionality of surface and chemical inertness are physico-chemical characteristics that differ depending on the type of adsorbent, and will be determined by the type of material used, the procedure chosen for preparation of the adsorbent and the conditions under which it is used (Sircar 2008). The adsorbent surface chemistry will eventually be determined by the final heat treatment and the subsequent chemical treatments applied to the adsorbent. Therefore, the adsorption of pollutants in sampling devices would be determined in great part by those physico-chemical characteristics (Hrouzková et al. 1998). On the other hand, the kinetic and thermodynamic properties of sorbents, such as breakthrough and the interaction mechanisms occurring at the adsorbate/sorbent interface, will be strongly influenced by sampling (Matisová & Škrabáková 1995, Matisová et al. 1999).

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1.1. Graphitized Carbon Blacks Graphitized carbon blacks (GCBs) are generally non-porous adsorbents; they have a homogeneous surface formed of loosely aggregated irregular particles of colloidal dimensions, and adsorb compounds on that external surface (Kovaleva & Shcerbakova 1990, Hrouzková et al. 1998, Dettmer & Engewald 2002, Tascón 2008). Hence, the entire surface of these materials (6-260 m2 g-1, Camel & Caude 1995, Dettmer & Engewald 2002) is available for interactions that depend on dispersion forces (London forces) and on the molecular size and shape of the adsorbed molecule. However, GCBs materials are soft and fragile, leading in some instances to very small particles that can enter the trap of the thermal desorber, causing problems in some cases (Harper 2000, Sunesson 2007). Due to its high sensitivity, GCBs are advisable sorbents to be applied in isomer separation of compounds with similar physical properties but different geometric structures. GCBs are formed by heating ordinary carbon blacks in an inert gas atmosphere at a temperature of 3000ºC (Kovaleva & Shcherbakova 1990), eliminating unsaturated bonds, lone electron pairs, free radicals and ions (Matisová & Škrabáková 1995). GCBs are generally hydrophobic (Gawlowsky et al. 1999, Harper 2000, Dettmer & Engewald 2003, Strandberg et al. 2005) due to the graphitization process, which eliminates the specific adsorption sites and impedes the formation of hydrogen bounds (Camel & Caude 1995). However, usually a few active sites remain (Hrouzková et al. 1998), as losses of reactive analytes have been reported in the literature (Rothweiler et al. 1991, Dettmer & Engewald 2003). On the other hand, due to their high hydrophobicity GCBs are suitable for sampling in humid atmospheres (Knoblock & Engewald 1995). GCBs are suitable for the adsorption of a wide range of organic compounds (C4-C5 hydrocarbons, polychlorinated biphenyls and polynuclear aromatics) (Camel & Caude 1995). They are generally used in multi-bed sorbent tubes (Ciccioli et al 1993, Dettmer & Engewald 2003)

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1.2. Carbon Molecular Sieves Carbon molecular sieves (CMSs) are almost uniform microporous solids, formed by rigid spherical mechanically stable particles (Hrouzková et al. 1998, Dettmer & Engewald 2003); generally used for collecting very small molecular-sized compounds (C2-C5) (Harper 2000, Sunesson 2007), due to its narrow porous entrance size, with high surface area and a high retention capacity (Camel & Caude 1995, Dettmer & Engewald 2003, Tascón 2008). Adsorption in carbon molecular sieves is generally founded on non-specific interactions (Dettmer & Engewald 2002). Their pore diameter is comparable with the molecular diameter of much gaseous pollutants (Sircar 2008). CMSs are formed by controlled pyrolysis of polymeric or petroleum pitch materials at temperatures above 400ºC. The efficiency of the analytes adsorption/desorption would be determined both by the size and the shape of the pores in the CMSs and the size and shape of the analyte molecule, as well as by the polymeric material used and the pyrolysis/carbonization technology (Hrouzková et al. 1998). However, due to their high retention capacity they are easily contaminated by air impurities, decreasing the homogeneity of the porous structure (Matisová & Škrabáková 1995). In addition to that, they are more affected by relative humidity (specially in RH conditions ≥ 50%, Helming & Vierling 1995) than graphitized carbon blacks due to the volume of their micropores and the presence of functional groups in their adsorbent surface (Gawlowski et al. 1999, Dettmer & Engewald 2003, Strandberg et al. 2005). CMSs are usually used combined with weaker adsorbents in multi-bed sampling tubes (Dettmer & Engewald 2003, Ribes et al. 2007).

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1.3. Polymeric Adsorbents Porous polymeric adsorbents cover a wide range of materials with distinct properties depending on the monomers used and the process of manufacture (Dettmer & Engewald 2003). They are generally hydrophobic, trapping low levels of ambient air water. However, polar polymeric adsorbents can trap higher amounts of water weakly bounded, being easily removed by a purge of the adsorbent by a drying gas (Gawlowski et al. 1999). Porous polymers permit the adsorption/desorption of high-boiling compounds (e.g. phtalates, glycols, aldehydes and acrylates); however, low-boiling compounds (e.g. C2-C5 alkanes) are not so well retained by these types of adsorbents (Uhde 1999). Polymeric adsorbents are sometimes incompatible with thermal desorption due to their limited temperature stability (Dettmer & Engewald 2003).

1.3.1. XAD-2 XAD resins are macro reticular resins non-ionic with moderate surface areas (Harper 2000). Their retention kinetics are determined by hydrophobic or hydrophilic interactions between the analyte and the adsorbent surface. XAD-2 resins are aromatic in character, very hydrophobic and do not have ion-exchange capacity. They are advisable for retaining large and semi-volatile organic compounds (e.g. polycyclic aromatic hydrocarbons, pesticides) (Harper 2000, Gallego et al. 2008a). In addition to that, adsorbates are extracted using solvent extraction techniques as they are very instable on heating (Camel & Caude 1995).

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1.3.2. Tenax Tenax TA has been broadly used to determine VOC in ambient air (McCaffrey et al. 1994, Baya & Siskos 1996, Donaldson et al. 2003, Sunesson 2007, Ras 2008), mainly due to its low affinity for water (< 3.3 mg of H2O g-1 of material, Helming & Vierling 1995) and methanol, thermal stability and reliable desorption kinetics. However, it is not recommended for sampling very volatile analytes (Rothweiler et al. 1991, McCaffrey et al. 1994, Camel & Caude 1995, Dettmer & Engewald 2002), as it has been observed that non-polar high molecular weight pollutants displace volatile and polar compounds (Borusiewicz & ZiebaPalus 2007) due to its low specific surface area (30 m2 g-1) (Dettmer & Engewald 2003). Compounds with boiling points lower than 100ºC would not be adsorbed correctly in Tenax TA (Sunesson 2007). On the other hand, due to the low surface area, Tenax TA is not recommended to be used to sample in high ambient air concentrations, as a reduction in sorbent capacity can occur since breakthrough is dependent on concentration (Harper 2000). Tenax TA is generally not influenced by artifact formation (Rothweiler et al. 1991, Cao & Hewitt 1994); however, after its exposition to relevant concentrations of O3 and NO2, artifacts can be generated (Camel & Caude 1995, Calogirou et al. 1996, Clausen & Wolkoff 1997, Dettmer et al. 2000, Harper 2000, Ras 2008). Besides, it has been noticed that decomposition processes in the surface of the sorbent may degrade adsorbed analytes (e.g. terpenes) during the sample step, when the adsorption of the compounds occur (Calogirou et al. 1996, Coeur et al. 1997), and during TD-GC analysis (Clausen & Wolkoff 1997, Dettmer et al. 2000). On the other hand, it has been observed that Tenax TA may also be influenced by storage time and temperature variations, and analyte concentrations (Volden et al. 2005, Barro et al 2009). Tenax GR is a composite material containing 70% of Tenax TA and 30% of graphite carbon. Therefore, Tenax GR has higher retention volume for the majority of compounds than Tenax TA.

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1.4. General Purpose Adsorbents Silica gel and activated charcoal have been extensively used as general purpose adsorbents followed with solvent extraction due tot their ability to adsorb/desorb a wide range of volatile compounds (NOISH 1994). However, they are not advisable for thermal desorption due to their high surface activity, which can favor sample degradation at high temperatures (Harper 2000).

1.4.1. Silica Gel Silica gel is particularly effective for retaining very polar compounds (methanol, amines and some inorganic species). However its affinity for water makes it not recommended when sampling in humid environments. Nowadays, silica gel has been generally replaced by other sorbents (Harper 2000). 1.4.2. Activated Charcoal Back in the ancient Egypt, activated carbon was the first sorbent used, and throughout the years has remained one of the most widely utilized. However, until the end of the 18th century

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activated charcoal was not used as an adsorbent to gases, both by active and passive samplings (Matisová & Škrabáková 1995, Dąbrowski 2001). Wood, coconut shell, fruit pits, fossilized plant matter, lignite or synthetic polymers are sources of activated charcoal (Wilson 1981, Sircar 2008). The original materials pass through a process of structure activation, which will produce a highly porous material, providing an extensive surface area (300-2000 m2 g-1) of adsorption with high sorption capacity (Camel & Caude 1995, Rudling 1990). The adsorption of the analytes is founded on specific and nonspecific interactions with the adsorbent (Dettmer & Engewald 2003). The precursor type and the method of activation would determine the pore structure, the polarity, and the active adsorption surface area (Sircar 2008). However, sorption capacity is very heterogeneous, and several compounds (e.g. alcohols) are affected by an irreversible adsorption process due to the high strength of the binding interactions between the analyte and the activated charcoal, as well as it has affinity for water (Rudling 1990, Dettmer & Engewald 2003). Hence, sensibility problems are accentuated when trace levels of analyte have to be determined (Camel & Caude 1995). On the other hand, important variations in physico-chemical proprieties are observed depending on the source of activated carbon (Matisová & Škrabáková 1995). In addition to that, the adsorbent can contain mineral impurities (e.g. metal oxides, oxygen complexes) that can reduce its sorbent capacity. Leaching activated carbon with several acids or depositing pyrolytic carbon on its surface area helps reducing impurities on the adsorbent (Rudling 1990). Activated charcoal is widely used in passive samplers (Dettmer & Engewald 2003).

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1.5. Classification and Characterization of Sorbents Kiselev (1967) classified sorbents in three different classes. Graphitized carbon blacks are Class I sorbents, interacting non-specifically with all groups of adsorbates: group A molecules (n-alcanes), group B molecules (aromatic hydrocarbons and chlorinated hydrocarbons), group C molecules (organo-metallic compounds) and group D molecules (primary alcohols, and organic acids and bases). Activated silica gel is a Class II sorbent, interacting non-specifically with several adsorbates (e.g. through London and van der Waals forces). Activated charcoal, carbon molecular sieves and porous polymers are Class III sorbents, interacting specifically with adsorbates (e.g. through strong dipole-dipole interactions) (Kiselev & Yashin 1969, Matisová & Škrabáková 1995). The characterization of sorbents and their suitability for trapping pollutants is done through the determination of specific retention volumes (breakthrough), adsorption coefficients and equilibrium sorption capacities. In addition to that, the knowledge of the physical properties of sorbents will help us to understand their performance in front of pollutants (Hrouzková et al. 1998).

2. FACTORS INFLUENCING ADSORPTION Sampling is a crucial step of air analysis. Hence, the adsorption of airborne compounds into solid sorbents is also a very important point (Ras 2008). Ambient air representative samples have to be taken; therefore, factors influencing adsorption (e.g. ambient variables,

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sampling variables, materials/adsorbents characteristics) have to be taken into account to reduce at maximum imprecision during the sampling stage.

2.1. Ambient Variables Environmental variables can affect negatively the performance of active, but mainly of passive samplers, due to that; their application in ambient air pollution determination is controverted (Tolnai et al. 2000, Seethapathy et al. 2008).

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2.1.1. Temperature In passive samplers, uptake rates are usually influenced by ambient temperature, as the diffusion coefficient of pollutants into the sorbent is dependent on temperature. It has been observed that an increase of one Kelvin degree will lead to an increase on uptake rate of about a 0.2-0.4% of its value determined in standard conditions (Seethapathy et al. 2008). Temperature value would be important in punctual determinations in extreme weather conditions (e.g. winter or summer minimum and maximum temperatures, respectively); however, it would have little influence in annual average results (Ballach et al. 1999, Strandberg et al. 2006). 2.1.2. Humidity High humidity conditions in the ambient atmosphere during sampling can lead to adsorption of water by the sorbent. Hence, a competition for the adsorbent active surface area would occur between water and the target compounds (Matisová & Škrabáková 1995), reducing the adsorption capacity of the sorbent (Strandberg et al. 2005). Hence, breakthrough values would be different from the obtained in less humid environments. In this case, the hydrophobic properties of the sorbent would be crucial for the obtention of reliable results. Therefore, hydrophilic sorbents (e.g. charcoal, silica gel) may be negatively affected by ambient humidity (Ballach et al. 1999, Harper 2000). For example, in an ambient air where relative humidity is higher than 60%, the sorption capacity of activated charcoal for some target compounds can be diminished up to 50% (Matisová & Škrabáková 1995). On the other hand, uptake rates for passive samplers can decrease if relative humidity is higher than 65% (Strandberg et al. 2005). It has to be taken into account that even reducing the relative humidity in the air sampled to a minimum, this will not prevent completely water adsorption, due to the fact that the presence of hydrophilic centers in highly hydrophilic adsorbents will lead to some water adsorption (Gawlowski et al. 1999). In addition to that, high humidity in ambient air can affect adsorption by passive samplers even when they are correctly sheltered, as condensation may occur on the diffusion barrier between the sorbent and ambient air (Strandberg et al. 2006). 2.1.3. Wind Velocity Passive samplers may be affected negatively in a highly variable way by wind speed (Dewulf & Langenhove 1999, Krupa & Legge 2000, Dettmer & Engewald 2003, Strandberg et al. 2006, Sunesson 2007), mainly as a cause of variations of the effective diffusion path length (Gair & Penkett 1995, Hori & Tanaka 1996). Increases or decreases of the diffusive

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path length may be caused by low and high wind speeds, respectively (Hori & Tanaka 1996, Ballach et al. 1999, Strandberg et al. 2005). Wind speeds between 0.5-3.0 m s-1 can be diminished to 0.2-0.6 m s-1 if samplers are located in proper shelter boxes (Mon & Hangartner 1996). On the other hand, in tube-type passive samplers, effects caused by wind velocity can be irrelevant if samplers are placed in appropriate protective structures (Brown et al. 1981, Gair & Penkett, 1995, Strandberg et al. 2006). In addition to that, the Radiello sampler presents extra resistance to wind speed due to its cylindrical diffusion body (Cocheo et al. 1996).

2.2. Active Sampling Variables Pre-concentration of pollutants in sample tubes containing solid sorbents is a method particularly useful when air concentrations are low and the analytical sensitivity has to be achieved with large sample volumes. A wide range of pollutants may be collected on a single porous material adsorbent (Harper 1993), and several normative methods (e.g. U.S. EPA and NIOSH) are based on this methodology (Ras 2008).

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2.2.1. Sorbent Volume Sorbent volume will determine (along with the type of sorbent used) the retention capacity of the sorbent tube employed for ambient air sampling. In addition to that, the concentration of the target pollutants present on the air sampled would also determine the maximum volume of air sample that could pass through a concrete mass of adsorbent without provoking breakthrough problems. Hence, when deciding a concrete volume of adsorbent or various adsorbents to make homemade sorbent tubes we are determining a concrete sorbent capacity, and this aspect would have to be taken into account when sampling concrete air volumes depending on the expected air concentrations. 2.2.2. Air Flow The air flow has to permit an adequate time of exposition between the analyte and the adsorbent surface material to allow correct interactions between them and make sure the retention of the target compounds in the samplers (Dettmer & Engewald 2002). Hence, high air flows through the adsorption tube may lead to a not efficient removal of pollutants from the air stream by the adsorbent material (Harper 1993). On the other hand, however, very low air flows (e.g. below 20 ml min-1) can lead to misinterpreted ambient air concentrations due to the interferences caused by the diffusive process between the adsorbent and the target compounds (Harper 2000). 2.2.3. Sample Volume The main objective of air sampling is to collect target compounds to determine their concentrations in ambient air. Hence, enough air sample has to be collected to assure being above the detection limit requirements of the posterior analytical methodology used. The sample volume would depend on the sampling rate of the pumps used and the duration of the sampling (Michulec et al. 2005). Determining accurately the volume sampled is an important parameter when determining air concentrations of pollutants. To control sample volume, the use of appropriate calibrated pumps and/or mass flow controllers and air meters is essential

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(Uhde 1999, Michulec et al. 2005, Roca 2006, Gallego 2008b, Gallego 2008c). The choice between active or passive sampling strategy would depend on the kind of airborne sample that we would achieve. Monitoring of concrete industrial processes or odorous episode peaks would require short sampling times and consequently short sampled volumes, being the use of active sampling recommended. On the other hand, if long-term averaged concentrations are the focus of our study, passive sampling strategy would be advisable, as very high volumes of sample would be required, and the use of active sampling could lead to breakthrough problems (Uhde 1999, Godish 2001). The maximum volume of air that can be sampled without loss of adsorbent must be known to avoid breakthrough troubles (Harper 1993, Dettmer & Engewald 2003), as if breakthrough occurs, the sample obtained would not be representative (Harper 2000). The knowledge of breakthrough volume values for the target compounds is very useful when tubes without back-up sections are used (Harper 1993).

2.3. Sorbent Capacity

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To understand the adsorbents performance characteristics it is important to identify and characterize their physico-chemichal properties. The sorbent morphology, surface area, particle size and shape, pore size and volume and specific retention volume for each target compounds (breakthrough) are the properties that have to be evaluated to determine the suitability of an adsorbent for a concrete pollutant (Hrouzková et al 1998). Sorbents having a higher surface area per mass unit, which will depend on the porous structure of the sorbent, will have a higher number of gathering points. Hence, surface area is a critical aspect of adsorbents, however, depending on the pore size not all molecules would be adsorbed due to their higher volume compared with the microporous. Therefore, microporous sorbents are generally characterized by their pore volume instead of their surface area (Harper 2000). On the other hand, pore size and distribution will also be crucial aspects related to adsorbent retention, but the size of the pollutants would also have to be taken into account when considering their penetration within the pores (Matisová & Škrabáková 1995, Hrouzková et al. 1998).

2.3.1. Breakthrough The capacity of a sorbent to retain specific compounds is usually evaluated by measuring the breakthrough volume of a concrete compound on the sorbent (Baya & Siskos 1996). To maximize sampling efficiency, the maximum volume of air that can be sampled without loss of adsorbent must be known (Harper 1993, Dettmer & Engewald 2003). Because, if breakthrough occurs, the sample obtained would not be representative of the concentrations present in ambient air (Harper 2000). To eliminate breakthrough problems, an appropriate sorbent for the range of target compounds expected concentrations must be selected (Dewulf & Van Langenhove 1999). However, a back supplementary sorbent part can be added to the main sorbent bed to determine if breakthrough has occurred (Harper 2000). Although breakthrough data are available for some materials, few data exist on multi-sorbent (combination of various sorbents) breakthrough (Ribes et al 2007). On the other hand, there are substantial differences between different breakthrough measurement methods (direct or indirect methods) (Harper 1993). Breakthrough, or specific retention value, is the volume of

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air passing through an adsorbent that causes adsorbate molecules to migrate from the front to the back of the adsorbent bed (Matisová & Škrabáková 1995). During breakthrough, pollutant collection starts to fall until no more sample is collected when the sorbent is saturated (Harper 1993). Breakthrough values can also be calculated as the percentage of target compound found in the back tube (in two tubes connected in series or in sample tubes with back up sections) relative to the total mass in both tubes. Typical organic compounds recommended breakthrough values are 0.03. No plateau at N = 2 is observed. The inflection at N ≈ 2 probably is caused by the fact that the crystalline methanolate CaCl2·2CH3OH coexists with a salt – methanol solution or a solid phase CaCl2 – CH3OH of variable composition in the silica pores. When the temperature decreases lower the inflection, the isobars become smooth curves and the methanol uptake growths gradually. This indicates clearly the formation of a CaCl2 – methanol solution inside the pores. Both the adsorbents demonstrate stronger affinity to methanol as compared to the bulk salt at low relative pressure of methanol that favors deeper methanol removal from gaseous mixtures (see below). At η > 0.43 the adsorption equilibrium of CaCl2(25 %)/SiO2(15 nm) composite coincides well with that for the bulk solution. Confinement of CaCl2 – methanol solution in the silica pores of 15 nm size does not affect its adsorption properties that agrees well with regularities of the water sorption on CSPMs. It seems quite reasonable taking into account that the diameter of a solvation sphere is much lesser than the pore diameter [60]. In the range of the methanol relative pressure 0.15 < η < 0.43 CaCl2(23 %)/SiO2(4 nm) is superior to CaCl2(25 %)/SiO2(15 nm) composite in sorption ability.

12 10

2 1

8 6

0,00

0,05

0,10

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4 2 0,0

0,2

0,4

0,6

0,8

PMeOH/P0 (T) Figure 7. Temperature invariant curves of methanol sorption on CaCl2(25 %)/SiO2(15 nm) (|) and CaCl2(23 %)/SiO2(4 nm) (Μ) composites as well as literature data for the bulk system CaCl2 – MeOH („).

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2

1

10

20

30

40

50

2θ, degree

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Figure 8. The XRD patterns of CaCl2(25 %)/SiO2(15 nm) (1) and CaCl2(23 %)/SiO2(4 nm) (2) recorded under helium flow at T = 150 °C.

The reason of the sharp distinctions between sorption equilibrium of the salt embedded in pores of different size is caused by difference of phase composition of the composites. The XRD patterns of both the composites indicate that a crystalline phase of CaCl2 (space group Pnnm) formes in both the silica gels. However, the integral intensity of reflexes for CaCl2(23 %)/SiO2(4 nm) composite was 2.5-3 times less than that for CaCl2(25 %)/SiO2(15 nm) composite. This indicates that content of the crystalline CaCl2 in the pores of 4 nm size is lower. In other words, a part of the salt in CaCl2(23 %)/SiO2(4 nm) composite is stabilized as highly dispersed or amorphous phase. Porous structure of the host silica was characterized by a pore size distribution in the range of diameters d = 3 – 6 nm. The crystalline salt probably occupies wider pores. The X-ray amorphous phase is stabilized in narrower pore, or as a thin layer on the silica surface [54, 61]. Sorption of methanol by the crystalline salt results in the formation of crystalline methanolate with monovariant equilibrium. In contrast, methanol sorption by the amorphous salt results in the formation of amorphous phase CaCl2 – CH3OH, whose composition changes continuously, and the equilibrium becomes divariant. Thus, confinement of the salt in the silica pores leads to the increase in an affinity of the salt to methanol. Adsorption equilibrium of CSPMs with methanol can be modified both quantitatively (shifting the temperature of methanolates formation) and qualitatively (transformation from mono- to divariant sorption equilibrium) by variation of the matrix pore size. It means that the pore size of the host matrix is an effective tool for goal-seeking design (or even nanotailoring) of CSPMs with predetermined sorption properties.

1.2.3. Effect of Supplementary Salt It is known that certain properties of a salt can be changed by a supplementary salt, which forms a solid solution with the main salt. For instance, addition of KCl and CaBr2·6H2O shifts the melting point of CaCl2·6H2O to that necessary to heat storage application [62]. Ammonia absorption equilibrium of alkaline earth metal halides (CaBr2 and CaCl2) was modified by an additional salt, forming solid solution, in order to meet requirements of the ammonia separation and storage during its synthesis [63, 64]. We have studied the possibility to vary the sorption properties of CSPM by modification of a basic salt with a supplementary one to

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form proper solid solutions inside the pores. Composites based on binary salt system (LiCl+LiBr) in silica gel pores with different salts fraction were prepared, and their sorption equilibrium with methanol was studied [65]. Both the composites based on the single salts were found to demonstrate high methanol sorption ability in different range of methanol relative pressure (figure 1). The LiBr based composite shows higher affinity to methanol and adsorbs vapor at the methanol relative pressure 0.03 < η < 0.05 according to reaction LiBr + CH3OH = LiBr·CH3OH .

(5)

Monomethanolate LiBr·CH3OH transforms to LiBr – methanol solution inside the silica pores. LiCl reacts with methanol at higher relative pressure 0.19 < η < 0.23

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LiCl + 3CH3OH = LiCl·3CH3OH and forms LiCl – methanol complex and solution as well. The isobars of methanol sorption on the binary salt composites (LiCl+LiBr)/SiO2 with various halide contents are presented on figure 9. Curves calculated as a sum of the sorption on the single-salt composites LiCl/SiO2 and LiBr/SiO2 taken with proper weight coefficients are presented for comparison. Essential distinctions between the experimental and calculated curves for LiBr-rich composites [(LiCl+LiBr(1:6))/SiO2, (LiCl+LiBr(1:3))/SiO2, (LiCl+LiBr(1:1))/SiO2] were found (figure 9 a-c): the temperature of the step corresponding to the transition of LiBr to the solvate LiBr⋅CH3OH decreased by some 10-15 °C. Small temperature shift by 5 °C in the transition of LiCl to LiCl⋅3CH3OH towards higher temperature was observed for LiCl-rich composite (LiCl+LiBr(3:1))/SiO2. The reason of the shift in temperatures of the LiCl and LiBr solvation is likely to be the formation of solid solutions. The XRD patterns of composites (LiCl+LiBr)/SiO2 are presented on figure 10 together with the patterns of the single-salt composites LiCl/SiO2 and LiBr/SiO2 given for comparison [50, 65]. The patterns of composites (LiCl+LiBr(1:6))/SiO2 and (LiCl+LiBr(1:3))/SiO2 exhibit symmetrical peaks assigned to a cubic LiBr (space group Fm-3m), but shifted towards larger angles with respect to those of the reference composite LiBr/SiO2. That indicates the formation of a homogeneous solid solution of LiCl in LiBr lattice. The XRD patterns of composites LiCl+LiBr(1:1))/SiO2, LiCl+LiBr(3:1))/SiO2 and LiCl+LiBr(6:1))/SiO2 are quite different and exhibit asymmetrical (LiCl+LiBr(1:1))/SiO2 and (LiCl+LiBr(6:1))/SiO2)) or double (LiCl+LiBr(3:1))/SiO2) reflections. This reveals the formation of a mixture of two solid solutions (SS) stabilized in the silica pores. One SS is enriched with LiCl (SSCl) and the other is enriched with LiBr (SSBr). The data obtained show the following regularities of the phase composition of the novel (LiCl+LiBr)/SiO2 materials. The formation of solid solutions takes place in all the composites. For the composites with dominant content of LiBr, the homogeneous SSBr was observed inside the pores indicating quite large solubility of LiCl in LiBr (sLiCl ≈ 36 mol. %) [65]. The increase in the LiCl content results in the transformation of the homogeneous solid solution to the mixture of two solid solutions SSCl and SSBr that reveals as asymmetrical or double reflections. Even composite LiCl+LiBr(1:6))/SiO2 with the smallest LiBr content

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contains the mixture of two solid solutions showing the poorer solubility of LiBr in LiCl (sLiBr ≈ 11 mol. %) inside the silica pores. 0.44

a

0.33 0.22 0.11 0 0.33

b

0.22 0.11 0 0.33

c

0.22 0.11 0 0.33

d

0.22 0.11 0 0.33

e

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0.22 0.11 0

50

60

70 80 90 Temperature, oC

100

Figure 9. Isobars of methanol sorption on composites (LiCl+LiBr(1:6))/SiO2 (a), (LiCl+LiBr(1:3))/SiO2 (b), (LiCl+LiBr(1:1))/SiO2 (c), (LiCl+LiBr(3:1))/SiO2 (d) and (LiCl+LiBr(6:1))/SiO2 (e) at the partial methanol pressure P = 107 mbar (7, solid line) as well as theoretical curves calculated as a sum of the sorption on the single-salt composites LiCl/SiO2 and LiBr/SiO2 taken with the proper weight coefficients (∀, dash line).

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123

(200)

LiCl/LiBr, mole/mole 1/0 6/1 3/1

1/1 1/3

1/6 0/1 25

30

35

40

2θ, degree

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Figure 10. XRD patterns of composites (LiCl+LiBr)/SiO2, T = 150 °C.

The data on methanol sorption equilibrium are in good agreement with those on the XRD analysis of (LiCl+LiBr)/SiO2 composites. The solubility of LiCl in LiBr is quite large and the formation of SSBr inside the silica pores results in an essential distortion of the crystalline lattice and reduction of the temperature of LiBr⋅CH3OH formation by 5–15 °C. In contrast, the solubility of LiBr in LiCl is negligible and the formation of SSCl only slightly changes the temperature of LiCl – LiCl⋅3CH3OH transition. Phase transformation in the composites during the methanol sorption was monitored by an XRD in situ. The XRD patterns of the composite recorded in the presence of methanol vapor at different temperatures showed that the two solid solutions SSCl and SSBr stabilized in the composites (LiCl+LiBr)/SiO2 adsorb methanol independently at different temperatures. Thus, embedding of the binary salt system, which forms solid solutions inside pores, allows the shift in the temperature of the salt solvation. The use of the binary salt systems confined to the matrix pores can be an effective tool for designing innovative materials with predetermined sorption properties.

1.2.3. Effect of Synthesis Conditions Besides above-listed tools, namely, the chemical nature of the active salt, the effect of the supplementary salt and the pore structure of the host matrix, some parameters variable during the composite synthesis affect the sorbent properties as well. The common procedure of the composite preparation is the impregnation of the predominantly dried matrix with an aqueous salt solution followed by thermal drying. It was observed that an interaction between the salt

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solution or the anhydrous salt and the matrix surface occurs during the composite preparation that results in formation of two salt phases inside pores: crystalline and amorphous salt [61]. The detailed study of the surface interaction proceeding during impregnation and drying stages showed that the ion exchange adsorption of metal cations (Men+) on silanol group of silica surface ≡Si–O–H during the impregnating causes the formation of surface complexes ≡ Si–O–Me(n-1)+···A–. The amount of these complexes is a function of the nature of metal cation, the solution pH and concentration. The surface complexes appear to affect the salt crystallization, resulting in stabilization of two salt phases in anhydrous composite: the volume crystalline and surface amorphous phases. The main parameters affecting the cation adsorption equilibrium and phase composition of the composite are the salt concentration and pH of the impregnating solution. X-ray diffraction patterns of CaCl2/SiO2 composites (figure 11) show that the intensity of the reflexes corresponding to CaCl2 diminishes with the increase in pH of impregnating solution, indicating partial formation of an X-ray amorphous phase. The alteration of phase composition of the CaCl2/SiO2 composites prepared at different pH of the solution changes qualitatively their methanol adsorption properties (figure 12). Thus, the sorption isobar for composite prepared from neutral salt solution (pH = 5.5) demonstrates the formation of stable CaCl2·2CH3OH, which undergoes the stepwise transitions to CaCl2 at high temperature. This behavior is typical for the composites containing the crystalline phase of the salt which transforms to the crystalline solvates during methanol sorption. In contrast, the water adsorption isotherm for the composite prepared from weak alkaline solution (pH = 9) is a smooth curve indicating no formation of crystalline hydrates that is typical for adsorption by the amorphous salt. *

* *

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*

*

1

2 20

40

60

2θ, degree

Figure 11. XRD pattern of CaCl2(23%)/SiO2(15 nm) composites prepared at pH = 5.5 (1) and 8 (2). * denotes reflexes of СaCl2·2H2O formed due to adsorption of water vapor from the atmosphere on the composites.

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4

3

2

1

2

1

0 20

40

60

80

100

120

Temperature, oC

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Figure 12. Isobars of methanol sorption on composites CaCl2(23%)/SiO2(15 nm) prepared at pH = 5.5 (1) and 8 (2), PMeOH = 101 mbar.

The novel approach to intent design of the CSPMs with specified methanol adsorption properties, which meet the requirements of particular applications, can be separated into the following two stages: (a) the determination of requirements imposed on an ideal adsorbent, whose properties are optimal for the given application and (b) the synthesis of a real adsorbent with properties identical or similar to the properties of an optimum adsorbent. Comprehensive study on the phase composition and methanol adsorption equilibrium of CSPMs allows disclosing a number of tools for the adsorbents design, among which are the chemical nature of confined salt, the encapsulation of the solid solutions of binary salt systems in pores, the porous structure of the matrix and conditions of preparation (pH of impregnating solution). Below we describe examples of the formulating the requirements to the optimal adsorbent for three processes where methanol adsorbents are used: adsorptive cooling, shifting the methanol synthesis towards target product and methanol removal from gaseous mixtures. The composites specified for the first two processes have already been prepared using the mentioned “tools”. The main steps of intent synthesis of CSPMs as well as the results of their lab-scale testing are presented below. The design of CSPMs for the last application is a task for our further research activity.

2. CSPMS FOR PARTICULAR APPLICATIONS 2.1. Adsorption Air Conditioning Serious limitations imposed by the Montreal and Kyoto protocols open a niche for adsorption heat pumps, which can play an important role in improving the environment by

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essential fuel savings. Adsorption cooling (AC) based on methanol as a working media is considered promising for air conditioning and ice making driven by low temperature heat: solar energy, automotive waste heat, etc [7-9]. Typical materials used for methanol adsorption in AC are activated carbons and hydrophobic zeolites. However, the net desorption per cycle under typical AC conditions, does not usually exceed 0.14-0.18 and 0.15-0.25 kg/kg for zeolites and activated carbons, respectively that results in quite low performance of the AC cycle. Based on the concept of goal-seeking design of CSPMs with predetermined properties, the methanol adsorbents for air conditioning driven by low temperature heat have been prepared and studied.

2.1.1. The Requirements to an Optimal Adsorbent for AC On the base of thermodynamic analysis of the AC cycle the requirements to an optimal adsorbent were formulated [13]. A single bed AC unit consists of an adsorber filled with adsorbent, an evaporator and a condenser. The general principles of the operation of these devices were considered previously [66]. The cooling effect is produced in AC cycle during the methanol evaporation, which is forced by adsorption of methanol vapor on the adsorbent. The working cycle, which consists of two isosters and two isobars, is presented in figure 13 in a pressure – temperature diagram. The cycle is defined by the following three temperatures: the condenser temperature Tc, the evaporator temperature Tev, and the adsorbent regeneration temperature Tdes. If these three temperatures are specified, the efficiency of the adsorption heat pump increases monotonically as the amount of working fluid (methanol) exchanged in the cycle (i.e., between the extreme isosters of the cycle (1–2 and 3–4)) increases [13]. Because the isosters are unambiguously characterized by the adsorption potential ΔF1–2 or ΔF3–4 (see Introduction) [49], the optimal adsorbent should have a maximum difference between the methanol uptake at these two values of ΔF.

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Pc

wmax

lgPMeOH

3

2

1

Pev

Tev

wmin

Tc

Tads

4

T2

T4

Tdes

Figure 13. Thermodynamic cycle of adsorptive cooling.

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Taking into account the following values of methanol pressure and temperatures, typical for air conditioning cycle (Tev = 7°C, Pev = 61 mbar; Tads = Tc = 35 °C, Рc = 274 mbar; Тdes = 85 °C) the corresponding values of free sorption energy were calculated: ΔF1-2 = 3158 J/mol and ΔF3-4 = 6216 J/mol. Thus, the main requirement of the AC cycle is large variation in the methanol uptake Δw = wmax - wmin between the calculated values of ΔF.

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2.1.2. The Adsorbent Preparation Since the chemical nature of the salt is the main parameter affecting the adsorption equilibrium of CSPM with methanol vapor, the first step in the adsorbent synthesis was a selection of the proper salts and their solvates, which form/decompose at ΔF between calculated ΔF1-2 and ΔF3-4 for the cycle considered. A number of solvates appear to fit this requirement (table 2) [42, 43, 46, 47]. The next criterion concerns the amount of methanol ΔN (or Δw) exchanged in the selected reaction. Taking into account these criteria, LiCl, Ca(NO3)2, Mg(NO3)2 and NiBr2 were selected as active salts for the composite preparation. Due to a lack of the equilibrium data on temperature and methanol pressure for crystalline solvates of MnCl2 (N = 2), LiBr·(N = 3), MgCl2 (N = 4, 6), MgBr2 (N = 6), composites based on these salts were prepared as well. Silica gels with large pore volume and rather wide mesopores Grace Gmbh SP2–8926.02 (Vp = 1.5 cm3/g, Ssp = 326 m2/g, dav = 15 nm) and Davisil Grade 646 (Vp = 1.15 cm3/g, Ssp = 300 m2/g, dav = 15 nm) were selected as host matrices in order to ensure large sorption capacity of the composites and monovariant sorption equilibrium. The composites were synthesized by an incipient wetness impregnation of the silica gels with aqueous salt solution followed by thermal drying at 200 °C. The salt content of the composite was in the range 25 – 30 wt.%. 2.1.3. The Sorption Ability of the Composites The methanol sorption on the composites under conditions of the AC cycle considered was studied by an express-method, which allows a quick screening of sorption ability of numerious adsorbents [49]. The influence of the chemical nature of confined salt on the sorption ability of composites is presented in figure 14. Sorption ability of common porous adsorbents under the same conditions are presented for comparison as well [9, 14-17, 67]. The composites based on LiCl and LiBr appear to demonstrate the highest net methanol sorption under the cycle conditions described above. The net sorption of composites containing NiBr2 and CaBr2 is lower, but they can be also of interest. Composite LiCl(31 %)/SiO2(15 nm) appears to show a very high sorption capacity wmax= 0.8 g/g. The methanol uptake after desorption stage decreases to wmin= 0.09 g/g giving the variation of uptake per cycle Δw= 0.71 g/g, that is much larger than that for conventional adsorbents, like porous carbons or zeolites. Composite LiBr (29 %)/SiO2(15 nm) possesses a high ability to sorb methanol wmax= 0.73 g/g. However, the temperature of desorption fixed at the cycle is not high enough to remove the methanol adsorbed. The uptake after desorption stage remains rather high wmin= 0.33 g/g giving the variation of uptake per cycle Δw =0.4 g/g. It is two times lower than that of LiCl based composites, but nevertheless far exceeds the sorption per cycle for conventional adsorbents. The increase in the desorption temperature Tdes will result in a rise of the sorption difference in the cycle. Thus, the LiBr based composite could be of

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interest when the heat source with a higher temperature Tdes is available for sorbent regeneration. The adsorption properties of the most promising LiCl(31 %)/SiO2(15 nm) composite were studied in more detail (figure 2) [50]. The composite demonstrates a strong affinity to methanol. The maximum amount of methanol sorbed wmax = 0.83 g/g is 2-5 times larger than the methanol sorption capacity for non-modified silica gel (0.15 g/g) as well as for conventional adsorbents like zeolites and activated carbons (0.2-0.4 g/g). This great enhancement of adsorptivity is due to the predominant contribution of methanol sorption by the salt embedded in the silica gel matrix. At a high sorption potential ΔF, composite LiCl(31 %)/SiO2(15 nm) sorbs a small amount of methanol (w ≤ 0.05 g/g, figure 2), which can be attributed to the methanol adsorption on active centers of the silica gel surface. As the temperature decreases, the salt starts to absorb methanol and the uptake reaches w = 0.7 g/g or N ≈ 3 mole/mole at the adsorption potential ΔF ≈ 4.5 kJ/mol that exactly meets the demand of the cycle considered. Afterwards, with decreasing adsorption potential a gradual rise of methanol sorption is observed, caused by methanol absorption by LiCl – methanol solution formed inside pores. 0.8

0.6

0.4

0.2

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0.0

Figure 14. Methanol uptake for composite sorbents and conventional adsorbents zeolites and activated carbons after adsorption (shaded bars), desorption (white bars) stages and variation of uptake per cycle (black bars). Reprinted with permission from Ind. Eng. Chem. Res. Influence of Characteristics of Methanol Sorbents “Salts in Mesoporous Silica” on the Performance of Adsorptive Air Conditioning Cycle 2007, vol. 46, p. 2747, Gordeeva, L. G.; Freni, A.; Restuccia, G.; Aristov, Yu.I. Copyright 2007 American Chemical Society."

2.1.4. Performance of Air Conditioning Adsorptive Cycle The data obtained allows an evaluation of a performance of the AC cycle based on LiCl(20%)/SiO2(15 nm) composite and methanol as a working pair. The thermodynamic

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Coefficient Of Performance (the ratio of a useful effect to a heat supplied to the adsorbent for regeneration) COP = 0.74 was obtained, that is noticeably higher than COP = 0.56 calculated for AC35 methanol adsorbent (figure 15) [68]. The real performance of the air conditioning cycle was measured by testing this novel material in a lab-scale adsorption chiller. The real cooling COP = 0.32-0.4 and the Specific Cooling Power SCP = 210-290 W/kg were obtained that exceed essentially those for “zeolite – methanol” and “CaCl2/SiO2 composite – water” working pairs (table 2). Such good performance is due to a very high methanol sorption ability of the composite designed, specified for particular working conditions of the AC cycle. The attractive performance measured demonstrates that the new composite sorbent can be efficiently used for realization of light and compact adsorption chiller driven by low grade waste or solar heat.

0.8

1

0.6

2

0.4

0.2

0 70

80 Tdes, C

90

o

Figure 15. Cooling COP for composite LiCl(20%)/SiO2(15 nm) (1) and commercial activated carbon AC35 (2), calculated at Tev = 10 °C and Tc = Tads = 35 °C.

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Table 2. Performance of various working pairs measured in the CNR-ITAE lab-scale adsorption chillers Working pair LiCl/SiO2 – methanol CBV901 zeo – methanol SWS-1L – water SWS-1L – water

Bed configuration Loose grains on finned flattube heat exchanger Layer coated on finned tubes heat exchanger Loose grains on finned tubes heat exchanger Layer coated on finned tubes heat exchanger

COP

Tdes, K

SCP, W/kg

0.32–0.4

353–368

210–290

0.1–0.12

353–368

30–60

0.4–0.6

363–373

20–40

0.15–0.3

363–373

150–200

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2.2. Shifting the Equilibrium in Methanol Synthesis

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The methanol synthesis from carbon monoxide and hydrogen is one of the most important processes in chemical industry. Conversion of the reactants in the synthesis is limited by the reaction thermodynamics. Due to unfavorable thermodynamics, the methanol synthesis is conducted over a catalyst at high pressure (5-10 bars), but only a fraction of raw materials converted. This requires recycling of the reactants and increases the energy consumption and the product cost. Removal of the product from the reactor by means of its adsorption by an adsorbent is considered as a promising way to increase the conversion of reversible reactions [69, 70]. The idea of binding methanol with adsorbent in the syngas reaction in countercurrent gas-solid-solid trickle flow reactor (CGSSTFR) in order to increase the conversion above the equilibrium one was suggested in [10, 12]. Fine particles of methanol adsorbent are trickled through the fixed catalyst bed countercurrently to syngas. The adsorbent selectively removes the methanol as soon as it forms and the conversion of 100% can be achieved. The circulation of solids stream, particularly in high pressure processes, encounters many problems on an industrial scale. To avoid the problems, a simulated countercurrent moving bed process was suggested instead of moving bed operation [11]. In a simulated countercurrent moving-bed reactor (SCCMBR) simulated countercurrent operation is mimicked by periodically changing feed and product locations sequentially along a fixed bed. Two different configurations of such reactors were studied. In the former one, a catalyst and an adsorbent are jointly placed in fixed-bed sections. In the second type, a catalyst and an adsorbent are packed separately in two different beds – a reactor and an adsorber. The adsorbent characteristics affect the process performance dramatically in both the reactors CGSSTFR and SCCMBR [12, 20]. The most important parameters are: a) the adsorbent selectivity with respect to methanol; and b) the high sorption capacity under operating conditions of the process. Amorphous LA-25 low alumina cracking catalyst (Akzo, Amsterdam) used for methanol removal [12, 20] adsorbed methanol selectively but its equilibrium uptake w = 0.08 – 0.13 g/g was low that leads to rather high adsorbent recycle ratio of 15-20 tons of the adsorbent per 1 methanol ton.

2.2.1. Formulating the Requirements to the Optimal Adsorbent For formulating the mentioned requirements, first, the value of adsorption potential ΔFsyn under typical conditions of methanol synthesis was calculated (table 3). Two operation modes have been considered. The former is the industrial methanol synthesis, namely, the stoichiometric initial mixture CO/H2 = 1/2, P = 50 bar and T = 180 - 240°C [71]. The latter one is related to the methanol synthesis in a lab-scale tubular flow reactor: the initial mixture composition CO/CO2/N2/H2 = 30.0/2.0/3.2/64.8, the total pressure P = 20 bar and temperature T = 200 - 240°C. For both the modes, the equilibrium methanol content in the reaction mixture and, hence, the value of ΔFsyn can vary in quite wide range depending on the reaction temperature 0.6 < ΔFsyn < 5.4 kJ/mol and 4.0 < ΔFsyn < 15.1 kJ/mol for the industrial and laboratory converters, respectively. For the second mode, the adsorbent optimal for methanol fixation has to adsorb methanol at more severe conditions, means at higher value of ΔF because of the lower total pressure in the reactor.

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Table 3. The equilibrium methanol concentration Сeq(СН3ОН) and the threshold adsorption potential ∆Fsyn for the two modes of methanol synthesis. Сeq(СН3ОН), % Т, °C Р = 2 MPa, CO/CO2/N2/H2=30.0/2.0/3.2/64.8 180 49.5 200 34.9 220 21.6 240 11.4 Р = 5 MPa, CO/H2=1/2 200 69 220 57 240 44

∆Fsyn, kJ/mol 4.0 7.0 10.6 15.1 0.6 2.8 5.4

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One more important demand is imposed by the fact that the methanol adsorbed should be easily extracted from the adsorbent at regeneration stage, for instance, by a pressure swing desorption method. Hence, the bonding between methanol molecules and the adsorbent should not be too strong in order to minimize purge gas and energy consumption. It is optimal that the desorption proceeds at the free sorption energy ΔFdes, which is just a little bit higher than ΔFsyn. Hence, a compromise between large adsorption at quite high temperature and easy regeneration has to be reached. And finally, the optimal adsorbent should be chemically inert and thermally stable under synthesis conditions.

2.2.2. The Composite Preparation Analysis of the data on methanol - salt equilibrium for the bulk salts was performed in order to select salts appropriate for shifting synthesis equilibrium under the two mentioned modes (table 1) [42-47]. Majority of the salts react with methanol vapor at the adsorption potential ∆Fr ≤ 5 kJ/mol that is lower than the required value ∆Fsyn. Among the salts, LiBr, Mg(NO3)2 and CaCl2 appear to be of benefit (∆Fr = 9.5, 6.9 and 12.0 kJ/mol respectively), thus meeting the formulated requirements. Unfortunately Mg(NO3)2·6CH3OH, can hardly be used because of its thermal instability [72]. The adsorption potential of Ca(NO3)2 solvatation ∆F = 4.5 kJ/mol is a little bit lower than the required value. However, confinement of the salt to matrix pores probably shifts the solvatation toward higher adsorption potentials. Thus, LiBr, CaCl2 and Ca(NO3)2 have been selected for synthesis of CSPMs for methanol reversible binding under the conditions of methanol synthesis. Composites LiBr(31%)/SiO2(15 nm), CaCl2(28%)/SiO2(6 nm) and Ca(NO3)2(34%)/SiO2(15 nm) were prepared by the dry impregnation method. 2.2.3. The Composite Testing The sorption capacity of the composites measured at temperature T = 20-130°C and methanol pressure PMeOH = 60-300 mbar is 2-3.5 times higher than that for conventional LA25 adsorbent in the whole range of adsorption potentials (figure 16) [20, 50, 58]. This gives a base for a good performance of the composites in the shifting the equilibrium of methanol synthesis. The ability of new composites to adsorb methanol vapor under typical operating conditions of methanol synthesis was tested by continuous flow method at the total pressure P = 20 bar, temperature T = 220 °C and composition of the feeding gas mixture, described

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above. Methanol synthesis was carried out in the reactor loaded with 8 g Cu-Zn-Al catalyst mixed with quartz particles. A contact time τ was 20-25 s that provides the conversion close to the equilibrium one (Ceq(CH3OH) = 22 vol. %). The reactor outlet gas mixture was passed through an adsorber loaded with the composite adsorbent (9 – 12 g). The composition of the outlet mixture was analyzed by chromatographic technique using flame-ionization and thermal conductivity detectors.

0,7

0,5

1

2

0,3 3 0,1 2

3

4

5

6

7

8

9

ΔF, kJ/mol

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Figure 16. Methanol sorption as a function of the adsorption potential ΔF: LiBr/SiO2(15) (1) and CaCl2/SiO2(15) (2) composites, the commercial adsorbent LA-25 (3).

At the beginning of the experiments in the lab-scale reactor, the methanol concentration in the adsorber outlet flow was Cout(CH3OH) = 1.1 - 6.0 vol. % for all the composites that was significantly lower than the methanol concentration in the reactor outlet gas mixture, which feeds the adsorber, or Ceq(CH3OH). This demonstrated that all the composites adsorbed methanol under conditions of laboratory methanol synthesis. In the course of time the outlet methanol concentration was continuously increasing but remained lower than the equilibrium value during at least 8-10 hours, showing rather large capacity of the adsorbents (figure 17). The CaCl2/SiO2 and Ca(NO3)2/SiO2 composites demonstrated the better performance and ensured Cout(CH3OH) < 10 vol. % for 5-8 hours. It is worth noting that the composites were tested under rather severe experimental conditions (P = 20 bar, T = 220°C) at the value of adsorption potential ΔF = 10.6 kJ/mol. Higher pressure typical for conventional methanol synthesis (P = 50-100 bar) would give larger equilibrium methanol concentration in the synthesis and, consequently, higher adsorption potential that could favor larger sorption capacity of the composites. Thus, at high-pressure methanol synthesis the tested adsorbents could demonstrate better performance. XRD analysis did not reveal any change in the phase composition of Ca(NO3)2)/SiO2 composite that preliminary demonstrated its thermal and chemical stability under reaction conditions.

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4 20

1

2

3 10

0

5

10

15

Time, hour Figure 17. Methanol concentration in the outlet mixture after methanol adsorption on LiBr/SiO2(15) - 1, Ca(NO3)2/SiO2(15) – 2 и CaCl2/SiO2(6) - 3 as well as the equilibrium one (4).

Thus, the composite adsorbent Ca(NO3)2)/SiO2, which was intently designed for shifting the equilibrium of methanol synthesis, demonstrated a high methanol sorption capacity under operating conditions of methanol synthesis. The composite testing in the lab-scale reactor of methanol synthesis confirmed its feasibility to increase the conversion in methanol synthesis.

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2.3. Methanol Removal from Gas Mixtures Volatile organic compounds (VOCs) which possess strong toxicity contribute in essential scale to atmospheric pollution. Methanol, which is often used in the processes of car painting, affects directly on human or animal tissues [24]. Nowadays the reduction of VOCs emission is attempted. The adsorption is suggested as a promising way of reduction in VOCs emission [73]. Activated carbons are usually considered as adsorbents for removal of VOCs. However their sorption capacity is quite low. For this reason, other related materials for VOCs (methanol particularly) removal are welcome [4-6, 24]. The embedding of the salt inside pores of the common adsorbents raises their sorption ability dramatically. So, the design of the CSPM for methanol removal can be a good solution of the problem mentioned. The main demands to the adsorbent for methanol removal relate to a) adsorption capacity or amount of methanol sorbed before its concentration in outlet flow reaches a maximum permissible value (breakthrough), and b) purification efficiency, or outlet concentration of methanol vapor skipped through the adsorbent layer. In order to define the requirements to the optimal adsorbent the Polanyi principle of temperature invariance is used. The adsorption capacity of the adsorbent under conditions of methanol abatement can be estimated on the base of its temperature invariant curve of methanol sorption as the equilibrium methanol uptake weq at ηads corresponding to the

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methanol partial pressure Pads and temperature Tads in the inlet gas flow weq = f(ηads) = f(Pads/P0(Tads)). The actual dynamic sorption capacity wdyn in a flow adsorber usually is lower than the estimated weq. However, in well-designed adsorbers, wdyn can be quite close to weq. To reach this, the adsorber length Lads should be much longer than a width of adsorption front λ. In the case of convex shape of the methanol sorption isotherm the adsorption front is getting narrower while propagating along the adsorber [74], and the dynamic capacity is approaching the static (or equilibrium) one. The second demand related to the purification efficiency can be defined as a methanol relative pressure ηMPC at which the adsorbent still has to sorb methanol vapor. The ηMPC can be calculated from the maximum permissible concentration MPCMeOH (mole fraction) in outlet gas flow as a ratio

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ηMPC = (MPCMeOH·P)/P0(Tads), where P is the total pressure, P0(Tads) is the saturated methanol pressure at the adsorption temperature Tads. It is worth noting that at low uptakes the adsorption of methanol by CSPMs is due to its interaction with active surface centers of the matrix (figures 1, 2) [50]. For this reason the salt should be embedded in pores of the matrix possessing high enough affinity to methanol vapor, and regeneration has to be performed at temperature Tdes that is high enough to activate these centers. The common way of adsorbent regeneration is its heating up to temperature Tdes under the air flux containing the residual methanol at the partial pressure Pdes, that corresponds to its relative pressure ηdes = Pdes/P0(Tdes), where P0(Tdes) is the saturated methanol pressure at the desorption temperature. If desorption is accomplished by purging the adsorber by air flow, free from methanol vapor, the temperature Tdes can be quite low. Thus, the optimal adsorbent for methanol removal from gaseous mixture should possess large variation in methanol uptake between the two mentioned values of the relative pressure of methanol ηads and ηdes, which correspond to the conditions at adsorption and regeneration stages. Hence, the requirements to the adsorbent optimal for methanol abatement depend on the conditions of particular technological process: Pads, Tads, Pdes and Tdes. Methanol is a reactant for a great number of industrial syntheses. Moreover, in many processes it can be formed as a by-product. A target product is contaminated by unreacted or formed methanol, which has to be removed to obtain clean product. Typical methanol output is ranged between 0.5-5.0 vol. %, and its partial pressure in the outlet stream equals Pads = 5 – 50 mbar (at the total pressure 1 bar). This gives at Tads = 20 °C the relative pressure ηads = Pads/P0(20 °C) = 0.04 – 0.4. Under these conditions, the sorption capacity of LiBr(29 wt%)/ SiO2(15 nm) composite reaches weq = 0.2-0.8 g/g, that far exceeds the methanol uptake on unmodified silica gel (0.05-0.15 g/g) (figure 1), activated carbons, zeolites, pillared clays, modified silica gels, etc. (weq = 0.1-0.4 g/g) [19, 24, 26, 29, 75]. This allows appropriate reduction of the adsorbent loading and the apparatus size. This preliminary evaluation demonstrates the advantages of CSPMs over common porous adsorbents used for methanol removal from flue gases.

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CONCLUSION In this communication we discuss the new approach of target-oriented design of the composite methanol adsorbents “salt in porous matrix” with sorption properties close to those which perfectly fit the demands of particular applications. It was proved that the phase composition and the sorption equilibrium of composites with methanol vapor can be intently managed by intelligent choice of the suitable salt, the average size of pores of the host matrix and modification of a basic salt with a supplementary salt to form proper solid solution inside the pores. All these tools can be used to adjust the real adsorbent to the optimal one which has been theoretically predicted before synthesis. Using this approach the requirements to such optimal adsorbent imposed by three important processes, namely, the adsorption cooling, shifting the equilibrium of catalytic methanol synthesis and methanol removal from gas mixtures, were formulated. This speculative image of the optimal adsorbent was used as a guide-star for synthesis of real CSPMs adapted to the first two processes. Testing of the new composites in appropriate lab-scale prototypes demonstrated their superiority to known single-component adsorbents that opens up encouraging opportunities of further application of these novel adsorbents.

ACKNOWLEDGMENTS This work was partially supported by the Russian Foundation for Basic Researches (project 09-03-00916a).

REFERENCES [1] [2]

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[3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13]

Yang, R. T. Adsorbents Fundamental and Applications; John Willey & Sons, Inc.: New Jersey, USA, 2003; 410 p. Groszek, A. In Adsorption and its Applications in Industry and Environmental Protection; Dabrowski, A.; Ed.; Elsevier: Amsterdam, NL; 1999; pp 143-175. Dabrowski, A. Adv. Colloid Interface Sci. 2001, 93, 135-224. Dekany, I.; Szanto, F.; Armin, W.; Lagaly, G. Ber. Bunsen-Ges. Phys. Chem. 1986, 90 422-427. Goworek, J.; Swiatkowski, A.; Zietek, S. Mater. Chem. Phys. 1989, 21, 357-365. Jerabek, K.; Prokop, Z. React. Polym. 1992, 18, 221-227. Clausse, M., Alam, K. C. A., Meunier, F. Solar Energy 2008, 82, 885-892. Wang, L. W.; Wang, R. Z.; Wu, J. Y.; Wang, K.; Wang, S. G. Energy Convers. Managem. 2004, 45, 2043-2057. Restuccia, G.; Freni, A.; Russo, F.; Vasta, S. Appl. Therm. Eng. 2005, 25, 1419-1428. Kuczynski, M.; Browne, W. I.; Fontein, H. I.; Westerterp, K. R. Chem. Eng. Sci. 1987, 42, 1887-1898. Kruglov, A. V. Chem. Eng. Sci. 1994, 49, 4699-4716. Westerterp, K. R.; Kuczynski, M. Chem. Eng. Sci. 1987, 42, 1871-1886. Aristov, Yu.I., J. Chem. Engn. Japan, 2007, v. 40, N 13, pp. 1241-1251.

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Larisa G. Gordeeva and Yuriy I. Aristov

[14] Leite, A. P. F.; Grilo, M. B.; Andrade, R. R. D.; Belo, F. A.; Meunier, A. Renewable Energy 2007, 32, 697-712. [15] Hamamoto, Y.; Alam, K. C. A.; Saha, B. B.; Koyama, S.; Akisawa, A.; Kashiwagi, T. Int. J. Refrig. 2006, 29, 315-327. [16] Dieng, A. O.; Wang, R. Z. Renewable Sustainable Energy Rev. 2001, 5, 313-342. [17] Gordeeva, L.; Aristov, Yu.; Freni, A.; Restuccia, G. In Proc. Int. Sorption Heat Pump Conf.; 2002, September 24-27; Shanghai, CN; p. 625. [18] Janchen, J.; van Wolput, J. H. M. C.; van Well, W. J. M.; Stach, H. Thermochim. Acta 2001, 379, 213-225. [19] Halasz, I.; Kim, S.; Marcus, B. J. Phys. Chem. B 2001, 105, 10788-10796. [20] Kuczynski, M.; Westerterp, K. R. Hydrocarb. process. 1986, 80-83. [21] Mirji, S. A.; Halligudi, S. B.; Mathew, N.; Jacob, N. E.; Patil, K. R.; Gaikwad, A. B. Mater. Lett. 2007, 61, 88-92. [22] Shim, W. G.; Lee, J. W.; Moon, H. Micropor. Mesopor. Mater. 2006, 88, 112-125. [23] Jiaohuan, L.; Xifu Yu; Ion Exch. Adsorpt. 1992, 8, 44-47. [24] Pires, J.; Carvalho, A.; De Carvalho, M. B. Micropor. Mesopor. Mater. 2001, 43, 277287. [25] Mirji, S. A.; Halligudi, S. B.; Mathew, N.; Ravi, V.; Jacob, N. E.; Patil K. R. Colloids Surf. A: Physicochem. Eng. Aspects 2006, 287, 51-58. [26] Nasuto, R. J. Therm. Anal. Calorim. 2000, 62, 581-585. [27] Schenkel, R.; Barth, J. O.; Karnatowski, J.; Jentys, A.; Lercher, J. A. Stud. Surf. Sci. Catal. 2004, 154, 1598-1605. [28] Kang, L.; Zhang, T.; Liu, Z.; Han, K.-L. J. Phys. Chem. C 2008, 112, 5526-5532. [29] Fletcher, A. J.; Cussen, E. J.; Bradshaw, D.; Rosseinsky, M. J.; Thomas, K. M. J. Am. Chem. Soc. 2004, 126, 9750-9759. [30] Khattak, A. K.; Mahmood, K.; Afzal, M.; Saleem M.; Qadeer R. Colloids Surf. A 2004, 236, 103-110 [31] Aristov, Yu.I. In Zeolites: Structure, Properties and Applications. Wong T.W.; Ed.; 2009, Nova Science Publishers (in press). [32] Gordeeva, L. G.; Aristov Yu. I. In Topics on Chemistry and Material Science; Hadjiivanov, K.; Valtchev, V.; Vayssilov, G.; Eds; Heron Press: Sofia, BU, 2008; Vol. 1, pp 1-6. [33] Gordeeva, L. G.; Aristov Yu. I. Kin. Cat. 2009, 50, 65-72. [34] Polanyi, M. Trans. Farad. Soc. 1932, 28, 316-333. [35] Dubinin, M. M. Progress in Surface and Membrane Science; Cadenhead A.; Ed.; Academic Press: New York, USA, 1975; Vol. 9, pp 1-70. [36] Yang, R. T. Adv. Chem. Eng. 2001, 27, 79-124. [37] Kluson, P.; Scaife, S.; Quirke, N. Separ. Purif. Technol. 2000, 20, 15–24. [38] Fleming, H. L. Stud. Surf. Sci. Catal. 1999, 120, 561-585. [39] Freni, A.; Russo, F.; Vasta, S.; Tokarev, M. M.; Aristov, Yu. I.; Restuccia, G. Appl. Therm. Engn. 2007, 27, 2200-2204. [40] Glaznev, I.; Alekseev, V.; Salnikova, I.; Gordeeva, L.; Shilova, I.; Elepov, B.; Aristov, Yu. Stud. Conserv. (in press). [41] Tanashev, Yu. Yu.; Parmon, V. N.; Aristov, Yu. I. J.Eng.Physics Thermophysics. 2001, 74, 1053-1058.

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Nanocomposites (Salt inside Porous Matrix) for Methanol Sorption

137

[42] Offenhartz, P. O'D.; Brown, F. C.; Mar, R.; Carling, R. W. J. Sol. Energ. – T. ASME. 1980, 102, 59-65. [43] Gmelins Handbuch der Anorganischen Chemie, Calcium Eraganzungs band. Pietsch. E. H. E.; Ed.; Verlag Chemie GmbH: Weinheim, GE, 1957; Sn. 28, Tl. B, Rf. 2. [44] Bixon, E.; Guerry, R.; Tassions, D. J. Chem. Eng. Data 1979, 24, 9-11. [45] Loid, E.; Brown, C. B.; Bonnel, D. G. R.; Jones., W.J. J. Chem. Soc. 1928, Part I, 658666. [46] Glynwyn, D.; Bonnel, R.; Jones, W. J. J. Chem. Soc. 1926, 321-328. [47] Menschutkin, B.N. Z. Anorgan. Chem. 1907, 52, 9-24. [48] Andersson, J. Y. Kinetic and mechanistic studies of reactions between water vapour and some solid sorbents; Department Phys. Chem., The Royal Institute of Technology: Stockholm, SW; 1986; pp 27-44. [49] Gordeeva, L. G.; Freni, A.; Restuccia, G.; Aristov, Yu.I. Ind. Eng. Chem. Res. 2007, 46, 2747-2752. [50] Gordeeva, L.; Freni, A.; Krieger, T.; Restuccia, G.; Aristov, Yu. Micropor. Mesopor. Mater. 2008, 112, 264-271. [51] Lyakhov, N. Z.; Boldyrev, V. V. Russ. Advanc. Chem. 1972, 41, 1960-1996 (in Russian). [52] Aristov, Yu. I.; Tokarev, M. M.; Cacciola, G.; Resticcia, G. React. Kinet. Catal. Lett. 1996, 59, 325-334. [53] Gordeeva, L. G.; Restuccia, G.; Freni, A.; Aristov, Yu. I. Fuel Proces. Technol. 2002, 79, 225-231. [54] Gordeeva, L. New Materials for Thermochemical Eenergy Storage; Ph.D. dissertation, BIC: Novosibirsk, RU, 1998; 170 p (in Russian). [55] Sergeev, G. B. Nanochemistry; Elsevier: Amsterdam, NL; 2006. [56] Simonova, I. A.; Aristov, Yu. I. Rus. J. Phys. Chem. 2005, 79, 1477-1481. [57] Tokarev, M. M.; Kozlova, S. G.; Gabuda, S. P.; Aristov, Yu.I. Rus. J. Struc. Chem. 1998, 39, 212-216. [58] Aristov, Yu. I., Gordeeva, L. G., Pankratiev, Yu. D., Plyasova, T. M., Bikova, I. V., Freni, A., Restuccia, G. Adsorption, 2007, 13, 121-127. [59] Gillier-Pandraud, H.; Philoche-Levisalles, M. C. R. Acad. Sci. 1979, 273, 949-951. [60] Aristov, Yu. I.; Tokarev, M. M.; Cacciola, G.; Restuccia, G. React. Kinet. Cat. Lett. 1996, 59, 335-342. [61] Gordeeva, L. G.; Glaznev, I. S.; Savchenko, E. V.; Malakhov, V. V.; Aristov, Yu. I. J. Colloid Interface Sci. 2006, 301, 685-691. [62] Feilchenfeld, H.; Fuchs, J.; Kahana, F.; Sarig, S. Solar Energy 1985, 34, 199-201. [63] Liu, C. Yi; Aika, K. Ind. Eng. Chem. Res. 2004, 43, 7484-7491. [64] Liu, C. Yi; Aika, K. Ind. Eng. Chem. Res. 2004, 43, 6994-7000. [65] Gordeeva, L.; Grekova, A.; Krieger, T.; Aristov, Yu. Micropor. Mesopor. Mater. 2009 doi:10.1016/j.micromeso.2009.06.015 [66] Alefeld, G.; Radermacher, R. Heat Conversion Systems; CRC Press Boca Raton Ann Arbor: London, Tokyo, 1994; 304 p. [67] Chernev, D. In Proc. Int. Sorp. Heat Pump Conf., 1999, March 24-26; Munich, DE; p. 65. [68] Gordeeva, L. G.; Freni, A.; Aristov, Yu. I.; Restuccia, G. Ind. Eng. Chem. Res. 2009, 48, 6197–6202.

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[69] Carr, R. W. In Preparative and Production Scale Chromatography; Ganetson, G.; Barker P. E.; Eds; Marcel Dekker: New York, USA, 1992; pp. 421-447. [70] Roes, A. W. M.; Van Swaaij W. P. M. Chem. Engng. J. 1979, 17, 81-89. [71] Haut, B.; Halloin, V.; Ben Amor, H. Chem. Eng. Proc. 2004, 43, 979-986. [72] Encyclopedia of chemical reactions VII.;, Jacobson C. A.; Ed.; Reinold Publishing Corporation: New York, USA; 1951, p 427. [73] Ruhl, M. J. Chem. Engng. Prog. 1993, 37. [74] Ruthven, D.; Principles of Adsorption and Adsorption Processes, John Willy & Sons, New York, U.S.A. (1984). [75] Nunes, C. D., Pires, J., Carvalho, A. P., Calhorda M. J., Ferreira, P. Micropor. Mesopor. Mater. 2008, 111, 612-619.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

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Chapter 4

A NOVEL USE OF SORBENTS FOR PHOTOCHEMICAL STUDIES: PHOTO-SOLID-PHASE MICROEXTRACTION (PHOTO-SPME) Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez, Carmen García-Jares and Marta Lores Departamento de Química Analítica, Nutrición y Bromatología, Facultad de Química, Instituto de Investigación y Análisis Alimentario, Universidad de Santiago de Compostela, Avda. das Ciencias s/n, 15782 Santiago de Compostela, Spain

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ABSTRACT Photo-SPME has recently been developed in our laboratory as a useful technique in elucidating the photodegradation mechanisms of a variety of environmental pollutants, permitting the simultaneous analysis of both primary compounds and photoproducts. This technique, in which a SPME fibre is used as support for photochemical studies, can be considered as an important innovation among SPME developments. Main kinetic parameters, the identity and photochemical behaviour of photoproducts, as well as the photodegradation pathways have been obtained for emergent pollutants or well-established substances of environmental concern (polycyclic and nitro musks, triclosan, PCBs, PBDEs, PAHs, pesticides). In addition to the successful results obtained with model solutions and controlled UV-irradiation conditions, photo-SPME has also demonstrated to be useful when extended to environmental conditions using real water samples and simulated solar irradiation. Comparison between photo-SPME with aqueous photodegradation followed by normal or classical SPME has been performed, underlining the advantageous use of photo-SPME in environmental photodegradation studies. It is worth noting the novelty of many of the applications, such as musks, PBDEs, triclosan and pyrethroid insecticides for which the data of photochemical degradation were scarce or nonexistent. In summary, in this chapter, the state-of-the-art and the advantages of using solidphase microextraction (SPME) fibres as a support for photochemical studies are reviewed and fully discussed. Trends and applications of photo-SPME to fields different of environmental are also explored.

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Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez et al.

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1. INTRODUCTION The extensive use of different organic chemicals in order to improve our life quality remains a substantial public concern due to the potential and, in most of the cases, unknown hazards associated with the exposure to these products. Persistent Organic Pollutants (POPs) are in general lipophilic and can be characterized as toxic, stable, and having a tendency to bioaccumulate and biomagnify [1]. Depending on the environmental compartment in which compounds are present, they undergo changes resulting from different chemical, physical, biological, or photochemical processes [2]. The rates of these processes depend on the compound and the matrix in which it is present, as well as on a variety of environmental factors. The result of these processes is the formation of new degradation products that may be more or less harmful for the environment and/or for human health than the original compounds. The studies about the degradability of POPs are crucial to establish the hazards associated to these compounds widespread in the environment. But these kind of studies are also indispensable for other purposes such as: (a) the research about the composition of environmental samples; (b) the degradation of organic compounds during the storage either of the sample or the chemical compounds themselves (for instance in the laboratory); and (c) to increase the knowledge about the effectiveness of the degradation in the cleaning up processes of particular contaminated compartments. These studies of degradability are carried out not only to know the degradation rate of the target compound, but also to determine the presence of its degradation products. These degradation products are usually the result of the modification of particular functional groups in the original compounds. The knowledge on the photochemical behaviour of organic pollutants is a key issue in terms of the formation and persistence of toxic transformation products. Therefore, the understanding on the fate of the organic pollutants is a fundamental question and one of the processes which mainly determine the fate of the contaminants is the photodegradation. Photodegradation and biodegradation are the major degradation processes which in principle can naturally clean the environment. Photodegradation, as a chemical reaction that occurs under the influence of photons or light, may take place in the atmosphere and on the surface of either water or soil [2]. In addition to visible light and infrared (IR) radiation, the sun emits ultraviolet (UV) radiation in the 290-400 nm range. Approximately 4 % of the total energy contained in sunlight occurs in the UV band. The intensity of the UV radiation depends on many factors: time of the year, time of day, latitude, height above the sea level, air density, cloud cover or the size of the ozone hole, among others [3]. The photodegradation can follow direct or indirect mechanisms. Direct photolysis takes place if the chemical absorbs light itself and then undergoes a transformation reaction from a excited state; whereas in indirect photolysis, naturally occurring substances may absorb light energy, which is then transferred to the chemical to form free radicals or to promote redox reactions that result in the transformation of the pollutant [4,5]. The studies about the photodegradation kinetics and pathways of organic pollutants have a considerable complexity due to different aspects such as: (a) the number of target compounds with completely different chemical and physical properties; (b) the formation of a wide range of different secondary products through a variety of multistep reactions involved in photodegradation; and (c) the complexity of the environmental matrices due to the

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presence of compounds, frequently at high concentrations, which may interfere with the analytes, and the very low concentration levels of the contaminants in the environmental samples [2]. The photodegradation studies are normally performed in several steps (figure 1):

1. Irradiation of the sample containing the target analytes, usually with UV lamps, sunlight simulators or natural sunlight.

2. Extraction of the target analytes and their byproducts. The expected concentrations of

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the degradation products are typically very low, so it is necessary to preconcentrate the sample or isolate the by-product, usually by Liquid-Liquid Extraction (LLE) [6,7] or Solid Phase Extraction (SPE) [8-10]. Some researchers have also employed the Solid-Phase Microextraction (SPME) as extraction procedure [6,11-13]. 3. Determination and analysis of the parent compound and the variety of products that may be formed. The identification is done, in most of the cases, by GC-MS or LCMS. As it was just mentioned, “classical” photodegradation studies can be carried out by LLE. This process entails several disadvantages: the sensitivity is not always enough to determine byproducts which can be formed in a very low concentration, and thus usually several steps of pre-concentration should be carried out, increasing the time and tediousness of the analysis and the possibility of making errors. The possibilities of losing some of the generated photoproducts are also drastically increased. Besides, the use of organic solvents is usually required, which are harmful for the environment and the operator (against of the principles of the “green chemistry”). In order to avoid some of these disadvantages, LLE has been replaced for SPE. But this methodology is also a multistep technique; therefore the time of each analysis and the possibility of byproducts losses are still high. Some of the previously commented disadvantages are prevented when the SPME is used as extraction and pre-concentration technique. SPME is a solvent free sample preparation technique developed in the beginning of the 1990s by J. Pawliszyn and coworkers [14,15]. Compared with traditional sample preparation techniques, SPME can be characterized as a fast, sensitive and economical approach, following the trend of “green chemistry” [16], since it eliminates the use of toxic solvents and saves labour and energy consumption in the analytical procedure, by combining the sample preparation and analysis in one step. In SPME, silica fibres coated with different sorbents are used to extract analytes from solid, aqueous or gaseous samples. After the extraction, the fibres can be desorbed by using small amounts of organic solvents or transferred directly into the injection port of the gas chromatograph to be thermally desorbed. SPME can be considered currently a matured technique which theoretical basis are described in a number of books [17,18] and its applications can be found in a enormous number of papers (e.g. [19-22]) as well as in some text books [23,24].

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Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez et al. 2. Extraction step. Mainly used: Drying agent

Liquid-liquid extraction (LLE):

N2

1. Extraction. 2. Drying. 3. Concentration.

hν

x3

Organic solvent

Solid phase extraction (SPE):

Sample N2

1. Irradiation: -UV lamps -sunlight simulator -natural sunlight

1. Preparation of the sorbent. 2. Sample application. 3. Drying. 4. Elution. 5. Clean and concentrate the extracts.

3. Analysis: GC-MS LC-MS

Steps SPE Solid Phase Microextraction (SPME): Extraction, preconcentration and injection in one step.

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Figure 1. “Classical” setup in the organic compounds photodegradation studies.

SPME has been applied in environmental sampling, food and pharmaceutical analysis. The polymeric coatings of the fibre have been used for the analysis of environmental pollutants in air [25,26], water [27-29], soil [30,31], and sediment samples [31,32]. Obviously, the cited references are just a small number of examples from the wide number of scientific works involving SPME applications. Another interesting application is the analysis of polar compounds by "in situ" derivatization in the sample [33] or on the SPME coating [34,35]. In this way it is possible to increase the recovery, selectivity and sensibility of the method, allowing the determination of substances with poor chromatographic response, high reactivity or thermally unstable. We have demonstrated that SPME can be applied for running photodegradation studies of organic compounds. In this proposed setup, the fibre coating is not only the extractant phase, but also the medium in which the photodegradation takes place. In this chapter, the state-ofthe-art and the advantages of using SPME fibres as a support for photochemical studies are reviewed and fully discussed. Photo-SPME has been applied to the photodegradation studies of different families of pesticides, synthetic fragrances, flame retardants, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and triclosan. The utility of the acquired data, trends and applications of photo-SPME to fields different of environmental are also explored.

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2. WHAT IS PHOTO-SPME? Using Photo-SPME (photodegradation in the fibre), the irradiation of the analytes takes place after the extraction, that is, when the fibre is already loaded with the analytes. The sequence of the process consists of three simple steps: (a) SPME of the sample; (b) irradiation of the fibre; and (c) injection of the fibre in the chromatographic system. The main innovation of this setup is that byproducts are generated in-situ in/on the fibre coating and directly inserted in the injection port of the chromatograph obtaining, in this way, high preconcentration levels and avoiding possible losses and artefacts formation. In a recent review about the advances in the determination of degradation intermediates of personal care products (PCPs) in environmental matrixes [36], the importance of establishing the chemical stability of the parent compounds is stressed out, since some of the degradation intermediates could also be produced as artefacts during the sampling handling. Photo-SPME clearly avoids these problems in photodegradation studies given that sample manipulation is minimised. Therefore, the advantages of the Photo-SPME can be resumed in the following points: The use of organic solvents is avoided, so Photo-SPME is an environmental friendly procedure. b. No tedious steps for the extraction of the target analytes and their byproducts are required, so the time to complete the photodegradation study of a given substance is shortened drastically. c. The formation of the byproducts takes place in the fibre, so their possible losses are minimised. d. It is possible to work at concentration levels similar to the ones found in the environment because of the high pre-concentration of the organic compounds in the SPME fibre. e. Compared with conventional assemblies, it is much easier to irradiate the fibre. Besides, the simplicity and lightness of the fibre greatly facilitated the field studies.

a.

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By Photo-SPME is possible to state the photodegradation kinetics of the analytes of interest, to identify formed byproducts and to establish the photodegradation pathways of the target compound. But also it is possible to study the evolution of these new formed degradation products with the irradiation time (photo-formation and decay kinetics).

3. HOW PHOTO-SPME WORKS? The process of the photodegradation on the SPME fibre (Photo-SPME) is simple and mainly consists of the stages showed in the figure 2. The first step is the usual SPME procedure of the analytes from the sample, under favourable conditions associated to each compound or family of compounds when available. Once the SPME extraction is finished, the target analytes are absorbed in the polymeric coating of the SPME fibre. Then the fibre is exposed to the radiation for the selected time and injected in the chromatographic system [37].

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Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez et al. Irradiation of the loaded SPME fibre. Different irradiation sources can be used

Natural sunlight

UV Photo-Reactor Simulated sunlight

SPME holder Injection of the fibre in the chromatographic system.

SPME fibre Sample

Fibre loaded with the target analytes after SPME extraction

SPME standard procedure

Figure 2. Photo-SPME procedure.

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3.1. Selection of the Support Sorbent The efficiency of the SPME process depends on the distribution constant between the acceptor phase (polymeric coating) and the donor (sample). Therefore, for extraction purposes it is important to find out the appropriate SPME fibre for each family of compounds. Various SPME coatings, commercially available, differ in chemical composition, structure, and thickness, leading to a wide spectrum of possible extraction alternatives. The selection of the fibre is based on overall fibre performance with regard to sensitivity, stability, and repeatability as well as other criteria. But when the purpose is to take advantage of the SPME to perform photodegradation studies, the commercial fibre coatings must be tested to establish if the absorbed/adsorbed analytes are photodegraded when the fibre is exposed to the radiation. For all the studied pollutants and under the selected irradiation conditions, the photodegradation took place significantly only in polydimethylsiloxane coating (PDMS). With other coatings such as carboxen/PDMS (CAR/PDMS), PDMS/divinylbenzene (PDMS/DVB), polyacrylate (PA) or carbowax/DVB (CW/DVB), the evaluation of the analytical responses indicated that the extent of photodegradation was very limited or nonexistent. Studies on photodegradation of p,p’-DDT can illustrate this fact (figure 3). Comparing the results of all the fibres in the control experiments (no irradiation after the extraction procedure), it is evident that PDMS has the highest extraction efficiency for this pesticide and, in this case, the p,p’-DDT analytical response reduction also happens, in a significant way, only when this compound is absorbed in the PDMS coating. Using this sorbent as a support for carrying out photodegradation studies, the peak area obtained in the irradiation experiments was < 2% of that obtained in the control experiment. However, in some cases this polymeric coating is not the best for the extraction of the target analytes (e.g. atrazine, alachlor [38]), but the photodegradation is only significant in PDMS. This finding was confirmed for the rest of the organic pollutants studied. Therefore,

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PDMS should be used in order to carry out photochemical studies using the SPME fibre as the coating support or medium where the photodegradation takes places.

Peak area (counts)

1.2E+06

8.0E+05

4.0E+05

0.0E+00 PDMS

CAR-PDMS (X10) PDMS -DVB

PA (X10)

CW-DVB

Control (no irradiation) 30 min of UV irradiation

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Figure 3. Effect of the type of sorbent of the SPME fibre as a support for carrying out photochemical studies of DDT (HS-SPME: 5 mL of the solution in 22 mL vials, extraction temperature of 100 ˚C and extraction time of 30 min. Irradiation: 30 min of UV irradiation of the loaded fibre).

The absence of photoreactions in the other tested SPME coatings could be due to several reasons, such as the strong absorption of radiation by the sorbent material or changes in the molecular configuration of the compound when it is retained in those sorbents. In fact, the most likely is the first one, that supports the statement that PDMS is the perfect sorbent for photochemical studies; since PDMS, a saturated polymer, exhibits strong absorption at wavelengths below about 193 nm, but exhibits little or no absorption at 253.7 nm [39] which is consistent with the observed behaviour against the irradiation sources tested in photoSPME experiments. This finding is confirmed by Egitto and Matienzo [40] using UV/ozone treatment of PDMS to produce thin surface films of SiOx. They treated samples of PDMS film using various combinations of UV (184.9 nm and 253.7 nm) and ozone. When eliminating irradiation at 184.9 nm (that is, irradiation at 253.7 nm only), no change was observed for PDMS. Moreover, from a practical point of view, the fact that photodegradation only takes place in PDMS involves an additional advantage, since this coating is one of the most used in the determination of organic compounds (e.g. emergent pollutants) due to its, in some sense universal response. Additionally, this fact reduces significantly the time required to complete the photodegradation studies; since it is not necessary the evaluation of the response obtained for a given compound using the rest of the coatings. It should be recalled and emphasized that the aim of the proposed methodology is the study of the photodegradation behaviour of organic contaminants and the optimization of the SPME conditions is not essential.

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3.2. Irradiation Sources There are not limitations regarding the use of different radiation sources when the photodegradation studies are carried out employing the Photo-SPME procedure. Up to now, Photo-SPME has been successfully combined with UV radiation (254 nm), simulated sunlight (Suntest CPS) and natural sunlight. The main characteristics of each irradiation setup are described below. UV irradiation source: A laboratory-made photochemical reactor built with two low pressure mercury lamps (8 and 10 W, 254 nm), was used for the UV-Photo-SPME experiments. b. Simulated sunlight: The photodegradation experiments under simulated sunlight were conducted in a Suntest CPS photosimulator (Atlas Material Testing Solutions, Chicago, IL, USA) equipped with a Xenon arc lamp 1500W (NXe 1500B, Atlas) as the radiation source. The lamp is usually set to medium intensity (550 Wm-2); the correspondent light dose for 1 h of irradiation was 1980 kJ/m2. The internal temperature of the photosimulator was maintained at 35 ◦C. In this set-up, the fibre must be protected in a quartz vial during the irradiation, due to the powerful fans placed inside the chamber of the simulator. c. Natural sunlight irradiation: Solar irradiation Photo-SPME experiments are evidently carried out under the sun. For example, PBDEs trials were made on clear days during the summer season (13th and 14th of July, estimated radiation average: 565 Wm-2). The SPME fibre loaded with the target analytes was exposed to sunlight on the roof of our Research Institute at the University of Santiago de Compostela (Santiago de Compostela, Spain, 42◦52’N, 8◦33’W), from 10 a.m. to 8 p.m. (see figure 4). The total time of exposure in that particular experiment was 20 h over 2 days [41].

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a.

Figure 4. Layout of the SPME fibre when natural sunlight is used as irradiation source.

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3.3. Control Tests (Thermal and Dark Tests) In all the laboratory scale photodegradation studies it is crucial to ensure that the possible changes in the analytical response are due to the action of the photons; and, therefore, volatilization or thermal degradation does not lead to any significant losses. Dark and thermal tests must be carried out with this aim and the procedure is represented in the figure 5.

Spiked water sample

SPME procedure

A) Control

B) Irradiation studies

C) Thermal test

D) Dark test

Chromatographic analysis

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Figure 5. Steps carried out in the Photo-SPME studies to ensure that the decrease in the analytical response is due to photo-degradative processes. The time period must be equal in all the control steps.

In the thermal tests, after the extraction, the fibre is placed inside a laboratory heater at 50 ˚C, temperature high enough since in the photoreactors it never differs from the ambient value by more than ± 1 ˚C (UV) or 35 ˚C (Suntest experiments) due to the cooling devices (figure 5, path C). Dark tests (figure 5, path D) can be conducted by inserting the fibre, with the corresponding compounds absorbed, inside a glass vial covered with aluminium foil and by placing the assembly inside the reactor, sun simulator, or outside (when natural sunlight is employed as radiation source) for the required time. The response obtained from both tests is compared with the one obtained in the control experiment (figure 5, path A: direct GC-MS analysis after the SPME procedure) and with the one obtained when the loaded fibre is exposed to the radiation for the same time (figure 5, path B: SPME procedure, irradiation of the fibre and GC-MS analysis). Table 1. Comparative responses obtained after dark test, thermal test and UV irradiation of the PDMS sorbent (30 min) of four pesticides (Direct SPME, 5 mL of the solution in 10 mL vials at 25 ˚C) Pesticide Atrazine Alachlor Dieldrin Endrin

Response (%) Dark test 101 99 100 101

Thermal test 98 88 117 119

UV irradiation 12 90% after 10 min of UV irradiation. The photochemical degradation of Cashmeran (with no benzene ring) is slower, as confirmed by the slowest photodegradation rate. As it has been mentioned above, from the slopes of the straight-line equations resulting from the lnC vs. time plot (figure 6C), the kinetic parameters can be determined (table 2). It is worth commenting here that, kinetic data are obtained simultaneously for all the compounds present in the mixture to be studied in the same PhotoSPME experiment. Table 2. Kinetic parameters of polycyclic musks calculated from photo-SPME experimental data: apparent first-order rate constants (kap), half-life times (t1/2) and the correlation coefficients (r) for the straight lines Compound Cashmeran Phantolide Tonalide Celestolide

t1/2 (min) 4.9 2.2 1.6 1.1

kap (min-1) 0.143 0.314 0.436 0.648

r 0.994 0.998 0.998 0.978

5. DRAWING PHOTODEGRADATION PATHWAYS The first task is to identify the byproducts obtained by Photo-SPME, and then it is possible to propose photodegradation pathways for each of the studied compounds.

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5.1. Identification of Photoproducts In general, after the irradiation of the loaded SPME coating, a large number of photoproducts from the target analytes were detected. These new unknown compounds were identified when possible by authentic standard comparison (retention time, mass spectra). If the standards are not commercially available, the tentative identification was made through alternative procedures, as on the basis of interpretation and structural elucidation from their mass spectra, with the aid of the NIST MS library and using information found in the literature. Since quite a number of isomers were identified, structures of the degradation products were proposed by considering the most likely fragmentation patterns in MS or MS/MS experiments, taking into account chemical structural details such as the position of substituents (e.g. in PCBs and PBDEs). Eleven and thirty four de-halogenated photoproducts were obtained from the PCBs [43,44] and PBDEs [41,45,46] photodegradation studies, respectively. From PAHs, just eight byproducts could be determined under the experimental conditions, among them photogenerated ketones, as anthracenedione and dibenzo[b,e]oxepin-11(6H)-one from

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anthracene and 9h-fluoren-9-one from fluorene. Fifteen different transformation products were obtained in the Photo-SPME of DDT, DDE and DDMU [47]; fourteen from nitro musks [48] and thirty from polycyclic musks [42]; more than sixty from the pesticides irradiation experiments [38]; eight from triclosan [49-51]; and fourty-three from the photodegradation of ten pyrethroids insecticides and one synergist [52,53]. The proposed identity of some of these photogenerated compounds matched the photoproducts chemical structures suggested for other authors. In some other cases, as the nitromusks moskene and tibetene, the six polycyclic musks or some of the pyrethroids studied, no previous studies concerning photodegradation pathways could be found.

5.2. Photodegradation Mechanisms

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The main photodegradation mechanisms of all studied compounds were easily deduced by photo-SPME. For PCBs and PBDEs, reductive dehalogenation is the first reaction, but in PBDEs the formation of furans by intramolecular cyclization has also been confirmed by this technique. These two reactions, among others like oxidation, reduction, isomerization, hydroxylation and the lost of alkyl radicals, have also been observed in pesticides, insecticides and musks. On some occasions, the photodegradation of a particular analyte has multiple simultaneous pathways. For example, the main photoproduct of atrazine is generated through the chlorine atom loss, and this photoproduct can lose the ethyl group, an important reaction since the dechlorinated product of atrazine loses the phytotoxicity of its parent compound. However, atrazine also undergoes ethyl or isopropyl group losses or the formation of a hydroxylated photoproduct [38]. Besides characterizing the photochemical persistence of the byproducts, it is also important to evaluate their toxicity. We found several cases where the photoproducts were more toxic than the starting compounds (see some examples in figures 7 and 8). Thus: 1. Several specific PCB coplanar congeners that are structurally related to 2,3,7,8tetrachlorodibenzodioxin (TCDD) have toxicological properties similar to this compound. With the rapid degradation of PCB 180, through successive dechlorination steps, the toxic coplanar congener 77 is largely produced, and the toxic equivalents (TEQs) increased rapidly (figure 7A). 2. The photochemical conversion of triclosan into the highly toxic dichlorodibenzo-pdioxin (DCDD) (a polemic photo-formation because it seems to primary depend on the experimental conditions) has been confirmed in the experiments of triclosan photodegradation using photo-SPME under all the radiation sources (UV and simulated sunlight) (figure 7B). 3. Two dibromodibenzofurans and one tribromobenzofuran have been identified as photoproducts of PBDEs, as explained above (figure 7C). 4. Some byproducts do not present high acute toxicity, but they have tendency to bioaccumulate, increasing their bioavailability; and therefore their long term toxicity should be considered [54]. This is the case of the PBDEs byproducts obtained through reductive debromination (figure 7C).

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Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez et al. 5. The proposed photodegradation pathways obtained by UV photo-SPME of the pyrethroid insecticide cyphenothrin [52] are shown in figure 8. To our knowledge, this was the first published study about the photodegradation of this compound. In this case, the formation of 3-phenoxybenzaldehyde (P16) and (3phenoxyphenyl)methanol (P18) as photoproducts is of some concern, because of their reported ability to interact with hormonal receptors [55,56].

B

A

OH

OH Cl

PCB 180

Cl Cl

Monochlorophenol

2,4-Dichlorophenol

PCB 153

Cl

PCB 138

O

O Cl

Cl

Cl

OH

Triclosan PCB 118

Cl

O

2,8-Dichlorodibenzo-p-dioxin

PCB 105

OH

O

O

or Cl

Cl

Cl

Hydroxydichlorodibenzofuran?

O

Cl

Dichlorodibenzodioxin?

PCB 77

C

O

Brx

Br

O

hν ‐HBr Bry

Polybrominated diphenyl ethers

Brx

Bry

Polybrominated benzofurans

O

O

hν Brx

Bry

Polybrominated diphenyl ethers

Brx'

Bry'

x’+y’=x+y-n (n ≥ 1)

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Less brominated diphenyl ethers

Figure 7. Examples of formation of toxic compounds observed by photo-SPME from: (A) PCBs; (B) triclosan; and (C) PBDEs [49,50].

Other photoproducts identified by photo-SPME could also be more toxic than the original compounds, but they have not been studied yet, such as those obtained in musks photodegradation studies.

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153

(-H) m/z 181 +

+O

O m/z 83

O CN

(+H) m/z 225 O

O

O

OH

O P22

CN

O

P1

O

P2

O

O + m/z 111

O

HO

O CN

O

P16

isomer P23

O

-CH

CN cyphenothrin

+

m/z 55

m/z 98 -CH3

NC

HO O

P21

O P18

H

O O

m/z 83

P16

Figure 8. Proposed photodegradation pathways for the pyrethroid insecticide cyphenothrin, UV PhotoSPME experiments. P1, P16, P18, and P21 were identified by using the NIST mass spectra database. P2 and P22 were identified on the basis of their mass spectrum [52].

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6. KINETIC BEHAVIOUR OF THE PHOTOPRODUCTS It has just been mentioned that one important issue about the photodegradation studies of organic pollutants is the identification of the generated byproducts. These new compounds are formed through radical reactions from the parent compounds. The mechanism of radical formation by photolysis consists of several stages. Firstly, the absorption of a quantum of energy (i.e., photon) by the molecule takes place. Then, the breakage of chemical bonds within the molecule occurs if the irradiation has energy enough. This step is followed by the formation of very reactive intermediates (radicals), which react with other molecules, generating new radicals and neutral compounds with different chemical structures. The physical and chemical properties of these new compounds could be dissimilar from those of the original compounds, e.g. different toxicity, persistence, and bioavailability, among others. Therefore, to extent the knowledge about the photostability of these photoproducts is also very important and it can be also done by photo-SPME following their kinetic profiles. In general, the obtained photoformation-photodegradation kinetic curves showed three different behaviours: (1) some photoproducts were detected after short irradiation times and tend to become undetectable at longer expositions, as 1-chloro-4-[2,2-dichloro-1-(4chlorophenyl)ethenyl]benzene (DDE) (figure 9A); they can be considered as easily photodegradable; (2) other photoproducts were hardly photodegradable during the evaluated time period or even their concentration increased for all the studied irradiation times, like 4,4,6,7,8-pentamethyl-5-nitro-4H-benzo[e][1,2]oxazine, a byproduct detected in the photodegradation of nitromusks (figure 9B); and (3) there was a group of photoproducts which showed an intermediate behaviour as 2,8-dichloro-dibenzo-p-dioxin (2,8 DDCD) (figure 9C).

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A

B

DDE

4,4,6,7,8-Pentamethyl-5-nitro-4H-benzo[e][1,2]oxazine 2.5E+04 2.0E+04

6.0E+03

Peak height

Peak height

8.0E+03

4.0E+03 2.0E+03

1.5E+04 1.0E+04 5.0E+03

0.0E+00 0

20 40 Irradiation time (min)

Peak height

C

60

0.0E+00 0

20 40 Irradiation time (min)

60

2,8-DCDD

1.2E+05 8.0E+04 4.0E+04 0.0E+00 0

20 40 Irradiation time (min)

60

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Figure 9. Time profiles for degradation-formation of: A) DDE, a p,p’-DDT photoproduct; B) 4,4,6,7,8pentamethyl-5-nitro-4H-benzo[e][1,2]oxazine, a musk moskene photoproduct; and C) 2,8-DCDD obtained in the photo-SPME studies of triclosan; after exposure of the SPME sorbent to UV light irradiation.

In some cases, for example in the particular case of homologous series (e.g. PCBs and PBDEs) this performance can be related to their chemical structures. Thus, in the photodegradation of one tetra-brominated flame retardant, BDE 47, new brominated compounds with lower number of bromine atoms are formed. The kinetic profiles of the debromination byproducts are shown in figure 10. By photo-SPME, two tri-BDEs, three diBDEs and two mono-BDEs, generated by successive losses of bromine atoms from the BDE 47 were confirmed as photodegradation products (in the figure, the sums of the areas for homologous congeners are represented). In this way, photo-SPME allows to determine primary and secondary photoproducts, since degradation occurs through a series of reactions in cascade (e.g. tetra⇒tri⇒di⇒monoBDEs).

7. PHOTO-SPME VERSUS AQUEOUS PHOTOCHEMICAL STUDIES So far it has sought to demonstrate and convince the reader about the advantages of carrying out photodegradation studies by Photo-SPME. But, the aim of this report is also to prove that photodegradation of pollutants absorbed in the polymeric coating mimics what may happen in the environment. In this way, photo-SPME can be used not only for increasing the knowledge about the photodegradation of organic

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compounds, but also about the fate of these pollutants once they reach the environment, especially the water compartments.

MonoBDE DiBDE TriBDE

Response (%)

100 80 60 40 20 0 0

10

20 30 40 Irradiation time (min)

50

60

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Figure 10. Time profiles for degradation-formation of different brominated photoproducts from the BDE 47 after exposure of the SPME sorbent to UV light irradiation (8 W). Results have been normalized to the maximum area obtained for each by-product [46].

In order to demonstrate this subject, aqueous photodegradation experiments have also been carried out for every studied compound, using SPME as an alternative extraction technique to the classical approaches. All of the photoproducts obtained in the aqueous photodegradation experiments were also found in the photo-SPME experiments, including the most toxic byproducts. In contrast, some photoproducts identified in photo-SPME did not appear in the water experiments. This can be explained, among other reasons (e.g. role of solvent in photochemical reactions), because in ‘on-fibre’ photodegradation, photoproducts are generated in situ on the fibre without any additional steps for extraction. However, in aqueous photodegradation studies, photoproducts are generated in the solution, and they must be extracted afterwards. In most cases, the behaviour of the analytes in these aqueous photodegradation experiments is similar to the one found in the photo-SPME experiments [38,41-43,46,47]; as it is shown in figure 11, where the photodegradation kinetics of the five studied PBDEs in the fibre coating and in water are compared. Even more important is the fact that this similarity has also been detected in real contaminated samples. Thus, Photo-SPME has been successfully applied for studying the photochemical behaviour of triclosan in real wastewater polluted samples (non-spiked). This compound is easily degraded by sunlight and UV light (figure 12), both in the fibre coating and in aqueous media. Six photoproducts were detected in the photo-SPME of real wastewater: dichlorophenol (DCP), monochlorophenol (MCP), monochlorohydroxydiphenyl ether, dichlorohydroxydiphenyl ether (three positional isomers), dichlorohydroxydibenzo

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furan and the toxic 2,8-dichlorodibenzo-p-dioxin (DCDD); and two of them, MCP and DCP, were already initially detected in the sample. A

100

Response (%)

80 60 40 20 0 0

10

20 30 40 Irradiation time (min)

B

100

Response (%)

Response (%)

C

80

60 40 20

60 40 20

0

0 0

10

20 30 40 Irradiation time (min)

50

60

0

D

100

10

20 30 40 Irradiation time (min)

50

60

E

100 80

Response (%)

80

Response (%)

60

100

80

60 40 20

60 40 20

0

0 0

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50

10

20 30 40 Irradiation time (min)

50

60

0

10

20 30 40 Irradiation time (min)

50

60

Figure 11. Photodegradation kinetics of: (A) BDE 47; (B) BDE 100; (C) BDE 99; (D) BDE 154; and (E) BDE 153. Continuous lines represent the results obtained in the Photo-SPME experiments and broken lines represent the results obtained in the aqueous photodegradation. (Radiation source: sunlight simulator) [41].

Based on our findings, we conclude that photo-SPME is the technique of choice in environmental studies of emerging contaminants at real concentration levels, because of its efficiency, ease of handling and excellent parallelism with the aqueous and real wastewater photolytic behaviour of contaminants.

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A Novel Use of Sorbents for Photochemical Studies B) UV radiation

100

100

80

80

Response (%)

Response (%)

A) Simulated sunlight

157

60 40 20

60 40 20

0

0 0

10 20 Irradiation time(min)

30

0

10 20 Irradiation time(min)

30

Figure 12. Photodegradation kinetics of triclosan in wastewater after sunlight irradiation (A) and UV irradiation (B) in photo-SPME experiments (filled line) and aqueous photodegradation experiments (broken line) [51].

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8. IMPACT AND CURRENT APPLICATIONS OF PHOTO-SPME DATA In addition to the publications that refer to the photo-SPME in a generic way [57, 58], some of the data obtained through this technique have been used as a comparative basis for discussions in a variety of fields. Some of the Photo-SPME work was done on the halogenated compounds PBDEs and PCBs, both degrading slowly in the environment. Photo-SPME was applied for the first time to the photolysis of PCB congeners [43,44] and the conclusions achieved were used by several authors [59,60]. Specifically, Izadifard et al.[60], discussed deeply the role of medium and quenching for dechlorination of PCBs, comparing their data with the photo-SPME degradation pathways from a mechanistic view. The evidence of PBDEs photodegradation obtained through Photo-SPME, among other techniques, has been used in posterior photolytic studies of these flame retardants. Thus, kinetic data of PBDEs and photochemical mechanisms for lower brominated PBDEs and other photoproducts formation (e.g. polybrominated dibenzofurans, PBDFs) has been used with comparative purposes in photodegradation experiments in hexane [61], in tetrahydrofuran hydroorganic mixtures[62] and in surfactant micelles[63]; and also in the development and validation of a congenerspecific photodegradation model for these organic pollutants [64]. The aryl-Br bond cleavage degradation mechanism caused by electron transfer proposed in PBDEs Photo-SPME studies has been similarly detected in BDE-209 photodegradation in the presence of a novel TiO2 immobilized hydrophobic montmorillonite photocatalyst [65]. Some authors consider PhotoSPME as a photochemical reaction that debrominate PBDEs on a solid surface [66] whereas others consider the on-fibre debromination of PBDEs as a direct photolysis reaction [67]. Thus, PBDEs photolysis demonstrated by our studies among others, is considered a process likely to be very important in the environmental fate of these flame retardants [68]; affecting highly brominated compounds in addition to microbial and/or metabolic processes, and finally leading to the formation of lower brominated PBDE congeners. These degradation processes will condition the real occurrence and tissue distribution of low to highly

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brominated compounds in human biological samples, as maternal adipose tissue, serum, breast milk and cord serum [69]. Regarding to the photo-SPME of DDT and related compounds [47], Jang et al. [70] proposed a stepwise photodegradation of DDT with Fe3+/TiO2 in UV radiation, contrasting the degradation kinetics of DDT and the byproduct formation with our reported results and concluding that they were very similar. The same conclusions are reached by Quan et al. [71] that proposed the photodegradation pathway of p,p’-DDT on soil surfaces under UV irradiation and suggested that fits quite well with the proposed photo-SPME route. Burniston el al. [72] studied changes in concentrations of semivolatile organic contaminants in aging snow, observing that the behaviour of p,p’-DDE is an interesting outlier from the trend displayed by the other organochlorine pesticides (OCPs). While most OCPs, including p,p’DDT, were lost from snow during the aging, the snowpack concentrations of p,p’-DDE generally increased. The authors stress that these detected sunlight induced conversions in snow from p,p’-DDT to p,p’-DDE are consisted with our photo-SPME findings. Kronimus et al. [73] investigated the release and thermodegradation of nonextractable anthropogenic organic compounds in riverine sediments, expecting high amounts of compounds structurally related to the pesticide DDT. The main degradation product was bis(4chlorophenyl)methoxymethane (BCMM) and its possible precursors were (4,4’dichlorobenzophenone (DBP) and bis(4-chlorophenyl)methanol (BCMeOH) both already described as photodegradation products of DDT by photo-SPME and therefore, considered by the authors as possible precursors of BCMM in the evaluated sediments. Photo-SPME is currently considered one of the two main applications of SPME for the determination of physicochemical properties of petroleum hydrocarbons, especially polycyclic aromatic hydrocarbons (PAHs) [74], being the other one the measurement of free concentrations [75]. The biodegradability of two major representatives of the polycyclic musk fragrances, Galaxolide (HHCB) and Tonalide (AHTN) and the formation of biotransformation metabolites has been studied by Martin et al. [76]. The fungi converted HHCB and AHTN into various products and the chemical structures of some of these metabolites have already been suggested for photo-oxidation of AHTN by photo-SPME [42]. The authors suggest that this fact is in support of a possible minor contribution of photodegradation to the AHTN removal observed in Myrioconium sp. cultures, a mitosporic aquatic fungus with ability to metabolize HHCB and AHTN in pure culture experiments. But undoubtedly one of the most successful applications of photo-SPME has been the study of the triclosan photodegradation [49,50,77], since the ability to form toxic degradates in the environment (e.g. low chlorinated dioxins) was clearly demonstrated (real wastewaters samples and sunlight [77]). This established potential of forming dioxin-like derivatives under sunlight conditions has been widely used as an argument for justifying multiple approaches to assess the environmental fate of triclosan and the need of its monitoring [7885] and even brings into question whether triclosan might contribute to the development of breast cancer [86]. Kinetic data of triclosan obtained by photo-SPME have also been used by other authors, as half-life times [87], photodegradation rate constants [88] and even the pH influence in the photocyclization process that converts triclosan to dibenzodichloro-p-dioxin [89].

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9. SPREADING THE PHOTO-SPME TECHNIQUE

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Photo-SPME has been proved to be a fast and powerful photo-tool, as can be inferred from all the above. However, a limitation that has so far not been commented exists, since these on-fibre studies cannot be carried out for highly volatile compounds due to analyte losses by volatilisation. In order to overcome this issue, cold-fibre SPME devices (CF-SPME; also called internally cooled SPME fibre devices) have been tested to provide a new powerful mean for investigating the photochemical behaviour of more volatile compounds. Thus, CFSPME is introduced for the first time in photo-SPME studies through the collaboration between one of the authors (L. Sánchez Prado) and the researchers E. Psillakis from Technical University of Creta, GR, and J. Pawliszyn from University of Waterloo, CA, the latter considered the father of the SPME [90]. The CF-SPME has been also used for simulating the photodegradation of organic pollutants in ice and for studying the influence of the temperature in the photodegradation kinetics, more research must be done in order to understand the interactions that may happen between the target compounds, the ice formed around the fibre coating and the UV irradiation. Despite the simplicity of the technique and the large amount of generated useful data, the employment of Photo-SPME technique as such by other authors has not yet taken off. In this sense, the intention openly expressed by M. Hakkarainen from the Royal Institute of Technology (KTH), Stockholm, SE [91] on the application of the technique in photodegradation studies of polymer additives is very welcome, arguing that the system provides unique qualitative and quantitative information regarding the degradation mechanisms and has great potential in evaluating the photo-transformation of organic compounds. The use of photo-SPME in areas other than environmental, e.g. food analysis, is also being explored. The idea is to survey the possibilities of the technique to function as an alternative to the traditional tests employed to evaluate oil quality and oxidative stability. The preliminary experiments have already been published [92] and the work is underway at this time within our research team and in collaboration with the investigation group of Dr. Waldemar Wardencki from the Gdansk University of Technology, PL. Finally, other challenges are being considered as using SPME devices to undertake photodegradation studies in the field under the natural changing surroundings or doping the fibre with sensitizers or radical initiators to evaluate photo-SPME under these conditions.

10. CONCLUSION Photo-SPME is now seven years old. In this period has ceased to be a potential tool for photodegradation studies to become a real photo-tool that simplifies the photochemical studies of environmental organic pollutants. To know the photochemical behaviour of such compounds is important in order to predict their fate in water, soil and plants, and to identify the photoproducts which could have diverse biological and toxicological properties. PhotoSPME data imply kinetic profiles and parameters, primary and secondary photodegradation pathways and identification and photochemical behaviour of the obtained photoproducts. These applications are well established and reported for a number of different environmental

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pollutants. Photo-SPME clearly avoids artefacts formation in photodegradation studies, since the sample manipulation is minimised. Besides, the photochemical behaviour in the fibre mimics the process taking place in matrices other than the SPME coating (e.g. water), even under natural sunlight radiation. In these cases, SPME is used as an extraction technique in a more classical approach, extraction after irradiation. The mentioned advantages of this ‘green technique’ are preserved in both cases. Thus, when the photochemical behaviour of a particular group of analytes needs to be known, photo-SPME may be the choice. Finally, some of the photo-SPME data have been used as a comparative basis for discussions in a variety of scientific fields and the technique is gradually dispersing and expanding their horizons to other areas.

REFERENCES [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]

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[13] [14] [15] [16] [17] [18] [19]

K.C. Jones, P. de Voogt, Environmental Pollution. 100 (1999) 209. D. Dabrowska, A. Kot-Wasik, J. Namiesnik, Critical Reviews in Analytical Chemistry. 35 (2005) 155. R.A. Larson, M.R. Berenbaum, Environmental Science & Technology 22 (1988) 354. The Handbook of Environmental Chemistry, Volume 2, Part L: Reactions and Processes: Environmental Photochemistry, Springer, Berlin, Germany, 1999. O. Hutzinger, The Handbook of Environmental Chemistry, Vol. 2, Pt. B: Reactions and Processes, Springer-Verlag, Berlin, Fed. Rep. Ger., 1982. M. Czaplicka, T. Manko, J. Wypych, Chemia Analityczna. 50 (2005) 887. J.J. Pignatello, Environmental Science & Technology. 26 (1992) 944. V.A. Sakkas, I.K. Konstantinou, T.A. Albanis, Journal of Chromatography. A 959 (2002) 215. G.A. Peñuela, D. Barceló, Journal of Chromatography. A 754 (1996) 187. C. Gonçalves, A. Dimou, V. Sakkas, M.F. Alpendurada, T.A. Albanis, Chemosphere. 64 (2006) 1375. T.M. Sakellarides, V.A. Sakkas, D.A. Lambropoulou, T.A. Albanis, International Journal of Environmental Analytical Chemistry. 84 (2004) 161 V.R. Hebert, C. Hoonhout, G.C. Miller, Journal of Agricultural and Food Chemistry. 48 (2000) 1916. M. D'Auria, R. Racioppi, V. Velluzzi, Journal of Chromatographic Science. 46 (2008) 339. C.L. Arthur, J. Pawliszyn, Analytical Chemistry. 62 (1990) 2145. Z. Zhang, J. Pawliszyn, Analytical Chemistry. 65 (1993) 1843. S. Armenta, S. Garrigues, M. de la Guardia, TrAC Trends in Analytical Chemistry. 27 (2008) 497. J. Pawliszyn, Solid Phase Microextraction: Theory and Practice, VCH, New York, N. Y, 1997. S.A. Scheppers Wercinski, Solid Phase Microextraction: A Practical Guide, Dekker, New York, N. Y., USA, 1999. S. Risticevic, V. Niri, D. Vuckovic, J. Pawliszyn, Analytical and Bioanalytical Chemistry. 393 (2009) 781.

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[20] F.M. Musteata, J. Pawliszyn, Journal of Biochemical and Biophysical Methods. 70 (2007) 181. [21] F.M. Musteata, J. Pawliszyn, TrAC Trends in Analytical Chemistry. 26 (2007) 36. [22] H. Kataoka, H.L. Lord, J. Pawliszyn, Journal of Chromatography. A 880 (2000) 35. [23] J. Pawliszyn, Applications of Solid Phase Microextraction, Royal Soc. Chem., Cambridge, UK, 1999. [24] S.J. Lock, Flavor and Taint Chemical Analysis: Is Solid Phase Microextraction (SPME) an Alternative?, Campden & Chorleywood Food Research Association, Chipping Campden, UK, UK, 1997. [25] C. Garcia-Jares, J. Regueiro, R. Barro, T. Dagnac, M. Llompart, Journal of Chromatography. A 1216 (2009) 567. [26] R. Barro, J. Regueiro, M. Llompart, C. Garcia-Jares, Journal of Chromatography. A 1216 (2009) 540. [27] M.Z.J.C. Xiang Li, Journal of Separation Science. 31 (2008) 2839. [28] J.L.R. Júnior, N. Ré-Poppi, Talanta. 72 (2007) 1833. [29] M. Llompart, K. Li, M. Fingas, Analytical Chemistry. 70 (1998) 2510. [30] M. Fernandez-Alvarez, M. Llompart, J.P. Lamas, M. Lores, C. Garcia-Jares, R. Cela, T. Dagnac, Journal of Chromatography. A 1188 (2008) 154. [31] C. Salgado-Petinal, M. Garcia-Chao, M. Llompart, C. Garcia-Jares, R. Cela, Analytical and Bioanalytical Chemistry. 385 (2006) 637. [32] S.-m. Chang, R.-a. Doong, Chemosphere. 62 (2006) 1869. [33] M. Llompart, M. Lourido, P. Landín, C. García-Jares, R. Cela, Journal of Chromatography. A 963 (2002) 137. [34] R.A. Trenholm, F.L. Rosario-Ortiz, S.A. Snyder, Journal of Chromatography. A 1210 (2008) 25. [35] L. Cai, J.A. Koziel, M. Dharmadhikari, J. van Leeuwen, Journal of Chromatography. A 1216 (2009) 281. [36] V. Matamoros, E. Jover, J. Bayona, Analytical and Bioanalytical Chemistry. 393 (2009) 847. [37] M. Lores, L. Sanchez-Prado, M. Llompart, C. Garcia-Jares, R. Cela, International Journal of Environmental Analytical Chemistry. 85 (2005) 281. [38] L. Sanchez-Prado, M. Llompart, M. Lores, C. Garcia-Jares, R. Cela, Journal of Chromatography. A 1047 (2004) 271. [39] V.-M. Graubner, R. Jordan, O. Nuyken, T. Lippert, M. Hauer, B. Schnyder, A. Wokaun, Applied Surface Science. 197-198 (2002) 786. [40] F. Egitto, L. Matienzo, Journal of Materials Science. 41 (2006) 6362. [41] L. Sanchez-Prado, M. Lores, M. Llompart, C. Garcia-Jares, J.M. Bayona, R. Cela, Journal of Chromatography. A 1124 (2006) 157. [42] L. Sanchez-Prado, M. Lourido, M. Lores, M. Llompart, C. Garcia-Jares, R. Cela, Rapid Communications in Mass Spectrometry. 18 (2004) 1186. [43] M. Lores, M. Llompart, R. Gonzalez-Garcia, C. Gonzalez-Barreiro, R. Cela, Journal of Chromatography. A 963 (2002) 37. [44] M. Lores, M. Llompart, R. Gonzalez-Garcia, C. Gonzalez-Barreiro, R. Cela, Chemosphere. 47 (2002) 607. [45] L. Sanchez-Prado, C. Gonzalez-Barreiro, M. Lores, M. Llompart, C. Garcia-Jares, R. Cela, Chemosphere. 60 (2005) 922.

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162

Lucía Sánchez-Prado, María Llompart, María Fernández-Álvarez et al.

[46] L. Sanchez-Prado, M. Llompart, M. Lores, C. Garcia-Jares, R. Cela, Journal of Chromatography. A 1071 (2005) 85. [47] M. Llompart, M. Lores, M. Lourido, L. Sanchez-Prado, R. Cela, Journal of Chromatography. A 985 (2003) 175. [48] L. Sanchez-Prado, M. Lores, M. Llompart, C. Garcia-Jares, M. Lourido, R. Cela, Journal of Chromatography. A 1048 (2004) 73. [49] M. Lores, M. Llompart, L. Sanchez-Prado, C. Garcia-Jares, R. Cela, Analytical and Bioanalytical Chemistry. 381 (2005) 1294. [50] L. Sanchez-Prado, M. Llompart, M. Lores, M. Fernandez-Alvarez, C. Garcia-Jares, R. Cela, Analytical and Bioanalytical Chemistry. 384 (2006) 1548. [51] L. Sanchez-Prado, M. Llompart, M. Lores, C. Garcia-Jares, J.M. Bayona, R. Cela, Chemosphere. 65 (2006) 1338. [52] M. Fernandez-Alvarez, M. Lores, M. Llompart, C. Garcia-Jares, R. Cela, Analytical and Bioanalytical Chemistry. 388 (2007) 1235. [53] M. Fernandez-Alvarez, L. Sanchez-Prado, M. Lores, M. Llompart, C. Garcia-Jares, R. Cela, Journal of Chromatography. A 1152 (2007) 156. [54] A.M.C.M.E. Pijnenburg, J.W.; Boer, J. de; Boon, I.P., Reviews of environmental contamination and toxicology. 141 (1995) 1. [55] C.R. Tyler, N. Beresford, M. van der Woning, J.P. Sumpter, K. Thorpe, Environmental Toxicology and Chemistry. 19 (2000) 801. [56] A.R. McCarthy, B.M. Thomson, I.C. Shaw, A.D. Abell, Journal of Environmental Monitoring. 8 (2006) 197. [57] C.J. Koester, S.L. Simonich, B.K. Esser, Analytical Chemistry. 75 (2003) 2813. [58] A.M. Peck, Analytical and Bioanalytical Chemistry. 386 (2006) 907. [59] X. Li, L. Fang, J. Huang, G. Yu, Journal of Environmental Sciences. 20 (2008) 753. [60] M. Izadifard, G. Achari, C.H. Langford, Chemosphere. 73 (2008) 1328. [61] L. Fang, J. Huang, G. Yu, L. Wang, Chemosphere. 71 (2008) 258. [62] S. Mas, A. de Juan, S. Lacorte, R. Tauler, Analytica Chimica Acta. 618 (2008) 18. [63] X. Li, J. Huang, L. Fang, G. Yu, H. Lin, L.N. Wang, Chemosphere. 73 (2008) 1594. [64] X. Zeng, S.L. Massey Simonich, K.R. Robrock, P. Korytár, L. Alvarez-Cohen, D.F. Barofsky, Environmental Toxicology and Chemistry. 27 (2008) 2427. [65] T.C. An, J.X. Chen, G.Y. Li, X.J. Ding, G.Y. Sheng, J.M. Fu, B.X. Mai, K.E. O'Shea, in 3rd China-Japan Workshop on Environmental Catalysis and Eco-Materials, Beijing, PEOPLES R CHINA, 2007, p. 69. [66] M. Kuivikko, T. Kotiaho, K. Hartonen, A. Tanskanen, A.V. Vahatalo, Environmental Science & Technology. 41 (2007) 7016. [67] P. Li, W.B. Dong, R.X. Zhang, L. Huang, Z.L. Ye, H.Q. Hou, Chemosphere. 71 (2008) 1494. [68] A. Zarnadze, L.A. Rodenburg, Environmental Toxicology and Chemistry. 27 (2008) 1636. [69] J.P. Antignac, R. Cariou, D. Zalko, A. Berrebi, J.P. Cravedi, D. Maume, P. Marchand, F. Monteau, A. Riu, F. Andre, B. Le Bizec, Environmental Pollution. 157 (2009) 164. [70] S.J. Jang, M.S. Kim, B.W. Kim, Water Research. 39 (2005) 2178. [71] X. Quan, X. Zhao, S. Chen, H. Zhao, J. Chen, Y. Zhao, Chemosphere. 60 (2005) 266. [72] D.A. Burniston, W.J.M. Strachan, J.T. Hoff, F. Wania, Environmental Science & Technology. 41 (2007) 4932.

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[73] A. Kronimus, J. Schwarzbauer, M. Ricking, Environmental Science & Technology. 40 (2006) 5882. [74] B. Tang, U. Isacsson, Energy & Fuels. 22 (2008) 1425. [75] M.B. Heringa, J.L.M. Hermens, TrAC Trends in Analytical Chemistry. 22 (2003) 575. [76] C. Martin, M. Moeder, X. Daniel, G. Krauss, D. Schlosser, Environmental Science & Technology. 41 (2007) 5395. [77] L. Sanchez-Prado, M. Llompart, M. Lores, C. García-Jares, J.M. Bayona, R. Cela, Chemosphere. 65 (2006) 1338. [78] T.E.A. Chalew, R.U. Halden, Journal of the American Water Resources Association. 45 (2009) 4. [79] T.R. Miller, J. Heidler, S.N. Chillrud, A. Delaquil, J.C. Ritchie, J.N. Mihalic, R. Bopp, R.U. Halden, Environmental Science & Technology. 42 (2008) 4570. [80] A.R.M. Silva, J.M.F. Nogueira, Talanta. 74 (2008) 1498. [81] A. Küster, K. Pohl, R. Altenburger, Environmental Science and Pollution Research. 14 (2007) 377. [82] L. Vidal, A. Chisvert, A. Canals, E. Psillakis, A. Lapkin, F. Acosta, K.J. Edler, J.A. Holdaway, F. Marken, Analytica Chimica Acta. 616 (2008) 28. [83] M.A. Ghanem, R.G. Compton, B.A. Coles, E. Psillakis, M.A. Kulandainathan, F. Marken, Electrochimica Acta. 53 (2007) 1092. [84] R.S. Zhao, J.P. Yuan, H.F. Li, X. Wang, T. Jiang, J.M. Lin, Analytical and Bioanalytical Chemistry. 387 (2007) 2911. [85] S. Song, Q.J. Song, Z. Chen, Analytical and Bioanalytical Chemistry 387 (2007) 2917. [86] R.H. Gee, A. Charles, N. Taylor, P.D. Darbre, Journal of Applied Toxicology. 28 (2008) 78. [87] N. Nakada, K. Kiri, H. Shinohara, A. Harada, K. Kuroda, S. Takizawa, H. Takada, Environmental Science & Technology. 42 (2008) 6347. [88] M.I. Hoq, K. Mitsuno, Y. Tsujino, T. Aoki, H.R. Ibrahim, International Journal of Biological Macromolecules. 42 (2008) 468. [89] P. Wong-Wah-Chung, S. Rafqah, G. Voyard, M. Sarakha, Journal of Photochemistry and Photobiology a-Chemistry. 191 (2007) 201. [90] J.P.a.E.P. Lucia Sanchez-Prado, (submitted 2009). [91] M. Hakkarainen, in A.C. Albertsson, M. Hakkarainen (Editors), Advances in Polymer Science, 2008, p. 23. [92] W.W. Justyna Gromadzka, Marta Lores, Maria Llompart, Maria Fernández-Álvarez, Katarzyna Lipinska Polish Journal of Food and Nutrition Sciences. 58 (2008) 321.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 © 2009 Nova Science Publishers, Inc.

Chapter 5

DYE WASTEWATERS, ALTERNATIVE PHYSIOCHEMICAL TREATMENT REAGENT F.N. Emengo, J.K. Nduka, C.N. Anodebe, P.A.C Okoye Pure & Industrial Chemistry Department Nnamdi Azikiwe University P.M.B. 5025 Awka, Anambra State, Nigeria

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ABSTRACT The adsorptivity of a basic dye-methylene Blue and an acidic dye - Eosin B, on wood was studied by monitoring colour reduction. The reaction was found to be feasible for methylene blue and negative for Eosin B, with respect to the various process variables investigated. It was found that the rate of reaction for methylene blue with the surface sites on the exterior of the wood particle controls the overall sorption during the early portion of the time course, though some mass transfer resistant due to boundary layer effect was apparent. The activation energies for the adsorption of methylene blue on the woods-obeche and Iroko were 31.125kg Mol-1 and 31.114kg Mol-1 'respectively. This variation in activation energy may be attributed to differed densities of the wood. In this work, the effect of stirring rate and particle sizes of adsorbent, effect of temperature on the rate processes and regressional analysis for computation of activation energy of adsorbents were determined. The data generated from the study suggest the implementation of wastewater treatment facility that is not for adsorptive properties alone but for either modified or combined properties that have been precisely determined and yet economical.

Keywords: Wastewater, Dye, wood, Particle Size, Temperature, Adsorption, Stirring speed.

INTRODUCTION Physicochemical classification of wastewater treatment, are unit operation processes which include adsorption, ion exchange, stripping, chemical oxidation and membrane separation, used for removal of pollutants that are not easily removed by biomass[1,2]. In the

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above content, adsorption process is the most widely used and known mechanism primarily used for the removal of soluble organics[1-4]. Activated carbon is the chief adsorbent[1-5], followed by others as shown below[6-8]. Table 1. Physical properties of representative adsorbents Adsorbent Substance Activated Alumina

Average pore diameter (10-10m) 34

Surface Area m2/g 250

Adsorptive capacity 0.14

Activated bauxite Activated clays Fuller’s earth Silica gel

250 100 25-30

150-225 130-250 200-600

0.04-0.21 1.0

Shell-base carbon Wood-base carbon Coal-base carbon Petroleum base carbon Anhydrous calcium sulphate Pumice Fused copper polymeric

20 20-40 20-38 18-22

180-1100 625-14000 500-1200 800-1100

45 6-9 0.4~0.4 0.6-0.7

Hydrophylic, Amorphous Hydrophilic/Hydroph obic, Amorphous Amorphous -

-

-

0.1

-

-

3.38 0.23 80-700

-

-

Nature

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Physico-chemical treatment is therefore a unique form of treatment which involves the essential features necessary for the removal of dye from wastewaters by adsorption mechanism previously employing activated carbon. This is because activated carbon was found not only to be excellent water and wastewater treatment reagent but also an effective broad-range scavenging sorbent[1-10]. The choice of wood as the treatment reagent employed in this study has its background, objectives, analytical method described in a previous report[11], thus, below are breakdown of the economic advantage of wood over activated carbon, a reason for its choice as stated previously[11]. 1. Virgin activated carbon is cost intensive[5,10], with sample grain , sample preparation and heating rate being the dominant factor determining its economic efficiency (1,9). 2. Loss of structural integrity of the material in the following instances. a. When it is thermally regenerated, 5-10% of the material is lost due to burning and attrition during each regeneration cycle[1]. b. Regenerated materials becomes progressively hard, abrasive, brittle as sample is recycled through thermal regeneration[1,9A, 10]. c. Diminishing change in average particle size after three cycles of sorption regeneration[9]. d. Resistance to removal by degassing due to the presence of some substance associated with the activated carbon by oxidation. The major interest in this study is to assay the feasibility and hence kinetics of postulated alternative[11], for the purpose of improving the economics dye wastewater treatment. This

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entails colour reduction measurement by visible spectrophotometery during the course of the investigation. The impact of process variable-stirring speed, particle size and temperature were also considered[6,10,13,14]. The test dyes used were a basic dye-methylene blue (Basic blue, 9, C. 1.52015) and an acidic dye, Eosin, (Acid red 91, C.1.45400; 4´,5´-dibromo-2´,7´dinitrofluorescien, disdodium salt)[15]. The woods employed are hard woods: Iroko (Chlorophora excelsa) and Obeche (Triphlochioton scleroxylon). A further interest in this study is to determine the surface area of the alternative treatment reagent so as to determine the most effective particles size and hence make comparison with the corresponding representative adsorbents available in literature. However, the principal focus in this research consists a broad range spectrophotometeric determination of treatment response of the pure solution of sorbate (dye compounds); therefore, the primary effluent (dye wastewater) was not sampled. A method previously derived[11,14], for determining the rate parameters with an arbitrary unit was utilized in determining the rate of adsorption. The activation energies was also determined by a clearly defined method[11,14].

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LITERATURE REVIEW Wastewater from dyeing operations are characterized by colour caused by both organic and inorganic compounds[4,16]. The organic compounds are more problematic in industrial effluent than inorganic materials [4,9,16,17,18], because apart from the colour it imparts on the wastewater, biodegradation of organic material in the dyes often deplete the dissolved oxygen[3] of the water resulting in obnoxious anaerobic conditions which are source of pollution complaints. Moreover, these organic compounds has shown to induce genetic damage and chromosome abnormalities. They are also carcinogenic[9,10,15-18]. These compounds are chiefly benzoid of the form-benzene, toluene, orthoxylyene and anthracene obtained from dye raw material- coal tar or petroleum[16-19]. Since these creates problem for water bodies, they require treatment before discharge. Consequently, there is a demand for a tailored concentration of these wastewater that will be discharged into our water bodies in order to control the amount of organic substances or colour introduced, which may impair their further use. Therefore, the pollution prevention act of 1990 established pollution prevention as a national policy; declaring that waste should be prevented or reduced at source whenever feasible. The environmental protection Agency (EPA) policy established the following hierarchy of waste management (i) Source reduction (ii) Recycling/reuse (iii) Treatment (iv) Ultimate disposal[1,10].

Concepts for Preliminary Design Criteria To meet treatment requirement and standard, the environmental and chemical engineer will develop a reactor design for treatment programs. However the basic design criteria in sizing the various treatment units he must obtain from chemist’s laboratory or pilot plant source data[4,8]. from this information expression for the intrinsic rates of chemical reactions involved i.e. the chemical kinetics will be extracted[8], and by laboratory projection, pilot

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plant or a large scale reactor data, any type of reactor may be designed by introducing the appropriate physical processes associated with the type of equipment employed, then with the knowledge of the permissible discharge concentration of the concerned regulatory body, any change in the desired concentration of wastewater could be adequately corrected, subsequent to analysis by the engineering body’s quality control unit[4].

Permissible Discharge Criteria The criteria, in principle for acceptable discharge is simply an essentially colorless to the eye effluent after primary treatment[9B], at a point called break point(bp or tb) in engineering terminology at a limiting permissible value with a relative concentration of 0.05 or 0.10. it is calculated from measurement profile of C/co versus time to give a curve, a break through curve when the concentration attains limiting permissible value or break point the flow is stopped or diverted to fresh adsorbent bed fixed bed [2]. The municipality established a policy that if 20:1 dilution of the dye wastewater with sewage produces a colorless to the eye effluent, it is then acceptable for discharge [9b,20],while the U.S environmental protection Agency (EPA) has this information in texts, more on the EPA guideline for best technology economically achievable in bringing dye wastewater to a permissible discharge color levels are well documented[10,21].

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Assessment Opportunities Earlier works on dye wastewater pretreatment emphasized removal of biochemical oxygen demand (BOD) but current concern has shifted to removal of chemical oxygen demand (COD), suspended solids, color and colloidal particles[9], details are available in literature which incorporated technical assistance from EPA- to provide equipment, or process modifications, or substitution for hazardous materials as well as other program centered on inspiring a company or individuals to explore pollution preventing alternatives through the use of case studies, economic[10,20,21,22] analysis and management studies. Critical review of some available technique for color removal and monitoring dye wastewater are discussed below viz: laboratory and industrial techniques. In laboratory, the procedure used to establish sorption consists contacting the sorbate solution with varying amounts of adsorbent particles and determining the change in sorbate concentration with time, several studies by different authors are discussed in case studies below.

Case Studies Hemphil et al [9a], weighed portions of activated carbon into a series of 125-ml Erlrenmeyer flask containing 100ml of sorbate solution. The mixture was then placed in a 22oc temperature controlled warbug apparatus or constant temperature bath. Aliquot samples of the incubated and continuously mixed solution were removed for analysis at 5-hr intervals. Terrence Allen[12] : Tumbled gently 0.05 to 0.50 g of sorbent sample with 10ml aqueous solution of dye at room temperature, for 10 to 30mins (sufficient contact time for nonporous

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powder) and 12 to 48hrs for porous powder. The tube was then centrifuged and the solution analysed spectrophotometrically, With porous powder, a rate curve develops; extrapolating back to zero gives the surface concentration of dye, the saturated value is accepted as a monolayer coverage. This feature makes this method attractive as one point techniques. If YM (in mm0l g-1) is the amount of dye adsorbed at monolayer coverage per gramme of adsorbent, δ the flat molecular area of dye and N is the Avogadro’s number, the weight specific surface area is given by Sw=Ym Nδ X where X is the coverage factor which is equal to the number of dye ion in a micelle. With this technique, some authors who used δ = 1.2nm2 and X=2, reported that it is preferable to buffer methylene blue (for which they are reporting) at pH 9.2, by using buffer tablets in order to reduce competition between H+ and the dye cations. The authors advised against test being made from solution outside the range of pH 5-8, others advised the avoidance of dye which may be adsorbed in a dual manner and any dye which may form covalent bonds with surface, since they may be liable to selective adsorption on particular sites. Use of methylene blue Bp, Brilliant basic red B, crystal violent Bp, Victoria pure lake blue BO, orange 11 or solway ultra-blue were recommended and that the two Bp dyes can be used as purchased while others need some pretreatment. Shaul et al[9b] have it that the experiment set up consist a series of stoppered glass vessels which contained increasingly amount of adsorbent (0.5 to 8.0g) solid into which a known concentration of dyes were spiked, followed by mixing the content of each for 24hrs via magnetic stirring apparatus. The content of the vessels were sampled and centrifuged at 10,000 revolution per minute for 15 mins and the content subsequently filtered through a 0.45 micron pore size filter. High performance liquid chromatography (HPLC) was used to analyse the residual dye in the sample filtrate, the residual dye concentration was then utilized with the amount of adsorbent in each vessel to calculate the adsorption isotherm according to the freundlich relation X/M = KCe i/n. The calculation was based on an equilibrium concentration of 1 mg/L i.e Ce=1 mg/L, using activated sludge as adsorbent. The result is tabulated in the table below.

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Table 1b. Freudlich constants for dye adsorption on activated sludge system Dye C.I. Acid blue 113 C.I. Acid Orange 7 C.I. Acid red 1 C.I. Acid red 88 C.I. Acid red 151 C.I. Acid blue 337 C.I. Acid Yellow 151

Slope, 1/n 4.1 1.2 24 0.82 0.98 1.3 1.5

Intercept, K 7.3 0.11 1.0 x 10-17 2.5 9.1 0.67 1.3

Correlation Coefficient 0.959 0.975 0.879 0.969 0.981 0.952 0.957

where: X= amount of solute (dye) adsorbed, mg/L M= concentration of adsorbent, g/L

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/M = amount of dye adsorbed per unit mass of adsorbent mg/g. Ce= equilibrium concentration of dye in solution, mg/L K,n= empirical constants. In their work, Mckay and poots[11] ; used a cylindrical vessel of 0.10m diameter containing four baffles evenly spaced around its circumstance. The extent of agitation was varied using a six – bladed impeller driven with a variable speed motor (20-800 rev. min-1). At each run 0.5dm3 of dye solution of known initial concentration was placed in the vessel with a fixed mass of absorbent. Samples were withdrawn at known intervals for spectrophotometric analysis, for both basic and acidic dye (Astrazone blue and Telon blue), it was found that at high degree of agitation, a certain amount of particle breakdown was observed, they therefore advised a stirrer speed of 400 rev.min-1 where particle breakdown was negligible even though data analysis indicated reduction in boundary layer surrounding the particle with increasing speed of agitation. Secondly, they defined rate parameter which was used to show the influence of agitation on boundary layer diffusion as the gradient of the linear portions of the curve as amount of dye adsorbed (X/M) vs the square root of time (t 0.5). this relationship was illustrated by dimensional analysis, for which batch experiments has shown to have the preferred function of time (t) for plotting purposes as to0.5 rather than t. They also determined activation energies using arrhenius relation, log K=log A-log Ea/2.303 RT, using the rate parameters obtained from the plot of the experimental contact time at varying temperatures, using arrhenius plot, they obtained activation energy of 16.8KJmol-1 for the adsorption of Astrazone blue and 9.6KJmol-1 for Telon blue

INDUSTRIAL PHYSIO-CHEMICAL TREATMENT TECHNIQUES FOR DYE WASTEWATER

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On industrial bases, the techniques most often involves contacting the wastewater with small particles of the adsorbent which selectively adsorbs or complexes with certain component of the feed at interface between the liquid and solid phase. This is accomplished by either of these method discussed below.

Fixed Bed Reactor [2,6,7,8] In fixed bed, the particulate solid are held in fixed positions, one particle resting upon another with no relative position among particle in a static bed. The fluid are passed continuously through the bed until the solid is nearly saturated. The flow is then switched to a second bed and saturated bed is replaced or generated. Obviously, fixed bed usually require cyclic (batchwise) operation because it is difficult to add or remove solids from replenishment for adsorption effectiveness while a unit is operating. Fixed bed is the design characteristics of several of practical processes, such as ion exchange reactors, regeneration of fowled catalysts by combustion with air and adsorption from gas or liquid streams[2,6,8].

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Fluid Bed (Moving - Bed) Method In this system, adsorbent particles move counter currently by gravity through a rising pressurized fluid stream, so that as the particles adsorb the desired material from the wastewater stream, they become heavier and eventually gravitate to the bottom of the vessel where they are removed and regenerated externally from the fluid per se; This is a continuous process. Stirred Tank reactor [2,6,8] This is an alternative method for treating wastewater in which powdered adsorbent is added to a tank of wastewater solution using mechanical stirrer or air spargers to keep the particles suspended. With the fine particle in this method, the adsorption is much faster than with granular adsorbent particles in the two previous methods, but large equipment is needed to remove the spent carbon by sedimentation or filtration. This can be done either batch wise or on continuous basis with metered addition of adsorbent to the waste stream and continous removal of the spent adsorbent or carbon per se. Contact Filtration [2] In this system, adsorbents are incorporated in the filtering medium. It is widely used for removing coloured and carbon-forming material from lubricating oil.

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Adsorber Design The design of an adsorber [2,8,9b,16,21] for wastewater purification involves choosing the adsorbent and the particle size, selecting an appropriate velocity to get the bed area and either determining the bed length for a given cycle time or calculating the breakthough time for a chosen length. All these information and calculation are obtained by the projection of data obtained from the chemist’s laboratory[4,8,16]. Thus using a shorter bed means a smaller inventory of sorbent and lower pressure drop in the bed. However, the shorter bed means more frequent regeneration and high regeneration cost, since a smaller fraction of the bed is saturated at breakpoint. For adsorption from liquid, smaller particle sizes are chosen, and the fluid velocity is much lower compared to that of gas. Typical condition are 20 x 50 – mesh carbon (Dp=0.3 to 0.8mm) and a superficial velocity of 0.3cm/s (0.01 ft/s about 4 gal/min ft2), much more details are available in cited literature[2,8,9,20,21].

EXPERIMENTAL Materials The days investigated in this work were methlyene blue (Basic blue 9 C.I. 52015) and Eosine B (Acid red C.I. 5400). See figure a below. They are both of analytical grade and were used directly without any pretreatment. Methylene blue was selected as the experimental sorbate material because it is a standard reagent used to evaluate activated carbon sorption

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capacity as well as its micropore capacity. In addition, dilute solutions of methylene blue conform to Beer-Lambert’s Law at 661nm and therefore provide a rapid convenient method for determining concentration. The latter (Eosin B) was chosen because it is similar to many components found in dye wastewater and like the former, it obeys Beer-Lambert’s Law (dilute solutions) at 514 (319)nm. The experiments were conducted using hard woods namely Iroko (chlorophora excelsa) and Obeche (Triphlochioton Scleroxylon) obtained from local timberyard in Anambra State, Nigeria. These materials (the alternative sorbent materials) were obtained as saw dust with moisture content 3.59% and 1.08% respectively. No form of pretreatment was applied after sun drying at ambient temperature. This is to retain the structural integrity of the sorbent material. It was sieved into different particle sizes of 425µm; 1000µm, and 2000µm. All data are on dry weight basis. The particles of the saw dust were assumed to be spherical having a diameter given by the arithmetic mean value given on the respective sieve sizes.

Figure a. Structures of test dyes.

Apparatus Flat-bottom flasks of sizes 1000dm3, 5000dm3, 250dm3, 50dm3, measuring cylinders of sizes 100dm3, 50dm3 and 5dm3; pascheur pippetes, testubes, glass funnels, sampling containers, biurette and 250cm3 conical flask.

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Instrumentation The instruments used comprised oven, Permutit Deionizer, Analytical balance, Standard 3-place Philis’ Laboratory Stirrer, Desicator, and Retort Stand.

METHOD Three sets of experiment were conducted to investigate (i) the effect of stirring speed on the rate of colour removal, (ii) the effect of particles size and (iii) the effect of temperature on colour removing performances of wood. Set (i) and (ii) is tagged phase one of the experiment and set (iii) phase two.

Phase One I. Effect Of Stirring Speed This was investigated using a cylindrical vessel of stainless steel material (lm in diameter) containing 4 baffles evenly spaced around its circumference. The extent of mixing was varied using Philip's mechanical stirrer with speed specification: low, intermediate and high level stirring speed. The stirrer is driven by an electric motor fully enclosed within its transmission case. In each experimental run, 1.0dm3 of dye solution of known initial concentration was placed in the vessel with a fixed mass of adsorbent. 3cm3 samples were taken at intervals for analysis. Effect of Particle Size Experiments were performed at room temperature using wood of different particle sizes 425µm, 1000µm and 2000µm. During the investigation, the three (3) speed specification were employed for comparative purposes.

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Phase Two Temperature Experiment Contact time and isotherm experiments were performed to investigate the effect of temperature on the second step of the reaction mechanism viz intraparticle diffusion into the particle. A constant temperature water bath, intermediate stirrer speed and a particle size 425µm were employed for the investigation.

Analysis The change in concentration of the test dyes solution with time during each run was determined from a calibration curve previously prepared. It was obtained by measuring changes in light absorbance at 661 and 514nm (Zeroed against distilled water) respectively

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using a single beam spectrophotormeter, spectrum lab 21A. The corresponding concentration was then interpolated appropriately from the graph or by calculation.

Instrument Performance Test This is done to effect corrective action, or schedules the instrument for performance efficiency. It was done by repeated measurement of a low-concentration of check sample (60mg/L of potassium dichromate). Recording its absorbance spectrum between 345 to 355nm (within the wavelength range of maximum absorbance). The maximum absorbance was found to be 0.664 and corresponds to 350nm. This was used to obtain the specific extinction, A (1 %, 1cm) using the equation, A = Alcm1% x b x c where Alcm1% = Specific extinction of check sample b = cell path length; c = concentration of check sample Therefore, from the cited equation, the specific extinction was evaluated to be 110.6cm2/g. This was in good agreement with the recommended A (1%, 1cm) value, 107.1 + 1.1 for acidic potassium dichromate solution. This suggests the capability of the instrument's performance with respect to the specific extinction of the suitable certified standard check sample.

Determination of Residual Concentration The residual concentration of bulk-phase with time of treatment with adsorbent until equilibrium is attained was obtained by straight-line graph interpolation.

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Other Calculations The gradient of the linear portions of the plot of dye adsorbed (X/M mg g dye per gramme wood) versus square root of contact time (S0.5) defines the rate parameter (K}. This parameter has an arbitrary dimension (mg/g/S0.5). This rate parameter is a characteristic of the rate of the adsorption process between 35-85% dye removal, when the smallest particle size was employed for the investigation. ii The gradient and intercept of the langmuir isotherm relation yield the ultimate adsorption capacity (Cm) and other kinetic constant K, b and n. Where K = adsorption capacity, b = langmuir constant, iii c = adsorption intensity and Cm = ultimate adsorption capacity. iv The slopes of Arrhenius plot of log K versus the reciprocal of absolute temperature (Kelvin) gives the activation energy, i.e. using the K values obtained from the result i

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of the adsorption experiments at several temperatures investigated. The activation energy computed is a characteristic of the strength of adsorption (weak < 40kg Mol-l or strong > 40 kg Mol-l) and the type of adsorption, physiosorption and chemisorpiton. The surface area is calculated from the ultimate adsorptlon capacity (Cm) obtained from the langmuir. Relation using

Sm = Cm Nδ0 where Sm = Specific surface area. Cm = ultimate adsorption capacity, Mol g-1 N = Avogadro's constant, Mol-1 δ0 = flat molecular area of the dye, nm2 or A0 The area of the particle exposed to the reaction is classified either as low (surface areas up to 10m2 g-1) or very high (surface area of 200m2 g-1 and greater).

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RESULTS AND DISCUSSION Using spectrumlab visible region spectrophotometer of mode 21A for colour removal performance of the alternative adsorbent, the results obtained are shown in tables. Attempt was made to allow for adsorption on Eosin by subjecting the wood to a favourable condition of higher concentration of dye (200mgldm3) and longer contact time of 24hrs, it showed a negative response as indicated in table 5c. For the first phase of this study - effect of stirrer speed and particle sizes on dye adsorption (colour removal), tables 2(a, b), 3(a, b), 4(a, b) and 5(a, b, c), only tables 2(a, b) 4(a, b) which is the treatment response for methylene blue were positive while table 5(a, b and c) which portrays that of Eosin indicated a negative response. In discussing the former, tables 2(a, b) - 4(a, b) with the rate curves of figures l(a, b), 2(a, b) and 3(a, b), it is seen that during the short interval (< 4min) of stirring the sorbate, the dye concentration drops quickly and then decreases gradually (bottle necking). This shows that the rate of reaction of methylene blue with surface sites on the exterior of the particles controls the overall sorption mechanism during the early portion of the time course. The gradual, decrease in the latter stage may be attributed to two processes, (a) chemisorption between sorbate and the point of association in particles that might limit the overall approach to sorptive equilibrium, (b) the limitation which occurs when sorbate molecule do not have enough time to move to all points of contact in and on the solid were they would be associated - this is referred to as mass transfer process. Comparing the figures, the two impact variable - particle size and stirring speed have somehow offset the second limitation, that is with respect to smaller size and higher stirring speed. They are discussed individually.

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Table 2a. Effect of Stirrer speed on dye adsorption by Obeche (425µm) Stirring speed Time (s) 30 60 90 120 150 180 210 240

(S0.5) Time

Low stirrer speed A X

5.477 7.746 9.487 10.955 12.247 13.416 14.491 15.492

0.701 0.373 0.147 0.089 0.054 0.069 0.036 0.034

5.00 7.30 9.00 9.40 9.65 9.50 9.75 9.80

X/M

Intermediate stirrer speed A X

0.500 0.730 0.900 0.940 0.965 0.950 0-.975 0.980

0.415 0.193 0.148 0.067 0.051 0.48 0.037 0.037

7.00 8.60 8.95 9.55 9.65 9.70 9.75 9.75

X/A

High stirrer speed A X

0.70 0.860 0.895 0.955 0.965 0.970 0.975 0.975

0.367 0.165 0.081 0.067 0.048 0.045 0.051 0.059

7.30 8.80 9.45 9.55 9.65 9.65 9.65 9.60

X/M 0.730 0.880 0.945 0.955 0.965 0.965 0.965 0.960

Table 2b. Effect of Stirrer Speed on dye Adsorption by Iroko (425µm) Speed Time (s) 30 60 90 120 150 180 210 240

Time 0.5 (S0.5) 5.477 7.746 9.487 10.955 12.247 13.416 14.491 15.492

Low speed A X 0.858 0.489 0.181 0.076 0.085 0.056 0.032 0.043

3.90 6.50 8.70 9.45 9.55 9.60 9.80 9.68

X/M

Intermediate speed A X

0.390 0.650 0.870 0.945 0.955 0.960 0.980 0.968

0.735 0.299 0.132 0.081 0.033 0.021 0.025 0.024

4.80 8.80 9.10 9.45 9.80 9.90 9.85 9.90

X/A

High speed A

X

X/M

0.480 8.880 0.910 0.945 0.980 0.990 0.985 0.990

0.776 0.203 0.078 0.030 0.024 0.026 0.027 0.020

4.97 8.50 9.45 9.80 9.85 9.80 9.80 9.90

0.497 0.850 0.945 0.980 0.985 0.980 0.980 0.990

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Table 3a. Effect of Stirrer Speed on dye Adsorption by Obeche (1000µm) Stirring Speed Time (S) 30 60 90 120 150 180 210 240

Low Speed A 0.578 0.492 0.283 0.232 0.224 0.172 0.167 0.172

X 4.80 6.50 7.55 7.97 8.15 8.75 8.50 8.75

X/M 0.480 0.650 0.750 0.797 0.815 0.875 0.850 0.875

Intermediate Speed A X 470 0.742 7.00 0.419 8.10 0.258 8.35 0.227 8.70 0.181 8.75 0.177 8.70 0.184 8.80 0.166

X/M 0.470 0.700 0.810 0.835 0.870 0.875 0.870 0.880

High Speed A 0.624 0.429 0.342 0.280 0.250 0.240 0.212 0.216

X 5.8 7.35 7.98 8.30 8.40 8.77 8.80 8.77

X/M 0.580 0.735 0.795 0.830 0.840 0.877 0.880 0.877

Table 3b. Effect of Stirrer Speed on dye Adsorption by Iroko (1000µm) Stirring Speed Time (S) 30 60 90 120 150 180 210 240

Low Speed A 1.080 0.992 1.014 0.894 0.765 0.709 0.620 0.588

Low Speed X 2.15 2.95 2.80 3.60 4.65 4.95 5.50 5.75

X/M 0.215 0.295 0.280 0.360 0.465 0.495 0.550 0.575

A 1.027 0.622 0.230 0.209 0.181 0.115 0.112 0.094

High Speed X 2.70 5.55 8.30 8.50 8.70 9.20 9.20 9.40

X/M 0.270 0.550 0.830 0.850 0.870 9.20 0.920 0.940

A 0.956 0.644 0.426 0.244 0.166 0.127 0.114 0.096

X 3.20 5.40 6.95 8.25 8.80 9.10 9.20 9.30

X/M 0.320 0.540 0.695 0.825 0.880 0.910 0.920 0.930

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Table 4a. Effect of Stirrer Speed on dye Adsorption by Obeche (2000µm) Speed Time (S)

Low Speed A

X

X/M

Intermediate Speed A X

30 60 90 120 150 180 210 240

1.395 1.362 1.023 0.824 0.682 0.592 0.540 0.487

0.40 0.25 2.75 4.10 0.515 0.575 0.610 0.650

0.004 0.025 0.275 4.10 0.515 0.575 0.610 0.650

0.994 0.606 0.425 0.367 0.303 0.290 0.274 0.260

2.90 5.65 6.95 7.35 7.80 7.90 8.00 8.10

X/M

High Speed A

X

X/M

0.290 0.565 0.695 0.735 0.780 0.790 0.800 0.810

0.716 0.520 0.399 0.339 0.300 0.281 0.292 0.255

4.90 6.25 7.10 7.50 7.70 7.98 7.90 8.15

0.490 0.625 0.710 0.750 0.770 0.798 0.790 0.815

Table 4b. Effect of Stirrer Speed on dye Adsorption by Iroko (2000µm) Speed Time (S)

Low Speed A

X

X/M

Intermediate Speed A X

30 60 90 120 150 180 210 240

1.326 1.242 1.081 1.077 0.948 0.842 0.715 0.612

0.53 0.95 1.45 2.30 3.25 4.00 4.90 5.60

0.053 0.095 0.145 0.230 0.325 0.400 0.490 0.560

1.134 0.770 0.583 0.446 0.336 0.267 0.236 0.194

1.85 4.50 5.70 6.80 7.60 8.05 8.30 8.60

X/M

High Speed A

X

X/M

0.185 0.450 0.570 0.680 0.760 0.805 0.830 0.810

0.950 0.620 0.452 0.337 0.263 0.212 0.189 0.171

3.20 5.50 6.80 7.55 8.10 8.50 8.60 8.80

0.320 0.550 0.680 0.755 0.810 0.850 0.860 0.850

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Table 5a. Effect of Stirrer Speed on Eosin Adsorption (Co = 5mg) Wood: Obeche (1000µm) High speed A X Nil 0.309 ““ 0.315 ““ 0.320 ““ 0.323 ““ 0.323 ““ 0.334 ““ 0.332 ““ 0.338

Time (S) 30 60 90 120 150 180 210 240

Wood: Iroko (425µ) Medium stirrer speed A X Nil 0.266 ““ 0.270 ““ 0.275 ““ 0.280 ““ 0.280 ““ 0.284 ““ 0.280 ““ 0.288

Table 5b. Effect of Stirrer Speed on Eosin Adsorption Co = 10mg/dm3 on Obeche (425µm) Time (min) 10 20 30 40 50

Low speed A 0.448 0.468 0.490 0.483 0.508

X Nil ““ ““ ““ ““

Intermediate A 0.449 0.473 0.524 0.521 0.542

X Nil ““ ““ ““ ““

High speed A 0.445 0.464 0.496 0.522 0.525

X Nil ““ ““ ““ ““

Table 5c. Adsorption response at Higher concentration of Eosin Particle Size

CO

AO

At (24 hrs)

Xi

1000µm

200mg

1.008

1.022

Nil

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Figure 1. Dye absorbed (x/m mg dye g-1 wood) vs contact time (s) for methylene blue (Co = 10mg/dm3) at various stirring speed on (a) Obeche (425um) (b) Iroko (425um) at a temperature of 30oc; Low Speed;

Intermediate Speed;

High Speed.

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Figure 2. Dye absorbed (x/m mg dye g-1 wood) vs contact time (s) for methylene blue (Co = 10mg/dm3) at various stirring speed on (a) Obeche (1000um), (b) Iroko (1000um) at a temperature of 30oc; Low Speed;

Intermediate Speed;

High Speed.

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Figure 3. Dye absorbed (x/m mg dye g-1 wood) vs contact time (s) for methylene blue (Co = 10mg/dm3) at various stirring speed on (a) Obeche (2000um), (b) Iroko (2000um) at a temperature of 30oc; Low Speed;

Intermediate Speed;

High Speed.

Effect of Stirrer Speed on Adsoption of dye by the Sorbates The rate of colour removal is controlled by the stirrer speed for basic dye, acidic dye (Eosin B) did not show positive response as tables 5(a - c) indicates). This effect shows that

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increasing the stirring rate decreases the mass transfer resistance (boundary layer thickness) between the bulk fluid and the surface of the adsorbent particle. The particles of the adsorbent being small tend to move with the liquid creating a layer of nearly stagnant fluid surrounding each particle. The data showed that beyond the intermediate stirrer speed, the colour removal is not much and as such the curve for intermediate and high stirrer speed' lie close together, indicating that the rate of removal is independent on the rate of stirring beyond the intermediate speed. This accounts for choice of intermediate speed in data evaluation and in the next phase of the study. Also colour removal performance by Iroko is better than Obeche. The tabulated result indicated that Obeche leads at the onset of each run while Iroko outruns later as seen towards the attainment of equilibrium. This could be attributed to mass transfer resistance and structural composition of the wood-inclined to high density of Iroko and therefore more pores and greater surface area. Extrapolating the linear portion of figures 4a and 4b to the time axis provides intercept that relates to the extent of boundary layer thickness while the gradient defines the rate parameter K without dimensions of rate constant. This is from experimental fact obtained by dimensional analysis in a previous paper[11] for batch process, which have shown that the square root of time (t0.5) rather than t is preferred for plotting purposes.

Effect of Particle Size

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Again referring to tables 2(a, b) - 4(a, b) and figures 4a and 4b, it shows that the rate of colour removal increases with decreasing particles sizes. This is due to the fact that heterogeneous reaction requires the presence of surfaces and thus the rate of reaction will under most conditions depend on the surface area. The smaller the particle, the larger the surface area, a larger surface will usually result in a faster reaction. This again explains the choice of particle size in the data evaluation and in the next phase of the investigation for the acidic dye, tables 5(a-c) shows that at the workable condition of small particle sizes, intermediate and high stirrer speeds, high concentration of dye solution (200mg/dm3) versus longer contact time (2 hrs), adsorption was not feasible to both wood types. This may indicate that there must be a portion of the structural component of the dye moiety that is resistant to adsorption on the wood [23] or due to the selective adsorption of cellulose material that make up the wood particle[19].

Phase 2: Temperature Experiment Effect of temperature on the rate processes The temperatures investigated are 40OC, 50OC and 60OC. Table 6a(i-iii): Effect of Temperature on dye removal on Obeche (425µm) at concentration of 10mg/dm3 and intermediate stirrer speed at different temperatures.

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Figure 4. Dye absorbed (x/m mg dye g-1 wood) vs square root of contact time (s0.5) for methylene blue (Co = 10mg/dm3) at various stirring speed on (a) Obeche (425um), (b) Iroko (425um) at a temperature of 30oc;

Low Speed;

Intermediate Speed;

High Speed.

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Table 6 ai. 40OC Mass of wood Time (S) 30 60 90 120 150 180 210 240

2g

4g

6g

8g

10g

A

X

A

X

A

X

A

X

A

X

0.601 0.458 0.392 0.354 0.319 0.281 0.278 0.250

5.70 6.70 7.20 7.45 7.70 7.95 7.95 8.20

0.648 .370 0.269 0.191 0.207 0.192 0.163 0.178

3.50 7.30 8.00 8.60 8.50 8.60 9.95 8.70

0.609 0.296 0.211 0.137 0.125 0.083 0.100 0.099

5.60 7.95 8.50 9.00 9.15 9.45 9.30 9.30

0.353 0.158 0.100 0.077 0.068 0.057 0.051 0.052

7.50 8.85 9.30 9.45 9.50 9.60 9.65 9.65

0.254 0.167 0.147 0.145 0.133 0.140 0.117 0.121

8.20 8.75 8.95 8.95 9.10 9.00 9.20 9.15

Table 6 aii. 50OC Mass of wood Time (S) 30 60 90 120 150 180 210 240

2g

4g

A 0.689 0.593 0.542 0.576 0.478 0.463 0.414 0.425

X 5.10 5.75 6.10 6.30 6.60 6.70 7.70 6.95

6g

A 0.435 0.336 0.288 0.267 0.227 0.218 0.195 0.222

X 6.85 7.55 7.90 8.00 8.30 8.40 8.55 8.40

8g

A 0.321 0.233 0.189 0.174 0.164 0.147 0.139 0.152

X 7.70 8.35 8.60 8.75 8.85 8.95 9.00 8.95

A 0.457 0.287 0.195 0.157 0.150 0.142 0.126 0.114

X 6.70 7.90 8.05 8.90 8.95 9.00 9.145 9.20

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Table 6 aiii. 60OC Mass of wood Time (S) 30 60 90 120 150 180 210 240

2g

4g

6g

8g

10g

A

X

A

X

A

X

A

X

A

X

0.652 0.572 0.468 0.448 0.406 0.381 0.349 0.336

5.35 5.90 6.65 6.80 7.05 7.25 7.50 7.55

0.427 0.255 0.248 0.213 0.208 0.196 0.181 0.186

6.90 8.10 8.20 8.50 8.50 8.60 8.70 8.65

0.450 0.241 0.177 0.145 0.131 0.118 0.110 0.108

6.75 8.25 8.70 9.00 9.10 9.15 9.20 9.20

0.384 0.193 0.145 0.126 0.116 0.107 0.101 0.095

7.25 8.70 9.00 9.15 9.20 9.25 9.30 9.35

0.408 0.193 0.142 0.117 0.108 0.096 0.089 0.085

7.00 8.70 9.00 9.20 9.75 9.35 9.40 9.45

Table 6b(i-iii) - Effect of temperature on Dye adsorption on Iroko (425) at Co of 10 mg/dm3 and intermediate stirrer speed at different temperatures.

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F.N. Emengo, J.K. Nduka, C.N. Anodebe et al. Table 6bi. 40OC Mass of wood Time (S) 30 60 90 120 150 180 210 240

2g

4g

A 1.332 0.776 0.728 0.655 0.494 0.324 0.449 0.349

X 0.49 4.55 4.80 5.30 6.50 7.70 6.70 7.50

6g

A 0.770 0.543 0.323 0.129 0.120 0.075 0.049 0.046

X 4.50 6.10 7.70 9.10 9.15 9.50 9.65 9.70

8g

A 0.913 0.303 0.078 0.056 0.045 0.032 0.030 0.032

X 3.50 7.70 9.45 9.60 9.70 9.78 9.80 9.78

A 0.494 0.066 0.061 0.029 0.022 0.023 0.020 0.021

10g X 6.50 9.55 9.60 9.80 9.88 9.88 9.90 9.88

A 0.661 0.197 0.017 0.060 0.046 0.044 0.038 0.028

X 5.25 9.55 9.30 9.60 9.70 9.70 9.75 9.80

Table 6b ii. 50OC Mass of wood Time (S) 30 60 90 120 150 180 210 240

2g

4g

A 0.643 0.628 0.477 0.428 0.349 0.294 0.298 0.233

X 5.40 5.50 6.60 6.90 7.50 7.90 7.95 8.30

6g

A 0.353 0.175 0.106 0.086 0.058 0.051 0.046 0.052

X 7.47 8.70 9.25 9.40 9.40 9.65 9.70 9.65

8g

A 0.491 0.138 0.053 0.039 0.030 0.028 0.027 0.029

X 6.50 9.00 9.65 9.65 9.75 9.80 9.80 9.80

A 0.161 0.059 0.040 0.032 0.031 0.029 0.028 0.039

10g X 8.80 9.55 9.75 9.80 9.80 9.80 9.80 9.65

A 0.180 0.034 0.016 0.021 0.016 0.011 0.009 0.009

X 8.60 9.80 9.90 9.90 9.90 9.95 9.95 9.95

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Table 6b iii. 60OC Mass of wood Time (S) 30 60 90 120 150 180 210 240

2g

4g

6g

8g

10g

A

X

A

X

A

X

A

X

A

X

0.444 0.331 0.254 0.214 0.169 0.121 0.095 0.090

6.80 7.60 8.20 8.50 8.75 9.15 9.30 9.35

0.213 0.084 0.052 0.027 0.029 0.022 0.021 0.021

8.50 9.45 9.65 9.85 9.80 9.90 9.90 9.90

0.306 0.090 0.066 0.049 0.048 0.048 0.044 0.044

7.80 9.35 9.50 9.65 9.60 9.65 9.75 9.75

0.133 0.052 0.041 0.038 0.034 0.031 0.066 0.037

9.00 9.65 9.75 9.75 9.80 9.80 9.50 9.75

0.059 0.322 0.019 0.022 0.026 0.021 0.019 0.022

9.55 9.80 9.90 9.85 9.85 9.90 9.90 9.85

6c. Effect of Temperature on the adsorption of Eosin on wood employing intermediate stirrer speed Mass of wood Time (S) 30 60 90 120 150

40OC, Co = 5mg/dm3 10g 20g A 0.271 0.284 0.287 0.291 0.291

X Nil Nil Nil Nil Nil

A 0.280 0.303 0.312 0.319 0.328

X Nil Nil Nil Nil Nil

50OC, Co = 5mg 10g

60OC 10g (5mg dye)

A 0.249 0.257 0.259 0.261 0.263

A 0.253 0.264 0.271 0.270 0.273

X Nil Nil Nil Nil Nil

X Nil Nil Nil Nil Nil

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10g (10 mg dye) A X 0.442 Nil 0.443 Nil 0.453 Nil 0.447 Nil 0.453 Nil

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Mass of wood Time (S) 180 210 240

40OC, Co = 5mg/dm3 10g 20g A 0.293 0.293 0.294

X Nil Nil Nil

A 0.38 0.334 0.334

X Nil Nil Nil

50OC, Co = 5mg 10g

60OC 10g (5mg dye)

A 0.262 0.270 0.276

A 0.273 0.274 0.277

X Nil Nil Nil

187

10g (10 mg dye) A X 0.449 Nil 0.454 Nil 0.454 Nil

X Nil Nil Nil

ACTIVATION ENERGY OF ADSORPTION Table 7a. Evaluated data from temperature experiment for methylene blue on Obeche (425µm) Temperature Time √Time (S0-5) (S) 5.477 30 7.746 60 9.487 90 10.955 120 12.247 150 13.416 180 14.491 210 15.492 240

30OC X 6.50 8.35 8.50 8.95 9.10 9.30 9.30 9.30

X/M

40OC X

0.650 9.835 0.850 0.895 0.910 0.930 0.930 0.930

5.60 7.95 8.50 9.00 9.15 9.45 9.30 9.30

X/M

50OC X

0.93 1.325 1.416 1.500 1.525 1.575 1.560 1.560

7.70 8.35 8.60 8.75 8.85 8.95 9.00 8.95

X/M

60OC X

X/M

1.283 1.389 1.430 1.458 1.471 1.491 1.500 1.491

6.750 8.250 8.700 9.000 9.100 9.150 9.200 9.200

1.108 1.370 1.450 1.500 1.510 1.520 1.530 1.530

Table 7b. Evaluated data from temperature experiment for methylene blue on Iroko (425µm)

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Temperature Time √Time (S) (S0-5) 5.477 30 7.746 60 9.487 90 10.955 120 12.247 150 13.416 180 14.491 210 15.492 240

30OC X

X/M

40OC X

X/M

50OC X

X/M

60OC X

X/M

4.80 7.80 9.10 9.45 9.80 9.90 9.85 9.90

0.480 0.780 0.910 0.945 0.980 0.990 0.985 0.990

3.50 7.70 9.45 9.60 9.70 9.78 9.80 9.88

0.683 1.280 1.575 1.600 1.616 1.630 1.633 1.646

6.50 9.00 965 9.75 9.80 9.80 9.83 9.80

1.08 1.50 1.608 1.625 1.633 1.633 1.638 1.633

7.80 9.35 9.50 9.65 9.60 9.65 9.75 9.75

1.30 1.558 1.580 1.608 1.600 1.608 1.625 1.625

Tables 6.(ai, aii and aiii), 6(bi, bii and biii) and figures 5 (a and b) shows the contact time experiment performed at different temperature for methylene blue and table 5c for that of Eosin. Whereas, Eosin, did not respond to the treatment, methylene blue gave an appreciable response. Result for methylene blue revealed that the rate of adsorption increases drastically with increase in temperature at onset of reaction and slows down toward the attainment of equilibrium. This agrees with the prediction of Arrhenius equation. The increase in the initial rate of the adsorption at higher temperature also enhanced the time taken to achieve equilibrium and therefore a reduction in the contact time, example, the time taken for equilibrium to be attained at 30°C is approximately 3mins (180s) while at 60°C it is just a minute (60s).

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Eosin (acid dye) showed no response as table 6c indicated this again showed that a portion of the structural component of the dye moiety may be resistant to treatment[23].

Figure 5. Dye absorbed (x/m mg dye g-1 wood) vs contact time (s) for methylene blue (Co = 10mg/dm3) on (a) Obeche (425um), (b) Iroko (425um) at a various temperature and an intermediate stirrer speed; 30oC;

40oC;

50oC;

60oC.

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Table 8. Rate parameter (k, mg dye g-1 wood S-0.5) for the adsorption of methylene blue (Co = 10mg/dm3) on Obeche and Iroko wood (425µm) at different temperature and at an intermediate stirrer speed Rate parameter (k)

Temperature (OC) 30 40 50 60

Obeche 0.0962 0.208 0.2125 0.300

Iroko 0.0957 0.2143 0.2418 0.2769

Table 9. Log rate parameter (k, mg dye g-l wood 5—0.5) for methylene blue (Co = 10mg/dm) on Obeche and lroko wood respectively at different reciprocal absolute temperature using the data from Table 8

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Log Rate Parameter Obeche - 1.017 - 0.681 - 0.673 - 0.523

Temperature (OK-1) Iroko - 1.038 - 0.669 - 0.617 - 0.558

3.305 x 10-3 3.196 x 10-3 3.096 x 10-3 3.003 x 10-3

The rate parameters defined before as the gradient of the linear portion of the plot, mg of dye adsorbed per gram, g-1 of adsorbent versus the square root of contact time, S0.5 were determined for experimental contact time at different temperatures. Tables 7a and 7b gives the data evaluation from contact time experiment of various temperatures, while figures 6a and 6b shows the plots for methylene blue on obeche and iroko respectively. 425µm particle size and intermediate stirring rate were employed in the experiment. The linear portions of the initial stages figures 6(a) and 6(b) were used to determine the relative rates of adsorption for comparative purposes, though the K values do not have the normal dimension of rate constant, relative value under similar experimental condition should be significant as rate parameters. The K values determined at various temperatures investigated were shown in table 8 for methylene blue on Obeche and Iroko Woods respectively. Using the data, Arrhenius plot of log K Versus the reciprocal of absolute temperature (K-1) was used to calculate the activation energy of adsorption for both woods, from Arrhenius relationship, log k = long A - Ea/2.303RT. To ensure that the best line is fitted to the experimental data, regression analysis, the method of least squares were used to obtain the slope of the line. This is used to compute the activation energy of adsorption. Y = bx + a a, intercept on the y–axis and b the slope can be calculated using equation (2) and (3)

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(2)

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(3)

Figure 6. Dye absorbed (x/m mg dye g-1 wood) vs square root of contact time (s0.5) for methylene blue (Co = 10mg/dm3) on (a) Obeche (425um), (b) Iroko (425um) at a various temperature and an intermediate stirrer speed;

30oC;

40oC;

50oC;

60oC.

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Using the data from table 9, the activation energies of obeche and iroko are computed respectively. From equation (3) 79.649 x 10-6 0.49 x 10-7 = 1625.4897K Ea But slope = 2.303R

Slope (b) =

Ea = 31.125kg mol -1 (for Obeche) while that of Iroko is Slope = b =

79.622 x 10-6 0.49 x 10-7

= 1624.938776K But slope =

Ea 2.303R

Ea = 31.114 kg mol -1 (for Iroko)

The activation energies computed from the slopes of the plots for the adsorption of methylene blue on Obeche and Iroko are 31.125KJ Mol-1 and 31.114 kj Mol-1, both are within the expected range of physiosorption (< 40KJ Mol-1). The data of the Arrhenius plot is shown in table 9.

TEMPERATURE ISOTHERMS

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The results of the isotherm experiments conducted at temperatures of 40, 50 and 60OC are shown in tables 10 and 11 for Obeche and Iroko respectively. The data was analysed using the Langmuir isotherm model. The model is presented both in standard and linearized form. Langmiur equation:

Cm = ultimate adsorption capacity (monolayer coverage), mg/g Ce = equilibrium concentration of dye in solution mg/dm-3 b = Langmuir constant, (mg/d-3)-1 n = adsorption intensity, gdm-3

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Table 10. Obeche mg dye adsorbed g-1 wood and equilibrium dye concentration, Ce Temperature Mass of wood (g) 2g 4g 6g 8g 10g

40OC X/M 3.975 2.175 1.550 1.206 0.915

(X/M) –1 0.252 0.460 0.645 0.829 1.093

Ce 2.05 1.30 0.70 0.35 0.85

1/Ce 0.488 0.769 1.429 2.857 1.177

50OC X/M 3.50 2.10 3.00 1.15 -

(X/M) –1 0.286 0.476 0.333 0.870 -

Ce 3.00 1.60 1.00 0.80 -

1/Ce 0.333 0.625 1.000 1.250 -

60OC X/M 3.775 2.175 1.530 1.160 0.940

(X/M) –1 0.265 0.460 0.650 0.862 1.064

Ce 2.45 1.30 0.80 0.70 0.60

1/Ce 0.408 0.769 0.962 1.374 1.666

Ce 0.70 0.10 0.25 0.20 0.10

1/Ce 1.429 10.00 4.000 5.000 10.00

Table 11. Mg dye adsorbed g-1 wood and equilibrium dye concentration, Ce (Iroko) Temperature Mass of wood (g) 2g 4g 6g 8g 10g

40OC X/M 3.750 2.425 1.630 1.235 0.970

(X/M) –1 0.266 0.412 0.614 0.810 1.031

Ce 2.50 0.30 0.30 0.22 0.30

1/Ce 0.40 3.33 4.54 8.33 3.33

50OC X/M 3.950 2.412 1.630 1.225 0.950

(X/M) –1 0.253 0.415 0.415 0.816 1.005

Ce 2.10 0.35 0.20 0.20 0.05

1/Ce 0.476 2.857 2.857 5.00 2.000

60OC X/M 4.650 2.475 2.475 1.625 0.900

(X/M) –1 0.215 0.404 0.615 0.816 1.010

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A plot of (X/M)-1 vs 1/Ce gives a straight line of slope (1/Cmb) and intercept 1/Cm for Langmuir model, illustrated by regression analysis to obtain the best value of the slope and intercept in a straight forward method rather than by graph plotting. Using equation (3)

0.7942198 3.387644

Slope = b = Slope = 1

Cmb

= 0.235

From equation (2)

Intercept = 1

Cm

= y - bx

= 0.6558 - (0.235 x 1.344) = 0.3407 C m = a -1 = (0.3407)

-1

= 2.935mg / g But 1

Cmb

= 0.235

b = 1 = 1

(C m x 0.235) (2.935 x 0.35)

(

= 1.450 mg dm3

)

-1

From table 10, the data of adsorption for 50OC has 4 determinations of which the 3rd determination is questionable and was rejected at 90% confidence level. This is because the Q-test yielded Qexp of 0.789, which is greater than Qcritical of 0.765 at 90% level, which corresponds to 4 measurements, therefore, 3 of the 4 measurements are used in the analysis.

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Using equation (3)

Slope = 1

Cmb

=

0.279086 0.177464

= 1.57263445

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F.N. Emengo, J.K. Nduka, C.N. Anodebe et al. Intercept =

1

C m = y - bx

= 0.736 - (1.5726 x 0.544) = 0.736 - 0.8555 = 0.1195 C m = (0.1195)

−1

= 8.36 7mg / g

1

But

C m b = 1.573 b =

1

(C m x 1.573)

=

1

(8.36 x 1.573)

= 1 13.1587

(

b = 0.076 mg dm3

)

-1

At 60OC (for Obeche)

Slope =

1 Cmb =

0.6357784 1.0394257

= 0.61166 Intercept, a =

1

Cm

= y - bx

= 0.661 - (0.61166 x 1.1044)

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= 0.661 - 0.6755 = - 0.01452 -1 Cm = a = -68.865mg/g But 1/Cmb = 0.61166 b = 1/Cm x 0.61166 b = 0.024 (mg/dm3)-1 From regression analysis for the computation of ultimate absorption capacity and kinetic constants, Langmiur model at 40OC (Iroko), (table 11).

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Dye Wastewaters, Alternative Physiochemical Treatment Reagent 1.4264532 9.48848 = 0.150335269

Slope = 1

Cmb

=

Intercept = 1

C m = y - bx

= 0.6274 - (0.150 x 2.988) = 0.6274 - 0.4492 = 0.178198214 C m = a -1 = 5.6117mg / g But 1/Cmb = 0.150 b = 1/Cm x 0.150 = 1.185 (mg/dm3)-1 At 50OC

1

Slope =

Cmb =

1.461257749 13.94680275

= 0.104773672 Intercept, = 1

Cm

= y - bx

= 0.52425 - (0.1048 x 3.33325) = 0.1750 C m = a -1 = 5.7139 mg / g

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But 1/Cmb = 0.1048 b = 1/Cm x 0.1048 b = 1.670 (mg/dm3)-1 At 60OC

Slope =

1 Cmb =

4.957488469 57.88596424

= 0.085642323

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195

196

F.N. Emengo, J.K. Nduka, C.N. Anodebe et al. Intercept, = a = 1

Cm

= y - bx

= 0.6322 - (0.0856 x 6.0858) = 0.6322 - 0.5212 C m = a -1 = 9.009mg / g

But 1/Cmb = 0.0856 b = 1/Cm x 0.0856 b = 0.772 (mg/dm3)-1 In general, the adsorption isotherms provided reasonably good adsorption estimate. The maximum adsorption capacity, Cm derived from langmuir equation for Obeche and Iroko at initial concentration of 10mg/dm3 and a minimum adsorbent concentration of 2g are approximately 8mg/g and 9mg/g respectively. This indicates favourable adsorptivity.

DETERMINATION OF THE SPECIFIC AREA OF WOOD PARTICLES The maximum value of Cm for both woods were used to compute the specific surface area of the particle (425µm) using SW = CmNδ0 (previously explained) Cm is in mg/g For Obeche: Cm = 8.367mg/g

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Converting to mole per gram, given that the molecular weight of methylene blue is 319.86g.

8.367 x 10-3 ( Mol / g) 3.19.86 = 2.6158 x 10-5 Mol / g

∴ 8.367mg / g =

Using δ = 1.2nm2 for methylene blue and N = 6.022045 x 10-23 SW = CmNδ0 = 2.6158 x 10-5 Mol/g x 1.2 x 10-9 m2 x 6.022045 x 1023 Mol-1 = 1.89 x 10-10 m2/g

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For Iroko,

C m = 9.001mg / g 9.001 x 10-3 Mol / g 319.86 = 2.814 x 10-5 Mol / g

=

SW = C m Nδ 0 = 2.814 x 10-5 Mol / g x 6.022045 x 1023 Mol -1 x 1. x 10-9 m2 SW = 2.034 m2 g These specific surface areas compared well with 200m2/g, which is classified as very high surface area in literature. Langmuir model was used for the computation of constants (k, b, n and Cm).

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CONCLUSION The work shows that wood, an inactivated form of carbon can adsorb dye material and that under favourable conditions of particle size, stirring speed and temperature can adsorb more dye in wastewater, The degree of colour removal depends on the type of wood as well as dye. Basic dye (methylene blue) was feasible with ultimate adsorption capacity, Cm derived from langmuir isotherm model - 9.090 mg/g and 10mg/g on Obeche and Iroko. Geographical location of wood is also a determining factor because similar work has established contact time of less than 1hr to 4hrs but this work is just few minutes (1-3 mins.). The work partly supports the work of Mckay and Poots, their work indicated that wood particle effectively reduced the colour of dye solution, of the dyes (acidic and basic) they chose, both showed appreciable colour reduction. But in Our own case the acidic dye investigated showed no adsorptive response, this can be attributed to the fact that the structure, which gives the dye its colour may not be affected physicochemically. We can conclude from this findings that the basic dye is adsorbed by wood which achieved almost 90-95% colour reduction and can serve as alternative Physicochemical treatment reagent.

REFERENCES [1] [2]

Robert, H. P;Don W.G. (1998). Perry’s Chemical Engineering Handbook, 7th ed. McGraw –Hill Inc. New York. Pp 25 58-80, 16. Warren, M.L; Smith, J.C, Harriot, P. (2001). Unit Operations of Chemical Engineering 6th ed. McGraw Hill Co. Inc 1221 Avenue of the America’s New York, NY10020. pp 814 – 852.

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198 [3] [4] [5]

[6] [7] [8] [9]

[10] [11]

[12] [13] [14]

[15]

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[16] [17] [18] [19] [20]

[21]

F.N. Emengo, J.K. Nduka, C.N. Anodebe et al. Met Calf and Eddy (1991). Wastewater Engineering, 3rd ed. Tata McGraw-Hill Publishing Co. Ltd. 4/12 Asaf Ali Road, New Delhi 11002 pp 49, 312-324. Hazardous Waste Measurements. (1991). Lewis Publishers Inc. 121 South Main Street, P.O. Drawer 519, Chelsea, Michigan 48118. pp 18-26, 170-173, 216-238, 274-280. Manahan, S. E. (1990). Hazardous Waste Chemistry, Toxicology and Treatment. Lewis Publisher, Inc. 121, South Main Street, Chelsea, Michigun 48118 pp 95-102, 168-216, 267-287. Van Nostrand’s Scientific Encyclopedia (1989) .7th ed. Van Nostrand Reinhold 115 fift Avenue, New York, New York 10003. pp. 42-44, 944-946. Seader, J.O; Henley E.J. (1998). Separation Process Principles. John Wiley and Sons Inc. New York pp. 784-801. Smith, J.M (1981). Chemical Engineering kinetics, 3rd ed. McGraw-Hill, Inc. Tokyo pp. 1-7, 322-334, 359, 636-656. A) Purdue University (1978). Proceedings of 32nd Industrial Waste Conference (May 1977). Ann Arbor Publisher, Inc. P.O.Box 1425, 230 Collingwood, Ann Arbor, Michigan 4106. pp. 1-9, 664-673. B) Purdue University (1987). Proceedings of 41st Industrial Waste Conference (May 1986). Lewis Publishers Inc. 121 South Main Street, Chelsea, Michigan 48118 pp 603-616, 422-427, 711-725. Masters, G. M. (1998). Introduction to Environmental Engineering and Science 2nd ed: Prentice Hall, Upper Saddle River, New Jersey 07458 pp. 185-197, 288-311. McKay, G. and Poots V.J.P. (1980). “Kinetics and Diffusion Processes in colour removal from effluent. Using wood as an adsorbent”. Journal of chemical technology and biotechnology. Society of chemical industry. Vol 3 pp 279- 292. Terrance A (1990). Particle size measurement, 4th ed. Chapman and Hall, 2-6. boundary Row, London SEI 8HN. Pp 220-223, 571-609. Schwarzenbach, R.P; Gschwend, P.M.; Imboden, D.M. (1993). Environmental Organic Chemistry. John Wiley and Sons, Inc. New York pp. 255-241, 328-341. The Open University (1996). Physical Chemistry: Principles of Chemical Change, Block 5. The Open University, Walton Hall, Milton Kynes MK7, 6Y2 United Kingdom pp 9-14. 51-54. Aldric Chemical Co (1998-99). Catalog Handbook of Fine Chemical. Aldric Chemical Co. P.O. Box 2060, Milwuukee, WI, 53201 USA pp 272, 1110. Crites R., Techobanoglous G. (1998) .Small and Decentralized Wastewater Management Systems. McGraw-Hill Book Co. Inc. Singapore. Pp 21-47, 67, 119, 1013. Moore, J.W; Moore. E.A. (1976) .Environmental Chemistry Academic Press Inc. (London) Ltd. 111 Fift Avenue, New York 1003 pp 375-382. Passivirta, J (1991). Chemical Ecotoxicology. Lewis Publishers Inc. 121 South Main Street, Chelsea, MI 48118 pp53-82. McGraw-Hill Encyclopedia of Science and Technology (1997). 9th ed. McGraw-Hill, Inc. New York, Vol. 1 pp 111-112, 163-158; Vol 13 p. 437; Vol 5 pp 473-474. Giles, P.G. and Chapman, D. (1989). Dynamic Modeling and Expert systems in wastewater engineering. Lewis Publishers. Inc. 121 South Main Street, Chelsea, Michigan 48118 pp.245-257. Rod B (1998). Integrated Pollution Control, Stanley Thorn (Publishers) Ltd. Ellenborough House, Wellington Street, Cheltenharm Glos. GL50ND pp. 52-94.

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[22] Freeman, H (1995). Industrial Pollution Prevention Handbook. McGraw-Hill Inc. New York pp. 829-843, 889. [23] Encyclopedia of Material Science and Engineering (1988). Pergamon Press Ltd. Headngton Hill Hall, Oxford, Ox3, OBW, England: Vol. 5pp. 3669-3616.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 © 2009 Nova Science Publishers, Inc.

Chapter 6

UTILIZATION OF PHLOGOPITE-RICH MINE TAILINGS IN ABATEMENT OF PHOSPHORUS LOADING TO WATERCOURSES Salla Venäläinen* University of Helsinki, PO Box 27, 00014 University of Helsinki, Finland

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ABSTRACT Phosphorus (P) from domestic sewage waters and other diffuse sources of pollution is a threat to natural water systems. Households in sparsely populated areas that are commonly outside a sewer network thus need an easily maintained purification technique to remove P from their wastewaters. Furthermore, the P load from other sources of loading, such as agricultural land, requires counteracting measures. In a given agricultural region, a major part of P loading to surface waters may originate from some critical source areas, such as feeding and queuing areas on pasture soils or in fields receiving repeated loading of manure from chicken houses or fur ranches. Environmentally sound measures are needed to amend this type of hotspot to reduce the mobility of P enriched in the surface soil layers. The present study was undertaken to unravel the P retention ability of phlogopiterich mine tailings produced in the enrichment process of apatite ore and its utilization as an adsorbent in wastewater treatment and in remediation of soil in critical areas. Due to its chemical and mineralogical properties, the material can be assumed to be suitable for P retention. The sorption of P was studied both in the solution phase to unravel the retention mechanisms as well as in more versatile soil environments. Sorption-desorption isotherms and various chemical extractions were employed to elucidate the P sorption reactions and retention components and capacity of the tailings. The contribution of artificial weathering of the material, as well as the reaction time and particle size, on P retention were also examined. In general, the results showed that phlogopite-rich mine tailings retain P efficiently. The isotherm determined for the untreated material was tortuous in shape, suggesting that several mechanisms and components, such as amorphous Al and Fe oxides and accessory calcite, are involved in P sorption. Artificial weathering, extended reaction time and decrease in particle size increased P retention. An *

Corresponding author; E-mail address: [email protected], Fax: +358 9 191 58686

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Salla Venäläinen incubation experiment with soil revealed that the tailings significantly improved the P sorption capacity of the soil, the artificially weathered material in particular. The untreated tailings did not affect the distribution of the sorbed P among various chemical pools while the acid-treated tailings decreased labile P and increased the amount of P retained by Fe oxides.

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1. INTRODUCTION Phosphorus (P) loading from domestic wastewaters originating in households outside a sewer network threatens the quality of natural watercourses. Chardon & Faassen (1999) focused on the major portion of P loading from agricultural fields, which originates in some critical source areas (CSAs), such as feeding and queuing areas on pasture soils or fields receiving repeated loads of manure from chicken houses or fur ranches. Preventing P leaching from such hotspots is particularly challenging, because the runoff waters cannot be controlled as restrainedly as domestic wastewaters. In wastewater plants, P in water from household consumption is commonly precipitated as scarcely soluble metal salts (e.g. Al2(SO4)3, AlCl3) (Galarneau & Gehr, 1997; Yang et al., 2006). Private households, however, require a purification system that, to begin with, meets the criteria set for wastewater released to the environment and, secondly, is inexpensive and easy to maintain. In soil and natural waters, P commonly occurs as phosphate anions (PO43-, HPO42-, H2PO4-), which are strong bases in nature and therefore susceptible to specific adsorption by Al and Fe oxides through ligand exchange (Hingston et al., 1967, Parfitt et al., 1975, Ryden et al., 1987, Beck et al., 1999). Thus, minerals rich in Al and Fe play an important role in controlling P mobility in soil. Acidification of such systems contributes to the formation of aquo-group ligands that are easily replaced by phosphate anions in the coordination sphere of the metal oxides, thus favouring such P retention (e.g. Ryden et al., 1977; Yang et al., 2006). Phlogopite (KMg3(Si3Al)O10(OH)2) is a trioctahedral mica mineral and an end member of the biotite series (annite-phlogopite) (Rieder et al., 1998). Members of this series commonly serve as parent material in clay mineral formation through weathering. At the early stage of formation, such minerals typically go through the isomorphic substitution of Al3+ for Si4+ in the tetrahedral layer and of Fe2+ for Al3+ in the octahedral layer. Weathering exposes these metal cations on the edge-faces of phlogopite and, furthermore, contributes to the formation of oxides on the fracture edges of the mineral. Such sites function as efficient P sorbents; thus, unweathered phlogopite, with an exiguous amount of oxides on the edge-faces and a small specific surface area, is rather poor in P sorption sites. The natural weathering can be roughly simulated by acid treatment. This contributes to the solubilization of Al and Fe cations, followed by precipitation of these as oxides and hydroxides. These weathering products also have an extensive specific surface area (Bigham et al., 1978; Borggaard, 1982, Gimsing & Borggaard, 2002). Consequently, acid treatment is likely to increase the P retention capacity of phlogopite. These aforementioned characteristics have recently given rise to interest in the employment of untapped phlogopite-rich mine tailings in an effort to reduce environmental P loading hazards from wastewaters and other terrestrial sources. Large deposits of phlogopite can be found e.g. in Ontario, Canada (Pan & Fleet 1992), in the Kola Peninsula, Russia (Krasnova 2001) and in Siilinjärvi, Finland (Puustinen 1973). In Siilinjärvi, 150 000 t of phlogopite-rich mine tailings are produced annually as a by-product

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in apatite ore beneficiation. In addition to phlogopite (75%), the tailings contains carbonate minerals (16%), residues of apatite from the flotation process and water. In addition to phlogopite, carbonate minerals are also known to retain P to some extent (Cole et al. 1953, Freeman & Rowell 1981, Borrero et al. 1988). Annually, some 50% of the tailings are further processed into Kemira Biotite, a commercial product used as a fertilizer, while the rest of the tailings is piled untapped. The objective of this study was to examine the retention of P by phlogopite-rich mine tailings from Siilinjärvi apatite ore and the potential utilization of these tailings in the fight against P loading to natural watercourses. The P sorption by the tailings from a simple aqueous solution was investigated to simulate the reactions in wastewater. To unravel the reactions of the tailings in a more complex system, the tailings were allowed to react with soil containing dissimilar P pools. The effect of artificial acid-induced weathering of the adsorbent on P retention was also studied. Since the ore beneficiation by flotation generates particles of various sizes differing in their mineralogical properties, the impacts of particle size and reaction time on P sorption by the tailings were investigated.

2. MATERIAL AND METHODS

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2.1. Tailings Weathering of the tailings had been simulated at the research centre of Kemira GrowHow Oyj by treating the material with 70% sulphuric acid. To remove any adsorbed water, the acid-treated reaction product was dried at 60 ºC for 12 h in the laboratory and the untreated tailings was air-dried at room temperature. The dry tailings were stored in airproof containers. In the laboratory, both tailings were passed through a Ø 0.2-mm sieve to obtain two particle-size fractions: Ø > 0.2 mm and Ø < 0.2 mm. Both fractions were included separately in all tests to elucidate their contribution to the P retention. The sieving revealed that particularly the coarsely sized fraction of the untreated tailings contained white mineral fragments, presumably representing apatite ore residues from the beneficiation process. Both the untreated and acid-treated tailings had a metallic lustre. Munsell's (1994) soil colour chart served in classifying the colours of the tailings. The physicochemical properties of all tailings samples are listed in table 1. The pH as well as the electrical conductivity (EC) were measured in four replicates in a deionized water suspension (v:v 1:2.5). Poorly crystalline Fe, Al and Mn hydroxides in both particle-size fractions as well as in the unsieved material were analysed for both the untreated tailings and the acid-treated tailings. This was carried out with a modification of the extraction method of Niskanen (1989) by extracting twice with 0.05 M ammonium oxalate (pH 3.3, 1:50 g:mL, shaking for 2 h in the dark) in four replicates. Prior to the actual extraction, calcite residues in the untreated tailings were removed in the form of CO2 by extracting with 1 M CH3COOH (pH 5.5). Both oxalate extracts were pooled together and analysed for Al, Fe and Mn with inductively coupled plasma-mass spectrometry (ICP-MS) (PerkinElmer Elan 6000, PerkinElmer, Waltham, MA, USA).

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Salla Venäläinen Table 1. Physicochemical properties of the tailings

Sample

Mesh

pH

EC

Amorphous oxides

Ø

H2O

μS cm-1

mmol kg-1 ± SD

> 0.2 mm

9.4

< 0.2 mm

9.1

Unsieved

9.3

> 0.2 mm

Mn

Fe

Al

0.2 ± 0.02

6.8 ± 0.5

0.6 ± 0.04

0.6 ± 0.02

17.8 ± 2.1

1.5 ± 0.05

0.3 ± 0.03

8.7 ± 0.7

0.8 ± 0.07

4.0

2.0 ± 0.07

150 ± 7

196 ± 8

< 0.2 mm

3.1

4.0 ± 0.12

299 ± 4

388 ± 6

Unsieved

3.6

2.6 ± 0.10

184 ± 9

240 ± 11

Untreated tailings

1500

Acid-treated tailings

26 000

EC = Electrical conductivity.

2.2. Experimental Designs

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2.2.1. Distribution of Added P among Various Chemical Pools in the Tailings Chang and Jackson's (1957) fractionation procedure modified by Hartikainen (1979) was adopted to describe the distribution of native and added P among various pools in the tailings materials. To obtain further information on the existing sorption sites, both particle-size fractions of the untreated and the acid-treated material were first enriched with P and then subjected to a sequential chemical fractionation procedure. The P enrichment of the tailings was carried out in three replicates by shaking 1-g untreated samples with 50 mL of KH2PO4 solution containing 1 mg P L-1 and 0.5-g acid-treated samples in 50 mL of the solution containing 50 mg P L-1. After a 1-h shaking, the suspensions were allowed to equilibrate for 23 h at room temperature and reshaken for 10 min before passing them through a 0.2-µm membrane filter (Nuclepore® polycarbonate; Nuclepore Corp., Pleasanton, CA, USA). The supernatants were then analysed for P as above. The P-enriched samples together with the filters were washed twice with 50 mL of deionized water, centrifuged and filtered once more. The distribution of the sorbed P among various chemical pools was determined with sequential extraction. Its principle is to distinguish between P reserves according to their sorption component, i.e. easily soluble P (extracted with NH4Cl), Al-bound P (extracted with NH4F, pH 8.5), Fe-bound P (extracted with NaOH) and Ca-bound apatitic P (extracted with H2SO4). The total degree of P saturation (DPS) of the oxides was calculated according to Peltovuori et al. (2002): DPS = (NH4Cl-P + NH4F-P + NaOH-P) / (0.5 × (Alox + Feox)) ×100 (%),

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where NH4Cl-P, NH4F-P, NaOH-P, Alox and Feox are given in mmol kg-1.

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2.2.2. Sorption Experiments with a P Solution The dynamic relationship between solid and solution P was depicted by expressing the sorption as a function of the P concentration in the equilibrium solution. Two sets of both particle sizes of untreated and acid-treated tailings were allowed to react with solutions of increasing P concentrations in four replicates (method modified from Hartikainen 1982). One set of samples was equilibrated for 23 h and the other for 7 d at 20 ºC. In both sets, 1-g untreated tailings samples and 0.5-g acid-treated tailings samples were shaken for 1 h with 50 mL of a standard KH2PO4 solutions of eight increasing P concentrations. The P additions were 0–4 mg L-1 and 0–5 mg L-1 for the 23-h and 7-d incubations of the untreated tailings, respectively, and 0–500 mg L-1 for both sets of acid-treated tailings. The equilibrated tailings suspensions were shaken for another 10 min before passing them through a 0.2-µm membrane filter (Nuclepore® polycarbonate). The filtrates were analysed for P with a Lachat Quick-Chem 8000 autoanalyser (Hach Company, Loveland, CO, USA) by an ascorbic acid method (Orthophosphate in waters, Quick Chem Method 10-11501-1-B) and their pH was recorded. The changes in the P concentrations during the equilibration were used to calculate the sorbed P at each P addition level. The peak quantity of P that the material retained was denoted as Qmax. During the equilibration, the formation of a white precipitate was detected in all incubation tubes containing the P solution. The emergence of this thick gel-like precipitate on the sample pellets was most significant in the acid-treated samples. The chemical composition of the precipitate was analysed with an x–ray diffraction (XRD) technique (Philips X'Pert with a Cu anode; Philips, Amsterdam, The Netherlands). The hypothesized contribution of hydrous metal oxides, apparently produced by the acid treatment, to P sorption was tested in an experiment with acid-treated tailings after the removal of oxalate-extractable metal oxides. The metals from the fine-particle-sized material were removed using ammonium oxalate extraction (Niskanen 1989) as described above, using however a solid:solution ratio of 1:100. Subsequent to extraction, the sample pellets were washed with 50 mL of saturated NaCl solution, centrifuged, washed with 50 mL of deionized water, centrifuged and air-dried overnight. Next, dry 1-g tailings samples were allowed to react with 50 mL of KH2PO4 solutions containing 0–3 mg P L-1 for 24 h before passing them through a 0.2-µm membrane filter (Nuclepore® polycarbonate). The supernatants were analysed for P as described previously.

2.2.3. Incubation Experiment with Soil To study the impact of the tailings P sorption dynamics in a chemically versatile medium, an incubation experiment with soil was conducted, in which 100-g portions of sieved (Ø 2 mm) clay soil were weighed into tared plastic vessels and mixed with 0.625 g of unsieved untreated or unsieved acid-treated tailings in three replicates. Three soil samples served as controls and, thus, received no tailings additions. All incubation units were moistened with 30 ml of milli-Q water (mQ-H2O; Millipore, Billerica, MA, USA) to adjust the water content equal to about 60% of that of field capacity. The incubation units were weighed, covered with a thin plastic film and stored at 20 ˚C for 2 months. To compensate for the evaporated moisture, water was weekly added to the samples according to the weight loss.

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Salla Venäläinen

After the incubation period, the samples were air-dried, ground and passed through a Ø 2mm sieve. The homogenized soil samples were analysed for pH in both H2O and 0.01 M CaCl2 (v:v 1:2.5), EC (v:v 1:2.5 in H2O), inorganic P fractions (as described earlier) and P desorption-sorption isotherms (method modified from Hartikainen 1982). The desorptionsorption isotherms were produced in four replicates by shaking 1-g soil samples with 50 mL of KH2PO4 solutions of eight increasing P concentrations (0–15 mg L-1) for 1 h. After the shaking, the suspensions were allowed to equilibrate for 23 h at 20 ˚C, shaken for 10 min and passed through a 0.2-µm membrane filter. The supernatants were analysed for P with a Lachat Quick-Chem 8000 autoanalyser using an ascorbic acid method (Orthophosphate in waters, Quick Chem Method 10-115-01-1-B). The amount of sorbed or desorbed P (Q) by the sample was calculated from the measured equilibrate P concentration (I). These values were plotted to produce a Q/I plot in which the point of intersection on the y-axis was taken to represent the amount of readily mobile P (Q0) and the point of intersection on the x-axis was taken to represent the equilibrium phosphate concentration (EPC0), i.e. the P concentration at which the sorption began. Again, Qmax refers to the maximum quantity of P that the soil was able to retain. The slopes (K) of the curves were also determined. The equation used to produce the curves was a modification of the Langmuir equation (Hartikainen & Simojoki 1997, Yli-Halla et al. 2002): Q = QmaxI / (1/K+I) - Q0, where K = 1/K1

2.3. Statistical Analyses

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The statistical differences in Qmax values between the various tailings gained with different reaction times and particle sizes were spotted with one-way analysis of variance, using Tukey's test for paired comparisons. The standard deviations and coefficients of variation (CVs) were calculated for each sorption point in the isotherms produced for the tailings. Student's T-test was employed to detect differences in P recovered in the various fractions and between the tailings of different particle sizes and between the reaction times. The statistical analyses were conducted with SPSS 13.0 for Windows. The statistical significance was determined as p ≤ 0.05.

3. RESULTS AND DISCUSSION 3.1. Distribution of P between Various Chemical Fractions The relative distribution of intrinsic P in the untreated tailings (table 2) shows that practically all P was in the H2SO4-soluble apatitic form. Furthermore, the H2SO4-soluble P pool was particularly large in the coarse particle-size fraction compared with the fine fraction (p ≤ 0.004). This can be explained by the assortment of the apatite residue fragments in the

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Table 2. Relative distribution of intrinsic and added P among various chemical pools and the changes in relative abundance of P in these fractions due to P enrichment ø

Added P

mm

mg kg-1

Relative abundance (%) of P in each chemical pool before and after the enrichment

DPS (%) a

NH4Cl-P Salt-soluble P

NH4F-P “Al-P”

NaOH-P “Fe-P”

H2SO4-P Apatitic P

Σ

Alox

Feox

Alox + Feox

Unenriched

0.0

1.1

0.0

98.9

100

38

0.1

6.2

Enriched Change (mg kg-1)b

0.0

0.3

0.6

100.8

101.7

11

2

4.7

±0

- 5.5

3.6

14

±0

Unenriched

0.1

2.1

0.6

97.2

100

9

0.5

1.6

Enriched Change (mg kg-1)b

0.3 0.5

2.0 - 0.4

1.5 1.9*

529 907***

533 0.5

8

0.2

2.2

Unenriched

0.2

4.4

5.8

89.6

100

0.4

16

1.1

Enriched Change (mg kg-1)b

10.5 68**

335 2183***

116 724***

158 454***

620 68**

31

0.8

50

Unenriched

3.2

11.0

25.6

60.2

100

0.2

19

0.9

Enriched Change (mg kg-1)b

24.4 54**

1120 2820***

435 1042**

169 277***

1750 54**

25

0.8

40

Untreated tailings 50 >0.2

50 0.2

5000

0.2 mm

< 0.2 mm

c

0.5 / 1

1.1 ± 0.0

4.5 ± 0.1

0.46 ± 0.00

0.91 ± 0.00

7.4

7.5

1/2

5.7 ± 0.3c

1.6 ± 0.0

0.86 ± 0.04

1.96 ± 0.03

7.5

7.5

2/4

2.7 ± 0.2

-1.3 ± 0.2

1.86 ± 0.03

4.03 ± 0.06

7.3

7.4

4/5

4.3 ± 0.9

-3.3 ± 1.4

3.80 ± 0.08

5.08 ± 0.04

7.3

7.5

0/0

-0.7 ± 0.1

-1.4 ± 0.1

0.01 ± 0.00

0.03 ± 0.01

8.3

8.5

0.05 / 0.1

0.2 ± 0.0

1.2 ± 0.1

0.04 ± 0.00

0.08 ± 0.00

8.5

8.3

0.1 / 0.3

0.2 ± 0.0

2.4 ± 0.1

0.08 ± 0.00

0.26 ± 0.01

8.6

8.4

0.3 / 0.5

1.7± 0.1

2.8 ± 0.2

0.24 ± 0.00

0.45 ± 0.01

8.2

8.5

c

0.5 / 1

2.4 ± 0.4

7.2 ± 0.6

0.42 ± 0.02

0.86 ± 0.02

7.9

7.8

1/2

7.6 ± 0.0 c

4.2 ± 1.3

0.81 ± 0.01

1.92 ± 0.03

8.0

7.7

2/4

3.8 ± 0.6

6.5 ± 2.4

1.80 ± 0.06

4.01 ± 0.23

7.6

7.6

4/5

3.3 ± 0.3

-1.9 ± 1.8

3.77 ± 0.06

5.01 ± 0.06

7.6

7.6

0

0±0

0±0

0.0 ± 0.0

0.0 ± 0.0

4.2

4.6

25

2305 ± 7

2329 ± 1

0.6 ± 0.4

0.0 ± 0.0

3.9

4.8

50

3870 ± 104

4666 ± 34

8.9 ± 1.0

0.6 ± 0.4

3.6

4.4

100

4590 ± 139

8117 ± 251

49.6 ± 1.4

21.3 ± 2.5

3.4

4.2

200

6910 ± 313

9589 ± 313

136.5 ± 3.1

109.3± 3.5

3.3

4.0

300

6953 ± 495

9702 ± 722

241.9 ± 4.9

203.1 ± 7.2

3.3

4.1

400

7310 ± 808

10 895 ± 754c

348.3 ± 8.1

306.6 ± 7.6

3.3

4.0

9508 ± 892

449.4 ± 5.4

409.5 ± 8.9

3.5

4.0

Acid-treated tailings

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> 0.2 mm

< 0.2 mm

c

c

500

8887 ± 537

0

0±0

0±0

0.0 ± 0.0

0.0 ± 0.0

4.2

4.5

25 50

2328 ± 9 2461 ± 38

2328 ± 1 4721 ± 3

0.4 ± 0.1 2.3 ± 0.4

0.0 ± 0.0 0.0 ± 0.0

4.2 3.8

4.6 4.7

100

7311 ± 159

10 227 ± 18

22.4 ± 1.6

0.3 ± 0.1

3.4

4.5

200

10 879 ± 303

15 211 ± 189

96.9 ± 3.1

54.4 ± 1.9

3.2

4.1

300

11 678 ± 579

15 465 ± 573

194.7 ± 5.8

145.5 ± 5.7

3.2

3.9

400

13 070 ± 487

17 110 ± 342

500

14 421 ± 227c

16 854 ± 641

c

290.7 ± 4.9

244.5 ± 3.4

3.2

3.8

387.8 ± 12.8

336.1 ± 6.4

3.2

3.8

Qmax = Peak quantity of P the material was able to retain.

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3.2. P Sorption Behaviour of the Tailings The data describing the sorption of P by the untreated and the acid-treated tailings at a given equilibrium solution P concentrations are given in table 3. All tailings proved to be efficient sorbents. The acid treatment promoted the retention ability substantially (p < 0.00). In fact, as assessed by the Qmax values, the peak retention by the acid-treated tailings was up to 1800-fold higher than that by the untreated tailings. However, when the incubation time was increased from 24 h to 7 d, the untreated tailings appeared to lose its retention ability at the higher P addition levels and began to desorb P. In response to the extended incubation time, the Qmax value increased in the acid-treated tailings in a statistically significant manner (p 0.00 and 0.01), while such a reaction pattern was not detected for the untreated tailings (p 0.06 and 0.35). The CV levels calculated for the sorption points varied between 0.3% and 20% for the 24-h samples and between 0.04% and 37% for the 7-dsamples. The peak sorption values were significantly higher for the fine particle-size fraction than for the coarse fraction in all tailings (p 0.00–0.01), but in the untreated 24-h samples the particle-size effect was not statistically significant (p 0.06). The time dependency of sorption by the acid-treated tailings may be attributed to the gradual diffusion of P into porous oxidic material formed as a result of the artificial weathering. However, further long-term studies on retention dynamics proceeds over the course of time are needed to acquire information on the total P sorption capacity available. Based on the abundance of P in the NaOH- and NH4F-extractable fractions (table 2), the small particle-size fraction higher in Al and Fe retained P more efficiently than did the coarse one (table 3), as expected. The only exception was the 24-h untreated tailings that showed no statistically significant difference in P sorption between the particles of various sizes (p 0.06). Further evidence of the contribution of Al and Fe oxides to P retention emerged in the sorption test carried out with acid-treated tailings after oxalate treatment. Removal of the amorphous Al, Fe and Mn oxides resulted in a 300-fold reduction in the initial peak sorption value (Qmax=14.4 g kg-1) of the acid-treated tailings (data not shown); within a 24-h incubation a P sorption peak of only 45 mg kg-1 was attained. However, had the P addition been higher, a greater peak sorption could possibly have been reached. The sorption capacity that still remained in the acid-treated tailings after oxalate treatment can be ascribed to the incomplete removal of the poorly crystalline metal oxides. The CV for the P sorption points of the sorption steps varied between 1% and 12%. In the untreated tailings, peak equilibration solution pH values of 8.3–8.6 were attained at low P addition levels, whereas those attained at higher P addition levels were lower, being a constant 7.3–7.6 (24-h samples) and 7.4–7.6 (7-d samples) at higher concentrations (table 3). A drastic drop in pH coincided with the peak P sorption over the 7-d period. The phenomenon related to the reaction mechanisms remained unclear. The increase in solution pH brought about by the untreated tailings can be explained by the calcium carbonate in the mineral material, although this increase may as well have been due to the flotation chemicals used in the enrichment procedure. Such compounds may interfere in the retention of P through competition for P sorption sites. Thus, the contribution of these chemicals to P retention requires further investigation. In the acid-treated tailings, the equilibrium solution pH during the 24-h reaction time regularly decreased from a value of 4.2 at zero P addition to 3.2. However, as the reaction time increased to 7 d, the solution pH at zero P addition level was higher (4.5–4.6) and the drop in pH with increasing P sorption was smaller (to 3.8–4.0). In

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summary, the pH of the initial enrichment P solutions (ranging from 5.4 to 6.3) increased by 1.9–2.2 units as a result of the reaction with the untreated tailings. As for the acid-treated tailings, the enrichment solutions were higher in KH2PO4 and, thus, their pH was lower (ranging from 5.1 to 4.6). The reaction with the acid-treated tailings further decreased their pH by 0.9 - 1.7 units. This decrease in the pH of the equilibrium P solution is clearly due to the strong acid used in the weathering of the mineral material. Since the anions of the conjugated strong acids are weak bases, they are not likely to form strong covalent bonds with metal oxides and, thus, cannot compete for the sorption sites with P. The tortuousness of P the sorption by the untreated tailings indicates the operation of various sorption mechanisms. One such mechanism may be the retention of P by calcium carbonate. A rapid monolayer sorption of P by CaCO3 at low P concentrations was described by Cole et al. (1953). They claimed that the mechanism of P retention changes along with the increasing solute P concentration, eventually leading to the precipitation of dicalcium phosphate:

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K2HPO4 + CaCO3 ↔ CaHPO4 + K2CO3 Lindsay (1979) showed that CaHPO4 and CaPO4- are relevant phosphate complexes in neutral and calcareous soils, especially when the activity of H2PO4- is > 10-5 M. In the present study, the H2PO4- activity in the P solution in equilibrium with the untreated tailings at the sorption peak was 2.9 × 10-5 M and therefore high enough to explain the precipitation of P at the equilibrium P solution concentration of about 0.9 mg L-1 in both the 24-h and the 7-d samples. In addition to the phosphate activity, the pH of the equilibrium solution at the sorption peak was between 7.5 and 8.0, at which the dominant P species in soil solutions are CaHPO40, MgHPO40 and HPO42- (Lindsay, 1979). Furthermore, the dissolution of the compound and the subsequent release of P into the solution may be due to the occurrence of soluble CaPO4- and CaH2PO4+ species, whose activities increase along with the increasing phosphate activity (Lindsay, 1979). Borrero et al. (1988) showed that the P retention capacity of calcite is significantly related to the specific surface area of the mineral. These authors also proposed that in the presence of Fe oxides and other P sorbents, the contribution of CaCO3 to P retention is insignificant. In our study, the specific surface area of CaCO3 in the tailings was not determined. However, due to the presence of Fe and Al oxides in the material and the relatively small abundance (16%) of carbonate minerals in the tailings, it is likely that the few Al and Fe oxides peeking from the edge-faces of phlogopite are rapidly saturated in contact with P and the contribution of CaCO3 to P sorption can be assumed to be only modest. Analysis of the precipitate that formed in the tubes after reaction between P and the tailings revealed that it mainly consisted of P (25–27%), Si (22–28%), Fe (14–15%) and Al (18–20%), as listed here in molar proportions in order of decreasing abundance. It is plausible that the Si in the precipitate may also have affected P retention. Silicate is known to compete with phosphate for sorption sites at high pH and may displace sorbed P (Hartikainen et al., 1996; Tuominen et al., 1998; Koski-Vähälä et al., 2001).

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3.3. Effect of Tailings Addition on Soil Chemical Properties The results of the incubation experiment (table 4) revealed that amending the soil with unsieved tailings did not decisively affect the distribution of the soil intrinsic P among various chemical pools. However, the acid-treated tailings markedly increased the EC of the soil, which may be disadvantageous for plants. The untreated tailings elevated the soil pH, presumably due to the presence of calcite. Interestingly, the acid-treated tailings had a modest increasing impact on soil pH when measured in the CaCl2 suspension. This may be explained by the buffering potential of phosphate anions released as a result of the dissolution of apatite residues during the acid treatment. However, since the acid-treated tailings have a very low pH, the impact of a larger tailings addition on soil pH should be tested in advance to ensure that the soil pH is not lowered to a level that promotes unfavourable conditions, e.g. Al leaching. Table 4. P in various chemical pools in the soil with and without tailings amendment pH

EC µS cm-1

H2O

CaCl2

Original Soil

5.6

5.1

241

P in various chemical pools mg kg-1 NH4Cl-P NH4F-P Salt-soluble P “Al-P” 5.9 134

Soil + Untreated tailings

5.9

5.5

255

5.8

132

673

388

Soil + Acid-treated tailings

5.5

5.3

887

4.8

133

705

429

NaOH-P “Fe-P” 673

H2SO4-P Apatitic P 413

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3.4. Tailings-Induced Changes in P Sorption by Soil The desorption-sorption isotherms for the soil with and without tailings amendment were of the L-type, i.e. they followed the normal Langmuir isotherm (see Giles et al. 1960). Their sorption parameters that can be used in the risk assessment are listed in table 5. The EPC0 describes the maximum solution P concentration maintained by soil or sediment under certain circumstances (Hartikainen 1982). Q0, in turn, describes the potentially labile P in soil or resuspended sediment as being easily desorbed (Koski-Vähälä & Hartikainen 2001), i.e. the direct risk of P loading. Amending the soil with untreated tailings did not alter EPC0 or Q0, whereas the acid-treated material markedly diminished EPC0 and the absolute value of Q0. Both materials elevated the sorption maximum, Qmax. The untreated tailings did not affect the sorption affinity of the soil significantly, as estimated by the slope of the sorption curves (K), but the acid-treated tailings increased it. Since low pH contributes to the specific sorption of P by Al and Fe oxides, amending with acid-treated tailings also decreased the amount of readily soluble P from 48 mg kg-1 to 40 mg kg-1 and elevated it by 13%. The sorption affinity (the slope of the isotherm) for the soil amended with acid-treated tailings was significantly larger than that of the isotherm for soil without tailings. Furthermore, the acid-treated tailings drastically lowered the EPC0. These results agree with the P sorption data obtained for the tailings itself (Table 3). Considering the low amount of tailings added to the soil (the addition corresponded to 0.6 mass-%), the contribution of the tailings to P sorption was quite

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significant, which provides evidence of the efficiency of this material as a P sorbent. Further studies are needed to quantify its sorption capacity at higher addition levels to the soil and to estimate its operating time in wastewater purification systems. The impact of the tailings as soil amendments on the distribution of intrinsic P in hotspots on fields also needs further detailed studies. Table 5. Sorption parameters for P retention by the soil with and without tailings amendment K

EPC0

Q0

Qmax

mg L-1

mg kg-1

mg kg-1

L mg-1

Original soil

1.2

-48

158

0.37

Soil + Untreated tailings

1.1

-49

183

0.33

Soil + Acid-treated tailings

0.5

-40

179

0.56

140 120 100 Q (mg kg-1)

80 60 40 20 0 -20 0

2

4

6

8

10

12

14

16

-40 -60 I (mg L-1)

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Figure 1. The desorption-sorption isotherms for soil with and without tailings amendment. ◊ = Original soil, × = Soil amended with untreated tailings, ■ = Soil amended with acid-treated tailings.

4. CONCLUSION The chemical analyses revealed that the phlogopite-rich mine tailings from apatite ore beneficiation is able to retain P efficiently from an aqueous solution. The retention occurs through specific sorption by amorphous Al and Fe oxides and possibly also by calcite. Compartmentalization of the material when added to soil also strongly enhances P sorption. Artificial weathering of the tailings through acid treatment significantly increases the formation of reactive oxides and, thus, increases its P sorption properties. The acid-treated material did not affect the soil pH negatively, but instead improved its sorption capacity. These results indicate that in areas of high P leaching risk, it may be advantageous to amend soil with the tailings to minimize the environmental hazard. Since the small particles

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generally retain P more efficiently than do the coarse particles, sieving the tailings is the favoured method for improving its P sorption capacity. The average total P concentration in unpurified sewage from sparsely inhabitated areas in Finland is 17 mg L-1 (Vilpas et al., 2005). The results obtained from the sorption experiments showed that treating such sewage with artificially weathered tailings would reduce the P concentration to less than 0.1 mg L-1. The reduction in P concentration would be more than sufficient to meet the Finnish standards set for purified sewage (2.8 mg P L-1). However, in considering the total P sorption capacity of acid-treated tailings and its use in sewage purification, it must be said that the P concentrations obtained in the equilibrium solutions at the peak sorption values greatly exceed the standards set for purified sewage in Finland. As for the untreated tailings, no accurate predictions about its function can be given. First, the P addition levels used in the tests were lower than those often measured in wastewater. Secondly, the sorption tended to diminish after the peak values. Overall, since the minerals in the tailings are natural components of the soil and the beneficiation process seems not to affect the soil unfavourably, the use of this material as an amendment is justified. Moreover, the tailings enriched with P during the operation of sewage purification plants could then be spread over arable land to function as P fertilizer or soil amendment. However, the desorption of sorbed P from the tailings has not yet been investigated.

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REFERENCES Beck, M.A., Robarge, W.P., Buol, S.W. Phosphorus retention and release of anions and organic carbon by two Andisols. Eur. J. Soil Sci. 1999, 50, pp 157-164. Bigham, J.M., Golden, D.C., Buol, S.W., Weed, S.B., Bowen, L.H. Iron oxide mineralogy of well-drained ultisols and oxisols: II. Influence on color, surface area, and phosphate retention. Soil Sci. Soc. Am. J. 1978, 42, pp 825-830. Borggaard, O.K. The influence of iron oxides on the surface area of soil. J. Soil Sci. 1982, 33, pp 443-449. Borggaard, O.K. The influence of iron oxides on phosphate adsorption by soil. J. Soil Sci. 1983, 34, pp 333-341. Borggaard, O.K., Szilas, C., Gimsing, A.L., Rasmussen, L.H. Estimation of soil phosphate adsorption capacity by means of a pedotransfer function. Geoderma 2004, 118, pp 55-61. Borrero, C., Peña, F., Torrent, J. Phosphate sorption by calcium carbonate in some soils of the mediterranian part of Spain. Geoderma 1988, 42, pp 264-269. Chang, S.C., Jackson, M.L. Fractionation of soil phosphorus. Soil Sci 1957, 84, pp 133-144. Chardon, W.J., Faassen, H.G. Soil indicators for critical source areas of phosphorus leaching, Rapporteh Programma Geïntegreerd Bodemonderzoek Deel 22; Grafisch Service Centrum van Gils B.V.: Wageningen, 1999. Cole, C.V., Olsen, S.R., Scott, C.O. The nature of phosphate sorption by calcium carbonate. Soil Sci. Soc. Am. Proc. 1953, 17, pp 352-356. Freeman, J.S., Rowell, D.L. The adsorption and precipitation of phosphate onto calcite. J. Soil Sci. 1981, 32, pp 75-84. Galarneau, E., Gehr, R. Phosphorus removal from wastewaters: Experimental and theoretical support for alternative mechanisms. Water Res. 1997, 31, pp 328-338.

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Giles, C.H., MacEwan, T.H., Nakhwa, S.N., Smith, D. Studies in adsorption. Part XI. A system of classification of solution adsorption isotherms, and its use in diagnosis of adsorption mechanisms and in measurement of specific surface areas of solids, J. Chem. Soc. 1960, 4, pp 3973-3993. Gimsing, A.L., Borggaard, O.K. Competitive adsorption and desorption of glyphosate and phosphate on clay silicates and oxides. Clay Miner. 2002, 37, pp 509-515. Hartikainen, H.,. Phosphorus and its reactions in terrestial soils and lake sediments. J. Sci. Agric. Soc. Finland 1979, 51, pp 537-624. Hartikainen, H. Effect of decreasing acidity on the extractability of inorganic soil phosphorus. J. Sci. Agric. Soc. Finland 1981, 53, pp 16-26. Hartikainen, H. Relationship between phosphorus intensity and capacity parameters in Finnish mineral soils. Ι interpretation and application of phosphorus sorption-desorption isotherms. J. Sci. Agric. Soc. Finland 1982 54, pp 245-250. Hartikainen, H., Pitkänen, M., Kairesalo, T., Tuominen, L. Co-occurrence and potential chemical competition of phosphorus and silicon in lake sediment. Water Res. 1996, 30, pp 2472-2478. Hartikainen, H., Simojoki, A. Changes in solid- and solution-phase phosphorus in soil on acidification. Eur J. Soil Sci. 1997, 48, pp 493-498. Hingston, F.J., Atkinson, R.J., Posner, A.M., Quirk, J.P. Specific adsorption of anions. Nature 1967, 215, pp 1459-1461. Koski-Vähälä, J., Hartikainen, H., Tallberg, P. Phosphorus mobilization from various sediment pools in response to increased pH and silicate concentration. J. Environ. Qual. 2001, 30, pp 546-552. Krasnova, N. The Kovdor phlogopite deposit, Kola peninsula, Russia. Can. Mineral. 2001, 39, pp 33-44. Lindsay, W.L. Chemical equilibria in soils; John Wiley & Sons, Inc, USA, 1979. Muljadi, D., Posner, A.M., Quirk, J.P. The mechanism of phosphate adsorption by kaolinite, gibbsite and pseudoboehmite I. the isotherms and the effect of pH on adsorption. J. Soil Sci 1966, 17, pp 212-229. Munsell Color (ed.). Munsell soil color chart. New Windsor, New York, 1994. Niskanen, R. Extractable aluminium, iron and manganese in mineral soils I dependence of extractability on the pH of oxalate, pyrophosphate and EDTA extractants. J. Sci. Agric. Soc. Finland 1989, 61, 73-78. Pan, Y. and Fleet, M.E. Mineral chemistry and geochemistry of vanadian silicates in the Hemlo gold deposit, Ontario, Canada. Contrib. Mineral. Petrol. 1992, 109, pp 511-525. Parfitt, R.L., Atkinson, R.J., Smart, R. St.C. The mechanism of phosphate fixation by iron oxides. Soil Sci. Soc. Amer. Proc. 1975, 39, pp 837-841. Peltovuori, T. Phosphorus in agricultural soils of Finland - characterization of reserves and retention in mineral profiles. University of Helsinki, Helsinki, 2006. Doctoral dissertation. Peltovuori, T., Uusitalo, R., Kauppila, T. Phosphorus reserves and apparent phosphorus saturation in four weakly developed cultivated pedons. Geoderma 2002, 110, pp 35-47. Puustinen, K. Tetraferriphlogopite from the Siilinjärvi carbonatite complex, Finland. Bull. Geol. Soc. Finland 1973, 45, pp 35-42. Rieder, M., Cavazzini, G., D'Yakonov, Y., Frank-Kamenetskii, V.A., Gottardi, G., Guggenheim, S., Koval, P.V., Mueller, G., Neiva, A.M.R., Radoslovich, E.W., Robert, J.,

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Sassi, F.P., Takeda, H., Weiss, Z., Wones, D.R.,. Nomenclature of the micas. Can. Mineral. 1998, 36. Ryden, J.C., McLaughlin, J.R., Syers, J.K. Mechanisms of phosphate sorption by soils and hydrous ferric oxide gel. J. Soil Sci. 1977, 28, pp 2-92. Ryden, J.C., Syers, J.K., Tillman, R.W. Inorganic anion sorption and interactions with phosphate sorption by hydrous ferric oxide gel. J. Soil Sci. 1987, 38, pp 211-217. Tuominen, L., Hartikainen, H., Kairesalo, T., Tallberg, P. Increased bioavailability of sediment phosphorus due to silicate enrichment. Water Res. 1998, 32, 2001-2008. Vilpas, R., Kujala-Räty, K., Laaksonen, T., Santala, E. Enhancing nutrient removal efficiency of onsite wastewater treatment systems – Ravinnesampo. Part 1: Treatment of domestic wastewater; The Finnish Environment 762, Vammala Printers, Finland, 2005. Yli-Halla, M., Hartikainen, H., Väätäinen, P. Depletion of soil phosphorus as assessed by several indices of phosphorus load in surface runoff by soil analyses. Agric. Ecos. Environ 2002, 56, pp 53-62. Yang, Y., Zhao, Y.Q., Babatunde, A.O., Wang, L., Ren, Y.X., Han,Y. Characteristics and mechanisms of phosphate adsorption on dewatered alum sludge. Sep. Purif. Technol. 2006, 51, pp 193-200.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 © 2009 Nova Science Publishers, Inc.

Chapter 7

NANOSTRUCTURAL CARBON SORBENTS FOR DIFFERENT FUNCTIONAL APPLICATION Z.A. Mansurov1 and M.K. Gilmanov2 1

2

al-Farabi Kazakh National University, Almaty, Kazakhstan M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry, Almaty, Kazakhstan

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ABSTRACT Physico-chemical parameters of the synthesis of carbonized sorbents based on plant raw material are investigated along with the properties of these sorbents. The data of FTIR, ESR spectroscopy & BET- method, as well as electron microscopy are reported. It is stated that carbonized sorbents possess high specific surface area and porosity. Carboxylic, carbonyl, hydroxyl groups are detected on the surface of the synthesized sorbents. It is assumed that high sorption ability with respect to Co, Ni, Pb, Cd, Cu ions is connected with the formation of chelate complexes. It was shown that carbonized nanostructured sorbents are able to: adsorb cesium-137 (137Cs), strontium-90 (90Sr) & lead-210 (210Pb) successfully; reduce ions of gold (III) on the surface selectively; separate fusicoccine and similar biostimulators effectively; remove LPS-endotoxines from blood plasma selectively. They may be used as carriers to introduce probiotics into intestine thanks to formation of stable colonies on their developed surface. A method of preparation of honeycomb monoliths from carbonized rice husk with developed mesoporous structure via modification of the porous structure by silica leaching has been developed.

INTRODUCTION Carbonaceous adsorbents are widely used in various processes involving the purification and recovery of valuable substances from liquid and gaseous media. Active carbon is used in oil processing, petroleum chemistry, wine making, butter and fats production, etc. They are

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increasingly widely used in medicine, for example, to remove some components from physiological liquids and to purify blood [1, 2]. The urgency of environmental problem has increased the interest of the development of accessible adsorbents based on active carbon. The demand for these products exceeds the volume of their production. Despite the fact that a plenty of kinds of activated carbon are well-known, tasks of diversification and synthesis methods improvement are still urgent. The traditional raw material for producing a high-quality activated carbon is wood [3]. Some kinds of vegetable cellulose (stones/seeds of fruits, nut shells, husk/bran of grains, and sawdust of wood) are among the available sources [4]. These materials are very attractive because of their low cost. They are annually renewable materials, of porous structure, developed upon carbonization. The production of carbon sorbents (CS) is environmentally safe; the sorbents are easily recovered [4]. These kinds of activated carbon are distinguished by perfect sorption properties; they meet the requirements to environmentally safe products [5, 6]. The goal of the present work is to highlight on some aspects of obtaining and investigation of carbonized sorbents based on walnut shells (WS), grape seeds (GS) & apricot (AS) stones, rice husk (RH) & wheat bran (WB). The Republic of Kazakhstan possesses large resources of uranic ores. Migration of underground waters results in the pollution of some oil fields and coal deposits with radioactive materials. Atmospheric precipitation may also cause the radioactive pollution of the environment far from the places of nuclear tests or accidents on atomic power stations [7]. In addition, mining, processing and transportation of ferrous and nonferrous metals, phosphorites, etc. result in the environmental pollution as well. Many of heavy metals are highly toxic. All these factors adversely affect the health of people. In this connection, purification methods of natural waters and sewage from toxic and radioactive elements become very important for the environmental protection [8]. One of the effective and widespread methods is sorption of elements. To this end, high temperatures and complicated equipment are not needed. Commercial sorbents on the basis of activated coals are obtained from various kinds of organic materials: black and brown coals, anthracite, turf, wood and products of its processing as well as materials of animal origin [9]. Nontraditional raw materials, which have not found a wide application yet, are, for example, rice husk and wheat bran (WB), which at present are production wastes [9]. Activated coal on the basis of vegetable raw materials is an inexpensive, easily available sorbent, characterized by high porosity [10]. In this connection sorbents on the basis of vegetable raw materials are of great interest. At present, carbon sorbents are widely used in industry, medicine and pharmaceutics [11].

EXPERIMENTAL Carbonization The dependence of carbonization of walnut shells, grape seeds and apricot stones, wheat bran and rice husk on temperature, nature of gas and on activating agent was investigated. The samples were carbonized according to the procedure developed in the R.M. Mansurova

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Laboratory of Carbon Nanomaterials at the Institute of Combustion Problems, using a flow setup within temperature range of 250–900 °C in Ar flow (50–90 cm3/min) [8].

Physicochemical methods of investigation

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Physicochemical characteristics of the carbon materials were investigated by means of modern methods (IR-Fourier, X-ray phase analysis, electron microscopy, EPR spectroscopy, BET method, etc). IR spectra of the studied samples were recorded on Fourier Transform IR spectrometers “Perkin Elmer”, in tablets pressed with KBr. X-ray phase analysis (XPA) of carbonized samples was performed with DRON-3M diffractometer at the accelerating voltage of 35kV, using tubes with copper cathode. Recording was performed at a rate of 2 deg/min within angle range of 5 to 50°. The samples were crushed into powder and placed on glass cuvettes greased with Vaseline. The electron-microscopy study on carbonized samples was carried out using JEM-100cx STM electron microscope with accelerating/operating voltage of 100 kV. The powder was deposited onto the substrate film by two procedures: as a suspension, and by dry deposition. The samples were placed in sample holder and then in the electron microscope. EPR spectra were recorded with IRES-1101-2M spectrometer of the homodyne type operating in a 3 cm range (the frequency of magnetic field modulation was 500 kHz; the sensitivity of the instrument was 1011 spins per sample). The spectra were recorded at the modulation amplitude of magnetic field of 3 Oe, amplitude or magnetic field scanning 3500 Oe; scan time 10 min, accuracy 3 %. The specific surface area of sorbents was determined by thermal desorption procedure based on the measurement of thermal conductivity of gas flow (helium and argon) passing through the tubes with the samples (BET method). The apparent porosity was determined according to the procedure described in [8]. The carbon content in the studied samples was determined by a method based on burning the sample in a flow of oxygen (excess) purified from impurities followed by the interaction of the formed carbon dioxide Ba(OH)2. The carbon percentage was calculated by the batch weight of the obtained barium carbonate.

Methods of sorption studies When determining the sorption property of sorbents based on carbonized plant raw materials with respect to metals, the tests were conducted in static conditions. Here is an example of the procedure: 0.5g of a sorbent sample was placed into a beaker, which contained 50 ml of the solution of metal salts in the following concentrations: copper- 5 mcg/cm3; cadmium- 0.1 mcg/cm3. After the fixed period of time elapsed, the residual content of metal ions in water was detected by atomic absobtion spectroscopy method. Then using the difference between the initial & final concentration, the degree of sorption was calculated.

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Gold sorption Investigation on gold sorption was carried out by two methods: chemical (standard) and electrochemical methods.

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Chemical (classic) method Sorption of gold was carried out in static & dynamic conditions [12]. In static mode the tests were conducted as follows. The specimen of 0.2 g was placed into beaker of volume of 50 ml then 10-25 ml of analyzed solution of gold (III) in certain concentration was added. The solution was stirred using magnetic stirrer during set time: from 1 to 90 min. Then the solution was filtered out using the filter paper (”yellow ribbon” marking). Chemical analysis of filtrate to detect the gold (III) content was performed by atom absobtion spectroscopy (AAS) method. The experiments for finding the dynamic capacity of sorbents were conducted according to the following technique. A fiberglass pellet was placed into column with diameter 7 mm and volume of 5 ml then the column was filled with 0.5g of sorbent then another fiberglass pellet was placed on top of the sorbent upper edge. The gold (III) solution was passing through the column with sorbent at rate of 2.5 ml/min. The eluted solution was collected in fractions 25 ml each, and then analyzed by AAS-method. Electrochemical method Kinetic curves of sorption of gold (III) were obtained by recording of I, t-curves at constant potential, which correspond to maximum current value (called the current limit) of electroreduction of gold (III) on platinum electrode. Recording of I, t-curves was conducted automatically by use of the controlling automatic recorder (CAR-4) on potentiostat P-5848. The experiments were carried out as follows. 20 ml of sample solution of gold (III) in certain concentration was added in the electrochemical cell. The cell, by use of salt bridges filled with saturated solution of KCl, was linked to the reference silver-chloride electrode and to auxiliary (counter) platinum electrode. Platinum indicator electrode was placed into the electrochemical cell. Cell was placed on a magnetic stirrer, and turned on. The potential of + 0.2 V was imposed to the indicator electrode by use of potentiostat “P-5848”. The value of this potential corresponds to the current limit of gold (III) electroreduction on platinum electrode [13]. The requisite current range was selected (usually 0.05 mA per 100 units of the recorder scale). Next, the recorder CAR-4 was turned on, filing printed paper chart at a speed of 1800 mm / hr. Then potentiostat was turned on, at this stage the recording of the current limit value of gold (III) reduction took place. After 0.5-1 min passed, 0.2-0.5 g of sorbent was added into electrolytic cell with gold (III) solution. As a result, the concentration of gold (III) in electrolyte decreased; a decrease of the current value gold (III) reduction also took place. As consequence I, t -curve had a downward pattern. The recording duration of I, t- curve was from 4 to 20 min, depending on steepness of the current decline. Then, using the I, t- curves data, the plot was built in coordinates: “the percentage of gold (III) in solution - time”.

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Fusicoccine extraction Fusicoccine was extracted from wheat seeds using method developed at the M.M. Aitkhozhin Institute of Molecular Biology and Biochemistry [14]. Obtained supernatant was placed into column with separating material. To control chromatographic separation the UV monitor of Uvicord S II type produced by the firm “LKB” (Sweden) was used. Spectroscopic investigation of purified bioactive compounds was made on Ultrospec 1100 pro spectrophotometer produced by the firm “Amersham Biosciences” (Great Britain) in ultraviolet and visible spectrum regions.

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Cell immobilization Lactobacillus fermentum AK-2 strain with good probiotical parameters i.e. high antagonistic and adhesive activity [15] was used in this work. A nanostrucured sorbent produced by high temperature rice husk (RH) carbonization in the Combustion Research Institute of KazNU named after al-Faraby was used to immobilize the test strain [16]. Immobilization was performed during 24 hours. Then the carrier was flushed with isotonic solution to remove loosely adsorbed cells and used in the subsequent experiments. Sorption efficiency was derived from the difference between the cell counts in the culture medium before and after sorption [17]. The JCXA-7334 scanning electronic probe microanalyzer was used for visual evaluation of modified sorbents surfaces and their interaction with bacterial cells. Experiments to assess the immobilized cells probiotical activity were performed using 68 weeks old not purebred rats with disbacteriosis induced by the antibiotic ciprofloxacin [15]. For this purpose the test animals had been divided into 3 groups after a bacteriological examination. Ciprofloxacin was administered to all rats but in the first group only the antibiotic was used whereas in the second group free lactobacilli cells of the above-said strain were introduced along with ciprofloxacin. For this purpose an aqueous suspension of lactobacilli cells at the concentration of 108 cells/ml was introduced intergastrally during 10 days after the etiotrops therapy. At the same time lactobacilli cells of the strain in question immobilized on the carbonized rice husk (CRH) were introduced in the third group of test rats. Analysis was done on the expiration of 24 hours after ciprofloxacin introduction was cancelled and after 15 days from the start of the experiment. In accord with the aim of the experiment enterobacteria were quantified in different parts of the gastrointestinal tract. Antimicrobial activity of the culture medium used for growing free and immobilized lactobacilli was estimated by agar diffusion test. The following enterobacteria from the KazNU chair of microbiology museum were used as test strains: Escherichia coli К-12, Klebsiella pneumoniae АК-2, Proteus vulgaris З-53, Proteus mirabilis 54, Enterobacter aerogenes Е-12, Salmonella typhimurium Р-1, Shigella zonnei А-22, Shigella flexneri А-2. Antimicrobial activity level was assessed by the inhibitory zones size. One more method was applied when enterobacteria strains were grown along with free and immobilized Lactobacillus fermentum AK-2 cells. In this case antimicrobial activity was estimated by viable test strains cells counts.

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LPS sorption Lipopolysaccharide concentration in the culture medium was determined photometrically in microtablets with the help of QCL-1000 Chromogenic LAL Endpoint Assay kit (Lonza Group Ltd, Switzerland) and photometric scanner (Bio-Rad Co., USA).

RESULT AND DISCUSSION Investigation of Carbonization Process Mass loss Pyrolytic setup (see Fig.1) was developed & set into operation. Its productive capacity is 5 kg of carbonized materials per hour.

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Figure 1. Pilot setup for carbonization of various plant raw materials.

It is discovered that the major mass loss (Fig. 2) occurs within temperature range 150500°C; the largest amount of volatile and liquid products released within the same range. It was discovered that in the process of carbonization occurs large mass loss of samples. The change of mass was about 65-75 %. In the case of rice husk, this process is not so intensive. At the same temperature range, the mass of sample is reduced on 50%. The difference in changing of mass loss of rice husk, compared with each other, can be explained by the fact, that the rice husk originally contains a large amount of silicon. Spectrum analysis shows, that the content of silicon oxide in the rice husk at 900 °C reaches a half of total mass of the sample.

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Figure 2. Dependence of mass loss on carbonization temperature: (1)- walnut shells; (2)-grape seeds; (3)- rice husk

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Figure 3 shows a nonlinear increase of the carbon concentration in the case of WBsamples. This means that with the temperature rise the carbonization runs through different stages. At comparatively low heating temperatures, a pyrolytic removal of water mainly takes place, but at higher temperatures, a removal of low-molecular-weight carboniferous products and various tars takes place.

Figure 3. Dependence of carbon content on carbonization temperature

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IR-spectroscopic investigation It was discovered that the IR spectra of the liquid and solid phases formed during the carbonization of WS and GS contained characteristic absorption bands in the region of C=C bending vibrations of the aromatic ring (833 and 1050 cm-1), absorption bands related to the stretching vibrations of the aromatic ring (1600, 1578, 1510 cm-1), and the bands related to C–H stretching vibrations of the aromatic ring (3053, 3030 cm-1). An increase of carbonization temperature leads to a sharp increase of the intensity of absorption bands related to aromatic condensed systems. This means that carbonization of agricultural wastes results in substantial changes in the structure of samples. The intensity of characteristic absorption bands related to C–H stretching vibrations of benzene ring at 730, 1380 and 1460 cm-1 increases by a factor of 3 with increasing carbonization temperature (from room temperature to 900 °C). A similar picture is observed in the region of the stretching vibrations of carbonyl, carboxyl (860-1299 cm-1) and phenol (3200-3400 cm-1) groups, bending vibrations of C–H groups of the aromatic ring (670 cm-1) and C–CH3 group (1365-1380 cm1). Absorption bands corresponding to the stretching (2870-2930 cm-1) and bending (15301650 cm-1) vibrations of NH2 group have lower intensity at low carbonization temperature (by a factor of 2) than at 500 °C; after carbonization at 900 °C, the intensity of the corresponding bands increases by a factor of 3. The IR spectrum of CS (GS) obtained at 500 °C contains intensive absorption bands at 1340, 1380, and 1460 cm-1, corresponding to the characteristic absorption bands of the stretching vibrations of C–H bonds of the aromatic ring, as well as the bands corresponding to bending (1590 and 1660 cm-1) and stretching (2900-2970 cm-1) vibrations of the NH2 group. Thus, the spectrum of the carbonized sorbent based on grape stone (at 500 °C) differs from the spectrum of CS of WS by the presence of more intensive bands corresponding to NH2 group and C–H of the aromatic ring. It is stated that the intensity of absorption bands of C– O–C, COOH, C=O, CH3 and CH2 of the aromatic ring increases with increasing carbonization temperature. An increase of carbonization temperature leads to the increase of the intensity of bands related to the aromatic condensed systems. Investigations showed that the spectrum of the initial GS sample contained characteristic bands of OH and NH2 groups in the region 3418.61.0.4 cm-1, and Ar–CH3 groups in the region 3009.97.0.1 cm-1. Absorption bands at 2926.27.0.4 and 2854.92.0.2 cm-1 are related to the vibrations of symmetrical and asymmetrical CH2 groups 1745.46.0.2 to C=O groups, 1517.71.0.2 to COO, 1448.28.0.2 to CH2 , 1376.93.0.1 to CH3, 1243.78.0.2 and 1158.72.0.2 to COOR, 1098.68.0.3 and 1057.57.0.3 to C–O–C (Fig. 4). When GS is carbonized at the temperatures of 600–850 °C, a sharp (10-fold) drop of the intensity of characteristic bands of OH and NH groups is observed. The intensity of characteristic C–O–C bands increases; bands related to CO32– groups appear and their intensity increases substantially with temperature rise. We also observe the bands related to CO2 group in the region 2486.19.0.3 cm-1. Carbonization of AS and RH proceeds similarly, but the intensity of the corresponding bands is lower [1]. Figure 5a represents IR-spectrum of initial AS-sample. IR-spectrum of initial AS-sample is composed of characteristic absorption bands of NH2 (3431.92 cm-1), ОН (3009.97 cm-1), С=О (1643.25 cm-1), С–О (1241.55 cm-1), С–ОН (1055.64-1157.28 cm-1), С=С, С=N (1662.55 cm-1) groups, Valence vibrations of СН2 (1378.87 cm-1).

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Figure 4. IR spectra of initial (1) and carbonized (T = 850 °C) grape seeds (2)

Figure 5a. IR-spectrum of initial (noncarbonized) sample of apricot stones.

IR-spectra of AS, carbonized at the temperature 500ºC are shown on Figure 5b. IRspectra indicate that during carbonization at 500ºC, the absorption bands’ intensity of the following groups lowers: NH2, С–ОН, С=О (5 times) & ОН (2 times); the intensity of the band of С≡С bond (2169.50 cm-1) manifests itself, while intensities of absorption bands due to aromatic ring valence vibrations are beyond detection.

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Figure 5b. IR-spectra of carbonized sorbent (T=500 0C) based on apricot stones.

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The higher the temperature of carbonization process is (up to 800ºC), the more intense the characteristic absorption bands of the groups of NH2, СОН, С=О, ОН as well as CH- of aromatic ring valence vibrations. IR-spectra of the samples carbonized at 800ºC are shown on Figure 6.

Figure 6. IR-spectra of carbonized sorbent (T=800 0C) based on apricot stones

IR-spectra, measured on IR-spectrometer “UR-20”, exhibit characteristic absorption bands 883 & 1050 cm-1 corresponding to С=С, deformation vibrations of aromatic ring, and the bands, related to valence vibrations of aromatic ring 1600, 1578 & 1510 cm-1 as well as –С-Н- 3053, 3030 cm-1. Using the method of IR-spectroscopy established the presence of

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structures of polyaromatic hydrocarbons. It is shown that the carbonization temperature rise leads to increase in intensity of absorption bands related to aromatic condensed systems. In the sorbents carbonized at 300-850°C, the following polyaromatic hydrocarbons are identified: pyrene, according to presence of absorption bands (cm-1) -720, 850; coronene547, 1320; fluoranthene- 600, 740, 820. Absorption bands assignment was conducted in accordance with the data from the references [18, 19].

INVESTIGATION OF THE STRUCTURE OF CARBONIZED SORBENTS It is stated by IR-spectroscopy that the basis of the structure of carbonized sorbents is formed by aromatic condensed systems. XPA investigation shows that the dimensions of microcrystallites increase with temperature increase to 950 °C (crystal height increases from 7.62 to 8.56 Å, crystal length increases from 34.54 to 41.76 Å); interplane distance decreases from 4.1 to 3.84 Å. This proves the destruction of cellulose structure in the material during its thermal treatment; this is also an evidence of densifying of the carbonized structure. It is demonstrated that the size of macro, micro- and mesopores increases and specific surface increases with rising carbonization temperature. Carbonized sorbents based on walnut shell and grape stone possess macro- and mesoporous structure (Table 1), which is preferable for the adsorption of large molecules [8]. The obtained results are in agreement with the data of Bulgarian scientists [20]. One can see in Table 1 that the specific surface and size of pores increase with increasing carbonization temperature to 700 °C; however, further increase of temperature causes the decrease of these parameters. A decrease of specific surface is connected with the increase of the density of carbonized sample according to the data of [20]. Table 1. Specific surface and pore size in carbonized samples at different temperature Sorbent

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WS

GS

T, °C 300 500 600 700 800 850 300 600 700 800 850

Size, μm Macropores 25 30 30 30 28 29 18 22 27 25 26

Ssp, m2/g Mesopores 12 13 16 16 14 15 12 14 15 13 14

Micropores 1.8 2.3 2.4 2.3 1.7 2.4 3 6 7 5 6

250 770 780 800 830 800 200 500 530 540 500

One can see in electron-microscopy images (fig. 7) that carbonization can allow one to obtain a developed structure with larger specific surface and porosity than that of the initial samples. An electron microscopic image of the GS sample carbonized at 800 °C is shown in fig. 7a; the porous structure of the sample is seen. The images of WS impregnated with copper and cadmium solutions are shown in figs. 7b & 7c. Carbon fibers with metal inclusions are observed.

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Figure 7. Electron-microscopic images of carbonized sorbents: a – GS (magnification 1000); b – WS + Cu2+ (magnification 120 000); c – WS + Cd2+ (magnification 120 000).

The research on initial and carbonized samples showed that by way of carbonization it is plausible to achieve more developed structure with more specific surface area and porosity. (Figs 8-9).

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Figure 8. Electron-microscopy image of AS.

As Figure 8 shows, the sample in initial form is very dense and firm. In the course of carbonization, the change in structure of the sorbent takes place. The Fig. 9a represents the sample of apricot stone carbonized at temperature of 500°C. It is discovered that at this same temperature the formation of transparent thin membrane films of a size (μ) 20-40 nm. At the temperature of 600°C & the duration of carbonization – 30 min, these thin translucent films roll into tubular structures of a diameter (d) 400-500 nm, length (l) 1400 nm (Figs: 9b & 9c). With further increase in the temperature and the time of carbonization, the resulting carbon material is represented by a variety of nanostructures of various morphology. At the carbonization temperature of 750ºC, carbon material contains spherically shaped forms having very advanced surface (Figs. 9d & 9e).

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(b)

(d)

229

(c)

(e)

Figure 9. Electron-microscopy images of carbonized sorbents AS: (a) at 500ºC, d=200-400 nm; (b) at 600ºC, d= 400-500 nm, l= 1400 nm; (c) at 650ºC, d= 500nm, l=500-1000 nm; (d) at 700ºC, d= 50-100 nm; (e) at 750ºC, d=500-600 nm;

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Experimentally, electron-microscopy research showed the formation of the morphology & structure of carbonized sorbents from thin membrane films to nanosize fibrous carbon represented in the form of spheres [9]. In the course of carbonization of rice husk noticeable change of the structure and morphology of the samples occurs (Figs 10 &11). As follows from Figure 10, the sample is composed of the particles of different kind: roundish particles, compact structures.

Figure 10. Electron-microscopy images of initial sample

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(a)

(b)

(c)

(d)

(e)

(f)

Figure 11. Electron-microscopy images of a sample of RH carbonized at 350 °C (RH-350)

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The main bulk of the sample carbonized at 350 °C is represented by big (0.5 – 1.5 microns) dense particles of different shape & film formations (Figs 11a & 11b). The fibrous (Fig. 11c) and the large-meshed formations (Fig. 11 d) are present. Undestroyed initial particles occur (Fig. 11e & 11f).

(a)

(b)

(c)

Figure 12 - Electron-microscopy images of a sample of RH-450

In a sample of RH-450 initial “scales” with “aciculae” could still be seen. (Fig. 12 a). As well as previous sample, RH-450 contains large fragments and films, however it is important to note that the particles are more incompact (flocculent) than in previous sample. There are many particles with a sign of transformation (under electron microscope). Emerging small congregations of rounded particles (Fig. 12 b) can also be observed. Appearance of fibrous structures should also be noted (Fig. 12 c).

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(d)

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(c)

(e)

(f)

Figure 13. Electron-microscopy images of a sample of RH-550

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The material of the sample RH-550 is composed of fragments, often porous (Fig. 13 a); filmy formations (Fig. 13 b), and various kinds of incompact (flocculent) formations (Fig. 18c & 13d). In composition of the sample there are numerous active phases which cause transformation of the substance during the observation under electron microscope (Fig. 13 e). Fine grains (spots) form bigger particles- films (Fig. 13 f). In the sample of RH-650 there are lots of small particles of different shapes & veil-like forms (Fig. 14 a, 14 b).Fine-grained particles (Fig. 14 c) together with differing in thickness fragmented & filmy particles (Fig. 14 d) are present as well.

a

b

Figure 14. Continued on next page.

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c

d

Figure 14. Electron-microscopy images of RH-650-sample.

In the sample of rice husk carbonized at 750 °C there are: incompact matter (Fig. 15 a), various filmy fragments (Fig. 15b), veil-like & porous particles (Fig. 15 c). On the edge of a particle shown on Fig. 15 c, one can see veil-like phase; interaction with which leads to “fusion” of grains. Figure 15 d represent the particles which probably are at final stages of this process.

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(a)

(b)

(c)

(d)

Figure 15. Electron-microscopy images of RH-750-sample.

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b

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c

Figure 16. Electron-microscopy images of RH-850-sample.In the sample of RH-850 fine-grained particles (Fig. 16 a), porous particles and fragments (Fig. 16 b,) as well as large films (Fig. 16 c) occur.

In order to confirm the assumption about the nanostructure generation in the carbonized WB samples, an electron microscopy investigation of samples taken at the temperatures corresponding to the most significant changes of the EPR line parameters was carried out.

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Figure 17- Electron microscopy pictures of WB, carbonized at 650 °C. Bars: 0.1μm.

Figure 18 Electron microscopy pictures of WB carbonized at 700 °C. Bars: 0.1μm.

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The results (Figs. 17-19) show the presence of a number of complex morphological formations having a nanoscale structure, and, consequently, determining a highly specific surface of the material. Cloudy-fuzz morphological structures of carbonaceous WB prevail at temperatures of up to 450-500 °C as well as pores appeared in fragments of the substance. Various forms of fibrous and shell-like nanoparticles are observed with the further temperature increase (650 °C, Fig. 17). A distinctive feature of the carbon materials obtained by carbonization of WB is the formation of poorly discernible rounded nanoparticles on the surface which formed unique nanotubes with a bulb at the base at 700-750 °C (Figs. 18 & 19). One can see that the surface of the carbon fibrous nanostructure contains a great number of small spherical nanoparticles (Fig.18). Thus, carbonized WB exhibits all of the morphological forms that were observed during carbonization of other raw vegetable materials [21].

Figure 19- Electron microscopy pictures of WB carbonized at 700 °C. Bars: 0.1μm.

SORPTION PROPERTIES OF CARBONIZED SAMPLES

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Walnut shells and grape seeds When carbonization of the samples of walnut shells (WS) & grape seeds (GS) were studied, it was found that during the rise of temperature from room to up to 250 °C, the maximum amounts of volatile products were given off. Further temperature rise up to 500°C leads to major loss of the mass of a sample. Since the studied substances in their initial state are represented by polysaccharides with gross formula (C6H18O5) n, then the dominant process of both hydrogen & oxygen removal, in the course of carbonization in argon media, first goes via dehydration, accompanied by elimination of five water molecules from each monomeric segment [22]. As a result of dehydration, in both samples unpaired electrons emerge; that causes paramagnetism of these compounds. Various carbonized systems underwent rather broad investigation by use of EPR-method. From the extensive analysis of published research results regarding the EPR-signal intensity as a function of carbonization temperature it follows that regardless the initial substance composition, when approaching the

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temperatures of 450-600°C, concentration of unpaired electrons reaches its maximum value; yet with further temperature rise, the concentration abruptly falls [23]. Analogous dependences are observed in our experiments. However they have drastic differences. The measurements by use of EPR-method were conducted for the initial samples of WS & GS, as well as for their carbonized states at different temperatures. Let us call EPRspectra, caused by the presence of unpaired electrons of carbon system the spectra resulted from free-radical states to distinguish from the spectra otherwise caused by paramagnetic ions of metals contained in WS & GS initially. For the initial samples (WS), somewhat differing in coloration intensity of walnut shells, the concentration of unpaired electrons falls within limits of (2.5-3.0) ×1016 spin/g. Carbonization of the WS-samples at temperatures as high as 150-200°C heightens the concentration of free-radical states almost by a factor of 3 (Fig.20, curve 1). Yet at temperature of 250°C on the graph of concentration of unpaired electrons as function of carbonization temperature, small-scale minimum emerges; whereas at temperatures of 350400°C, the spin concentration reaches its maximum value of 1.4×1019 spin/g. Further increase of carbonization temperature leads to a sharp drop of the intensity of EPR-signal. Analogous pattern bears the curve of concentration of unpaired electrons as a function carbonization temperature for GS (Fig.20, Curve 2), with the only difference that maximal concentration values of free-radical state of GS is lesser than those of WS. It is interesting to note that for both samples the ratio of the concentrations of unpaired electrons, corresponding to high-temperature maximum and to the second in row, a lower-temperature maximum, amounts to about 3.9. As was stated previously, the typical situation for carbonized samples is the presence of just one maximum [23].

Figure 20- Graph of concentration of free-radical states as function of carbonization temperature of the vegetable row materials. Curves: 1- WS; 2- GS; 3- BSD

The presence of 1st maximum at temperature 150-200°C for carbonized samples is unusual [24]. Let us note that whereas our WS & GS-samples in fact showed the presence of

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1st maximum, the paper [25] suggested that during carbonization of certain polymers approximately at the same temperature span the research team had found that the concentration of unpaired electrons does not depend on pyrolysis temperature. This leads to a step-shaped plateau formation on the graph of concentration of unpaired electrons as function of carbonization temperature. Its appearance, the team interpreted, was due to formation of mesophase in the sample at this temperature range. Thereby, the increase of concentration of unpaired electrons due to dehydrogenation of the polymers is compensated by the process of mesophase formation leading to coupling of broken bonds. The key resulting process at this range of carbonization temperature with these tested samples is formation of a high percentage of tar fractions. This in turn leads to the fact that unlike common charcoals, the carbonized samples, because of their high viscosity are hardly to get triturated into powder. All the abovementioned facts give evidence of that the structure of WS- & GS- samples carbonized at the temperature range up to about 250°C differs drastically form the structure of various charcoal samples investigated earlier. If WS& GS- samples carbonized up to 250°C are treated with ethanol, then the 1st maximum on the curve of intensity of EPR-signal as function of carbonization temperature disappears. This is also an indirect confirmation of that the 1st maximum is mainly caused by tar substances which, when treated with ethanol, are apparently “washed away”. For the sake of comparison we studied pyrolyzed samples of birch wood. Burch sawdust (BSD) samples were carbonized at the same conditions as WS- & GS- samples. The EPRspectra of these samples were also recorded at the same conditions as the spectra of WS- & GS- samples. Fig.20 (curve 3) represents the graph of concentration of unpaired electrons as function of carbonization temperature for BSD- samples. It appears that for this sample the two maximums are also present, yet for BSD, the concentration of unpaired electrons for the 1st maximum is almost by a factor of two lower than those corresponding accordingly to the 1st maximums of WS- & GS- samples. Hence, BSD- samples at the temperature range of 150-200оC form tar fraction as well, but its content in the final product is almost 100 times lesser than in those from WS & GS carbonized at the same conditions. Perhaps for this reason, at early stages of investigation on carbonized samples of different kinds of wood, the matter of formation of this small maximum was “overlooked” or simply disregarded. Experimental EPR-data of linewidths & g-factor values of free-radical states of WS, GS & BSD carbonized at various temperatures in argon atmosphere are present in Table 2. Table 2 shows that g-factor for all three samples with carbonization temperature rise accompanied by the increase in developing cyclic condensed structure have a trend to diminish in its value tending to the value of g-factor for free electron. As to the linewidths of EPR, no specific function of carbonization temperature is found. However, it is worthy of mentioning that within temperature range of 400-500°C the most narrow EPR-lines with the linewidths of 4.0-5.2 Oe are observed, whereas for initial samples and at some certain carbonization temperature, EPR-linewidths reached values of 6.8-7.4 Oe. Besides the freeradical states, the signals from trivalent iron in the initial and carbonized WS-, GS- & BSDsamples are detected. Some parameters of these spectra for WS are shown in the Table 3.

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Table 2. Some parameters of EPR- spectra for free-radical states in WS, GS & BSD carbonized in argon atmosphere. Carbonization Temperature (T, °C) Initial sample 100 150 200 250 300 350 400 450 500 700 800 900

WS

GS

BSD

Δ H(Oe)

gfactor

Δ H(Oe)

g-factor

Δ H(Oe)

g-factor

7.4 5.2 5.2 5.5 5.5 5.6

2.0036 2.0028 2.0027 2.0025 2.0025 2.0025

6.1 5.9 5.7 5.9 6.1

2.0032 2.0030 2.0027 2.0022 2.0024

6.1

2.0023

5.2

2.0025

5.2

2.0023 2.0021

2.0021 2.0021 2.0022

2.0032 2.0036 2.0035 2.0034 2.0028 2.0029 2.0032 2.0026 2.0025 2.0026

5.8

4.6 4.0 5.5

6.4 6.8 6.5 6.7 5.3 5.3 6.4 6.4 4.8 5.7

We already mentioned that the concentration of free-radical states in three initial WSsamples, depending on its coloration, varies within the limits (2.5-3.0)×1016 spin/g. For these same samples total (including all EPR-lines) concentration of Fe+3 ions varies from 0.4×1020 spin/g for the initial sample #3 (of the lightest color) till 1.4×1020 spin/g for the initial sample #2 in which WS had the darkest color. The initial sample #1 regarding the concentration of Fe+3 ions and the coloration intensity of WS is in between the samples #2 & #3. Therefore it may be concluded that there is a correlation between concentration of Fe+3 ions and the color intensity of WS.

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Table 3. Some parameters of EPR-spectra of Fe3+ in WS Carbonization Temperature (оC)

ΔН1 ( Oe)

ΔН» (Oe)

ΔН3 (Oe)

g1factor

g2factor

g3factor

Init. Sample #1 Init. Sample #2 Init. Sample #3 100 150 200 250 300 400 500 900

325 350 310 200 380 340 180 250 300 250 640

1025 1000 250 1030 1000 1060 1130 1030 1340 1150 1560

250 190

2.01 2.01 2.01 2.01 2.08 2.01 2.01 2.01 2.01 2.01 2.08

2.26 2.18 2.40 2.2 2.15 2.3 2.15 2.15 2.25 2.25 2.25

4.3 4.3

190 230

4.3 4.3

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Total concentration Fe+3 ions [N×1020 (spin/g)] 1.0 1.4 0.4 6.2 3.4 6.5 4.8 2.4 7.7 1.4 116.8

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It may be noted that for the samples carbonized at temperatures from 100°C to 300°C and 900°C there are two signals observed for Fe+3 ions. The 1st signal is broad, with EPRlinewidths from 1000 Oe to 1560 Oe and with g-factor value ranging from 2.15 to 2.25. The 2nd signal is narrower; its linewidth for these carbonization temperatures varies from 180 Oe to 640 Oe while g-factor values fall within limits of 2.01-2.08. For the samples carbonized at 400°C & 500°C, the 3rd EPR-signal emerges with g =4.3 and linewidths of 190 Oe & 230 Oe respectively. The presence of the signals derived from Fe+3 with different g-factor values gives evidence of that Fe+3 ions reside in different environments; besides, some of them suit the location in highly distorted crystal lattice [26]. When it comes to the changing intensity of EPR-spectra of Fе+3 ions as function of carbonization temperature, there would not be found any specific relations to discuss. The EPR-spectra parameters from Fe+3 ions in carbonized GS are shown in Table 4.

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Table 4. Some of the EPR-spectra parameters from Fe+3 ions contained in carbonized GS Temperature (T, °C)

g1

ΔH1 (Oe)

G2

ΔН2 (Oe)

Initial 100 150 200 250 350 500 700 800

2.15 2.00 2.08 2.08 2.08 2.08 2.0 2.01 2.01

290 425 420 430 310 270 500 120 100

2.2 2.55 2.7 2.48 2.42 2.49 2.58 2.03 2.01

875 190 160 220 250 250 220 545 275

g3

ΔН3 (Oe)

2.9 3.06 2.87 2.92 3.09

160 370 310 200 186

G4

ΔН4 (Oe)

4.71 5.36 4.2 4.06

190 250 200 250

G5

ΔН5 (Oe)

5.8 5.59

250 190

C[Fe+3] {N×1020} (spin/g) 2 1.6 1.25 1.6 2.7 3.9 8.7 7.0 2.4

As may be inferred from the Table above, the number of the lines in EPR-spectra for Fе+3 ions in carbonized WS depends on the temperature drastically. If in the initial sample & in the samples carbonized at temperatures Tk=100, 700 & 800°C the spectra have just two lines each, then at Tk=150оC there are three of them, at Tk=200оC & 250°C there are four already but at Tk=350 & 500оC there are five lines still. Such a situation often takes place when Fе+3 ion is situated in tetrahedral environment with diverse degree of tetrahedron distortion. It should be noted that Fе+3-ion concentration in these samples substantially depends upon the sort of starting raw material. Ions of trivalent iron are also discovered in the samples of birch sawdust (BSD), which EPR-spectra characteristics are present in Table 5. For these samples there is just one broad line observed in the area of g∼2; the linewidth varies from 650 Oe to 1370 Oe, depending on the carbonization temperature.

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Table 5. Some parameters of EPR-specters of Fe+3 ions in carbonized birch sawdust. Carbonization Temperature (T,°C) Initial sample 100 150 200 250 300 350 400 450

ΔН (Oe) 664 650 700 995 720 720 1230 1200 1370 1190

gfactor 2.18 2.04 2.06 2.1 2.04 2.08 2.24 2.17 2.17 2.14

Total concentration of Fe+3 ions [N×1020spin/g] 0.26 0.23 0.48 2.8 0.8 0.32 13 6.3 6.6 6.1

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It is of interest to proceed with further studies by EPR-method to measure paramagnetic properties of these charcoals (carbonized materials) after their absorption of some metals from solutions of the metal salts. Preliminary experimental studies revealed that the highest sorption capacity have the materials obtained at the carbonization temperature of 800°C. The research on the influence of absorption on the parameters of EPR-spectra was conducted with the use of WS-samples carbonized in the atmosphere of air & argon at temperature of 800°C. Metal salts were used in concentrations 10 times higher than the corresponding Threshold Limit Values (TLV). Upon saturation of charcoals (carbonized materials) with corresponding salt solutions, the samples were dried out at room temperature and then EPR-spectra were recorded. The samples of WS- samples obtained in air conditions were able to sorb the salts of the following metals: Cd, Mo, Fe, Co & Mn. The parameters of the EPR-spectra for WS, carbonized in air conditions at temperature of 800°C, after absorption of metals are shown in Table 6. In the same place the data for the initial carbonized WS-sample are presented. Table 6. EPR-spectra parameters of WS carbonized in air at 800°C, upon sorption of metal salts Adsorbed Complex Free-radical state Ratios of concentration of metal ΔH (Oe) N (spin/g) ΔH (Oe ) N (spin/g) paramagnetic centers in complexes to Fe+3 concentration in initial state Cd 470 5.5 100 8 ×1020 4 ×1016 Mo 460 1.3 ×1020 4.8 2.8 ×1016 16.3 Fe 150 11 0.2 ×1020 11 ×1016 2.5 Co 120 1.3 0.1 ×1020 9 8 ×1016 Mn 290 7.4 0.6 ×1020 5.6 ×1016 7.5 Initial sample 100 6.2 8 ×1018 7 ×1016 Carbonized @800°C

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EPR- spectrum of this sample is composed of two lines. Narrow line is caused by freeradical states with spin concentration- 7×1016spin/g; g-factor =2.0024 & linewidth equaled to 6.2 Oe. Broad line is caused by Fe+3 ions, its linewidth=100 Oe & Fe+3concentration is equivalent of 8×1018 spin/g. Upon absorption, the pattern of EPR- spectra change significantly. Instead of broad line from Fe+3 ions, the lines emerge, the linewidth of which depends on the kind of adsorbed metal. We believe that during the absorption process of various metals by the carbonized walnut shells, the formation of paramagnetic complexes take place: metal-carbon-unpaired electron (Me[C-Un.e]) [29]. The mechanism of formation of these complexes in details is unknown to date. It is a surprising fact, by the way, that the concentration of these paramagnetic complexes exceeds Fe+3 ion concentration in initial sample: the minimal excess is for cobalt (1.3 times), the maximal- for cadmium (100 times), while the concentration of free-radical states are by the factor 3-4 higher (see Table 6). The formation of additional paramagnetic sites during the metal sorption is not quite obvious and reasonable explanation for this phenomenon faces difficulties. However it may be assumed that in the course of absorption of metals, dissociation of monolithic cyclic condensed system into separate fragments takes place. That may be the reason for additional unpaired electrons popup. Possible role of water and oxygen participation in formation of paramagnetic complexes apparently may not be ruled out. Let’s note that the maximum concentration of paramagnetic complexes is observed for Cd & Mo, when for these complexes with Fe & Co metals it is minimal; the concentration of manganese complexes takes intermediate value. As a result of metal sorption, concentration of free-radical states somewhat changed. For Cd & Mo it decreased compared to initial sample while for ferromagnetic metals Fe & Co it actually increased. In the case of Mn[C-Un.e]) - complex, the concentration of free radical states takes intermediate value. It is interesting to take note on the change of EPR-linewidth for paramagnetic complexes depending on the kind of metal contained in them and for freeradical states corresponding to these complexes. For the complexes with Cd & Mo, their EPR-linewidths have the maximum values of 470 Oe & 460 Oe respectively when for corresponding free-radical states the values are 5.5 Oe & 4.8 Oe respectively. For complexes with ferromagnetic metals: Fe & Co, maximal EPR-linewidths are 150 Oe & 120 Oe, while the corresponding free-radical states have maximal EPR-linewidths: 11 Oe & 9 Oe respectively. Linewidths for Mn-complex take intermediate values for both cases. It maybe inferred that the ions of ferromagnetic metals in the complexes are bonded by exchange interaction, probably via delocalized unpaired electrons and that leads to narrowing of their EPR-lines. In the complexes that contain Mn, this interaction may be weaker and their linewidths have the values in between. Linewidths of the complexes with Cd & Mo are most probably caused by their dipole-dipole interaction with unpaired electrons. WS-samples, carbonized at 800°C in argon atmosphere, for experiments of metal sorption ware preliminary treated with 0.1N HCl solution during 24 h. The EPR-spectra parameters for the samples both initial and upon sorption of cadmium and copper salts are shown in Table 7. After activation of the samples by hydrochloric acid, the broad line of EPR-spectrum corresponding to ions of trivalent iron has disappeared, when concentration of free-radical states got equal to1.4×1019 spin/g. Upon sorption process of cadmium and copper salts, EPRspectrum for these samples is composed of two lines. The broad line is caused by Me[C-u.e], while the narrow line- by free-radical states. Concentration of Cu-containing paramagnetic

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complexes equals to1.6×1019 spin/g, their EPR-linewidth: 280 Oe. The narrow linewidth equaled to 9.2 Oe, when concentration of free-radical states remaining after absorption4.6×1016 spin/g. Cadmium complexes with concentration of 1.1×1019 spin/g have the linewidth of 140 Oe, which is two times lesser than that of copper. The narrow linewidth is 5.6 Oe for this case, while concentration of free-radical states equals to 4.7×1016 spin/g. Table 7. EPR-spectra of WS carbonized in argon atmosphere and treated with 0.1N HCl. Element

COMPLEX ΔH (Oe)

N (spin/g) 19

Cu

280

1.6 ×10

Cd

140

1.1×1019

Initial sample Carbonized @800°C

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Free-radical state ΔH (Oe)

N (spin/g)

9,2

4.6 ×1016

5,6

4.7×1016

5,5

1.4×1019

Hence, it could be seen that in this case concentration of formed paramagnetic complexes for both metals is practically the same. The residual concentration of free-radical states, upon metal salts sorption, can also be considered equal for both metals. However their value decreased almost by an order of 3 compared to initial state. And again the question arises about the nature of formation of paramagnetic complexes of metals in such high concentration. Supposing that this difference in three orders of magnitude of the number of unpaired electrons plays a role in formation of paramagnetic complexes, then some sixteen orders of magnitude of concentration of unpaired electrons unaccounted for must be somehow built up during sorption process. If in first case it may be assumed that the formation of paramagnetic metal complexes somehow takes place due to possible d-electrons participation of trivalent iron ions, then in activated carbonized WS-samples they are absent. In such case we have to suggest that in the course of metal salts sorption, bond braking of monolithic cyclic condensed carbon system takes place. Of course, we do not exclude other possible mechanisms of formation of such complexes. In order to establish a complete picture of formation of paramagnetic metal complexes, further research should be done in this field. It may be concluded that during the sorption of salts of metals varying in their magnetic properties by adsorbents obtained on the basis of carbonized WS and GS, the essential role is played by the magnetic properties of a metal.

Apricot stones Sorbents based on carbonized apricot stones are considered to be promising [28, 29].In this regard, they were studied using EPR-method. The results of the measurements are presented in Table 8 and Fig.21.

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Z.A. Mansurov and M.K. Gilmanov Table 8. Changing parameters of EPR-spectra of carbonized apricot stones. Carbonization temperature (ToC)

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Initial sample 50 100 150 200 250 300 350 400 500 550 600 650 700 750 800 850 900

Concentration of free-radical states spin/g×1017

0.39 0.79 0.74 0.57 0.77 0.60 0.11 0.06 258.00 236.16 0.40 113.73 85.83 0.16 240.78 32.11 0.84 40

EPR-linewidth, ∆H (Oersted)

g-factor

6.3 6.6 6.5 6.0 6.5 6.3 6.7 8.1 5.7 5.6 5.5 6.5 8.5 7.4 5.5 5.9 8.6 5.8

2.0032 2.0036 2.0034 2.0032 2.0033 2.0033 2.0019 2.0021 2.0021 2.0019 2.0019 2.0020 2.0022 2.0020 2.0022 2.0020 2.0017 2.0025

Fig. 21 Graph of concentration of free radicals as function of carbonization temperature of AS.

As can be seen from the table above and the figure below, carbonized AS-samples behave in special way. Their behavior in terms of carbonization temperature is characterized

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by many differences from the features found common to the vegetable raw materials considered above. For example they do not express tendency to have narrowing effect of EPR-lines at high carbonization temperatures. Furthermore, on the graph of C -[FRC] (concentration of free-radical states) as function of temperature a number of minimums and maximums are observed. First minor minimum falls within the temperature range of 300350оC. It is preceded by a small plateau-like maxim. This is followed by a successive row of sharp maximums and minimums for which the difference in concentrations of free-radical states reaches about two to three orders of magnitude. The 1st largest maximum lies within the temperature span of 400-500оC, when the minimum is about 550оC. Successive minimums are observed at the temperatures of 700оC & 850оC while the maximums are at 600оC & 750оC. It is interesting to note that the minimums in high temperature field are spaced from one another by 150оC (T1=550оC, T2=700оC, T3=850оC) (Fig. 21) Let us note that at 900оC concentration of free-radical states rises again and it is not improbable that at temperatures of 950 - 1000оC next maximum may appear. What can be the cause of such succession of maximums and minimums of concentration of free-radical states on the curve of carbonization of apricot stones? It was assumed that at temperatures corresponding to the minimums of concentration of free-radical states, the formation of various carbon nanostructures takes place. These nanostructures may include nanoforms of different size and structure, cones, carbon fiber etc. The point is that nanostructures possess diamagnetic properties and therefore this may lead to abrupt fall of intensity of EPR-signal. This model agrees with obtained EPR-data. The drop of the signal intensity may be caused by the fact that during formation of nanotubes, for instance, convolution, so to speak, of graphite planes takes place. In such case free electrons may participate in linking of the edges of graphite planes and thus consumed. Apparently, at temperatures corresponding to the maximums on the concentration curve, nanostructures do not form. At temperatures corresponding to the minimums of free-radicals concentration, the formation of nanostructures of various shapes and size occur. It is considered that nanotubes and structures the like have diameters of a few nm, their length may reach a few microns. There are cases when nanostructures are formed in polyhedral and spherical shapes of a size from 50 to 200 nm, while cylindrical structures are observed to be longer, with diameters up to 300 nm. In order to disclose the nature of nanostructures formed at temperatures of 550°C, 700°C & 850°C, electron-microscopy studies on corresponding samples were conducted. The obtained results correlate well with proposed assumption of presence of great number of various nanostructures at these temperatures. Consequently, EPR-method may be successfully used for identification of temperatures at which the maximal formation of nanostructures in the course of the reactions of carbonization of the materials.

Rice husk Results of EPR-spectroscopy showed that the initial sample of rice husk (RH) possesses the following parameters: Concentration of free radicals (FRC) – N = 2.6×1016spin/g, EPRlinewidth (ΔH) = 6.9 Oersted & g-factor amounted to 2.0035.

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Figure 22. Effect of the process temperature on the concentration of free radicals

As follows from Fig. 11, at carbonization temperature of 350 °C, a sharp increase in the concentration of free radical states begins. The value of FRC at this temperature rose by an order of two, while ΔH narrowed to the value of 6.7 Oersted (Fig. 12). In the course of further temperature rise, value of CFR continues to grow and reaches the 1st maximum at 400°C, N = 6.4 ×1018spin/g, the linewidth (ΔH) & g-factor reach the values of 6.9 Oersted & 2,0032 respectively. At carbonization temperature of 450 °C, the minor minimum is observed: value of CFR- N = 4×1018spin/g (Fig. 22). However with further temperature rise of 50°C, unexpected abrupt changes in the pattern of EPR-specter take place: FRC increases 30 times reaching the 2nd maximum, g-factor value decreases from 2.0032 до 2.0025. At this temperature (450 °C), the spectrum linewidth falls from 5.8 to 5.2 Oersted. Further on, CFR gradually decreases reaching the value of N = 1 ×1017spin/g at temperature of 850 °C (Fig. 23). Value of g-factor increases up to 2.0026 at 500 °C, and then reaches the plateau at the value of 2.0025, except for the temperature of 650 °C where it decreases to 2.0023; then again it rises to 2.0025. The linewidth ΔH gradually decreases to 2.7 Oersted (850 °C). However within temperature range of 550-650 °C, the transition “maximumminimum” is observed with the following values of ΔH: 5.3 Oersted at 550 °C, 4.0 Oersted at 600 °C & 4.6 Oersted at 650 °C. It was proposed that at temperatures corresponding to minimal concentration of freeradical states, the formation of various nanostructures occur. As a matter of fact such structures possess diamagnetic properties.

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Figure 23. Characteristic curve of EPR- linewidth for RH-samples as function of carbonization temperature.

This should lead to a sharp drop in intensity of EPR-signal. Apparently the temperature rise at some point leads to destruction of nanostructures, and that in turn leads to the appearance of a maximum on concentration curve. Further temperature rise causes the reappearance of nanostructured formations of a different type.

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Wheat bran [30] The EPR study was carried out at room temperature on an IRES-1001-2M EPR spectrometer of the homodyne type operated at the X-band frequency. For the control of the measurement condition of the sample and determination of the EPR line width and g-factor value, Mn2+ ions in MgO were used as reference sample. The spectrum was recorded between the third and fourth lines of the reference sample. With the g-factor value of these lines and the distance between them (in Oersteds), one can determine the width of the studied line and its g-factor value with sufficient precision. The concentration of free radicals in the samples was determined by a comparison of the double integral values of their spectra with the spectrum of the third line of a standard calibrated Mn2+ sample. At a carbonization temperature above 600 C the EPR line shares are, in certain cases, influenced by the conducting properties of the samples [31], due to the appearance of the graphite structure in these samples. If the size of the sample particles exceeds the skin layer value an asymmetric EPR line of the Dyson from appears. In order to prevent that, the

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carbonized samples were ground in an agate mortar. The sample batch weights were usually 20-40 mg. The results of EPR investigation are presented in Figs. 24-26. As follows from fig. 24, the free radical concentrations (FRC) has its main maximum value of FRC is usually within the temperature range of 450-600 C [31]. In the obtained dependence there is a small minimum at 600 C° which can be caused by the formation of graphitelike layers and the appearance of nanostructures of various shapes. It may be assumed that at 650 C°, formation of different forms of nanostructures took place that requires the use of a smaller quantity of unpaired electrons resulting in the appearance of a small maximum at this temperature. When the temperature increases only by 50 c (to 700 C°), a sharp decrease of the unpaired-electron concentration by almost three orders of magnitude occurs. Such a strong change of the FRC may be explained not only by the formation of typical graphitelike structures, as it is usually supposed, but also by the formation of a sufficiently large quantity of various nanoscale carbon structures. It is interesting to note that at 700 C° the EPR line width reaches its minimal value, ΔH = 1.1 Oe (Fig. 25). Such a strong narrowing of the EPR line of carbonized materials is observed rarely.

Fig. 24. Dependence FRC on WB carbonization temperature

The EPR line narrowing from 8.7 (initial) to 3.5 Oe (the material carbonized at 650C ) is caused by the intensification of the exchange interaction in the spin system of free radicals the maximal value of which reaches 2.1× 1019 spin/g. Further narrowing of the EPR line at 700 C with a simultaneous sharp decrease of the spin concentration down almost to the level in the initial sample is to be discussed in more detail.

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Fig.25. Dependence of EPR linewidth on WB carbonization temperature.

Fig. 26. Influence of carbonization temperature on g-factor

It may be considered that the concentration of the unpaired electrons at high carbonization temperatures, in general, is due to the delocalized conduction π electrons in the graphite structures also indicated by the decrease of the g-factor value from 2.0036 (initial) to 2.0023-2.0024 (carbonized at high temperatures) (Fig. 26). In this case, the dipole-

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dipole interaction between conduction electrons is averaged out, resulting in the EPR line narrowing. With the temperature increase to 750 °C a small maximum in the FRC dependence appears again (Fig. 24, N = 3.9×1016 spin/g), the EPR line width increasing to ΔH=3.4 Oe. This can indicate that at the given temperature the formation of such forms of nanostructures which need less unpaired electrons for their generation took place. Similar phenomena were observed earlier when overcarbonized ferrochromium spinel was studied by EPR [32, 33]. For some model systems it was shown that an increase in the concentration of nanotubes in the sample leads to a decrease of the EPR signal intensity [34]. It is natural that the formation of a number of nanostructures results from the interaction of unpaired electrons (coupling). The sharp decrease of the EPR line intensity at 700 °C could be explained by this fact.

SORPTION PROPERTIES OF CARBONIZED SAMPLES

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Water purification Influence of various factors (process temperature, sorption time, nature of activating agent, and pH value) on sorption properties of the synthesized nanocarbon materials for cesium-137 (137Cs), strontium-90 (90Sr), lead-210 (210Pb) and ions of toxic metals (Cd, Pb & Cu), as well as such a common industrial contaminant as phenol was investigated. An important characteristic of the sorbents is their ability to adsorb iodine & methylene blue (Fig. 27). Sorption activity with respect to iodine was determined using the procedure described in [35]. One can see from Figure 27 that the sorption ability of samples increases with the rise of carbonization temperature. The obtained carbonized sorbents based on plant raw material are characterized by large iodine number and high bleaching ability. The carbonized sorbent activated with acid possesses high sorption ability for iodine and methylene blue. Table 2 shows the sorption characteristics of carbonized sorbents (CS) on the basis of apricot stones. High sorption ability is determined by large specific surface and porous structure of sorbents (the presence of a large number of macro-, micro- and mesopores), as well as by chemical interaction with the surface functional groups present in carbonized samples. Poorly dissociated compounds (surface complexes of chelate type) shown in fig. 29 can be formed by the substitution of protons in one, two or three closely located carboxyl or carbonyl and phenol groups. Comparative analysis of obtained experimental data suggests that the highest sorption ability is exhibited by Carbonized samples based on WS, while the lowest one is exhibited by the CS based on AS, which is likely to be connected with high density of samples. CS based on AS can be used for absorption of chlorine and iodine ions, which is the subject of further studies.

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Figure 27. Absorption of molecular iodine and methylene blue by carbonized sorbents based on GS (1, 4, 5, 7) and WS (2, 3, 6, 8) without (3, 4, 7, 8) and after (1, 2, 5, 6) treatment with acid: 1–4 – iodine number, 5–8 – methylene number.

Table 9. Absorption characteristics of CS based on apricot stones

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The temperature of carbonization 600 600 600 650 650 650 700 700 700

The time of carbonization 1 2 3 1 2 3 1 2 3

а

The specific surface area, m2/g 310 475 575 520 710 735 645 820 785

Iodine number, mg/g

Methylene number, mg/g

350 505 600 490 665 730 600 895 880

30 80 135 145 160 185 190 285 205

b

Figure 28. dependence of sorption (quantity of, %) of copper ions (a) and lead ions (b) from the sorption time by materials obtained at 500 ºC (1), 600 ºC (2), 700 ºC (3) & 800 ºC (4)

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Sorption capacity of carbonized samples was tested & measured by the absorption of heavy metal ions (Pb2+, Cu2+).The longer the contact time of solution of metals with CS, the bigger the amount of adsorbed metal ions. Figure 28 (a, b) shows the curves of absorption of metals by sorbents based on carbonized AS [36].

Figure 29. Formation of chelate complex

The ability of the materials based on carbonized rice husk to extract ions of toxic elements (copper and cadmium) from water was studied, depending on the carbonization temperature and time of sorption. The study was conducted in static conditions. The results of sorption of copper and cadmium are presented in Tables 10 and 21.

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Table 10. Dependence of the degree of absorption of divalent copper ions from the solution, depending on the carbonization temperature of the sorbent and contact time with the solution RH-550 (Сinitial =5.1 mcg/cm3) m, g t, min Concentration, mcg/cm3 1.0075 5 1.828 1.0041 15 1.552 1.0032 30 1.241 1.0078 60 1.069 1.0135 90 1.003 RH-600 (Сinitial =5.1 mcg/cm3) m, g t, min Concentration, mcg/cm3 1.0013 5 0.223 1.0022 15 0.145 1.0043 30 0.115 1.0065 60 0.068 1.0079 90 0.065

absorption, % 77.1 86.2 87.5 88.4 88.5 absorption, % 95.6 97.2 97.7 98.6 98.7

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Nanostructural Carbon Sorbents for Different Functional Application RH-650 (Сinitial =5.1 mcg/cm3) m, g t, min Concentration, mcg/cm3 1.0023 5 0.077 1.0048 15 0.067 1.0046 30 0.029 1.0015 60 0.029 1.0033 90 0.027

251

absorption, % 97.5 98.8 99.5 99.6 99.8

Table 11. Dependence of the degree of absorption of divalent cadmium ions from the solution, depending on the carbonization temperature of the sorbent and contact time with the solution RH-600 (Сinitial =0.1 mcg/cm3) t, min

Final concentration, mcg/cm3

% поглощения

5

0.0275

72.5

15

0.0256

74.4

30

0.0158

84.2

60

0.0121

87.9

90

0.0076

92.4

RH-650 (Сinitial =0.1 mcg/cm3) t, min

Final concentration, mcg/cm3

Absorption, %

5

0.0062

93.8

15

0.0021

97.9

30

0.0019

98.1

60

0.0023

97.7

90

0.0018

98.2

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RH-700 (Сinitial =0.1 mcg/cm3) t, min

Final concentration, mcg/cm3

Absorption, %

5

0.0071

92.9

15

0.0064

93.6

30

0.0039

96.1

60

0.0028

97.2

90

0.0014

98.6

RH-750 (Сinitial =0.1 mcg/cm3) t, min

Final concentration, mcg/cm3

Absorption, %

5

0.0018

98.2

15

0.0017

98.3

30

0.0015

98.5

60

0.0016

98.4

90

0.0015

98.5

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a

b

Carbonization temperature: 400 (1), 450 (2), 500 (3); 550 (4), 600 (5), 650 (6); 700 (7), 750 (8), 800 C (9) Figure 30. Influence of time on sorption of copper (a) and cadmium (b) ions by carbonized RH

As follows from Tables 10-11, the largest amount of ions was adsorbed during first 5 minutes. Also an influence of carbonization temperature on sorption capacity was observed. For example, samples obtained at temperatures below 600 °C, have the characteristics worse than those of materials, carbonized at higher temperatures.

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Figure 31. Influence of contact time on sorption of the radioactive isotopes.

Investigation of sorption kinetics has also been carried out on the carbon material obtained at temperature 600, 700, and 800 °C, and activated by 10 % solution of caustic ammonia (рН=7) (Figure 31). All three investigated elements were successfully sorbed by activated sorbent during first 5 minutes. Sorption degree of strontium (90Sr) increases with the increase of pH value (from 1.5 to 11) achieving 87.7 % – for sorbent based on carbonized wheat bran (WB), synthesized at the temperature below 700 °C and activated by Н2О2. There is the same dependence of the sorption degree on the pH value for WB- sorbent, activated by NH3, but influence of the carbonization temperature on sorbent properties have been observed: maximal sorption degree occurs with the samples carbonized below 400 °C, reaching 86.4 %. Of all three elements studied, the worst performance is for cesium (137Cs) sorption on carbonized WB,

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activated with steam: the maximal sorption degree reaches about 80% and remains constant within pH range of 3 - 11.5. One of the most toxic pollutants of waste water from chemical industry is phenol, which can be effectively eliminated via absorption by carbon sorbents. In this part of the research, the features of modified agricultural debris in terms of their sorption activity with respect to phenol were studied. For the sorption of phenol, the contents of which in solution exceeded its Threshold Limit Value (TLV) 10 times, initial and carbonized WS- & GS- samples were used for the sake of comparison (Figure 32). Concentrations were calculated by measuring optical density using photocolorimeter KFK-2 MP in standard cuvettes with optical path length of 1 cm at a wavelength of 440 nm. The quantity if phenol, adsorbed by 1 gram of dry sorbent, was calculated using the difference between the initial and equilibration concentration of phenol in analyzed solutions.

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Figure 32. Dependence of the degree of extraction of phenol (%) as function of the time of stirring for the sorbents prior to: GS(1), WS(2) and upon carbonization: CGS(3), CWS(4)

Comparing the results obtained, one can see that for all studied systems, the equilibrium state is reached during stirring of the phases for 25-30 minutes. Sorption capacity of noncarbonized materials phenol was applied to equals to 20% for WS & 10% for GS. As can be seen from the data presented (Fig. 32), extraction ratio of phenol using CWS for the singlestep extraction at equilibrium conditions is 96%, with the use of CGS, it is 93%. This gives evidence of the high efficiency of the studied sorbents with respect to phenol.

SORPTION OF GOLD Investigation of gold sorption by the carbonized materials AS and RH was carried out by a common chemical method under static and dynamic conditions by the decrease of gold (III) content in a sorption system. In this case, the content of gold (III) in the solution was determined by the method of atom-absorption spectroscopy (AAS).

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The sorbents based on carbonized apricot stones (CAS-sorbents) have rather low redox potential, which depending on the brand varies within the range of 0.20 to 0.25 V. Hence, the CAS-sorbents possess reducing properties, which are likely to relate to reduction groups carboxyl, phenolic, hydroxyl, amine on the surface of these carbon materials [1]. Measured stationary (real) potential of [AuCl4]- in hydrochloric acid media is 0.76 V. Potential difference between the gold-oxidizer and the sorbent-reducer reducing sorbent is 0.51-0.56 V. For a redox reaction completion (99.9%), the potential difference should be at least 0.24 V [37].These data suggest that there is a real possibility of recovery of gold (III) to the metallic state. This possibility is confirmed by the values of potentials of CAS-sorbent upon sorption of the gold (III) on its surface. The value of this potential in the case of the sorbent “CAS-2”amounts to 0.4 V. During sorption of gold (III) the grains of materials are covered by a film of yellow color which is metallic gold, according to microscopic pictures (Fig. 33).

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Figure 33. Microphotographs of sorbents carbonized RH-1 and CAS-3 after Au sorption

Deposition of metallic gold due to restoration does not occur evenly across the surface of CAS-sorbent, instead it takes place on its discrete regions. It follows that the process of isolation of metallic gold and oxidation of sorbent’s reducing groups is electrochemical, i.e. there are cathodal and anodal sites on the surface. Cathodal sites are formed at the initial moment of absorption, on which later on the reduction of the gold (III) occurs. The effects of the following various factors on the sorption of gold (III) were studied: brand of sorbent, concentration of Au (III) in solution, mass of sorbent, the diameter of particles, acidity of hydrochloric acid media, the influence of impurities of metal ions. To determine the numerical values of sorption rate of gold (III) a method was used known in chemistry as method of initial rates. In this method the initial region of the kinetic curve is used for calculation, when the sorbent surface is steel free from the reaction products, and the mass of the reaction products changes only slightly from the initial concentration of active sites of sorbent and from initial concentration of gold (III). Sorption rate (W) was calculated using the equations:

ΔС × V Δt × 1000 ΔC × V Wsp = Δt × M × 1000 Wa =

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(1) (2)

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where Wa – absolute sorption rate at certain mass & grain size of a sorbent, mg/sec; Wsp – specific sorption rate at certain grain size of sorbent, assigned to 1 g of sorbent, mg/sec×g; ΔС – change of concentration of gold (Ш) transferred from solution onto sorbent (mg/l) during ∆t (sec) V - volume of the solution of gold (Ш), ml; Δt – time during which change ∆C occurred, sec M – mass of sorbent, g; 1000 –coefficient of recalculation of liters into milliliters.

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Figure 34. Kinetic curves of sorption of gold (III) on different sorbents in solution of 0.1N HCl.

The mass of sorbent -0.2 g, the diameter of particles- 0.5 mm, the concentration of gold17.75 mg/l, the solution volume- 20 ml. The sorbents: CAS-1(1), CAS-2 (2), CAS-3 (3). As seen in Figure 34, the highest sorption rate of gold (III) has the sorbent CAS-2 (curve 2). It takes 8 minutes for practically complete sorption of gold (III) with this sorbent of the highest performance. Time of complete sorption of gold (III) on CAS-1 is 11 minutes, when on CAS-3 - 16 minutes. The numerical values of sorption rate and corresponding rate constants of gold adsorbed on CAS are presented in Table 12. Table 12. Kinetics of sorption of gold (III) on sorbents of CAS- series. The mass of sorbent -0.2 g; the diameter of particles- 0.5 mm; the concentration of gold (III) - 17.75 mg/l. Sorbent brand CAS-1 CAS-2 CAS-3

Wa, mg/sec 2.29×10-3 5.9×10-3 0.99×10-3

Wsp, mg/sec×g 1.1×10-2 2.9×10-2 0.49×10-2

τ½, Min 1.75 1.35 3.65

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ks , sec-1×g-1 (of sorbent) 3.7×10-2 4.6×10-2 2.5×10-2

256

Z.A. Mansurov and M.K. Gilmanov Table 12 suggests that sorption rate of gold (III) decreases in row: CAS-2>CAS-1>CAS-

3. Based on these data, further studies were carried out with the sorbent CAS-2. Figure 3 presents the kinetic curves of sorption of Au (III) at different concentrations on the sorbent CAS-2. Within the range of studied concentration of gold (III) (8.88-35.5 mg/l) regardless of its concentration the total sorption of gold (III) occurs within 8 minutes. In this case the slope of I,t-curve of gold (III) gradual elimination from the solution and, consequently, its sorption increases with rise of the initial concentration of gold (III).

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Figure 35. Kinetic curves of sorption of gold (III) on CAS-2 sorbent in solution of 0.1N HCl. The solution volume- 20 ml; the mass of sorbent -0.2 g; the diameter of particles- 0.5 mm. The concentrations of gold (III), mg/l - (corresponding curve #): 8.88-(1); 17.75-(2) & 35.5-(3).

Figure 36. Kinetic curves of sorption of gold (III) on CAS-2 sorbent in solution of 0.1N HCl. The solution volume- 20 ml; the mass of sorbent -0.2 g; the diameter of particles- 0.5 mm. The concentrations of gold (III), mg/l - (corresponding curve #): 8.88-(1); 17.75-(2) & 35.5-(3).

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If the data shown on figure 35 to recalculate into the relative terms: «percentage of gold (III) in a solution -the time elapsed», it turns out that the kinetic curves for different amounts of gold (III) almost merge into one curve (Fig. 36). The time of absorption of a half the original content of gold or half-time of sorption (τ1/2) does not depend on the initial concentration of gold (III) and equals to 1.2 minutes. Independence of τ1/2 from the content of gold (III) suggests that for the studied span of gold (III) concentration, the kinetics of the sorption process is governed by the first-order equation:

kS =

2 .3

τ

1/ 2

×

lg C 0 C

(3)

By plotting a graph in the coordinates lg C-τ [35] constants of rate are found, they are shown in Table 13. Table 13- Kinetics of sorption of gold (III) on CAS-2 sorbent in solution of 0.1N HCl. The solution volume- 20 ml; the mass of sorbent -0.2 g; the diameter of particles- 0.5 mm. СAu(III), mg/l

W Wа, mg/sec

8.87 3.4×10-3 17.75 5.9×10-3 35.50 10.3×10-3 Average value for ks

Wsp, mg/sec×g 1.6×10-2 2.9×10-2 5.1×10-2

τ½, min

ks, sec-1×g-1 (of sorbent)

1.15 1.17 1.25

4.3×10-2 3.9×10-2 4.0×10-2 4.1×10-2 sec-1×g-1

The rate of absorption depends on the concentration of gold (III) in solution, mass and diameter of sorbent particles. The sorption rate increases with increasing concentration, the increase in mass of sorbent and decrease of the diameter of sorbent particles. The relationship of sorption rate with these factors can be represented as the following equation:

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W = k ×Сn ×M y ×d z ,

(4)

where k – constant of the rate; C – concentration of gold (III) in solution, mg/l; M – mass of sorbent, g; d - diameter of sorbent particles, mm; n, y, z – an order of the reaction by concentration, by mass & by diameter respectively. To determine the orders of the reactions, a series of experiments was conducted in which just one variable was changing at a time when the others sustained constant. In particular, when studying the dependence of the rate on the mass of sorbent, the concentration of gold in solution and the diameter of sorbent particles ware kept constant. During studying of the dependence of the rate on the diameter of the sorbent, the concentration of gold and the mass

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of sorbent remained constant. In accordance with the abovementioned, equation (4) is rewritten as follows:

Wa = k a × C n , where k a = k × M y × d z

(5)

Wm = k m × M y , where k m = k × C n × d z

(6)

Wd = k d × d z , where k d = k × C n × M y

(7)

Let us express the equations above in the following form:

Y = A× X n

(8)

Upon taking the logarithm of equation (8), we have:

lg Y = lg A + α lg X

(9)

Equation (9) represents the equation of the straight line in coordinates lg Y-lg X. In which case, the reaction order- α (n) is expressed in form of equation:

α=

Δ lg Y Δ lg X

(10)

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Kinetic curves of sorption of gold (III) on the sorbent CAS-2, depending on the mass and size of the sorbent particles are presented in Figures 37 and 38, respectively.

Figure 37. Kinetic curves of sorption of gold (III) on CAS-2 sorbent depending on its quantity, in solution of 0.1N HCl. The concentration of gold(III)- 17.75 mg/l; the solution volume- 20 ml; the diameter of particles- 0.5 mm; the mass of sorbent: 0.6g- (1), 0.4g- (2) & 0.2g -(3).

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Figure 38- Kinetics of sorption of gold (III) at different grain size of the sorbent in solution of 0.1N HCl. The mass of sorbent -0.2 g; the concentration of gold (III)- 17.75 mg/l; the solution volume- 20 ml. The diameter of particles: 0.1 mm(1), 0.2 mm - (2) & 0.5 mm -(3).

Data on the values of the sorption rate are given in Tables 14 and 15. Table 14 - Kinetics of sorption of gold (III) on various quantities of CAS-2 sorbent in solution of 0.1N HCl. The concentration of gold (III)- 17.75 mg/l; the diameter of sorbent particles- 0.5 mm. Mass of the sorbent, g

τ½, Minutes

Wа, mg/sec

Wsp, mg/sec×g

0.2

1.20

5.4×10-3

2.7×10-2

0.4 0.6

0.45 0.35

1.1×10-2 1.5×10-2

2.7×10-2 2.5×10-2 2.6×10-2

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Average (mean) value

Table 15 - Kinetics of sorption of gold (III) at various grain size (the diameter of particles) of the sorbent in solution of 0.1N HCl. Concentration of gold (III)-17.75 mg/l; the sorbent mass- 0.2g. d, mm

τ½, Minutes

Wа, mg/sec

Wsp, mg/sec×g

Weff, mg×mm/sec×g

0.1

0.15

2.5×10-2

1.3×10-1

1.3×10-2

0.4

0.2

7.4×10-3

3.7×10-2

1.5×10-2

0.5

1.2

5.4×10-3

2.7×10-2

1.4×10-2

Average (mean) value

1.4×10-2

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Processing of these tables by the method described above (Van’t Hoff method) showed that the order of the reaction by mass of the sorbent is equal to one (1), while the order of the reaction by the diameter of sorbent particles is equal to minus one (-1).When assigned to the mass unit of the sorbent (g), the value of the Wsp-rate of gold (III) sorption on CAS-2 amounts to 2.6×10-2 mg/sec×g (Table 14). When assigned to the unit of the particle size of CAS-2 sorbent (mm), the rate (Weff) also remains constant with the value of 1.4×10-2 mg×mm/sec×g (Table 15). Thus, the rate of sorption of gold (III) on CAS-2 is subject to the equation:

W = k × C × M × d −1

(11)

From this equation it follows that at the same concentration of gold (III), the rate of its sorption can be changed in one direction or the other (larger or smaller) by changing the −1

−1

product M × d .Therefore, let the product M × d be called the sorption efficiency factor. While the rates assigned to the mass unit of the sorbent & to the unit of its particle size- the specific & the effective rates respectively. The effect of the acidity of hydrochloric acid media on the process of gold (III) sorption on CAS-2 was found out. The acidity of media was changing within range of hydrochloric acid concentration of 0.1-5N. The results of these experiments are presented in Table 16.

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Table 16 - Kinetics of sorption of gold (III) on CAS-2 sorbent at various concentrations of hydrochloric acid media. Concentration of gold (III)-17.75 mg/l; the sorbent mass0.2g; the diameter of particles- 0.5 mm. HCl concentration, N

Wsp , mg/sec×g

ks,sec-1×g-1 (of sorbent)

0.1 1.0 3.0 5.0

1.4×10-2 1.4×10-2 1.2×10-2 0.98×10-2

4.0×10-2 4.0×10-2 3.6×10-2 2.9×10-2

Gold (III) is almost quantitatively sorbed (97-98%) within wide acidity range of 0.1-5N HCl. Complete sorption (100%) takes place in solutions of up to 2N HCl for 8 min, when in 5N HCl solution during the same time period, sorption value is up to 97%. With the increase of the solution acidity, not only decrease of sorption degree occurs, but also some decrease in sorption rate. Regardless of the media acidity, during the sorption process, gold (III) is reduced and deposited on the sorbent in the form of metallic gold. The effect of the impurities of certain metal salts on the gold (III) sorption was also disclosed. The obtained data show that all the metals mentioned below in quantities prevailing considerably (100-800 times) do not have negative effect on gold sorption (III). These metals, according to the published sources [38] should be adsorbed by carbon sorbents. The fact that they do not have negative interference with the process of gold (III) sorption indicates that the absorption rate for gold (III) is considerably higher than those for the rest of metal impurities. The fact that they do not have negative influence on gold (III) sorption suggests that the sorption rate of gold (III) is considerably higher than the sorption rates of metal impurities.

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Moreover, the ions of metals Ni, Cd, Co, Zn have less positive standard redox potential, than stationary potential of CAS-2 sorbent. Therefore, these metals cannot participate in the redox interaction with this sorbent. Sorption of these metals should be going via ion exchange process. It is known that the rate of electrochemical processes is always higher than that of ion exchange. This may explain the reason why these metals do not affect the gold (III) sorption. In presence of the salts of copper (II) & iron (III), the rate of gold (III) reduction rises considerably. In the case of copper (II) presence, full sorption of gold (III) takes 5 min; in case of iron (III) - 1.5 min, while in absence of these admixtures it takes 8 min. Such an increase in the rate of gold (III) sorption on CAS-2 sorbent may be explained by catalytic effect: the sorbent reduces iron (III) to iron (II), when copper (II) to copper (I). Iron (II) & copper (I) ions are formed at the surface layer of the sorbent, and immediately participate in redox reaction with gold (III) ions. Since gold (III) reduction by iron (II) & copper (I) ions takes place on in the surface layer of sorbent, then metallic gold is also deposited on this surface. In fact, the process of gold (III) sorption in presence of salts of iron (III) may be schematically presented as follows: CAS -Red + Fe (III) → CAS +Fe (II) + Ox Au (III) + Fe (II) → Au 0 + Fe (III) while in presence of copper (II) salts: CAS -Red + Cu (II) → CAS +Cu (I) + Ox

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Au (III) + Cu (I) → Au0 + Cu (II) Facilitation of reduction of gold (III) by iron (II) is widely used in analytical methods of gold detection [37]. The sorption capacity of CAS-2 sorbent was determined with gold (III). In order to find static & dynamic sorption capacity with gold, the CAS-2 sorbent with particle diameter of 0.4 mm of was chosen. For the sorbent static capacity measurements with gold (III), the experiments were conducted as follows: the sorbent specimen of certain mass was added to gold (III) solution and left for 96 hours. The residual quantity of gold (III) in solution was found using the method of potentiometric titration with Mohr’s salt solution. The amount adsorbed gold was calculated according to the equation:

M Au = Q − V × N × 65.67 where M – amount adsorbed gold, mg; Q – initial amount of gold (III) in solution, mg; V – volume of Mohr’s salt solution, spent for titration, ml; N – normality of Mohr’s salt solution, N;

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1 2)

262

Z.A. Mansurov and M.K. Gilmanov 65.67 – molar mass of gold (III) equivalent.

Dynamic capacity of sorbent, i.e.: the exchange capacity before a fall-through of gold ions into column effluent (eluate emerging from the column with sorbent), was measured according to the method described above; its value equaled to 86.6 mg/g. The results of the experiments showed that CAS-3 sorbent static capacity (the capacity until the complete saturation of the sorbent by gold) amounted to 226.2 mg/g.

EXTRACTION OF FUSICOCCINE AND SPHEROSOMES [39] Laboratory tests of sorbent were carried out by group of Gilmanov M.K., academician of National Academy of Sciences of Kazakhstan in the M.A. Aitkhozhin Institute of Molecular Biology and Biochemistry. Fusicoccine was obtained by the procedure, developed in the Institute of the molecular biology and biochemistry. And there was a task to extract it from a complex mixture of bioactive compounds. For solving this problem we used the method of liquid chromatography with sorbents based on rice husk. An organic gel (Octylcepharose 4BCL (Sweden)) was used as comparison standard. The results of investigation are presented in figure 11.

a

b

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Figure 39. Extraction of fusicoccine on column with RH (a) and Octylcepharose 4B-CL (b)

The first peak (Fig. 39) contained the substances unbounded with sorbent. For removal of unadsorbed compounds the column was washed by 10 % alcoholic solution and then bonded compounds were extracted by 60% ethanol (2-peak). The analysis shows that synthesized sorbent have dividing characteristic which equal of world analysis. The experimental results allow to conclude that carbonized RH works better then organic gel. As an example, separation proceeds faster, in case of RH. In addition, the biggest advantage of RH is a high resistance in the microbiological media. Basis of Octylsepharose 4B-CL is agarose, which have decay during a month by reason of attack bacteria. Use of carbonized RH for separation of bioactive compounds allowed to obtain a quantity of biostimulator, which was sufficient for its field test and to carry out other experiments. This sorbent was called “Nanocarbosorb”.

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Using this sorbent allows us to purify sperosomes which is 2-3 times faster and which has 4-5 times higher activity than by Sepharose 4B column chromatography [40]. Results of purification of sperosomes from filling grains of wheat are presented in Figure 40. The fraction of sperosomes was eluted in the first peak after chromatography on column with “Nanocarbosorb” ARK type. Extracted spherosomes were used for medical application. we prepared the nanocontainers, loaded by medicine for treatment of eye diseases in the Institute of eye diseases (Almaty, Kazakhstan) under supervision of doctor Dzhumatayeva Z.A. The tests showed that our nanocontainers loaded by vasoprostan – one of prostaglandins as vasodilator show good therapeutically effect for treatment of glaucoma. The next tests were carried out in of Facial-mandible clinique under supervision of Doctor Myrzakulova U.R. Ointment with vasoprostan was used for treatment of saliva glands inflammatory processes. After four days of the ointment application a good therapeutically effect was achieved. Another advantages of vasoprostan are that it is used efficiently which makes treatment course cheaper, it has not irritating effect on alimentary canal, it is painlessness and more precise addressing. Thus we developed the new generation of drug delivery systems namely PI nanocontainers. These nanocontainers have obvious advantages on contrast to other drug delivery systems: they do not block blood vessels, have no toxic effect, have a good therapeutic effect and medicine action is prolonged. Using of nanocontainers allow to make effective treatment without toxic damaging effect on other organs. А280 1,8

1,6

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1,4

1,2

25

50

75

Figure 40. Separation of cell-free extracts obtained from filling seeds of wheat. Column size is ø3cm*20. Column was filled with “Nanocarbosorb” ARK type and washed and eluted by 0,05M MES buffer, pH~7.4

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CREATION OF PROBIOTICS [41, 42] Probiotics are the major therapeutical remedy for correction of intestinal microbiocenose. Probiotics represent preparations of living microorganisms and their metabolites which have positive physiological, biochemical and immunological effects on the host organism via optimization of the host’s microbial ecosystem when introduced in a natural way [43]. Since lactobacilli are the essential component of the normal microflora which is usually the first to decrease in number when disbacteriosis develops it is obvious why lactobacilli-containing probiotics are used to re-establish intestinal microbiocenose [44]. Probiotics are primarily designed to improve microecological condition of the large intestine. However the precalculated activity of such preparations is usually significantly reduced on passage through upper parts of the gastrointestinal tract. That is why it is necessary to develop completely new approaches not only to the production but also to the delivery of probiotics to target organs. The solution to this problem may be found in new techniques in biotechnology based on the use of immobilized preparations in which bacterial cells are adsorbed on the surface of a carrier. Among these of special interest are the carbonized sorbents with nanostructural surface which manifest not only high affinity to bacterial cells but also detoxifying activity [45]. It means that such sorbent will act as carrier for probiotical microorganisms and at the same time neutralizes various toxins which enter the gastrointestinal tract. One can expect that an increase in probiotical activity as a result of a more effective delivery of health-giving exogenic bacteria to the large intestine will allow re-establishing intestinal microbiocenose relatively quickly and efficiently by means of elimination of pathogenic and opportunistic microflora. On one hand such technique will bring to the decrease in the number of gram-negative bacteria and on the other hand will reduce the amount of endotoxins due to the sorption on the carrier. Since the range of probiotical preparations with immobilized lactobacilli cells is extremely limited and nanostructured sorbents have not been used for these purposes. The main goal of this study was to investigate adhesive and detoxifying properties of new carbonized sorbents with nanostructured surface with the aim of developing and detoxifying agents capable of binding toxic shock lipopolysaccharides. The carrier material pore size is very important for efficient adhesive immobilization. Sorbents with pores 2-3 times larger than microbial cells are considered the most suitable for these purposes [46]. One can see on Fig. 41 (a) that RH natural surface is very solid and doesn’t have any pores.

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a

b

c

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Fig. 41. Electron microscope images of surface of the rice husk: initial (a) and carbonized at 650 oC (b, c)

The sorbent surface undergoes changes in the process of high temperature carbonization. A more complex and solid structure with a large specific surface is formed. Pores increase in number and size, new ones appear, two or more pores can merge into one, pores surface and volume change (Fig. 41 – b, c). One can see on rice husk surface electron microscope images that a regular structure which consists of rows of cells appears after carbonization. Lactobacilli cells fit well into them (Fig. 42). Sorptional interaction between microbial cells and carbonized material has been revealed by electron microscopy. One can see that the cells are not scattered one by one over the CRH surface but form microcolonies. The fact may be of essential importance because intercellular aggregation in microcolonies is the initial stage in the formation of biofilms in which bacteria are much better protected against various adverse factors. Besides their metabolic activity is higher as it is controlled in mcirocolonies and biofilms by “Quorum sensing”. This system is called so because it coordinates the genes that are expressed only at a certain density of a microbial population (not less than 107 cells/ml). The system also controls the genes which code for enzymes involved in the production of some antimicrobial factors such as bacteriocines and microcines [44].

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Fig. 42 Lactobacillus fermentum AK-2R microcolonies adsorbed on the CRH surface.

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Cellular loading on the sorbent is pretty high and reaches 62 % with 108 adsorbed cells/g at an optimal cells/carrier ratio. The ability of microorganisms to fix themselves on a carrier is determined by their adhesive properties. Adhesion includes a number of stages in which microbes become fixed on or stick to the surface. At the first stage non-specific mechanisms are involved based on a number of physical, chemical and biological factors of which hydrophobic interaction is the most important one [47]. Hydrophobic is one of the most important features of the cell surface. It underlies such biological processes as biofilms formation, microbial cells adsorption on solid surfaces and host organism tissues [48, 49]. However these long-range disperse interactions as they are do not result in a firm sorption. They just provide optimal thermodynamic conditions. Sorption becomes stronger due to specific covalent, electrostatic bonds and other interactions within the direct contact zone in which various reactive clusters on the surface of the carrier take part. Thus, phenolic, carboxylic, carboxylic, esteric, enolic and various types of lactonic clusters have been found on the surface of carbonized nonmaterials [50]. At the same time phosphoric, amines, sulphohydrilic, phenolic, hydroxyl, carboxylic, clusters are present on the surface of lactobacilli cells [51]. Of special importance for the adhesion processes is the so-called S-layer which is found in many lactobacilli and particularly in (Fig. 43).

Fig.43. Lactobacillus fermentum AK-2R cell wall outer protein S-layer

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The S-layer consists of non-glycolized proteins which contain primarily aspartic and glutamic acids [44, 51]. This means that peptide bonds may be formed between the cells and the carrier surfaces (fig. 44).

Fig. 44. Interaction of microbial cells with a carrier surface

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Lactobacilli have a number of other surface biopolymers. Glycoprotein’s, polysaccharides, teyhoice acids also have various functional clusters [52]. Carbohydrate composition of lactobacilli glycopolymers is pretty varied but D-mannose, D-galactose, Lphucose, D-glucose, N-acetyl-D-glucoseamine, N-acetyl-D-galactoseamine, sialic acid can always be found [53]. These glycocalix components can stand out of the fragmented S-layer [54]. This may cause the cell surface charge to change which often enhances interaction between oppositely charged clusters on the surface of disperse particles (fig. 45).

Fig. 45. Interaction of microbial cells with a carrier surface.

When the cells interact with these particles various types of bonds and their combinations can arise, namely: electrostatic, hydrogen, covalent, hydrophobic [55]. Besides, new binding sites which may exhibit a higher specificity towards lactobacilli cells emerge on the surface of carbonized sorbents during the high temperature treatment.

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Immobilized bacterial cells are known to be more resistant to various negative environmental factors [56]. In our experiments high stomach acidity was one of such factors. Most microbial cells die on passage through this part of the digestive tract. Gastric juice obtained by gastroscopy was used to study free and immobilized cells sensitivity. The juice was added to a lactobacilli culture in MRS-1 medium with 109 cells/ml. The culture was then incubated for one hour and viability measured afterwards.

variants

before exposure

after exposure

0

2

4

6

8

10

Viable cells titre lg CFU/ml liquid concentrate of lactic suspension

lactobacilli on CRH

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Fig. 46. The effect of an artificial gastric medium on the free and immobilized lactobacilli cells viability

Lactobacilli biotitre (viable cells concentration) in the liquid suspension is reduced by a factor of 104 after exposure to gastric juice (Fig 46). This means that only a small portion of viable lactobacilli cells in a suspension taken orally reaches the large intestine. For this reason such a suspension should be considered a valuable source of enzymes and vitamins but not a medicine designed to colonize intestines with lactobacilli. In the experiments with the “stomach model” and immobilized lactobacilli cells it has been revealed that microbial cells adsorbed on the CRH are to a certain extent protected against the action of gastric juice. Most probably this phenomenon is ascribable to a membrane which covers every microcolony as a whole and provides additional protection against bactericides and adverse environmental factors [44]. Therefore immobilized probiotics surpass liquid cell suspension in resistance to gastric juice significantly and are capable to easily overcome the “stomach” barrier when taken orally. Another advantage of immobilized lactobacilli is that their microcolonies on carbon sorbents possess an ability to adhere relatively quickly to the intestinal mucous membrane [44]. As a result therapeutical effect of such probiotics in the treatment of disbacteriosis shows faster. Disbacterioses with an increased number of gram-negative bacteria particularly lactose-negative E. coli and other opportunistic enterobacteria attract special attention [45]. In order to test therapeutical effect of lactobacilli immobilized on CRH an experimental disbacteriosis was induced in laboratory animals with the help of a of phtorhinolones

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antibiotic ciprofloxacin. The use of this medicine brings to an excessive number of enterobacteria in the large intestine of experimental animals. Enterobacteria are transferred to the small intestine resulting in bacterial overgrowth syndrome [15] accompanied by endotoxinemia which in its turn leads to the cytokine chain activation and toxic shock [45]. Enterobacteria number was determined by plating homogenized small and large intestines walls on Endo agar before the antibiotic administration, 24 hours and 15 days after the end of therapy. This data as well as data on enterobacteria quantification in rats which CRHimmobilized probiotical cells were fed to following antibiotic therapy are summarized in table 17 Table 17. Enterobacteria number in laboratory animals with ciprofloxacin-induced disbacteriosis. Bacteria number in 1 g (М±m) large intestine small intestine wall cavity wall Before antibioitic therapy Control (2,8±0,4)х104 (7,2±0,6)х 106 (0,9±0,2)х102 24 hours after the end of therapy Without (3,1±0,5)х105 (8,1±0,7)х107 (3,5±0,3)х104 probioitic LLS (0,7±0,6)х105 (1,2±0,3)х107 (8,4±0,4)х104 Probiotic on (7,1±0,5)х105 (1,0±0,2)х107 (7,9±0,3)х104 CRH 15 days after the end of therapy Without (2,1±0,4)х105 (1,2±0,3)х108 (8,4±0,6)х104 probioitic LLS (6,1±0,7)х104 (9,6±0,8)х107 (3,1±0,4)х103 Probiotic on (4,2±0,6)х104 (8,5±0,7)х106 (2,2±0,3)х102 CRH Foot note: LLS – liquid lactobacilli suspension; CRH – carbonized rice husk.

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Group of animals

cavity (1,5±0,2)х103 (1,2±0,4)х105 (9,1±0,5)х105 (8,2±0,6)х105

(9,5±1,1)х105 (2,1±0,9)104 (1,2±0,7)х103

It was established that opportunistic enterobacteria number on the wall and in the cavity of the small intestine increased significantly (by a factor of 102) after 5 days of antibiotic therapy. At the same time bifidobacteria and lactobacteria number fell drastically. Situation was different in rats which got liquid lactobacilli suspension. Enterobacteria number on the wall and in the cavity of their small and large intestines was much smaller after the end of antibiotic therapy and lactobacilli feeding than in rats which didn’t get probiotics. The use of lactobacilli immobilized on CRH was even more effective in suppressing antibiotic-induced disbacterosis. Opportunistic enterobacteria number in this group decreased by a factor of 102 whereas bifidobacteria and lactobacteria number returned to normal. It’s been established that a colony of at least 20 bifidobacteria cells is needed to colonize 1 mm2 of the intestinal mucous membrane [57]. Under the electron microscope one can see lactobacilli colonies of 20 – 200 cells on the surface of carbonized rice husk sorbent particles. Such number provides conditions for cells to remain viable and multiply in the community. The results obtained testify that indigenous bacteria colonize intestinal mucous membrane more efficiently when introduce into the host organism in the form of microcolonies adsorbed on the sorbent.

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Decrease in enterobacteria number in animals of this group can be related with CRHimmobilized lactobacilli antimicrobial activity and with a more effective enterobacterial LPS sorption by the sorbent. Antimicrobial activity is the most important characteristic of probiotic effectiveness. The fact was a good reason to investigate the influence of immobilization on this parameter. Two methods were applied to compare antimicrobial activity of L. fermentum AK-2 free and immobilized cells. First an inhibitory zone was measured on an agar medium surrounding holes with liquid culture medium used to grow free and immobilized antagonist strain cells. 8 species of Enterobacteriacea family were used as target (test) strains (Fig. 47).

Kl.pnemoniae E.coli

20

S.thyphimurium

15 10 Sh.zonnei

50

P.vulgaris

P.mirabilis

Sh.flexneri E.aerogenes

Liquid of lactobacilli suspension

Immobilized on CRH

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Fig. 47. Antimicrobial activity of L. fermentum AK-2 free and CRH-immobilized cells with respect to enterobacteria.

It was found that CRH-immobilized cells antimicrobial activity increased by 25 – 60 % depending on a test strain. The result was confirmed with the use of another technique. In this case the number of viable enterobacteria test strain cells was determined following combined cultivation of the test strain with free or immobilized lactobacilli at the concentration of 108 CFU/ml. The sorbent without any cells was used for control. Lactobacilli were added to 10 ml suspension of test strains (108 CFU/ml) i. e. the cultures ratio was 1:10. It is seen from the table 18 that free lactobacilli cells obviously suppress the growth of all 3 test strains. At the same time the sorbent itself can bind up to 28-33 % of enterobacteria cells. However probiotic immobilized on CRH is more effective in suppressing test strains. Test strains growth and viability tends to zero within 48 hours of combined cultivation.

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SORPTION OF LIPOPOLYSACCHARIDES [42] Normal human microflora maintains biochemical, metabolical and immunological equilibrium which is essential for health [43]. Intestinal microflora plays the key role in colonial resistance of the host’s intestines with respect to pathogenic and opportunistic microorganisms. Gut microflora biological equilibrium is disturbed by various endo- and exogenic factors. As a result a clinical laboratory syndrome may arise which is characterized by gastrointestinal upset defined as disbacterioses [44]. Table 18. L. fermentum AK-2 free and CRH-immobilized cells antagonistic activity in joint cultivation with enterobacteria. Variants

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Probiotic on CRH Probiotic CRH Without probioitic

Viable test strain cells number, % Salmonella Shigella zonnei А-22 typhimuriumР-1 5,8 4,6 17,5 26,5 67,5 70,3 100 100

Proteus vulgaris З-53 2,3 9,6 72,5 100

Over the past years one can observe an increase in the number of people with severe diseases caused by gram-negative bacteria endotoxins which represent non-secreted heatstable lipopolysaccharides (LPS) that are the main components of the cell’s outer membrane. The endotoxin is released when pathogenic microorganisms die which results in general infections with the endotoxic shock in the most severe cases. Gram-negative gut microflora is the constant source of LPS in human organism. Normally in healthy persons small amounts of LPS entering the bloodstream are considered to be necessary to support immunity. When human gastrointestinal microecology is disturbed one can often observe an increase in the number of gram-negative opportunistic enterobacteria that are transferred to other organs resulting in endotoxinemiya [45]. The aim of the study was to examine the ability of carbonized materials (RH and AS) to adsorb a bacterial lipopolysaccharide (LPS, also called endotoxins) from water solutions. This can be interesting from the point of view of construction of new medical devices to treat septic shock by removing endotoxins from biological liquids. The following experimental protocol was used. The known dry weight of the material was put into an Erlenmeyer flask, washed 3 times with sterile PBS buffer to remove highly dispersed components, autoclaved at 121°C for 30 min to remove air from the pores and then was brought in contact with LPS-containing PBS solution. The initial concentration of LPS was 1ng/mL, which corresponds to typical concentrations of LPS in blood plasma in case of severe sepsis. After mixing the carbonised materials and LPS-containing liquid together, the flasks were gently shook and the probes were taken in triplicates after certain periods of time. The concentration of non-adsorbed LPS was determined by LAL LPS assay kit, using a chromogenic substrate. The absorbance was read at 590 nm by microplate reader (Bio-Rad Co.).

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1,4

Concentration (ng/ml)

1,2 1 0,8 0,6 0,4 0,2 0 0

1

3

5

10

20

40

60

80

100

Time (min)

Figure 48. LPS adsorption on GS and RH

In accordance with receiving results 100% sorption of LPS on carbonized RH is observed in 20 minutes, on GS – in 80 minute (fig. 48).

PREPARATION OF HONEYCOMB MONOLITHS [58]

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Monoliths preparation Currently, the studies are proceeded on alteration of the obtained carbonized materials via their modification by various functional groups. The production of honeycomb monoliths is carried out as well: that will allow to extend (widen) the scope of their application, in particular as carriers for catalysts. The experimental results of honeycomb monoliths production from rice husk are listed below. Honeycomb monoliths have some advantages over granulated and powder materials. Low pressure drop and large geometric surface area per unit volume make them attractive for catalysis. Chemical composition of the monoliths, morphology of their components, porous structure and geometrical parameters determine their properties, mechanical strength, surface area, resistance to the action of water and various chemical agents, which in turn determine the functional properties of the monoliths in adsorption and catalytic processes [59-61]. For direct extrusion of carbon monoliths, a large amount of binder should be added because of low plasticity of carbon materials. Natural clays, in particular montmorillonite Ca0.2(Al,Mg)2Si4O10(OH)2·4H2O (Ca-M), are commonly used as a binder [66, 67, 69]. On the one hand, binder increases the plasticity of carbonaceous molding composition and mechanical properties of monoliths. On the other hand, the increased mechanical strength of products has negative effect on their porous structure since a part of pores is plugged with a binder. To enhance the porosity of composite monolith substrate the chemical treatment of finished monoliths or their initial components with KOH and Na2CO3 solutions can be applied. This technique of alkaline treatment early was used for carbonized rice husk and a considerable development of the porous structure achieved [62-65],

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The alkaline treatment being applied for monolithic structure, will allow modifying the porous structure of monoliths due to formation of new pores upon removal of silica both from the carbon component of monolith and from montmorillonite that was used as a binder. For monoliths preparation we used rice husk carbonized at 700ºC and Camontmorillonite. The CRH, initial or after the alkaline treatment, was grinded into powder with particle size of ca. 50-100 μm. Ca-M was dispersed in water under intense stirring with electric stirrer to obtain a homogeneous suspension. The suspension was poured into a flat vessel and allowed to stay open for several days until the clay swelled and a viscous mass with the moisture content 65-68% formed. The CRH powder and Ca-M suspension were blended in a Z-shape mixer for 15-30 min. The optimal weight ratio of CRH to Ca-M necessary to obtain a plastic mass is 6: 4 in terms of the calcined substance. Moisture content of the mass ready for molding is 45–50%. First the mass was consolidated and compacted by vacuum, then extruded through a die plate 10 mm in diameter using a pneumatic press with vertical piston. This was followed by drying, which is an essential preparation step. Moisture transfer and shrinkage proceeding in a wet monolith have impact on the finished product shaping (bending, channels rupture, cracking) and mechanical strength. Thus, the formed monoliths were first seasoned for 3 days in cartons permeable to water vapor, then dried at 100°C, and calcined at 700°C in flowing Ar. The chosen calcination temperature provides the 100% water resistance of monoliths.

Chemical treatment with alkaline agents

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The finished monoliths made of CRH were treated with a 12% solution of KOH or Na2CO3 at 80-100°C for 3 h. The volume ratio of liquid and solid was 10 : 1. After treatment in the KOH solution, samples were washed out repeatedly with a large amount of distilled water to remove soluble compounds of Si. Then the monoliths were blown by air to remove moisture from the channels and dried at 100°C for 2 h. The steps of alkaline treatment and washing with water were repeated up to four times. The same KOH treatment procedure was used for initial CRH and Ca-M when monoliths were prepared by using preliminarily treated components. The monolith samples were treated also by impregnation with a saturated Na2CO3 solution followed by drying at 100°C and calcination at 700°C in Ar. Then the sample was washed repeatedly with distilled water and dried at 100ºС for 2 h. The steps of treatment with sodium carbonate and washing with water were repeated four times.

Physical methods of investigation The textural properties of CRH samples, Ca-M and monoliths were studied by lowtemperature nitrogen adsorption with an ASAP-2400 analyzer (Micromeritics Instrument Corp., Norcross, GA, USA) after samples pretreatment at 150°C and residual pressure lower than 0.001 mm Hg. The nitrogen adsorption isotherms were determined at the liquid nitrogen temperature, 77 K, in the range of relative pressures from 0.005 to 0.991, which was followed by a standard processing by the Barret–Joyner–Halenda scheme to calculate the total surface area ABET, total pore volume VΣ and micropore volume Vμ.

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The pore volume available to water, VH2O (moisture capacity), of CRH samples, Ca-M and monoliths was determined by immersion of samples in water until complete saturation of pores with moisture, generally for 4 h. Then the weight amount of absorbed water referred to the weight of dry sample was calculated: VH2O = (m1 -m0)/ m0, where m1 and m0 are the weights of wet and dry samples, respectively. Thermogravimetric analysis of CRH and CRH-based monoliths was made with a NETZSCH STA 449C instrument upon heating the 10 mg samples from room temperature to 1000°C at a ramp rate of 10°/min. The XRD analysis of CRH, both initial and after the alkaline treatment, was made with a HZG-4С instrument (FRE/Berger Prazisionmechanik, Germany) using monochromated cobalt radiation in the 2θ angle range of 15-75°. The morphology of CRH and monoliths was studied by scanning electron microscopy (SEM) using a JSM 6460LV microscope (JEOL, Japan) with accelerating voltage 25 kV. For the study, samples were fixed on a copper holder with conductive glue or scotch tape. A thin conductive gold layer 5-10 nm in thickness was deposited onto the samples surface in a special vacuum unit to eliminate charging effects. Carbon content in the samples was determined with a VARIO ELEMENTAR III elemental analyzer. Silicon content was measured by X-ray fluorescence spectroscopy using a VRA-30 analyzer equipped with a Cr anode of X-ray tube and by means of a SPRUT-001 energy dispersive analyzer. Mechanical crushing strength of monoliths was tested with an MP-9C device (Russia) by measuring the force required to destruct a monolith fragment with diameter 10 mm and length 10 mm between two parallel planes. Strength (P, kg/cm2) was calculated by the formula: P = p/S = p/(πD2/4),

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where p is the indicator reading, kg; S is the cross-section area of monolith, cm; D is the diameter of monolith, cm.

Alkaline activation of CRH For monoliths preparation, we chose the RH sample obtained by carbonization at 700ºC, the temperature at which the monoliths will be calcined. The CRH sample contains 49 wt % of carbon and 17 wt % of Si, the rest being represented by N, H, O and tracers of K, Ca, Fe, Zn, Ti, Al, Cl, S, P, Cu, Ni and Mn. First we studied the morphological and textural properties of CRH and explored the possibility of modifying the porous structure by alkaline treatment. The SEM images of RH sample carbonized at 700ºC are displayed in Fig. 2. Textural characteristics of the sample, BET specific surface area, pore volume available to water, volume of meso- and micropores, and diameter of mesopores according to the nitrogen adsorption data are presented in Table 19.

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Table 19. Dependence of textural properties of carbonized rice husk and monoliths prepared from it on a number of leaching operations and on the monolith preparation method. Dpore P, mesopore VH2O, ABE Number of VΣ, /Vμ, № Samples* , nm

0.095/0.07

fraction, % vol. 26

T m2/g 165

cm3/g

cm3/g

3.8

kg/cm2

1

CRH-0

2 3 4

CRH-1K

leachings alkaline agent before leaching 1 - КОН

370

5.2

0.38/0.06

84

3.0

CRH-3K

3- КОН

390

5.7

0.39/0.05

87

3.2

CRH-4K

4- КОН

395

5.7

0.39/0.055

86

3.0

0.44

0.09/0.04

56

2.3

60

0.70

0.20/0.05

75

2.8

45 40

Preparation of monoliths by scheme 1 M1-0 before 120 leaching 1- КОН 205 6 M1-1 K

5

7 8 9 10

M1-2 K

2- КОН

260

0.76

0.26/0.046

82

2.9

M1-3 K

3- КОН

280

0.80

0.27/0.043

84

2.8

40

M1-4 K

4- КОН

350

0.85

0.32/0.05

84

2.7

29

M1-4 Na

4- Na2CO3

185

0.60

0.14/0.046

67

2.3

56

0.89

0.28/0.042

85

2.7

23

Preparation of monoliths by scheme 2 306 M2-3 K 3- КОН leaching of initial components

11

1.7

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*- samples designation: 1-4 - CRH-lA, where CRH is carbonized rice husk; l – number of leaching operations; A-cation of an alkaline agent. 5-11 - MN-lA, where M is monolith; N - number of the scheme of monolith preparation; l – number of leaching operations; A-cation of alkaline agent.

One may see from the SEM images that macrostructural particles following the shape of rice husk form during carbonization. The particles are made of plate walls and virtually round channels of various size inside the plates (Fig. 49a). The skeletal part of the particle is microporous; the nitrogen adsorption study revealed that ca. 75% of the porous space is occupied by micropores (see Table 19, sample 1). Morphology of the particle walls is uniform, dense, with local formation of carbon fibers on the surface (Fig. 49b). The presence of channels with diameter 5-10 μm in the CRH structure determines a remarkably high moisture capacity. External wall of the sample is structured by regular cambers (Fig. 49c), which are called button-like or bumps by the authors of [70]. According to the data reported in [70], the channels emerge from the rice husk pores upon removal of cellulose during pyrolysis, while the bumps form due to fast removal of volatile components from the particle surface. Summing up the SEM and nitrogen adsorption data, one may conclude that the CRH sample is comprising mainly the macropores of size 5-10 μm, micropores of size less than 17 Å, and a minor amount of mesopores.

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b

c

d

e

a – CRH cross-section showing the channel structure formed after removal of cellulose; b – carbon fibers on the CRH walls; c – the ‘button-like’ structure of CRH external surface; d and е – CRH after three operations of leaching with KOH solution Fig. 49. SEM images of the rice husk carbonized at 700ºC:

The development of our method for alkaline treatment of CRH was based on the literature data. In [24, 38] it was demonstrated that КОН is preferable for the preparation of carbon materials with high specific surface area and large pore volume, due to activation of the surface upon interaction of carbon with KOH by the reaction:

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6КОН + 2С → 2К + 3H2 + 2К2СO3.

(1)

In the process, mainly the formation of microporous structure is facilitated. In the case of silicone containing carbon composites the use of Na or K carbonates as alkaline agents [24, 25] is another method to obtain mesoporous materials due to washing out from the matrix the water-soluble Na or K silicates forming by the reaction: Me2CO3 + SiO2 → M2SiO3 + CO2,

(2)

where (Me = Na, K), and SiO2 serves as a template for pore formation. In reported methods of impregnation or mechanical mixing of carbon material with a alkaline agent the weight ratio of KOH and K2CO3 (Na2CO3) to carbon material is 4 : 1 and 3 : 1, respectively. The treatment is performed in inert atmosphere at 650-1000ºC since

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reaction (1) is thermodynamically allowed at T ≥ 580°C [71], and reaction (2) at T ≥ 700°C [65, 71]. Taking into account the role of mesoporous structure in functionalization of monoliths, most preferable for us is the procedure of leaching by Na or К carbonates. However, the application of procedure including impregnation of monoliths in an excess of concentrated Na2CO3 solution, drying, and calcination at 700°C in Ar atmosphere resulted in cracking of the monolith and appearance of the Na2CO3 thermal decomposition products on the external surface of monolith structure. Evidently the porous space of monoliths is insufficient for introduction of the Na2CO3 amount necessary for leaching, so this procedure is not convenient for monolith samples. We assumed that the use of more reactive KOH at temperatures far lower than those reported in the literature would allow us to modify the porous structure by SiO2 leaching accompanied by the formation of mesopores. Thus, further alkaline treatment of CRH and CRH-based monoliths was carried out at 80-100ºC using a 12% solution of potassium hydroxide. As shown in Table 19, the application of this procedure considerably enhances all the parameters of CRH porous structure. Even after a single leaching operation, the specific surface area increases more than twofold, and the total pore volume increases nearly 4-fold (Table 19, sample 2). It is essential that the development of porous structure occurs mainly due to mesopores formation (Fig. 50) caused by silica removal from the matrix, which is confirmed by the Si content analysis of alkaline solutions and wash water. Note that main changes in the porous structure occur in a first leaching operation, and repeated treatment with KOH virtually does not change the porous structure (Table 19, samples 2-4). A similar dynamics of Si washing out of the CRH matrix is observed: main decrease of silicon concentration in the sample occurs in the first leaching operation (Fig. 50, curve 1). After three operations of KOH treatment, washing with water and drying under the IR lamp, the Si content in CRH sample decreases from 17 to 1.6%, while the carbon content increases from 50 to 81%. 1.0

2

Сi /Co

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0.8

0.6

3

0.4

4 1 0.2

0.0 0

1

2

3

4

number of treatment leaching

Fig. 50. The Si concentration versus the number of leaching operations in the samples: 1 – CRH; 2 – Ca-M; 3 – experimental curve for CRH monolith (scheme 1); 4 (dots) – calculated curve for CRH monolith

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Intensity, a.u.

Note that leaching enhances also the CRH moisture capacity from 3.7 to 5.7 cm3/g, probably due to increasing the diameter of channels (macropores). However, the SEM study of CRH sample after three leaching operations (Fig. 49d) can give only an assumptive answer to this question. There are some changes in the morphology of CRH walls: due to removal of silicon from the wall surface they become more loose and brittle (Fig. 49 d,e) as compared to the initial sample

2

1

10

20

30

40

50

60

70

80

2θ

Fig. 51. Diffraction pattern of carbonized rice husk: 1 – before leaching; 2 – after triple leaching

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The XRD characterization of CRH samples before and after leaching did not reveal any significant changes in the samples structure. XRD pattern of the initial sample (Fig. 51, curve 1) of carbonized rice husk shows the first maximum in the range of 18-35º, which is a superposition of the most intense maximum of amorphous SiO2 (2 θ = 22–26º) and graphitelike material with interfacial distance d/n = 3.86 Å. After three leaching operations and SiO2 removal from CRH, a maximum appears in the diffraction pattern (Fig. 51, curve 2), which virtually corresponds only to finely dispersed graphite-like carbon with d/n = 3.81 Å.

Monoliths preparation and alkaline treatment Considering the effect of СRH to binder (Ca-M) ratio on plasticity of the molding material its composition was optimized and contains 60% of CRH and 40% of Ca-M in terms of the calcined substance. Our previous publications [66-69] showed that Ca-M provides good plasticity of the molding composition due to its ability to swell in the presence of water that penetrates into the interlayer space of this clay. On the other hand, Ca-M as a monolith component retains its ability to absorb water, whereas the monoliths should have high water resistance for their further application as catalyst supports or adsorbents. So the monoliths with montmorillonite clays were calcined at 700°C, the temperature that provides irreversible joining of the interlayer space, which makes it possible to obtain products with high mechanical strength and water resistance.

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0.10

0.06

3

-1

dV/dD, cm ·g ·nm

-1

0.08

-1 -2 -3 -4 -5

0.04

0.02

0.00 10

100

pore diameter, nm

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Fig. 52. Differential pore size distribution in CRH monolith samples prepared by scheme 1 versus the number of leaching operations: 1 – before leaching; 2 – after single leaching; 3 – after double leaching; 4 – after triple leaching; 5 – after quadruple leaching.

We explored two schemes (differing mostly from one another in the order of procedural steps) for preparation of monoliths with developed mesoporous structure from carbonized rice husk. By the first scheme, the monoliths were first produced from CRH and binder, dried, calcined, and only then treated repeatedly with KOH. Textural properties of the monoliths were tested after each treatment cycle (Table 19, samples 5-9). The KOH treatment enhances all the textural parameters of monoliths (pore volume available to water, volume of microand mesopores according to nitrogen adsorption, and BET specific surface area). Similar to the case of CRH itself, porous structure of monolith samples is developing mainly due to mesopores (Fig. 52); at that, in distinction to CRH material, parameters of the porous structure are enhanced gradually, increasing with each leaching cycle. A slower dynamics of SiО2 removal from the monolith structure (Fig. 50) is related with the presence of Ca-montmorillonite, which contains bound silicon in alumosilicate composition. Experiments on SiO2 leaching from monoliths by Na2CO3 solution revealed a lower efficiency of this alkaline agent as compared to KOH (Table 19, sample 10). Figure 53 shows a general view of CRH monolith. SEM images of cross-sections of monolith (Fig. 53b) and monolith material at high magnification (Fig. 53c) demonstrate that morphological properties of the material are determined by the morphology of monolith components, fragments of CRH and Ca-M. After silica leaching (the triple treatment with KOH), the sample morphology remains virtually the same by the SEM data (Fig. 53d), but becomes more defective due to SiO2 removal from CRH and Ca-M. This is evidenced by a minor decrease in mechanical strength of monolith samples after each cycle of KOH treatment.

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a

b

10 mm c

d

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Fig. 53. CRH monoliths (scheme 1): a – external appearance of the monolith; b – SEM image of monolith partitions; c – SEM image of the monolith material before leaching; d – SEM image of the monolith material after triple leaching with KOH.

The monoliths preparation by the 2nd scheme includes preliminary triple treatment of CRH and Ca-M powders with KOH solution followed by washing with water after each leaching cycle, forming, drying, and heat treatment. The following steps are similar to the scheme 1: mixing, extrusion, seasoning, drying and calcinations. As a result, monoliths were produced having the porous structure parameters close to those of sample M1-3K which was prepared by scheme 1 and subjected to triple alkaline treatment (compare samples 8 and 11 from Table 19). These two samples produced by different schemes are characterized by close contents of carbon phase, which burning out is accompanied by exoeffect in the range of 470500ºC (TGA data, Fig. 54). However, sample M1-3K shows a much higher mechanical strength than sample M2-3K; it means that preliminary leaching of Ca-montmorillonite leads to loss its binding ability in the finished monolith. Thus, the method for preparation of honeycomb monoliths from carbonized rice husk by the 1st scheme followed by triple treatment with KOH solution and washing out the watersoluble potassium silicates is optimal for obtaining the monoliths with high textural and mechanical properties.

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DTA, uV

DTA, uV

100

100

TGA, mg

o

TGA, mg

T, C1000

o

470 C

4

o

T, C

o

502 C

80

80

800

800 2

2 60

60

600

600

40

0

40

0

400

400 20

1000

4

20

-2

- 41 %

-2

- 46 % 200

200 0

0

-4

-4

0

0

0

20

40

60 Time, min

80

100

0

20

40

60

80

100

Time, min

Fig. 54. TGA of CRH monolith samples: on the right – a monolith prepared by scheme 1 after triple leaching with KOH, weight loss due to carbon burn-out is 41 wt %; on the left – a monolith prepared by scheme 2, weight loss due to carbon burn-out is 46 wt %

CONCLUSION

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Thus, the investigations confirm the possibility to obtain efficient carbonized sorbents from agricultural raw materials. Carbonized materials based on walnut shells, grape seeds, apricot stones and rice husk are efficient adsorbents for heavy metal ions and organic compounds since they possess large specific surface area, high porosity, and have reactive carboxyl, carbonyl, phenol, amine, hydroxyl and other functional groups on their surface. The advantage of the considered method of obtaining the sorbents is the use of agricultural wastes of plant origin, environmental safety and high sorption ability of the carbonized sorbents.

REFERENCES [1]

[2] [3]

Mansurov Z. A., Zhylybaeva N. K., Ualieva P.S., Mansurova R.M. Obtaining Procedure and Properties of the Sorbents from Plant Raw Material// Chemistry for Sustainable Development. – 10 (2002), pp.: 321-328 Mansurov Z. A. Some Applications of Nanocarbon Materials for Novel Devices// R. Gross et al (eds.), Nonoscale-Devices – Fundamentals, Springer, 2006.- pp.: 355-368. Khokhlova G.P., Shyshlyannikova N.Yu., Patrakov Yu.F. Possibilities of Obtaining Carbon Sorbents on the Basis of a Composition of Wood Waste and Gumlike Products of Coal Processing // Chemistry for Sustainable Development. 2005. №13. P. 103-110.

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282 [4]

[5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21]

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

[22] [23] [24] [25] [26] [27]

[28]

Z.A. Mansurov and M.K. Gilmanov Galushko L. Ya., Khazipov V.A., Pashenko L.V., Saranchuk B.I. Obtaining of activated carbon from fruit stones // Solid fuels chemistry. 1998. V.56, №3. - P. 33-38 (in Russian). S. L. Medvedev, V. A. Trikhlev, E. N. Lukachina, Pat. 5019710/26 R., 1994. V. P. Golubev, V. M. Mukhin, A. N. Tamamyan et al., Pat. 97110295/25 R., 1998. Ryabikin, Yu.A., Gaitinov, A.Sh., Polyakov, A.I, Andreeva, N.P., Zashkvara, O.V.: Appl. Magn.Reson. 30, 25-34 (2006) R. M. Mansurova. The Physico-chemical Bases of the Carbon-containing Composition Synthesis. Monograph, Almaty, «XXI Century», 2001 (in Russian) Mansurov, Z.A., Zhylybayeva, N.K., Tazhkenova, G.K., Ryabikin, Yu.A., Shabanova, T.A., Mansurova, R.M., in: Carbon'03 Conference, Oviedo, Spain, 2003. Mansurova, R.M., in: Khimiya i Khimicheskaya Tekhnologiya. Problemy Segodnyshnego Dnya, pp-152-175. XXI vek, Almaty (2001) Mansurov, Z.A., Zhylybayeva, N.K., Ualieva, P.S., Mansurova, R.M.: Khimiya v Interesakh Saldadze K. M., Kovilova-Valieva V. D. Complexing Ions (Complexites). – Moscow, Chemistry, 1980; p 336. Songina K. M. Zakharov V. A. Amperometric Titration. - Moscow, Chemistry, 1979 – p 303 M. K. Gilmanov, R.Dilbarkanova, Structure and functions of spherosomes of plant cells. Almaty: Gylym, 1997, pp. 52-88. Savitskaya I.S., Izvestiya NAS RK. The biological and medical series. 2:49 (2007). Taipova R.A., Маnsurova R.М., Маnsurov Z.А., Vestnik Kazsu, chemical serials. 2: 91 (2004). Nikovskaya G.N., Gordienko A.S., Globa L.I. Microbiology. 58(3):448 (1989). Kazitsina L. A., Kupletskaya N. B. Application of UV, IR, NMR and Massspectrometry in Organic Chemistry. Moscow., MSU, 1979, p 147 Mironov V. A., Yankovskiy S.A. Spectroscopy in Organic Chemistry. Moscow.: Chemistry, 1985, p.76 R. Gergova, N. Petrov and S. Eser, Carbon, 4 (1994) 693. Mansurov , Z. A., Shabanova, T. A., Mansurova, R. M.: Vestn. Kaz. Natl. Univ. 2, 129135 (2001). Bagreev A. A., Broshnik A. P., Strelko V. V., Tarasenko Y. A.// Journal of Applied Chemistry (Russia), 1999, Vol.72, #6, pp.:942-946. Ingrem D. Electron Paramagnetic Resonance in Biology. Moscow: Mir, 1972, p.157. RyabikinYu.A., Mansurova R.M., Zashkvara O.V., Mansurov Z.A. Zhylybaeva N.N. //Third Asia-Pacific EPR/ESR Symposium, Abstracts, Kobe, Japan, 2001, 2P05. Fialkov A. S., Tian L. S., Samoilov V. G., Smirnov B. N.// Reports of Academy of Science of USSR, 1971, Vol.198, №3, pp649-650. Wickman H.H., Klein M.P., Shirley D.A. //J. Chem. Phys. 1965, v.42, p.2113-2117. Ryabikin Yu.A., Mansurova R.M., Zashkvara O.V., Mansurov Z.A. // The 4th Int. Conference. “Modern Problem of Nuclear Physics”, Abstracts, Tashkent, 2001, p.280281. Mansurov Z. A., Tazhkenova G. K., Zhylybaeva N.K., Riyabikin Yu. A., Zashkvara O. V., Mansurova R. M. Studying of sorbent synthesis process on the basis of rice husk,

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Nanostructural Carbon Sorbents for Different Functional Application

reed, apricot stones and grape seeds// Thesis of Reports of XVII Mendeleev congress in general and applied chemistry. – Kazan (Russia), 2003. –p. 263. Mansurov Z. A, Riyabikin Yu. A., Riyabikin Y., Zashkvara O. V., Mansurova R. M. Research of possibilities of nanostructures formation during carbonization process of apricot stones, using EPR-method// Thesis of Reports of XVII Mendeleev congress in general and applied chemistry. – Kazan (Russia), 2003, –p. 265. Ryabinkin Yu. A., Yemuranov M. M., Zashkvara O. V., Biisenbaev M. A., Shabanova T. A., Mansurov Z. A., Influence of Carbonic Nanostructure Formation on EPR Line Parameteres during Carbonization of Wheat Bran// Appl. Magn. Reson. (2008) 35, pp. 231-238 Singer, L. S. Lewis, I. C.: Appl. Spectrosc. 86, 52-57 (1982) Ryabikin, Yu. A. Baitimbetova, B., Zashkvara, O. V, Mansurova Z. A.: Izv. Vyssh. Uchebn. Zaved. Fiz. 1, 82-92 (2007) Mansurov, Z. A., Mansurova, R. M., Ryabikin, Yu. A., Akmetova, T., Zashkvara, O. A.: Russ. J. Phys. Chem. 75, 1598-1602 (2001) Demishev, S. V., Luchinin, P. L., Obraztsova, E. D., Pronin, A. A., Terekhov, S. V.: Sbornik Trudov XLV Nauchnoi Konferencii Moskovskogo Fiziko-Tehnicheskogo Instituta, Moscow, pp. 11-13. 2002, http://www.lt.gpi.ru/mipt2002/luchinin.htm/ Mansurova R.M., Ryabikin Yu.A., Akhmetova Zh.T., Mansurov Z.A. Journal of Physical chemistry. V. 10. 2001. P. 17-48. Mansurov Z. A., Zhylybaeva N. K., Ualieva P.S., Mansurova R. M. Vestnik PGU, v.1, 2002,-p. 38-44. Sorgina O. A., Zakharov V. A. Amperometric titration. – Moscow: Chemistry, 1979 – p 303. Grabovskiy A. I., Ivanova L. S., Matskevich E. S., Storozhuk R. K. Research of gold and silver sorption process from cyanic solutions on activated charcoal// Journal of Applied Chemistry (USSR). – 1978. – Vol 51, №;7 – p. 1515. Mansurov Z.A., Kerimkulova A.R., Biisenbaev M.A., Ibragimova S.A., Basygaraev Z.N., Gilmanov M.K. New nanostructural carbon sorbent for bioregulator purification // Book of abstracts. International conference “Carbon’08”, Nagano (Japan), 2008. M. K. Gilmanov, R.Dilbarkanova, Structure and functions of spherosomes of plant cells. Almaty: Gylym, 1997, pp. 52-88. Mansurov, Z.A., Zhubanova, A.A., 2008. Vestnik KazNU Biologicheskaya seria, 1(36), 139-142. Mansurov Z.A., Zhubanova A.A., Digel I., Artman G., Artman A., Savitskaja I.S., Kozhalakova A.A., Kistaubaeva A.S. The sorbtion of LPS toxic shock by nanoparticles on base of carbonized vegetable raw materials // Book of abstracts. International conference “Carbon’08”, Nagano (Japan), 2008. Rolfe R.D., J. Nutr. 130 (2):396 (2000). Bondarenko V.M., Gracheva N.М., Matsulevich T.V. Vorobeva А.А. J. Gastroenterol., gepatol. and koloproktol. 4:66 (2003). Likhoded V.G., Yuchuk N.D., Yakovlev M.Yu., Arkh. Patol. 58 (2): 8 (1996). Samonin В.В., Еlikova Е.Е., Microbiology. 73(6):8-10 (2004). Chakrabarti B.K., Benerjee P.S., Can. J. Microbiol. 37(9):692 (1999). Кurdich I.К., J. Microbiol.63(6):71(2001). Colleen S., Mardh F.A., Scanol. f. Wel. and Nepfarol. 15(3):181(1981). .

[29]

[30]

[31] [32] [33] [34]

[35] [36] [37] [38]

[39]

[40]

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

[41] [42]

[43] [44] [45] [46] [47] [48] [49]

283

Sorbents: Properties, Materials and Applications : Properties, Materials and Applications, Nova Science Publishers, Incorporated, 2009. ProQuest Ebook Central,

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

284

Z.A. Mansurov and M.K. Gilmanov

[50] Аbisheva А.К. Carbonized of sorbents on based of walnut and grapes stones: autoreferats. chemical science degree: Almaty - 2002 - p. 24. [51] Boonaert C.J.P., Rouxhet P.G., Appl. Env. Microbiol, 67(6):2548 (2000). [52] Onicshenko А.М., Коrоbкоvа К.S., Коvаlеnко N.К., J. Microbiol. 61(6): 22 (1999). [53] Kovalenko N.K., Podgorskiy В.С., Kasumova S.А., J. Microbiol. 66(4): 62 (2004). [54] Crittenden R., Laitila A., Forselli P., Matto J., Saarela M., Mattila-Sandholm T., Myllarinen P., Appl. Env. Microbiol. 67(8): 3469 (2001). [55] Orazumbetova А.B. Colloid – chemical property of yeasts cells Torulopsis kefir var. kumis and Sacharomyces cerevisiae: autoreferats. … chemical science degree: Almaty, 2002, p. 24. [56] Zhubanova A.A., Rep. NAS RK 1:82 (1995). [57] Syerov V.N., Ilienko L.N., Sudzhan E.V., Bondarenko V.M., New medicinal drugs 1:3 (1996). [58] Nadezhda V. Shikina, Zinfer R. Ismagilov, Irina P. Andrievskaya, Nina A. Rudina, Zulkhair A. Mansurov, Mukash M. Burkitbaev, Makhmut A. Biisenbaev, Arkhat A. Kurmanbekov. Preparation of carbonized rice husk monoliths and modification of the porous structure by SiO2 leaching// Proceedings ICOSCAR-3, September 27-30 , 2009 Ischia, Naples Italy [59] V.N.Parmon, Z.R. Ismagilov and M.A. Kerzhentsev, in J.M. Thomas, K.I.Zamaraev (Editors), Catalysis for Energy Production. In Perspectives in Catalysis: Chemistry for 21st Century, Oxford, Blackwell Scientific Publication, 1992, p.337. [60] A. Cybulski and J.A. Moulijn, Catal. Rev.- Sci. Eng., 36 (2) (1994) 179. [61] J.A. Moulijn and A. Cybulski, Structured Catalysts and Reactors, Marcel Dekker, 1998. [62] Y. Guo, S. Yang, K. Yu, J. Zhao, Z. Wang and H. Xu, Mater. Chem. Phys., 74 (3) (2002) 320. [63] Y. Guo, K. Yu, Z. Wang and H. Xu, Carbon, 41 (8) (2003) 1645. [64] P.M. Yeletsky, V.A. Yakovlev, V.B. Fenelonov and V.N. Parmon, Kinet. Catal., 49 (2008) 708. [65] P.M. Yeletsky, V.A. Yakovlev, M.S. Mel’gunov and V.N. Parmon, Microporous Mesoporous Mater., 121 (2009) 34. [66] S.A. Yashnik, Z.R. Ismagilov, I.V. Koptyug, I.P.Andrievskaya, A.A.Matveev and J.A.Moulijn, Catal. Today, 105 (3-40 (2005) 507. [67] S.A. Yashnik, I.P. Andrievskaya, O.V. Pashke, Z.R. Ismagilov and J.A. Moulijn, Catalysis in Industry, 1 (2007) 35. [68] Z.R.Ismagilov, S.A.Yashnik, A.A.Matveev, I.V.Koptyug and J.A.Moulijn, Catal. Today, 105 (3-4) (2005) 484. [69] Z.R.Ismagilov, R.A. Shkrabina and N.V.Shikina, 4th Conf. Scientific Based for Preparation and Technology of Catalysts, Sterlitamak, Russia, 29 Aug.-1 Sept. 2000, 131. [70] A. Bharadwaj, Y. Wang, S. Sridhar and V.S. Arunachalam, Res. Commun., 87 (7) (2004) 981. [71] M.A. Lillo-Rodenas, D. Cazorla-Amoros and A. Linares-Solano, Carbon, 41 (2003) 267.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 ©2009 Nova Science Publishers, Inc.

Chapter 8

CALIXARENE BASED SORBENTS FOR THE EXTRACTION OF IONS AND NEUTRAL MOLECULES Mustafa Yilmaz*a, Shahabuddin Memon†b a

b

Department of Chemistry, Selçuk University, Konya, Turkey National Center of Excellence in Analytical Chemistry, University of Sindh, Jamshoro, Pakistan

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ABSTRACT Sorption of ions as well as organic molecules from aqueous media by calixarene based materials has been a widely developing area in material science and technology since last few decades. Mostly, it is achieved by the immobilization (physically or chemically) of modified calixarenes onto various supports such as polymers, silica, and resins. The calixarene macrocycles due to their bowl-shaped geometry are indeed used as hosts allowing organic and inorganic guests to coordinate/sorb onto their cavity. The possibility of designing versatile organic, coordination and organometallic architectures at the lower (narrow) and upper (wide) rims of the calixarenes are also very appealing for extending the cavity, or to take advantage of the proximity to promote substituent interactions. Thus, novel calixarene derivatives are continue to being synthesized and appended in polymeric materials in order to obtain regenerable resins for the recovery of various elements (metals/metalloids/non-metals) and neutral molecules. The calixarene based sorbents are generally applied in various fields such as catalyst recovery, power plant, agriculture, metals finishing, microelectronics, biotechnology processes, rare earths speciation, and potable water. Besides this, they find applications in the area of selective ion extractions, receptors, catalysis, optical devices, chemical sensor devices, the stationary phase for capillary chromatography, ion transport membranes, biomimetics, and luminescence probes etc. This survey is focused to have an overview of calixarene based sorbents for the extraction of ions and neutral molecules. The article does not, however, attempt to cover all of the different approaches to extraction processes.

* e-mail: [email protected], [email protected] † e-mail: [email protected], [email protected]

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INTRODUCTION Being inspired from the nature chemists have discovered new molecular architectures and changed their approach from molecular chemistry (chemistry of covalent bonds) to supramolecular chemistry (chemistry of non-covalent interactions) with more sophisticated molecular dimensions being constructed either through self-assembly of subunits or by selective host-guest interactions. As chemistry beyond the molecule, supramolecular chemistry has been developed enormously and its goal is to gain control over the intermolecular non-covalent bond [1-3]. Starting with the investigation on the basis of hostguest phenomenon, it has explored the synthetic routes on the basis of design or with the selection of components that mimic natural enzyme activities, which are enabled owing to the presence of weak non-covalent forces based on hydrogen bonding, van der Waals interactions, electrostatic or cation–π interactions and hydrophobic effects, etc [4-6]. The release of metallic as well as organic pollutants into the environment, either through man-made or natural processes is a topic that generates substantial scientific interest and public concern [7-10]. Significant attention has been paid to chemical separation techniques that involve the design and synthesis of new sorption materials. Such attention results from environmental concerns, efforts to save energy, and reprocessing at the industrial level. Supramolecular chemistry has provided solutions in the search for molecular structures that can serve as building blocks for the production of various receptors for charged species or neutral molecules. A relatively new class of synthetic macrocyclic building blocks has recently been emerged among molecular receptors of numerous types, capable of binding specific substrates with high efficiency and selectivity. The “Calixarenes” or “Calix[n]arenes” are a fascinating class of macrocyclic molecules (Fig. 1) which have been used extensively in supramolecular chemistry [11-22]. Calix[4]arene, calix[6]arene and calix[8]arene are very common and conveniently synthesizable members of the series. The highly ordered structures of calixarenes offer not only boundless possibilities for chemical modification, but also make them extremely useful in the study of molecular recognition and supramolecular processes.

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3+ n OH

n

OH HO OH n = 1, 3, 5

HO HO OH

OH n

Figure 1. The structural representation of p-tert-butylcalix[n]arenes.

The name ‘calix[n]arene’ was proposed by Gutsche for the cyclic oligomers obtained by condensation of formaldehyde with p-substituted phenols. The use of the word ‘calix’ which means ‘vase’ in Greek was suggested by the shape of the tetramer which can adopt a beaker-

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287

like conformation (Fig. 2). The suffix ‘arene’ indicates the presence of aryl groups in the molecule and ‘n’ being the number of aromatic rings joined by methylene bridges [11, 17]. For instance, calix[4]arene is a cyclic compound constituted by four phenolic units linked by methylene sub-groups. Because of very diverse nature calix[4]arene has been studied extensively as compared to the other members of the family.

OH HO

OH OH

OH

HO

OH

OH OH

OH

OH

HO

Figure 2. Different structural representations of calix[4]arene.

One of the most fascinating property of calix[4]arene is the variety of conformations that it can assume. Conformation mobility results from quasi-free rotation about α-bonds of the Ar-CH2-Ar moieties and formation of cooperative hydrogen bonds [11-20]. It presents four conformations: cone, partial cone, 1,2 alternate and 1,3 alternate (Fig. 3).

OR OR OR

RO

Cone

OR

OR OR OR

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Partial Cone

RO OR

RO

OR OR

1,3-Alternate

RO

OR

RO

1,2-Alternate

Figure 3. The conformations of calix[4]arene.

Architectural designing of the basket type calixarene derivatives led a competition among the scientists working in different fields to acquire the macromolecules according to their

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choice and desired goal. Thus, several novel calixarene derivatives have been synthesized by the modification of upper or lower rims (Fig. 4) of these molecules [21-53]. UPPER RIM 4

HO

OH

OH OH OH

OH

OH

HO

LOWER RIM

Figure 4. The representation of upper and lower rims of p-tert-butylcalix[4]arene.

It is a well known fact that there are almost unlimited possibilities for the derivatization of calixarenes by using simple organic synthetic methods (Fig. 5) to acquire a suitable macromolecule for a particular purpose [54-58], i.e. catalysis, ion selective electrode (ISE) preparation, semi-permeable membranes, selective recognition of ions or molecules, etc [5975]. The inclusion of ions or molecules mainly occurs due to the structural features of calixarenes including cavity with a suitable size that provides possibility to complex guests in an extended cavity based on multiple interactions through three-dimensional molecular cleft with binding sites at the upper and/or lower rim of the compound [19,76]. R

R R = S O 3H R = NO2

4 OH E lectro p h ilic S u b stitu tio n

OH

4

R = C H 2C H 2N H 2 R = C H 2C H 2C N R= CHO R=CH=NOH

p -C la isen R ea rra ng em en t

p -C h lo ro m eth yla tio n

CH2Nu

U p p e r r im Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

R= H R= CH3 R = C 6H 5 4

OH

H

OH D ealk ylatio n

C H2R

Nu Nu Nu Nu

= CN = OCH3 = N3 =H

4 OH p -Q uino n e-m eth id e M e tho d

4

OH OH OH

HO

L o w e r r im

OR E sterificatio n

4

R= COCH3 R = C O C 6H 5

R = C H 2C O R R = C H 2C O O R R = C H 2C O O N H 2 R= M e

4 OR W illiam so n E th er S yn th esis

Figure 5. The derivatization schemes of p-tert-butylcalix[4]arene.

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The inclusion phenomenon of calixarenes may be understood conveniently by schematic representation as shown in Fig. 6, in which a calixarene molecule act as a basket forming either, “endo” or “exo”, complex [20]. R

R

R

R

OH OH HO

OH

Ionic Guest

Neutral Guest

R

R

R

R

R

R

OH OH

OH OH OH

R

R

HO

Endo Complex

OH

HO

Exo Complex

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Figure 6. A schematic representation of “endo and exo complexes” of calix[4]arene.

However, calixarenes have been proved as excellent ligands for ions as well as neutral molecules [18,19,57,58,77-92]. The extraction processes for ions or molecules those generally have been employed are of two types, (i) liquid phase extraction (LPE) and (ii) solid phase extraction (SPE). Various researchers [93-98] have emphasized the advantages of SPE over other techniques and in particular over LPE. Subsequently, several researchers have used calixarene based sorbents in SPE; in particular, polymeric calixarenes, i.e. calixarene molecules immobilized onto a polymeric resin and/or attached to a polymeric matrix. These materials have extended set of properties such as durability, chemical and thermal stability and reusability even in harsh environments [99,100]. Thus, herein it is intended to provide an overview of calixarene based sorbents for inorganic and organic species.

1. CALIXARENE BASED SORBENTS FOR CATIONS Detection, quantification and remediation of cations are very important for many scientists, including chemists, biologists, clinical biochemists and environmentalists [101]. For instance, sodium, potassium, magnesium and calcium are involved in biological processes such as transmission of nerve impulses, muscle contraction, regulation of cell activity, etc. [102,103]. Moreover, various metal ions belong to metalloenzymes. In medicine,

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it is important to control the serum levels of lithium in patients under treatment for manic depression, and potassium in the case of high blood pressure. Regarding aluminum, its toxicity has long been recognized and there is a controversy about its possible implication in Alzheimer’s disease [104]. In chemical oceanography, it has been demonstrated that some nutrients required for the survival of microorganisms in sea water contain zinc, iron, and manganese as enzyme cofactors [105]. Consequently, it is well known that mercury, lead and cadmium are toxic for organisms, and early detection in the environment is desirable [106]. For convenience, calix-sorbents for cations have been categorized according to the group of the element as below.

1.1. Calix-Sorbents for Alkali and Alkaline Earth Metals. Calixarene based polymers have just begun to receive attention, as these new polymers are mostly used as materials suitable for the metal ion sorption in solid phase extraction processes. X C H2 O

O

HO

O O

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1.

C H2 m

CH C

O

n

O CH2 O

CH2

CH3

O (But)4

(But)4

C H

O O

O O

O CH3 2. X = phenyl

The extraction experiments of calix-crown monomer 1 and copolymer 2 were performed, which confirm [107] the preference of 2 toward lithium among alkali metal picrates. In the sorption event conformational preference has been assumed to explain the greater complexation ability of the copolymer 2 with respect to calix-crown monomer 1. Same trend has been noticed by Akkus et al. [108] in case of copolymer 4, which shows significant higher sorption ability for potassium as compared to its precursor 3.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

[(

291

]n

)m

O

NH

O O

O

N

OH

NH2 N

O

O

O

O

O

O

N

O

O O

O

N

OH

O

4.

3.

The synthesis and sorption capacity of polymers 5a-c and 6a-c has been illustrated as in Table 1. It is observed that the sorption capacity for hard cations like Na+ and K+ of 6a-c is greater than 5a-c due to oxygen crown chain in polymers; preferably due to hard and soft acid base concept [109].

O

O

N N

6

O

O O

O

O

O O O

N donator O

N donator O

O N donator

O

m (But)6

m

6 a-c

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5 a-c

N-donators: a. NH2CH2CH2NH2 b. NH2CH2CH2NHCH2CH2NH2 c. NH2CH2CH2NHCH2CH2NHCH2CH2NH2

Table 1. Sorption capacities (10-5 mol/mg) of polymers 5a-c and 6a-c for Na+ and K+.

Na+ K+

5a 3.2 4.9

5b 2.8 4.5

5c 0.9 1.2

6a 12.1 10.0

6b 19.5 8.1

6c 18.2 10.7

Recently, Zhang and coworkers [110] have reported the preparation of calix[4]arenecrown (7) and macroporous silica-based supramolecular recognition agent impregnated material (8) abbreviated as (Calix[4]+Oct)/SiO2-P.for Na+, K+, Rb+ and Cs+ (Scheme 1). It is

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demonstrated that (Calix[4]+Oct)/SiO2-P (8) is promising to apply in the separation of Cs+, one of the heat emitting nuclides, from an acidic HLLW by extraction chromatography. O

O

HO O

O O

O O O

+

+ SiO2 = (Calix[4]+Oct)/SiO2 - P 8.

O

O

7.

Scheme 1.

Since, Cs+ and Sr2+ are heat emitting nuclides and harmful elements for the verification of high level liquid waste in its final geological disposal therefore; their remediation from aqueous environment is of great importance. However, in another study [111] compound 7 has been impregnated onto silica particles with tri-n-butyl phosphate (Scheme 2) to obtain calix[4]arene R14/SiO2-P (9). This composite material (9) was found an effective sorbent for the complete separation of Cs+ and Sr2+ from the non-sorption group. O

O

O

O O

O

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O O

+ SiO2 - P = (Calix[4]arene R14/SiO2 - P + Tri-n-butyl phosphate + 9.

O

O

7.

Scheme 2.

The synthesis and sorption capacity of p-tert.-butylcalix[6]-1,4-crown-4 (10) and p-tert.butylcalix-[6]-1,4-crown-4 tetraethylacetates (11) toward alkali metal ions (Li+, Na+, and K+),

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293

were determined [111]. The order of sorption capacity of 10 and 11 for alkali metal ions is Li+Pb2+>Cd2+> Cu2+>Ni2+>Co2+. The same group has also prepared a couple of novel sorbent materials from cellulose grafted with calix[4]arenes (31 and 32) and studied their sorption properties [126] for heavy metal cations (i.e. Co2+, Ni2+, Cu2+, Cd2+, Hg2+ and Pb2+). The results show that 32 is a good sorbent for heavy metal cations while 31 is ineffective may be due to absence of proper binding sites onto the lower rim of the calixarene molecule.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules Sel

Sel O Ti O

O Ti O

O

O

O Si O

O Si O

O OH

OH

HN

CN

OH

OH O

299

NC

OH O

O

O O

32

31

A chelating polycalixarene (33) has been synthesized by introducing the hydroxamate chelating group onto the calixarene units and its sorption studies were evaluated [127]. This polycalixarene has shown high sorption capacity for Ga3+, In3+ and Tl3+.

OH

OH

OH

OH

OH COOH OH

C HO

NH

NO2

HO

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HO

N

OH

COOH OH

HOOC OH

O COOH HOOC

O HO

NO2

HO

NO2

OH

C

C N

OH

OH

OH

OH

OH

N

HOOC OH

O COOH HOOC OH

O HO

C NO2

N

HO

NO2

HO

OH

OH

n

HN

OH

NO2

HO OH

33 Dumazet-Bonnamour and co-workers [128] have described a convenient and effective method to study the sorption properties of unsupported calixarenes as solid extracting agents (34-42). The reproducibility of the solid–liquid extractions was studied along with the calixarene recycling. Results (Table 2) obtained by this method for Cu2+, Cd2+ and Pb2+ have greatly enhanced the interest to use calixarenes as solid phase extracting agents.

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Mustafa Yilmaz and Shahabuddin Memon Table 2. Extraction percentages of Pb2+, Cd2+ and Cu2+ by 34-42 Compounds 34 35 36 37 38 39 40 41 42

CH2

CH2 4

O 34. COOH

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6

O 38. COOEt

CH2

CH2 4

O

CH2 4

37. COOEt

CH2

OH 41.

Cu2+ 90 >30 >95 50 80 20 80 10 20 Cd2+ >Co2+ >Ni2+ > Zn2+.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules t-Bu

301

t-Bu t-Bu

t-Bu

O

O

O

CH2

CH2

C

OC

O

O

O O

O

O

43.

Calix[4]arene carboxylate resin 44 was prepared from calix[4]arene carboxylate immobilized on a matrix of polyallylamine to explore the resin’s sorption behavior toward some metal ions including Pb2+ [130,131]. The selectivity sequence among the base metal ions on the resin was Pb2+ >> Cu2+ >> Zn2+ = Ni2+ = Co2+.

CH2

CH CH2

m

NH CH2

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CH2 OCH2COOH

4

PAA-Calix

44

The origin of this selectivity sequence was not attributed to the amino groups in the polymer matrix, but to the functional groups of the introduced calix[4]arenecarboxylic acid units. Although the maximum loading capacity for Pb2+ was not very high, the resin showed high Pb2+ selectivity and the separation of a trace amount of Pb2+ from a large excess of Zn2+ was achieved.

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Calix[4]arene and phosphorylated calixarene were immobilized onto cross-linked polystyrene supports by Alexandratos and Natesan [132]. Cooperation of the ligating groups induced high selectivity in metal ion complexation by these polymers. The calix[4]arene phosphorylated version 45 was found specific for the complexation of Fe3+ and Pb2+.

CH2 CH n OC2H5 O P OC2H5

O

O

CH2 4 45

Chelating calix[4]arenehydroxamates attached to silica gel particles (46) were studied by Hutchinson et al. [135] for their uptake of different transition metal ions at varying solution pH. While Pb2+ was quantitatively complexed at a pH of 3.5 and Cu2+ at pH of 7, the other metal ions (Co2+, Mn2+, Ni2+, and Zn2+) were not removed above 90% even at higher pH values.

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silica

CH2 O NH

4

OH

O 46 The polymers 2 and 4 already discussed in section 1.1., for alkali and alkaline earth metal ions have also been employed for the sorption of selected transition metal cations. It has been observed that both copolymers (2 and 4) were efficient sorbents for Hg2+ [112,113]. Likewise,

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303

the sorption behavior of 5a-c and 6a-c for the transition metal ions has also been investigated [114]. From Table 3, it is apparently clear that polymers 6a-c are good sorbents for Cu2+, Co2+ and Ni2+. Table 3. Sorption capacities (10-5 mol/mg) of polymers 5a-c and 6a-c for Hg2+, Cu2+, Co2+ and Ni2+.

Hg2+ Cu2+ Co2+ Ni2+

5a 31.7 10.6 23.5 25.7

5b 14.3 10.3 21.3 18.6

5c 4.4 9.3 18.6 20.5

6a 7.1 64.5 58.9 64.1

6b 4.9 60.8 62.7 70.2

6c 11.4 52.6 54.8 65.3

1.3. Calix-Sorbents for Lanthanides and Actinides The recovery of lanthanides and actinides from high level of nuclear waste is an area of world-wide concern. Various approaches have been carried out by different research groups for their remediation through solid-liquid extraction processes using calixarene based solid supports.

n

n

O

OR OR

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R'

O

R' OMe OH

47. R=-CH3, R'=-N=N HC

N

H N

NH2 S

However, Jain and coworkers [134] have proposed solid phase extraction, preconcentration and separation of La3+ and Ce3+ using calix[4]arene-ovanillinesemicarbazone immobilized on a polymeric matrix (47). The uptake and stripping of these metal ions on the resin was observed fast, showing better accessibility of La3+ and Ce3+ toward the chelating sites. The total sorption capacity of the resin was found to be 25190 and

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28143 μg/g for La3+ and Ce3+ respectively. In another study [135], this group has used 47 for the simultaneous separation and preconcentration of U4+ and Th4+. Previously, Jain et al. [136] had reported a calix[4]arene-semicarbazone derivative linked to commercially available Merrifield’s resin at the lower rim to obtain polymeric chelating resin 48. The resin was used for the preconcentration and separation of Ce3+, La3+, Th4+, and U4+. The resin exhibited good separating ability with maximum sorption between pH 2.5-4.5 for Th4+ and pH 5.5-7.0 for U4+; whereas La3+ and Ce3+ were found to have maximum sorption at pH 6.8-8.5. CH=NR'

CH=NR'

OR

OR

O

O CH2

CH2

-(CH2-CH)-n - - - - - -(CH2-CH)-n

R= CH2CH2CH3

48

R'= NHCONH2

OH

6

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O

S

O

NH

n

49. Moreover, polymer-bound calix[6]arene 49 was described in a patent by Shinkai [137], which states that the hexakis(carbethoxymethyl)ether of p-sulfonatocalix-[6]arene was partially nitrated, aminated, and fixed on cross-linked chloromethylated polystyrene. This resin sorbed 108 mg of uranium from sea water per 0.10 g of resin in seven days at a flow rate of 30 meters/minute. Another polymer-bound analog was reported by Shinkai et al. [138],

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305

who treated p-(chlorosulfonyl)calix[6]arene with polyethyleneimine to obtain a gel-like product with one calixarene unit for every 15 ethyleneimine units. This polymer showed the same binding power and selectivety for UO22+ as did the parent p-sulfonatocalix[6]arene. Chitin is one of the most abundant organic materials that can be easily obtained from nature. Chitin can be readily degraded to chitosan by N-deacetylation to give a nitrogenous polysaccharide composed mainly of β-(1,4)-2-amino-2-deoxy-D-glucopyranose repeating units. Because of its specific structures and properties, chitosan has recently received intense attention for its industrial and medical applications, such as artificial skin and to capturing metal ions from waste water [139-142]. Furthermore, the free primary amino groups and hydroxyl groups at the six positions in the pyranose ring of chitosan enable a variety of modifications. Calixarene-modified chitosans were synthesized by Li et al. [143] by reaction of chitosan with 1,3-bis-chloroethoxyethoxy-2,4-dihydroxy-p-tert-butylcalix[4]arene. Sorption of Pd2+ by polymer 50 has been evaluated. The sorption of 50 for Pd2+ at different pHs i.e. 4.0, 5.0 and 7.0 were found 75, 76 and 78 % respectively. CH2OH

NH2 O OH

OH

O NH

O

CH2O

O O

OR

O OR

(

O

)4

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50.

To facilitate the separation of uranium from uranium contaminated waters, immobilized calixarenes have been proved to be versatile candidates. A novel innovation has been launched by Schmeide et al. [144] for the purification of uranium contaminated waters by means of calixarenes immobilized on a textile material. For this, a calix-uranophile (51) functionalized with n-nonyl group was fixed onto the textile material. The results have shown that the calixarene modified textiles are useful for remediation of uranium contaminated water. The rare elements such as uranium(VI), thorium(IV) and cerium(IV) were preconcentrated and their chromatographic separations were fulfilled by Trivedi et al. [145] even from their binary and ternary mixtures as well as from monazite sand and environmental samples. For this, a polymer supported calix[6]arene hydroximic acid (52) has been synthesized by reacting the acid chloride 37,38,39,40,41,42-hexahydroxy-1,8,13,19,25,31hexa-carboxycalix[6]arene with poly(styrene β-hydroxylamine).

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OH 6 C O N O O

5

OH

O

m O

OH

HO 51.

52.

Selective extraction of lanthanides and actinides by magnetic silica particles with modified calix[4]arenes has reported by Dozol et al. [146]. They have developed a magnetic particle based process which applies a pre-organized and modified calix[4]arene ligand covalently attached on the particle surface. Efficient extraction of americium, and europium from simulated nuclear waste conditions has been achieved together with surprisingly high levels of cerium extraction.

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2. CALIX-SORBENTS FOR ANIONS Anion recognition and sensing is an increasingly important research topic in supramolecular chemistry due to the importance of various anions in biological and environmental locations. For instance, chromate and dichromate anions are important because of their high toxicity [147-149] and their presence in soils and waters [150,151]. For a molecule to be effective as a host it is necessary that its structural features are compatible with those of the guest anions. Chromate and dichromate (CrO42- and Cr2O72-, respectively) are dianions in which the anion periphery has oxide moieties. These oxygen atoms are potential sites for hydrogen bonding to the host molecule. Fascinating efforts have been made to synthesize modified calixarenes that can be used as hosts for simple anions [24, 26, 19, 152-162]. Most of them were used in liquid-liquid extraction processes. The objective is to synthesize an extractant based on a calixarene framework, which can easily be immobilized in a polymeric matrix and will be suitable for anion extraction in solidliquid processes. In this connection few reports have been found for the sorption of anions especially on dichromate. Memon et al. [163] has reported the sorption extraction experiments of polymeric calix[4]arene amino-derivative 53.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules H C

H2 C

307

n

OH OH OH O

NH2

H2N NH2 NH2 53.

The solid-liquid batchwise sorption extraction experiments of polymeric calix[4]arene amino-derivative 53 were performed into the aqueous solution of Na2Cr2O7 at 25 oC for 1 h at different pH. It has been observed that there is a significant sorption ability of the resin 53 at low pH. Fig. 10 shows the packed-column sorption extraction of Na2Cr2O7 with 53 at pH 1.5. Observations show that the maximum sorption occurs in first 10 mL and then it gradually decreases till 30 mL, after that, the sorption of the dichromate anions is more or less same about 20 %. 100

(E %)

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0

5 10 15 20 25 30 35 40 45 50 55

(mL) Figure 10. Packed column sorption percentages of dichromate anions with 53 at pH 1.5.

Recently, Qureshi et. al. [99] has described a convenient synthesis and Cr(VI) extraction efficiency of a novel p-tert-butylcalix[8]areneoctamide impregnated Amberlite (XAD-4) resin (55). Using p-tert-butylcalix[8]arene macrocyclic building block, two strategies have been developed; i.e., derivatization of p-tert-butylcalix[8]arene framework with sophisticated ionophoric groups having efficiency to extract oxoanions from aqueous media and, impregnation of p-tert-butylcalix[8]arene derivative onto the polymeric support.

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O O

O

R

R O

R O

54.

R=

O O

R O

O O

NH

O O R O

R O

N

+ XAD-4

O R O

Calix-XAD-4 55.

R

N H

The sorption capacity of 55 for chromium(VI) has been evaluated (Fig. 11) and was found that the maximum Cr(VI) sorption (80%) occurs at pH 3. However, it is well known that at higher acidic conditions Cr2O72− is converted into the H2Cr2O7 form, and after the ionization in aqueous solution it exists in the HCr2O7− and/or Cr2O72− form as shown in equation below. HCr 2O7

Cr 2O72- + H +

In acidic conditions the equilibrium shifts toward left hand side of the above equation and in such conditions mostly there is an extraction of HCr2O7-. The favorable effect of low pH can be attributed to the neutralization of negative charges on surface of the sorbents by excess hydrogen ions, thereby facilitating the diffusion and the subsequent sorption of hydrogen dichromate ions (HCr2O7−).

(b) 100

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E%

80 60 40 20 0 1

2

3

4

5

6

pH

Figure 11. Study of the pH effect on % sorption of 55.

The dependence of ion sorption at various flow rates was optimized at pH 3. Maximum percent sorption was observed at 2 mL min-1. An increase in flow rate decreases the sorption gradually, because of less contact time and weak hydrogen bonding. It was found that resin 55 extracts Cr(VI) more efficiently as compared to the ligand 54, may be due to larger surface area provided for the interaction by the resin.

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309

O R' OMe

Si

NH

O

O O

Si

OH OH O

O

R' R

R

R

NH

R O

3-5

R':

O OH OH O

O

56 : R=H, R'=a 57 : R=H, R'= b 58 : R=But, R'= b a

NH

b

R

R

R

R

59 : R = H, R'=a 60 : R = H, R'=b 61 : R = But, R'= b

O

Bozkurt and co-workers [164] has synthesised new silica based immobilized calix[4]arene polymers (59-61) for the remediation of Cr2O72-/HCr2O7- anions from (56-58). The sorption percentages and distribution coefficients were calculated as given in Tables 4 and 5. Table 4.

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Extraction and sorption percentages of dichromate anion by 56-58 and 59–61a, b, c pH 1.5 2.5 3.5 4.5 4.63 0.34 0.67 0.00 56 4.63 0.00 1.00 0.00 57 5.69 1.02 1.67 0.98 58 80.14 77.53 66.40 63.43 59 62.12 55.26 30.97 20.20 60 86.61 82.19 77.94 68.89 61 a Solid phase, sorbent = 25 mg silica-gel immobilized calix[4]arene derivatives; aqueous phase, Na2Cr2O7 = 1.0 x 10-4 M at 25 ºC for 1 hour. b Aqueous phase, [metal dichromate]=1x10-4 M; organic phase, dichloromethane, [ligand]=1x10-3 M or solid phase [ligand]=1x10-3 M at 25 ºC, for 1 h. The percentage extraction is given by [initial aqueous anion]-[final aqueous anion]/[initial aqueous anion]x100. c Averages and standard deviations calculated for data obtained from three independent sorption experiments.

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Mustafa Yilmaz and Shahabuddin Memon Table 5. Distribution coefficients for dichromate anions (Kd) by 59-61a pH 1.5

2.5

3.5

4.5

59

807

690

395

347

60

328

247

89

51

61

1293

923

706

443

a

Solid phase, sorbent = 25 mg silica-gel immobilized calix[4]arene derivatives; aqueous phase, Na2Cr2O7 =1.0 x 10 -4 M at 25 ºC for 1 hour.

The % sorption given in Fig. 12 indicates that the monomers 56-58 have not significantly extracted HCr2O7-. However, the conversion of 56-58 into the immobilized polymeric structures 59-61 has notably increased the anion extraction ability. This increase can be explained by the fact that the calixarene derivatives in the polymeric matrix may have gained a more rigid and appropriate structure, which assists the transfer of dichromate anions when compared with monomers. It is also possible that the polymer plays a role, whereby it folds into conformations that place functional groups on several of the calix[4]arene moieties in the polymer in a preferred conformation where they can associate with the oxoanion. The much higher levels of dichromate removal by calix[4]arene polymers suggest a role of Na+ complexation by the calix[4]arene units. To probe this possibility, the levels of residual Na+ in the aqueous phases following solid-liquid extraction of the dichromate were determined by atomic absorption spectroscopy.

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%E 40,00 20,00

1,5 2,5 pH 3,5 4,5

0,00 56

59

57

60

58

61

Figure 12. Extraction and sorption percentage of dichromate anion with 56-58 and 59-61 at pH 1.5-4.5.

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311

Table 6. Removal of Na+ from the aqueous layer by extraction with 59-61 at pH 1.5 (%)a Compound

59

60

61

Extraction %

73

59

75

a

Solid phase, sorbent = 25 mg silica-gel immobilized calix[4]arene derivatives; aqueous phase, Na2Cr2O7 = 1.0 x 10-4 M at 25 ºC for 1 hour.

The results given in Table 6 showed that the pronounced Na+ removal suggests an ionpair extraction mechanism in which Na+ coordinates with the calix[4]arene moiety, while the dichromate anion interacts with amide hydrogens (Fig.13). Among the silica-gel immobilized calix[4]arene derivatives, the best sorption percentage and the highest distribution coefficient values were obtained with polymer 61. This implies the better preorganization of fixed 61 which have tert-butyl groups in the cone conformation in solution. However, the sorption efficiencies of sorbents decreased with the increase in pH of the aqueous phase and the best results were obtained with a pH of 1.5. Tabakci [165] has synthesized aminopropyl silica gel-immobilized calix[6]arene (62) possessing both amide and acid moieties was prepared and its Cr(VI) sorption properties were evaluated. Through sorption studies 62 was found highly effective at pH 1.5 for Cr(VI). Maximum sorption capacity was observed as 37.66 mg g-1 by batch method.

O Si

Na+ O-

O O

Si

Cr

O

O

O O

Cr

O

OH

N H

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OH O

HO

OH

H N O O

Figure 13. The proposed interactions of 61 with Na+ and HCr2O7- ions.

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n

O

O HO H N 2

O NH

Si O

O

6-n

O

Si O

O

O

O

62.

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An interesting work regarding the sorbents prepared from cellulose-grafted with calix[4]arene polymers (31 and 32) was presented by Yilmaz et al. [126]. Their sorption properties for dichromate anions (Cr2O72-/HCr2O7-) were studied. It was observed that 32 was highly effective sorbent at pH 1.5 than 31. Calix[4]arene based polymer supported chelating resin 47 has been synthesized by covalently linking calix[4]arene-o-vanillinthiosemicarbazone via its ‘lower rim’ to Merrifield resin by Jain et al. [134, 166]. Resin 47 was competently used to separate and preconcentrate toxic metal ions Cr(VI), As(III) and Tl(I) in a column prior to their determination by UVvisible and GF-AAS with R.S.D. between 1.0–1.4%. Various physico-chemical parameters like pH, concentration of eluting agents, flow rate, total sorption capacity, metal-ligand stoichiometry, exchange kinetics, preconcentration factor, distribution coefficient, breakthrough capacity, resin stability, effect of electrolytes and associated metal ions have been studied. Resin 47 was successfully applied to the separation and trace determination of Cr(VI), As(III) and Tl(I) from natural water samples and the standard environmental, biological and geological reference materials.

3. CALIX-SORBENTS FOR NEUTRAL MOLECULES The beginning of solid-phase has gained great attention of researchers because of its simple, solvent-free, time-efficient and selective properties [167]. Besides this, it has been applied to determine benzene derivatives [168,169], chlorinated hydrocarbons [170], herbicides [171,172], polycyclic aromatic hydrocarbons (PAHs) [173–175], phenols [176], aromatic amines [177,178], polychlorinated biphenyls (PCBs) [179], organometals [180–184] and so on. However, calixarenes chemistry has provided a great deal of interest in the use of designable hosts for the specific sorption of small guest molecules [13]. The poor solubility of calixarenes in protic solvents such as water has boosted up the use of these compounds in solid phase extraction studies [185]. Moreover, calixarene immobilization offers another

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advantage to avoid host solubility limitations. It requires either the synthesis of calixarene derivatives that contain reactive functional groups for self polymerization or having groups for linking on a surface (e.g., groups capable of sol-gel hydrolysis and condensation) [186190]. The immobilized calixarenes are expected to find widespread use in fundamental studies, as well as in technological applications, including catalysis [191], sorption [73], and sensing [192-194].

3.1. CALIX-SORBENTS FOR AROMATIC MOLECULES Since, calixarenes are easy to modify with different functional groups to produce the material for desired purpose in the form of host molecules or resins. The application of calixarene fibers will undoubtedly improve the development of not only the solid phase extraction (SPE), but also the solid phase microextraction technology (SPME). Li et al. [195] has prepared 5,11,17,23-tetra-tert-butyl-25,27-diethoxy-26,28-dihydroxycalix[4]arene/hydroxy-terminated silicone oil coated fiber (63) and applied for solid-phase microextraction (SPME) with sol–gel technology. The calixarene fiber was proved to be a selective and sensitive material for polar (aromatic amines), nonpolar (benzene derivatives, polycyclic aromatic hydrocarbons) and high boiling point compounds (phthalates). The coating has high thermal (380 ◦C) as well as solvent stability (organic and inorganic), which shows its longer lifetime than the conventional fibers. CH3

CH3 CH3

O p Si CH3

Si

O Si

O

O

Si

O

O

O

O Si

O

Si

O

Si

n

O

Si CH3

Oq

CH3

CH3

CH3

CH3

Si

O

Si

CH3

CH3 m

O

Si

CH3

CH3

O

CH3

CH3

CH3

Si

n

O

O p Si CH3

Si

O

CH3

Si

63. R = CH3

CH3

Si

p

Si

C H

H2 C

OCH2CH3 O

H2 (C)3

O O

Si

O

O O O

CH3

H2 C

C H

H3CH2CO

H2 C

O

O OR

H2 (C)3

O

OCH2CH3

Si

O

O

CH3

CH3 CH3

O

O

H2 C

CH3 O q Si

CH3

m

CH3

CH3 O

Si

OR O

H3CH2CO O

CH3

CH3 CH3

CH3 Si

O

O

O Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

O

CH3 Si

Si CH3

CH3 O

Si CH3

CH3 O

q

Si

CH3

CH3

In continuation of above study sol–gel-coated novel fiber (64) was also applied for direct analysis of chlorophenols (2-chlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol) [196]. The results reveal that the development of 64 fiber can improve the carry-over of chlorophenols. The complete analytical procedure was applied to analyze river

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Mustafa Yilmaz and Shahabuddin Memon

water and soil samples after ultrasonic extraction. The recoveries of those compounds studied in river water were 94.7, 97.4, 97.0 and 86.3% and for the soil sample, it was 98.6, 97.0, 90.2 and 81.0% respectively. CH3

CH3 CH3

Si

O p Si CH3

O Si

O

Si

O Si

O

O

O

O Si

O

Si

Si CH3

n

CH3

CH3

Si

Si

CH3

CH3

CH3

CH3

CH3

Si

O

Oq

O

Si

CH3

CH3

O

CH3

CH3

n

Si

O

O

Si

CH3

CH3

CH3

CH3

CH3

O p Si CH3

Si

O

O

(HC2)3 O

CH2

CHCH2

OH

O

(HC2)3 O

CH2

CHCH2

OH

O Si

O

O

O q Si

CH3

OCH2CH3

O

m

O

Si

O

OH O

H3CH2CO

O m

O

Si

O

O

CH3

O

H3CH2CO

OCH2CH3

O OH

CH3

CH3

64.

O CH3

CH3 CH3

Si

O p Si CH3

O Si

O

Si

O

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O Si

O

Si O

CH3

Si CH3

O

O

O

O

CH3

O

Si

n

O

Si

O q Si

CH3

CH3

CH3

CH3

Si

O

Si

O

CH3

CH3

O

CH3

CH3

Si

n

O

Si

O

Si

O

CH3

CH3

CH3

CH3

CH3

O p Si CH3

O

Si CH3

HO

CH3

O q Si

CH3

O

NH O NH O O

O m

O

Si

O

(HC2)3 O

CH2

CHCH2

OH

O

(HC2)3 O

CH2

CHCH2

OH

O

O m

O

Si O

O

O NH O

CH3

CH3

NH O

O

HO

65.

The work has further been extended for aromatic amines [197] using a new solid-phase microextraction fiber coated with 25,27-dihydroxy-26,28-(10,100-dioxo-40,70-diaza-30,80-

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315

dioxooctamethylene)-p-tert-butylcalix[4]arene (65). The new fiber shows good sorption ability for the tested amines (aniline, o-toluidine, 2,4-dimethylaniline, 3,4-dimethylaniline, Nethyl-m-toluidine, and N,N-diethylaniline). The higher sorption efficiency of 65 proposed due to the polar amide bridge in calixarene moieties, which increases the polarity of the fiber coating. From the results it has been deduced that the functionalized calixarene can be expected to improve the solid-phase microextraction fiber’s performance as well as thermal and chemical stability. A novel synthetic method for immobilizing p-tert-butylcalixarene on a silica surface was reported by Katz et al. [198]. This method does not require derivatization with flexible ether units. In part because of rigidity the ether linkage between the calixarene and the silica that results from the method, immobilized site densities in excess of 0.2 mmol/g were obtained. To date, this is the highest values reported on a per gram of material basis for calixarene immobilization on silica. Thermal desorption spectroscopy was performed for a sample of 66 onto which phenol was sorbed from aqueous solution. The data indicate that phenol sorption onto 66 was reversible.

O

O

O HO

Si O Si

O

Si

O

Si

O

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

66. Suh et al. [199] has prepared poly methylsiloxane based calix[4]arene (67) and applied as stationary phase in isothermal capillary gas chromatographic separation of positional isomers (i.e. aminophenol, nitrophenol, cresol, chlorophenol and methoxyphenol). The elution order for aminophenol isomers is the same as that for nitrophenol isomers. It is likely that the stronger intramolecular hydrogen bonding interactions between the nitro (or amino) and hydroxyl group on the o-isomers of these phenols predominate over the weaker orientation and induction interactions between the polar groups on the phenol and the stationary phase. This will reduce retention of o-isomers significantly compared to m- or p-isomers where both the hydroxyl and the polar substituent group are available for interactions with the stationary phase. Isomers of other compounds whose substituent group is not capable of strong intramolecular hydrogen bonding interactions with the hydroxyl group are eluted in the order of their increasing boiling points.

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Mustafa Yilmaz and Shahabuddin Memon

Si

O

O

O

O

Si

O n

Si

O

67

3.2. Calix-Sorbents for Azo Dyes and Aromatic Amines Azo dyes are readily decolorized by splitting into the azo bond(s) in anaerobic environment. Azo dye reduction leads to the formation of aromatic amines. Aromatic amines are generally not degraded and accumulate under anaerobic conditions [200] with the exception of a few compounds characterized by the presence of hydroxyl and/or carboxyl groups [201]. Yilmaz et al. [202, 203] has reported calix[4]arene-based oligomer 68 synthesized by the condensation of p-tert-butylcalix[4]arene with hexamethylene diiso-cyanate and utilized to sorbed water-soluble azo dyes [i.e. Titanium Yellow (TY), Direct Violet 51 (DV51), Tropaeolin 000 (TP), Methylene Orange (MO) and Direct Blue 71 (DB71)]. The sorption studies of selected azo dyes have been evaluated and the polymer 68 was found to be a good azo dye sorbent.

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O C

N

O

O N H

C

O

O

OH OH

O

O

C

H N

O N H

C 2

68.

Subsequently, a Mannich base 69 was synthesized by the treatment of calix[4]arene with a cyclic secondary amine (1,4-dioxa-8-azaspiro-[4.5]decane) and formaldehyde [204]. The compound 69 was then treated with dibromoxylene to obtain a calix[4]arene-based copolymer 70. In batch sorption experiments, 69 and 70 were found better sorbents for azo dyes than for the aromatic amines. The maximum percent sorption of azo dyes was 95–99% for 69 and 83–

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97% for 70 when the pH of the dye solution was in the range of 2.0–8.0. The sorption of azo dyes and aromatic amines by calix[4]arene-based compounds indicates that amino groups play the major role for the formation of hydrogen bonds and electrostatic interactions.

n

HO

OH OH

O

OH

OH

N

N

O

O

O

O

N N

N

O

O

O

O

OH

N

N

N

O

O

O

O

O

O

69.

O

O

O

70.

The higher level of dye removal by calix[4]arene sorbent (70) suggest that a Coulomb interaction exist between the amino groups of calix[4]arene and the sulfonate groups of azo dyes (see Fig. 14). H O

N

H

H

O O

-

O

O

n

DYE

-

H

N

N

H H

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

O

O

O

N

N N H

O

O H

O

O

O

O

Figure 14. Proposed interaction of azo dye with 70.

Aromatic amines were expected to form inclusion complexes with insoluble calix[4]arene derivatives 69 and polymer 70. Solid–liquid batch sorption experiments were used to assess their ability to remove the water-soluble aromatic amines from aqueous solution. The aromatic amines removal was analyzed by means of HPLC. It observed that 69 has a little affinity for selected aromatic amines. But when it was converted to a rigid structure by anchoring it in a polymeric backbone it showed remarkable extraction ability. The polymer 70 showed higher affinity for the guest compounds than compound 69. In this case, hydrogen bonding was considered to determine the complex stability to a large

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Mustafa Yilmaz and Shahabuddin Memon

extent. This is not a surprising result because a positively charged surface site on the sorbent does not favor the sorption of protonated aromatic amines due to electrostatic repulsion (Fig. 15).

H

H

H

N

H

O

n

O

O

o

aryl amine N

N

N

N N H

O

O

O

H

O

O

O

O

O

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Figure 15. Proposed interaction of aryl amine with 70.

The conversion of calix[4]arene derivative 69 into its polymeric form 70 significantly increases the aromatic amine sorption ability. This can be explained by the fact that the calixarene derivative in the polymeric matrix may have gained a more rigid and appropriate structure, which assists the sorption of amine in SPE system. It is possible that the polymer plays a role in which it folds into conformations that place functional groups from multiple calix[4]arene moieties in the polymer into a preferred conformation where they can associate with the aromatic amines. Ozmen and coworkers [205] have reported the synthesis of different calix[n]arene derivatives (71-76) with different internal cavity sizes (Scheme 4) and evaluated the ability of these sorbents to extract carcinogenic direct azo dyes from water by a solid-liquid extraction process. The results obtained were compared with the un-substituted calix[n]arenes. The results of batch sorption studies carried out for the removal of the azo dyes from aqueous solutions are summarized in Table 7. However, results have found that the parent calixarenes (71) and (72) showed less sorption capacities for azo dyes (i.e. event Blue (EB), Direct Blue (DB15), Chicago Sky Blue (CSB)). The conversion of compounds (71) and (72) into their corresponding ester derivatives (73) and (74) resulted in a remarkable increase of their sorption abilities towards all azo dyes. Here, it should be pointed out that the p-tert-butylcalix[n]arene ester derivatives show binding abilities towards sodium cations [58, 82]. The pronounced Na+ binding suggests an ion-pair extraction mechanism in which Na+ coordinates with the ester binding site, while the azo dye anion inserts into the hydrophobic calixarene cavity (see Fig. 16).

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

Methylbromoacetate CH2

CH2

K2CO3/Acetone

n

OR

319

n

OR

R = CH2COOCH3

R=H R=H R = CH2COOCH3 R = CH2COOCH3 R = CH2COOH R = CH2COOH

KOH

Ethanol

71. n = 6 72. n = 8 73. n = 6 74. n = 8 75. n = 6 76. n = 8

CH2 n

OR

R = CH2COOH Scheme 4. Synthetic roots for calix[n]arene derivatives. SO3-Na+

DYE

O

O O

Na+

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O O

O

O

SO3-

O O

O O

O

O O

O

O O

O

Figure 16. Proposed interaction of sulphonated azo dye with calix[6]arene hexaester.

In the aqueous solution, the acid dye is first dissolved; consequently the sulfonate groups of the acid dye (dye-SO3Na) are dissociated and converted to dye anions. The direct dye is a relatively large molecule and is negatively charged at most of the pH ranges (>5). Dye - SO3Na

Dye - SO3 + Na+

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Mustafa Yilmaz and Shahabuddin Memon

The higher levels of dye removal by calix[n]arene carboxyl derivatives (75) and (76) compared with the other calix[n]arene sorbents (71) to (74) suggest that a Coulomb interaction exist between the carboxylic acid groups of calix[n]arenes and the sulfonate groups of azo dyes (Fig. 17). (

O

O

O

O

O

H

H -

O3S

O

)6

O

O O O

O

OO

H

H DYE

O H O

O

O O

O

O

H

H

SO3

-

H O

O H

H O

O O O O- S O O H O

DYE

O H O H

O

O S OO O O H O O H O

O

O

H O

O O H

O

O

O

O O O

)6

O

O

(

(

)6

O

O

O

O O

H O

Figure 17. Proposed interaction of calix-sorbent (75) with azo dye.

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Table 7. Percent sorption of azo dye by calix[n]arenes. Compound 71 72 73 74 75 76

EB 13 5 18 40 67 75

DB15 10 7 16 25 50 45

CSB 11 6 36 66 96 89

The substitution patterns of EB and CSB are similar to each other whereas DB 15 contains the sulfonate groups at different positions on the naphthalene rings. It might causes the lower sorption rates of DB 15 (Table 7). Carboxyl groups of calix[n]arenes (75) and (76)

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form intermolecular hydrogen bonds to these sulfonate groups. Hence, the cyclic structure, cavity size and functional groups of calixarene derivatives were found to be the important factors for sorption of azo dyes.

ACKNOWLEDGEMENT The authors wish to acknowledge support from the Technical Research Council of Turkey (TUBITAK Grant No. 107T873) and Ministry of Science and Technology IslamabadPakistan [(Grant No. 12 (106-B)/2004-ASA(IL)], Higher Education Commission (Grant Number 20-713/R&D/06) Islamabad and National Centre of Excellence in Analytical Chemistry, University of Sindh, Jamshoro-Pakistan.

REFERENCES [1] [2] [3] [4] [5] [6] [7]

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[8] [9]

[10] [11] [12] [13]

Lehn, J-M. Supramolecular Chemistry: Concepts and Perspectives. John Wiley & Sons, 1995. (ISBN:3-527-29311-6). Advances in Supramolecular Chemistry. Vol. 1-8, Gokel, GW., Ed., Cerberus Press, Inc. 1990-2002. Lehn, J-M. From Supramolecular Chemistry towards Constitutional Dynamic Chemistry and Adaptive Chemistry. Chem. Soc. Rev., 2007, 36, 151–160. Dodziuk, H. Introduction to Supramolecular Chemistry. Dordrecht, The Netherlands: Kluwer Academic Publishers; 2001. Steed, JW; Atwood, JL. Supramolecular Chemistry. New York: John Wiley & Sons Inc; 2000. Lhoták, P; Shinkai, S. Cation–π Interactions in Calix[n]arene and Related Systems. J. Phys. Org. Chem., 1997, 10 , 273–285. Readman, JW; Fowler, SW; Villeneuve, JP; Cattini, C; Oregioni, B; Mee, LD. Oil and Combustion–product Contamination of the Gulf Marine Environment Following the War. Nature, 1992, 358 (6388), 662-665. [8] Kvenvolden, KA; Cooper, CK. Natural Seepage of Crude Oil into the marine Environment. Geo-Mar. Lett., 2003, 23 (3-4), 140-146. Brun, GL; Vaidya, OMC; Leger, MG. Atmospheric Deposition of Polycyclic Aromatic Hydrocarbons to Atlantic Canada: Geographic and Temporal Distributions and Trends 1980-2001. Environ. Sci. Technol. 2004, 38 (7) 1941-1948. Roundhill, DM. Extraction of Metals from Soils and Waters. Dordrecht, The Netherlands: Kluwer Academic Publishers: 2001. Gutsche, CD. Calixarenes Revisited. Eds.; Cambridge: The Royal Society of Chemistry; 1998. J. Vicens and V. Böhmer (Eds.): Calixarenes. A Versatile Class of Macrocyclic Compounds. Dordrecht, The Netherlands: Kluwer Academic Publishers: 1991. Böhmer, V. Calixarenes, Macrocycles with (almost) Unlimited Possibilities. Angew.Chem. Int. Ed. Engl., 1995, 34, 713-745.

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[14] Asfari, Z; Böhmer, V; Harrowfield, MMcB; Vicens, J. Calixarenes 2001. Dordrecht, The Netherlands: Kluwer; Academic Publishers; 2001. [15] Yilmaz, M. Solution State Metal Complexes of Calixarenes and Polymeric Calixarenes Handbook of Engineering Polymeric Materials. (Edited by Cheremisinoff, N. P.); New York: Marcel Dekker Inc.; 1997. [16] Lhotak, P; Shinkai, S. Calix[n]arenes-Powerful Building-Blocks of Supramolecular Chemistry. J. Synth. Org. Chem. Jpn., 1995, 53 (11), 963-974. [17] Gutsche, CD; Mukhukrishnan, R. Calixarenes.1. Analysis of the Product Mixtures Produce by the Base-Catalyzed Condensation of Formaldehyde with p-Substitued Phenols. J. Org. Chem., 1978, 43 (25), 4905-4906. [18] Ikeda, A; Shinkai, S, Novel Cavity Design Using Calix[n]arene Skeletons Toward Molecular Recognition and Metal Binding. Chem. Rev., 1997, 97, 1713. [19] Memon, S; Roundhill, DM; Yilmaz, M. Remediation and Liquid-Liquid Phase Transfer Extraction of Chromium(VI). Collect. Czech. Chem. Commun., 2004, 69 (1), 12311250. [20] Yilmaz, M; Memon, S; Tabakci, M; Bartsch, R.A. Design of Polymer Appended Calixarenes as Ion Carriers. in: (Eds), ‘New Frontiers in Polymer Research’. Hauppauge, NY: Nova Science Publishers; 2006. pp-125-171. [21] Leeuwen, FWB.; Beijleveld, H.; Kooijman, H.; Spek, AL.; Verbooma, W.; Reinhoudt, DN., Cation Control on the Synthesis of p-t-Butylthiacalix[4](bis)crown Ethers. Tetrahedron Lett. 43 (2002) 9675–9678. [22] Karcı, F.; Şener, İ.; Deligöz H., Azocalixarenes. 1: synthesis, characterization and investigation of the absorption spectra of substituted azocalix[4]arenes, Dyes and Pigments 2003, 59, 53–61. [23] [24]. Memon, S.; Yilmaz, A. and Yilmaz, M. Synthesis and Comparative Complexation Studies of Schiff Base Derivatives of p-tert-Butylcalix[4]arene Copolymers J. Macromol. Sci. Pure and Appl. Chem., 2000, A37 (8), 865-879. [24] Memon, S. and Yilmaz, M. A Complimentary Study of Calixarene Based Bifunctional Receptor for Alkali or Transition Metal Cations and Cr2O72-. J. Mol. Struct., 2001, 595, 101-109. [25] [26]. Akkus, GU, Memon, S., Sezgin, M., and Yilmaz, M. A Versatile Approach Toward Calix(Aza)Crown Oligomers: Synthesis and Metal Ion Extraction J. Macromol. Sci. Pure and Appl. Chem, 2003, 40 (2) 95-106. [26] Yilmaz, A.; Memon, S. and Yilmaz, M. Synthesis and Study of Allosteric Effects on Extraction Behaviour of Novel Calixarene-based Dichromate Anion Receptors Tetrahedron, 2002, 58 (38) 7735-7740. [27] Uysal, G.; Memon, S. and Yilmaz, M. Synthesis of Oligomeric Calix[4]arene-crowns as Novel Ionophores for Alkali and Transition Metals Polycyclic Aromatic Compounds, 2002, 22 (5), 1075-1086. [28] Memon, S. and Yilmaz, M. An Excellent Approach Towards The Designing of a Schiff-Base Type Oligocalix[4]arene, Selective for the Toxic Metal Ions J. Macromol. Sci. Pure and Appl. Chem, 2002, A39 (1&2), 63-73. [29] Tabakci, M., Memon, S., Yilmaz, M and Roundhill, DM. Synthesis and Evaluation of Extraction Ability of Calix4-crown-6 Cone Conformer and Its Oligomeric Analogue. React. and Funct. Polym., 2004, 58 (1) 27-34.

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[30] Ediz, O., Tabakci, M., Memon, S., Yilmaz, M and Roundhill, DM. A Convenient Approach Towards the Synthesis of a ‘Proton Switchable’ Chromium (VI) Extractant Based on Calix[4]arene. Supramolecular Chemistry, 2004, 16 (3) 199-204. [31] Tabakci, M., Memon, S., Yilmaz, M and Roundhill, DM. Oligomeric Calix[4]areneThiacrown Ether for Toxic Heavy Metals J. Polym. Sci.: Part A: Polym. Chem., 2004, 42 (1) 186-193. [32] Tabakci, M., Memon, S., Sap, B., Roundhill, DM. and Yilmaz, M. A Calix[4]arene Derived Dibenzonitrile Receptor Modified at Its ‘Lower rim’ by a Polymerizable Group. J. Macromol. Sci. Pure and Appl. Chem, 2004, 41 (7) 811-825. [33] [34]. Tabakci, M., Memon, S., Yilmaz, M and Roundhill, DM. Synthesis and Extraction Studies of a Versatile Calix[4]arene-Based “Proton-Switchable Extractant for Toxic Metals and Dichromate anions. J. Incl. Phenom. Macro. Chem. 2003, 45, 265-270. [34] Deligöz H., Synthesis and Properties of a Series of Novel Calix[6]arene Diazo Derivatives. J. Inclusion Phenomena and Macrocyclic Chem. 2002, 43: 285–289. [35] Sirit, A., Kocabas, E., Memon, S., Karakucuk, A. and Yilmaz, Synthesis and Metal Ion Recognition Properties of A Novel Chiral Calix[4](azoxa)crown-7. Supramolecular Chem. 2005, 17 (3) 251-256. [36] Akkuş, UG.; Aslan S.; Taktak, FF. and Memon, S. Synthesis and selective extractant properties of calix[4]arene thioether derivative and its oligomeric analogue Turkish J. Chem. 2008, 32, 635-643. [37] Ak, M.S.; Deligöz H., The Synthesis of Ester and Ketone Derivatives of Azocalix[4]arene Containing Chromogenic Groups, J. Inclusion Phenomena and Macrocyclic Chemistry (2006) 55:223–228. [38] Karakucuk, A., Kocabas, A., Sirit, A.; Memon, S., Yilmaz, M., and Roundhill, DM. “Polymer Supported Calix[4]Arene Schiff Bases: A Novel Chelating Resin For Hg2+ and Dichromate Anions” J. Macromol. Sci. Pure and Appl. Chem., 42 (6) 691-704, [39] [40]. Tilki, T.; Şener, İ.; Karcı, F.; Gülce, A.; Deligöz H., An approach to the synthesis of chemically modified bisazocalix[4] arenes and their extraction properties, Tetrahedron 61 (2005) 9624–9629 [40] Memon, S., Tabakci, M., Yilmaz, M and Roundhill, D. M. “A Useful Approach Toward the Synthesis and Evaluation of Extraction Ability of Thioalkyl Calix[4]arenes Appended with a Polymer” Polymer, 46 (5) 1553-1560, 2005. [41] Kocak, A., Ceran, S., Memon, S., and Yilmaz, M. “Synthesis and Evaluation of Extraction Properties of p-tert-Butylcalix[6]arene Nitrile Derivatives for Toxic metals and Dichromate Anions J. Macromol. Sci. Pure and Appl. Chem., 2008, 45 (5) 353-357. [42] Tabakci, M., Memon, S., and Yilmaz, M. Synthesis and extraction properties of new ‘proton-switchable’ tri- and tetra-substituted calix[4]arene derivatives bearing pyridinium units. Tetrahedron, 2007, 63 (29) 6861-6865. [43] Sirit, A., Karakucuk, A., Memon, S., Kocabas, A. and Yilmaz, M. Synthesis and Characterization of A Novel Chiral Chromogenic Calix[4](azoxa)crown-7. Tetrahedron: Asymmetry, 2004, 15 (22) 3595-3600. [44] Gutsches CD.; Reddy PA.; Calixarenes. 25. Conformations and Structures of the Products of Arylmethylation of Calix[l]arenes. J. Org. Chem. 1991,56, 4783-4791. [45] Reddy, PA.; Gutache, CD., Calixarenes. 32. Reactions of Calix[4]quinines. J. Org. Chem. 1993, 58, 3245-3251.

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Mustafa Yilmaz and Shahabuddin Memon

[46] Kanamathareddy, S.; Gutache, CD., Calixarenes. 29. Aroylation and Arylmethylation of Calix[G]arenes. J. Org. Chem. 1992, 57, 3160-3166. [47] Xie D.; Gutsche CD., Calixarene Anhydrides as Useful Synthetic Intermediates. J. Org. Chem. 1997, 62, 2280-2284. [48] Gutsche, CD.; Nam KC., Calixarenes. 22. Synthesis, Properties, and Metal Complexation of Aminocalixarenes. J. Am. Chem. Soc. 1988, 110, 6153-6162. [49] Kanamathareddy S.; Gutsche, CD., Calixarenes: Selective Functionalization and Bridge Building. J. Org. Chem. 1995, 60, 6070-6075. [50] Sharma SK.; Gutsche CD., Upper Rim Substitution of Calix[4]arenes via Their Upper Rim A,C Dinitro Compounds. J. Org. Chem. 1999, 64, 998-1003. [51] Kanamathareddy S.; Gutsche, CD. Synthesis and Conformational Properties of Calix[ 6larenes Bridged on the Lower Rim: Self-Anchored Rotaxanes. J. Am. Chem. Soc. 1993, 115, 6572-6579. [52] Kanamathareddy S.; Gutsche, CD., Selective Upper Rim Functionalization and Lower Rim Bridge Building with Calix[4]arenes and Calix[6]arenes. J. Org. Chem. 1996, 61, 2511-2516. [53] Sharma, S.K.; Gutsche, C.D., Calixarenes. 40. Arylmethylenation of p(Cyanomethyl)calix[4a]r ene, J. Org. Chem. 1994,59, 6030-6037. [54] Wang J.; Gutsche, C.D., Complexation of Fullerenes with Bis-calix[n]arenes Synthesized by Tandem Claisen Rearrangement, J. Am. Chem. Soc. 1998, 120, 1222612231. [55] Alam, I.; Sharma, SK.; Gutsche, CD. The Quinonemethide Route to Mono- and Tetrasubstituted Calix[41arenes. J. Org. Chem. 1994, 59, 3716-3720. [56] Gutsche, CD.; Lin, L-G. Calixarene 12: The synthesis of functionalized calixarene Tetrahedron, 1986, 42(6), 1633-1640. [57] Iwamoto, K., Shinkai, S. Synthesis and ion selectivity of all conformational isomers of tetrakis[(ethoxycarbonyl)methoxy]calix[4]arene. J. Org. Chem., 1992, 57 (26) 70667073. [58] Arneud-Neu, F., Collins, E.M., Deasy, M., Ferguson, G., Harris, S.J., Kaitner, B., Lough, A.J., McKervey, M.A., Marques, E., Ruhl, B.L., Weill, M.J.S., Seward, E.M. (1989) J. Am. Chem. Soc., 111(23): 8681-8691. [59] Alpoguz, HK.; Memon, S.; Ersöz, M. and Yilmaz, M. Transport of Hg2+ Through Bulk Liquid Membrane Using Biscalix[4]arene Nitrile Derivetive as Carrier:Kinetic Analysis. New J. Chem., 2002, 26, 477-480. [60] Jin, T.; Kinjo, M.; Kobayashi, Y.; Hirata, H. Ion Transport Activity of Calic[n]arene (n=4,5,6,7,8) esters Toward Alkali-metal Cations in a Phospholipid Bilayer Membrane. J. Chem. Soc. Faraday Trans. 1998, 94, 3135-3140. [61] Alpoguz, HK.; Memon, S.; Ersöz, M.; and Yilmaz, M. Transport of Metals Through a Liquid Membrane Containing Calix[4]arene Derivatives as Carrier Sep. Sci. and Tech. 2002, 37 (9), 2201-2213. [62] Alpoguz, H.K., Memon, S., Ersöz, M., and Yilmaz, M. “Kinetics of Mercury(II) Transport Through a Liquid Membrane Containing Calix[4]arene Derivatives as Carrier” Sep. Sci. and Tech., 38 (7), 1649-1664, 2003. [63] Kuruoglu, D., Canel, E., Memon, S., Yilmaz, M., and Kilic, E. Hydrogen Ion-Selective Poly(vinyl chloride) Membrane Electrode Based on a Calix[4]arene. Anal. Sci., 2003, 19 (2), 217-221.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

325

[64] Alpoguz, HK., Memon, S., Ersöz, M., and Yilmaz, M. Transport Kinetics of Hg2+ Through Bulk Liquid Membrane using Calix[4]arene Ketone Derivatives as Carrier. Sep. Sci. and Tech., 2004, 39 (4) 799-810. [65] Kim, JS.; Quang, DT., Calixarene-Derived Fluorescent Probes, Chem. Rev. 2007, 107, 3780-3799. [66] Prasanna de Silva, A.; Gunaratne, HQN.; Gunnlaugsson, T.; Huxley, AJM.; McCoy, CP.; Rademacher, JT.; Rice, TE. Signaling Recognition Events with Fluorescent Sensors and Switches, Chem. Rev. 1997, 97, 1515-1566. [67] Demirel, A., Dogan, A., Canel, E., Memon, S., Yilmaz, M. and Kiliç, E. Hydrogen IonSelective Poly(Vinyl Chloride) Membrane Electrode Based on A p-tert-butylcalix[4]arene-Oxacrown-4. Talanta, 2004, 62 (1), 123-129. [68] Alpoguz, HK., Memon, S., Ersöz, M., and Yilmaz, M. Transport of Hg2+ Ion Through a Supported Liquid Membrane Containing Calix[4]arene Nitrile Derivatives as a Specific Ion Carrier. Sep. Sci. and Tech., 2005, 40 (11) 2365-2372. [69] Cacciapaglia, R.; Casnati, A.; Mandolini, L.; Reinhoudt, DN.; Salvio. R.; Sartori, A.; Ungaro, R. Di- and trinuclear arrangements of zinc(II)-1,5,9-triazacyclododecane units on the calix[4]arene scaffold: Efficiency and substrate selectivity in the catalysis of ester cleavage. Inorganica Chimica Acta. 2007, 360, 981–986. [70] Lugtenberg, RJW.; Egberink, RJM.; Berg, A.; Engbersen, JFJ.; Reinhoudt DN.,The effects of covalent binding of the electroactive components in durable CHEMFET membranes-impedance spectroscopy and ion sensitivity studies. J. Electroanalytical Chem. 1998, 452, 69–86. [71] Visser, H.C.; Jong, F.; Reinhoudt D N., Kinetics of carrier-mediated alkali cation transport through supported liquid membranes: Effect of membrane solvent, cotransported anion, and support Journal of Membrane Science 107 (1995) 267-276. [72] Redshaw, C. Coordination Chemistry of the Larger Calixarenes. Coordi. Chem. Reviews. 2003, 244, 45-70. [73] Ludwig, R. Calixarene in Analytical and Seperation Science Chemistry. Fresenius J. Ana. Chem. 2000, 367, 103-128. [74] Alpoguz, HK., Kaya, A., Memon, S., and Yilmaz, M. Kinetic Study of Hg2+ Transport Through a Liquid Membrane Containing Calix[4]arene Dinitrile Oligomer as Carrier. J. Macromol. Sci. Pure and Appl. Chem., 2005, 42 (9) 1159-1168. [75] Pu, L., Fluorescence of Organic Molecules in Chiral Recognition Chem. Rev. 2004, 104, 1687-1716. [76] Erden, S.; Demirel, A.; Memon S.; Yilmaz M.; Canel E.; and Kiliç, E. Using of hydrogen ion-selective poly(vinyl chloride) membrane electrode based on calix[4]arene as thiocyanate ion-selective electrode. Sensors and Actuators B, 2006, 113 (1) 290-296. [77] Alpoguz, HK., Kaya, A., Memon, S., and Yilmaz, M. Facilitated Supported Liquid Membrane Transport of Hg2+ Using Calix[4]arene Derivatives. J. Macromol. Sci. Pure and Appl. Chem., 2007, 44 (1) 17-20. [78] Douteau-Guevel, N.; coleman, AW.; Morel, JP.; Morel-Desrosiers, N., Complexation of basic amino acids by water-soluble calixarene sulphonates as a study of the possible mechanisms of recognition of calixarene sulphonates by proteins. J. Physical organic chem. 1998, 11, 693 -696.

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Mustafa Yilmaz and Shahabuddin Memon

[79] Pathak, DA.; Street, NC.; Roundhill, DM.; Yilmaz, M.; Memon, S.; Bhanger, MI. Computations between metallocalix[4]arene host and a series of four oil-based fuel pollutant guests. Pak. J. Anal. Environ. Chem., 2006, 7(1), 48-55. [80] Chang, S-K., Cho, I. New metal cation-selective ionophores derived from calixarenes. Chem. Lett., 1984, 4 477-478. [81] Chang, S-K., Kwon, S-K., Cho, I. Calixarene-based amide ionophores for group iia metal cations. Chem. Lett., 1987, 5, 947-948. [82] Chang, S-K., Cho, I. New metal cation-selective ionophores derived from calixarenes: their syntheses and ion-binding properties. J. Chem. Soc. Perkin. Trans. 1, 1986, 211214. [83] Arimura, T., Kubota, M., Matsuda, T., Manabe, O., Shinkai. S. Formation of solventseparated ion pairs in calixarene ester–alkali picrate complexes. Bull. Chem. Soc. Jpn. 1989, 62 (5) 1674.-1676. [84] Arnaud-Neu, F.; Barrett, G.; Cermin, S.; Ferguson, MDG.; Harris, SJ.; Lough, AJ.; Guerra, L.; Owens, M.; McKervey, MA.; Schwing-Weill, MJ.; Schwinte, P. Selective alkali-metal cation complexation by chemically modified calixarenes. Part 4. Effect of substituent variation on the Na+/K+ selectivity in the ester series and X-ray crystal structure of the trifluoroethyl ester. J. Chem. Soc. Perkin Trans. 2, 1992, 1119-1125. [85] Yamato, T.; Iwasa, T.; Zhang, F. Synthesis and ion selectivity of tetrakis[(n,ndialkylaminocarbonyl) methoxy]homocalix[4]arenes. J. Incl. Phenom. Macrocycl. Chem. 2001, 39 (3), 285-294. [86] Deligöz, H.; Yilmaz, M. Selective complexation of Na+ by polymeric calix[4]arene tetraesters. J. Polym. Sci. Part A: Polym. Chem., 1995, 33 (16) 2851-2853. [87] Shinkai, S., Fujimoto, K., Otsuka, T., Ammon, HL. Syntheses and ion selectivity of conformational isomers derived from calix[4]arene. J. Org. Chem., 1992, 57 (5), 15161523. [88] Oh, H.; Chio, EM.; Jeong, H.; Nam KC.; Jeon, S. Poly(vinyl chloride) membrane cesium ion-selective electrodes based on lipophilic calix[6]arene tetraester derivatives. Talanta, 2000, 53 (3) 535-542. [89] Ludwig, R.; Dzung, NTK. Calixarene based molecules for cation recognition. Sensors, 2002, 2 (10) 397-416. [90] Memon, S., Yilmaz. M. Liquid-liquid Extraction of Alkali and Transition Metal Cations by Two Biscalix[4]arenes Sep. Sci. and Technol., 2000, 35 (3):457-467. [91] Miyaji, H.; Dudic, M.; Tucker, JHR.; Prokes, I.; Light, ME.; Hursthouse, MB.; Stibor, I.; Lhotak, P., Bis(amidopyridine)-linked calix[4]arene: a novel type of receptor for dicarboxylic acids. Tetrahedron Letters, 2002, 43, 873-878. [92] Gungor, O.; Yilmaz, A.; Memon, S.; Yilmaz, M. “Evaluation of the performance of calix[8]arene derivatives as liquid phase extraction material for the removal of azo dyes” J. Haz. Mat., 158 (2008) 202-207. [93] Rao, TP.; Gladis, JM. Oxines as preconcentration agents in inorganic trace analysis. Rev. Anal. Chem. 2001, 20, 145-159. [94] Rao, TP.; Preetha, CR. Naphthols as reagents for solid phase preconcentrative separation of inorganics. Sep. Purif. Rev. 2003, 32 (1) 1-17. [95] Camel, V. Solid phase extraction of trace elements. Spectrochim, Acta Part B. 2003, 58, 1177-1233.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

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[96] Masque, N.; Marce, RM.; Borull, F. New polymeric and other types of sorbents for solid-phase extraction of polar organic micropollutants from environmental water. Trends. Anal. Chem. 1998, 17, 384-394. [97] Preetha, CR.; Gladis, JM.; Rao, TP. Solid phase extractive preconcentration of thorium onto 5,7-dichloroquinoline-8-ol modified benzophenone. Talanta 2002, 58 701-709. [98] Memon, JR.; Memon, SQ.; Bhanger, MI.; Khuhawer, MY; Banana Peel: A green and economical sorbent for Cr (III) removal, Pak. J. Anal.Envirno. Chem. 2008, 1, 20-25. [99] Qureshi, I.; Memon, S. and Yilmaz, M. Estimation of chromium(VI) adsorption efficiency of novel regenerable p-tert-butylcalix[8]areneoctamide impregnated Amberlite XAD-4 Resin. J. Haz. Mat. 2009, 164, 675–682. [100] Solangi, IB.; Memon, S. and Bhanger, MI. Synthesis and application of a highly efficient tetraestercalix[4]arene resin for the removal of Pb2+ from aqueous environment. Anal. Chim. Acta, 2009, 638, 146-153. [101] Valeur, B.; Leray, I. Design principles of fluorescent molecular sensors for cation recognition. Coord. Chem. Rev. 2000, 205 (1) 3–40. [102] Lamm SH.; Parkinson M.; Anderson, M. Determinants of lung cancer risk among cadmium-exposed workers. AEP 1991, 2 (3) 195-211. [103] James MA.; Michael DT.; Anthony TZ.; Jenny RR. Pulmonary responses to welding fumes: role of metal constituents. J Toxicol Environ Health Part A 2004, 67(3) 233249. [104] Brookmeyer R, Gray S, Kawas C. Projections of Alzheimer's disease in the United States and the public health impact of delaying disease onset. Am J Public Health 1998, 88 (9), 1337–1342. [105] Riley, JP. and Skirrow, G. Chemical Oceanography, Vol. 1-10 (2nd Ed.) Academic Press 1975-1989. [106] Roundhill, DM.; Solangi, IB.; Memon, S.; Yilmaz, M. The Liquid-liquid extraction of toxic metals (Cd, Hg and Pb) by calixarenes. Pak. J. Anal. Environ. Chem., 2008, 9 (2) . [107] Memon, S.; Uysal, G.; Yilmaz, M. Synthesis and Binding Properties of Polymeric Calix[4]crown-4. React. and Funct. Polym., 2001, 47 (3) 165-174. [108] Akkus, G.U.; Cebeci, C. Synthesis and Extraction Studies of Polymeric Phthalimido Functionalized Calix[4]arene. J. Incl. Phenom. Macrocycl. Chem. 2008, 62, 303-309. [109] Yang, F.; Guo, H.; Cai, X.; Chen, X. Synthesis and Adsorption properties of Noval Calixarene polymers: Calix[6]-1,4-crown-4-based netty polymers. React. and Funct. Polym., 2005, 64, 163-168. [110] Zhang, A.; Wang, W.; Xue, W.; Chai , Z. Chromatographic Separation of Cesium by Macroporous Silica-Based Supramolecular Recognition Agent Impregnated Material. Sep. Pur. Tech. 2008, doi:10.1016/j.seppur.2009.02.002. [111] Zhang A.; Kuraoka E.; Kumagai, M. Development of the chromatographic partitioning of cesium and strontium utilizing two macroporous silica-based calix[4]arene-crown and amide impregnated polymeric composites: PREC partitioning process. J. Chromatography A, 2007, 1157, 85–95. [112] Li, H.; Chen, Y. The sol–gel technique to prepare calix[6]crown-containing organosilicon resins and their adsorption properties towards metal ions. React. and Funct. Polym., 2003, 55, 171–178. [113] Roundhill DM. Novel Strategies for the Removal of Toxic Metals from Soils and Waters, J. Chem. Educ., 2004, 81, 275-282.

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[114] Yordanov, AT.; Whittlesey, BR.; Roundhill, DM. Calixarenes Derivatized with SulfurContaining Functionalities as Selective Extractants for Heavy and Precious Metal Ions. Inorg. Chem., 1998, 37, 3526-3531. [115] Meng, L.; Huang, H.; He, Y.; Chen, Y.; Wang H. Preparation and Behavior of Calix[4]arene-containing Organosilicone Resins (I). J. Applied Polymer Sci. 2001, 80, 58–64. [116] Tabakci, M.; Yilmaz, M.; Sorption characteristics of Cu(II) ions onto silica gelimmobilized calix[4]arene polymer in aqueous solutions: Batch and column studies J. Haz. Mater. 2008, 151, 331-338. [117] Ho, T-L. The Hard Soft Acids Bases (HSAB) Principle and Organic Chemistry. Chem. Rev, 1975, 75, 1-20. [118] Memon, S.; Yilmaz, M. Solvent Extraction of Metal Cations by Chemically Modified Biscalix[4]arenes Sep. Sci. and Tech, 2001, 36, 2785-2798. [119] Memon, S.; Yilmaz, M.; Synthesis and Complexation Studies of 1,3-Dialkylated p-tertButylcalix[4]arene Telomers React. and Funct. Polym, 2000, 44, 227-233; Uysal, G.; Memon, S.; Yilmaz, M. Synthesis and Binding Properties of Polymeric Calix[4]arene Nitriles React. and Funct. Polym, 2001, 50, 77-84. [120] Solangi, IB.; Memon, S.; Memon, N.; Bhanger, MI. Exploration of Pb2+ selective behavior of calix[6]arene ester derivative J. Macromol. Sci. Pure and Appl. Chem, 2008, 45 (12), 1005-1010. [121] Zhang, D.; Wang, J.; Lawson, TR.; Bartsch, RA. Synthesis and lead(II) sorption of silica gel-immobilized, di-ionizable calix[4]arenes. Tetrahedron 2007, 63, 5076-5082. [122] Pathak, R.; Rao, GN. Synthesis and metal sorption studies of p-tert-butylcalix[8]arene chemically bound to polymeric support. Analytica Chimica Acta, 1996, 335, 283-290. [123] Li, C.; Gong, S-L.; Meng, L-Z.; Hu, L.; Huang, H.; He, Y-B. Polysiloxane Resins Modified by Bisglycidyl Calix[4]arene: Preparation, Characterization, and Adsorption Behavior toward Metal Ions. J. Applied Polymer Science, 2005, 95, 1310–1318. [124] Matsumiya H.; Yasuno, S.; Iki, N.; Miyano. S. Sulfinylcalix[4]arene-Impregnated Amberlite XAD-7 Resin for the Separation of Niobium(V) from Tantalum(V) J. Chromatography A, 2005, 1090, 197–200. [125] Tabakci,M.; Yilmaz, M. Synthesis of a chitosan-linked calix[4]arene chelating polymer and its sorption ability toward heavy metals and dichromate anions. Bioresource Technology 99 (2008) 6642–6645. [126] Tabakci, M.; Erdemir, S.; Yilmaz, M. Preparation, characterization of cellulose-grafted with calix[4]arene polymers for the adsorption of heavy metals and dichromate anions. J. Hazard. Mater. 2007, 148, 428-435. [127] Gidwani, MS.; Menon, SK.; Agrawal, YK. Chelating polycalixarene for the chromatographic separation of Ga3+, In3+ and Tl3+ React. and Funct. Polym., 2002, 53, 143–156. [128] Toumi, N.; Kajo, F.; Fournier, D.; Vocanson, F.; Lamartine, R.; Dumazet-Bonnamour I. A useful approach towards solid–liquid extraction of metal cations with unsupported calixarenes. Materials Science and Engineering C. 2008, 28, 645–652. [129] Seyhan, S.; Çolak, M.; Merdivan, M.; Demirel, N. Solid phase extractive preconcentration of trace metals using p-tert-butylcalix[4]arene-1,2-crown-4-anchored chloromethylated polymeric resin beads. Ana. Chim. Acta. 2007, 584, 462-468.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

329

[130] Ohto, K.; Tanaka, Y.; Inoue, K. Adsorptive Separation of Lead and Zinc Ions by Novel Type of Calix[4]arene Carboxylate Resin Immobilized with Polyallylamine, Chem. Lett., 1997, (7) 647-648. [131] Ohto, K., Tanaka, Y., Yano, M., Shinohara, T., Murakami, E., and Inoue, K., Selective Adsorption of Lead Ion on Calix[4]arene Carboxylate Resin Supported by Polyallylamine, Solv. Ext. Ion Exch., 2001, 19(4), 725-741. [132] Alexandratos, SD; Natesan, S. Synthesis and Ion-Binding Affinities of Calix[4]arenes Immobilized on Cross-Linked Polystyrene. Macromolecules 2001, 34, 206-210. [133] Hutchinson, S; Kearney, GA; Horne, E. Solid-phase Extraction of Metal-ions Using Immobilized Chelating Calixarene Tetrahydroxamates. Anal. Chim. Acta., 1994, 291 (3), 269-275. [134] Jain, VK; Pandya, RA; Pillai,SG; Agrawal, YK.; Kanaiya, PH. Solid-Phase Extractive Preconcentration and Seperation of Lanthanum(III) and Cerium(III) Using a PolymerSupported Chelating Calix[4]Arene Resin. J. Ana. Chem. 2007, 62, 104-112. [135] Jain, VK; Pandya, RA; Pillai,SG; Shrivastav, PS. Simaltaneous Preconcentration of Uranium(VI) and Thorium(IV) from Aqueous Solution Using a Chelating Calix[4]arene Anchored Chloromethylated Polystyrene Solid Phase. Talanta, 2006, 70, 257-266. [136] Jain, VK; Handa, A; Pandya, R; Shrivastav, P; Agrawal, YK. Polymer Supported Calix[4]arene-semicarbazone Derivative for Separation and Preconcentration of La(III), Ce(III), Th(IV) and U(VI). React. Funct. Polym., 2002, 51, 101-110. [137] S. Shinkai, O. Manabe, Y. Kondo, T. Yamamoto (Kanebo Ltd.), Jpn. Kokai Tokkyo Koho, JP 62,136,242 (1986); Chem. Abstr., 108 (1988) 64410q. [138] Shinkai, S; Kawaguchi, H; Manabe, O. selective adsorbtion of Uo22+ to a polymer resin immobilizing calixarene-based uranophiles. J. Pol. Sci., Part C; Polym. Lett., 1988, 26, 391-396. [139] Majeti, NV; Ravi, K. A. Review of chitin and chitosan applications. React. Funct. Polym., 2000, 46, 1-27. [140] Inoue, K; Yoshizuka, K; Ohto, K. Adsorptive Separation of Some Metal Ions by Complexing Agent Types of Chemically Modified Chitosan. Anal. Chim. Acta, 1999, 388, 209-218. [141] Aly, AS; Jeon, BD; Park, YH. Preparation and Evaluation of the Chitin Derivatives for Wastewater Treatments. J. Appl. Polym. Sci., 1997, 65, 1939-1946. [142] Peng, CH; Wang, YT; Tang, YR. Synthesis of Crosslinked Chitosan Crown Ethers and Evaluation of These Products as Adsorbents for Metal Ions. J. Appl. Polym. Sci., 1998, 70, 501-506. [143] Li, H-B; Chen, Y-Y; Liu, S-L. Synthesis, Characterization, and Metal Ions Adsorption Properties of Chitosan-Calixarenes (I). J. Appl. Polym. Sci., 2003, 89, 1139-1144. [144] Schmeide, K.; Heise, KH.; Bernhard, G.; Keil, D.; Jansen, K.; Praschak, D. Uranium(VI) Separation from Aqueous Solution by Calix[6]arene Modified Textiles. J. Radioanal. Nuclear Chem., 2004, 261, 61-67. [145] Trivedi, UV.; Menon, SK.; Agrawal, YK. Polymer supported calix[6]arene hydroxamic acid, a novel chelating resin. React. Funct. Polym., 2002, 50, 205-216. [146] Grüttner, C.; Rudershausen, S.; Matthews, SE.; Wang, P.; Böhmer, V.; Dozol, J-F. Selective Extraction of Lanthanides and Actinides by Magnetic Silica Particles with CMPO-Modified Calix[4]arenes on the Surface. Eur. Cells Matr. 2002, 3, 48-51. [147] Burrows, D. Chromium: Metabolism and Toxicity. Boca Raton, FL: CRC Press, 1983.

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Mustafa Yilmaz and Shahabuddin Memon

[148] De Flora, S; Wetterhahn, KE. Mechanisms of Chromium Metabolism and Genotoxicity. Life Chem. Rep., 1989, 7, 169-244. [149] Stearns, DM; Kennedy, LJ; Courtney, KD; Giangrande, PH; Phieffer, LS; Wetterhahn, KE. Reduction of Chromium(VI) by Ascorbate Leads to Chromium-DNA Binding and DNA Strand Breaks in vitro. Biochemistry, 1995, 34, 910-919. [150] Wittbrodt, PR; Palmer, CD. Reduction of Cr(VI) in the Presence of Excessive Soil Fulvic Acid. Environ. Sci. Technol. 1995, 29, 255-263. [151] Roundhill, DM; Koch, HF. Methods and Techniques for the Selective Extraction and Recovery of Oxoanions. Chem. Soc. Revs. 2002, 31, 60-67. [152] Cooper, JB; Drew, MGB; Beer, PD. Alkali Metal Cation Cooperative Anion Recognition by Heteroditopic Bis(calix[4]arene) Rhenium(I) Bipyridyl and Ferrocene Receptor Molecules. J. Chem. Soc., Dalton Trans., 2000, 2721-2728. [153] Beer, PD; Cooper, JB. Calixarene Based Anion Receptors, Calixarenes in Action, pp 111-143, Eds. Mandolini, L; Ungaro, R. London: Imperial College Press, 2000. [154] Matthews, SE; Beer, PD. Calixarene-based Anion Receptors, Calixarenes 2001, pp 421-439 Eds. Z. Asfari, V. Böhmer, J. Harrowfield, J. Vicens, Dordrecht, The Netherlands: Kluwer Academic Publishers, 2001. [155] Gale, PA. Anion Receptor Chemistry: Highlights from 1999. Coord. Chem. Rev., 2001, 213, 79-128. [156] Gale, PA. Anion and Ion-pair Receptor Chemistry: Highlights from 2000 and 2001. Coord. Chem. Rev., 2003, 240, 17-55. [157] Tuntulani, T; Poompradub, S; Thavornyutikarn, P; Jaiboon, N; Ruangpornvisuti, V; Chaichit, N; Asfari, Z; Vicens, J. Aza Crown Ether Calix[4]arenes Containing Cation and Anion Binding Sites: Effects of Metal Ions Towards Anion Binding Ability. Tetrahedron Lett., 2001, 42, 5541-5544. [158] Aeungmaitrepirom, W; Hagege, A; Asfari, Z; Vicens, J; Leroy, M. Solvent Extraction of Selenate and Chromate Using a Diaminocalix[4]arene. J. Incl. Phenom. and Macrocyclic Chem., 2001, 40 (3), 225-229. [159] Falana, OM; Koch, HF; Roundhill, DM; Lumetta, CJ; Hay, BP. Synthesis and Extraction Studies of 1,2- and 1,3-Disubstituted Butylcalix[4]arene Amides with Oxyions; Geometric and Conformational Effects. J. Chem. Soc., Chem. Commun., 1998, 503-504. [160] Georgiev, M; Wolf, N; Roundhill, DM. Lower Rim Alkylammonium Substituted Calix[4]arenes as "Proton Switchable" Extractants for Chromate and Dichromate Anions. Polyhedron, 1997, 16 (9), 1581-1584. [161] Wolf, NJ; Georgiev, EM; Yordanov, AT; Whittlesey, BR; Koch, HF; Roundhill, DM. Synthesis and Crystal Structures of Lower Rim Amine and Carbamoyl Substituted Calixarenes as Transfer Agents for Oxyanions between an Aqueous and a Chloroform Phase. Polyhedron, 1999, 18, 885-896. [162] Yordanov, AT; Wolf, NJ; Georgiev, EM; Koch, HF; Falana, OM; Roundhill, DM. Derivatized Calix[4]arenes as Selective Phase Transfer Extractants for Heavy Metal and Oxyion Salts. Comments Inorg. Chem. 1999, 20 (4-6), 163-175. [163] Memon, S.; Tabakci, M.; Roundhill, DM. and Yilmaz, M. Synthesis and Evaluation of the Cr(VI) Extraction Ability of Amino/Nitrile Calix[4]arenes Immobilized onto a Polymeric Backbone React. and Funct. Polym., 2006, 66 (11) 1342–1349.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

331

[164] Bozkurt, S.; Kocabas, E.; Durmaz, M.; Yilmaz, M.; Sirit, A. Synthesis, dichromate anion sorption of silica gel-immobilized calix[4]arenes. J. Hazard. Mater., doi:10.1016/j.jhazmat.2008.10.096 [165] Tabakci, M. Immobilization of calix[6]arene bearing carboxylic acid and amide groups on aminopropyl silica gel and its sorption properties for Cr(VI). J Incl Phenom Macrocycl Chem 2008, 61, 53-60. [166] Jain, VK.; Pandya, RA.; Pillai, SG.; Shrivastav, PS.; Agrawal, YK. Merrifield Resin Supported Chelate Forming Calix[4]arene-ovanillinthiosemicarbazone Resin Employed for the Separation,Preconcentration and Trace Determination of Cr(VI), As(III) and Tl(I) in Water Samples. Sep. Sci. Tech., 2006, 41, 123–147. [167] Belardi, RP.; Pawliszyn, J. The applications of chemically modified fused silica fibers in the extraction of organics from water matrix samples and their transfer to capillary columns. J. Water Pollut. Res. J. Canada. 1989, 24, 179. [168] Thomas, SP.; Ranjan, RS.; Webster, GRB.; Sarna, LP. Protocol for the analysis of high concentrations of benzene, toluene, ethylbenzene and xylene isomers in water using automated solid-phase microextraction-GC-FID. Environ. Sci. Technol. 1996, 30, 15211526. [169] Yang, M.; Zeng, ZR.; Qiu, WL.; Wang, YL. Preparation and investigation of polymethylphenylvinylsiloxane-coated solid-phase microextraction fibers using sol-gel technology. Chromatographia. 2002, 56 (1-2) 73-80. [170] Fattore, E.; Benfenati, E.; Fanelli, R. Analysis of chlorinated 1,3-butadienes by solidphase microextraction and gas chromatography-mass spectrometry. J. Chromatogr. A. 1996, 737 (1) 85-91. [171] Lambropoulou, DA.; Albanis, AT. Headspace solid phase microextraction applied to the analysis of organophosphorus insecticides in strawberry and cherry juices J. Agric. Food Chem. 2002, 50, 3359.3365. [172] Shen, G.; Lee, HK. Hollow fiber-protected liquid-phase microextraction of triazine herbicides. Anal. Chem. 2002, 74, 648-654. [173] Wu, J.; Hian Kee Lee, HK. Injection port derivatization following ion-pair hollow fiber-protected liquid-phase microextraction for determining acidic herbicides by gas chromatography/mass spectrometry. Anal. Chem., 2006, 78 (20) 7292–7301. [174] Langenfeld, JJ.; Hawthorne, SB.; Miller, DJ. Quantitative analysis of fuel-related hydrocarbons in surface water and wastewater samples by solid-phase microextraction. Anal. Chem. 1996, 68, 144-155. [175] Doong, RA.; Chang, SM.; Sun, YC. Solid-phase microextraction and headspace solidphase microextraction for the determination of high-molecular-weight polycyclic aromatic hydrocarbons in water and soil samples. Chromatogr. Sci. , 2000, 38(12), 528534. [176] Zeng, ZR.; Qiu, WL.; Huang, ZF. Solid-phase microextraction using fused-silica fibers coated with sol−gel-derived hydroxy-crown ether. Anal. Chem. 2001, 73, 2429-2436. [177] Zeng, Z.; Qiu, W.; Yang, M.; Wei, X.; Huang, Z.; Li, F. Solid-phase microextraction of monocyclic aromatic amines using novel fibers coated with crown ether. J. Chromatogr. A. 2001, 934 (1-2) 51-57. [178] DeBruin, LS.; Josephy, PD.; Pawliszyn, JB. Solid-phase microextraction of monocyclic aromatic amines from biological fluids. Anal. Chem. 1998, 70 (9) 1986-1992.

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[179] Poerschmann, J.; Górecki, T.; Kopinke, FD. Sorption of very hydrophobic organic compounds onto poly(dimethylsiloxane) and dissolved humic organic matter. 1. Adsorption or partitioning of VHOC on PDMS-Coated solid-phase microextraction fibers-a never-ending story? Environ. Sci. Technol. 2000, 34 (17) 3824-3830. [180] Carro, AM.; Mejuto, MC. Application of chromatographic and electrophoretic methodology to the speciation of organomercury compounds in food analysis. J. Chromatogr. A. 2000, 882 (1-2) 283-307. [181] Tutschku, S.; Mothes, S.; Wennrich, R. Preconcentration and determination of Sn- and Pb-organic species in environmental samples by SPME and GC-AED. Fresenius’ J. Anal. Chem. 1996, 354 (5-6) 587-591. [182] Guidotti, M. Determination of Se4+ in drinkable water by solid-phase microextraction and gas chromatography/mass spectrometry. J. AOAC. Int. 2000, 83 (5) 1082-1085. [183] Forsyth, DS.; Dusseault, L. Determination of methylpentadienyl manganese tricarbonyl in beverages by solid-phase microextraction. Food Addit. Contam. 1997, 14 (3) 301307. [184] Moens, L.; Smaele, TD. Dams, R.; Broeck, PVD. Sandra, P. Sensitive, simultaneous determination of organomercury, -lead, and -tin compounds with headspace solid phase microextraction capillary gas chromatography combined with inductively coupled plasma mass spectrometry. Anal. Chem. 1997, 69, 1604-1611. [185] Bauer, LJ; Gutsche, CD. Calixarenes. 15. The Formation of Complexes of Calixarenes with Neutral Organic-Molecules In Solution. J. Am. Chem. Soc., 1985, 107 (21), 60636069. [186] Glennon, JD; O’Connor, K; Srijaranal, S; Manley, K; Harris, SJ; McKervey, MA. Enhanced Chromatographic Selectivity for Na+ Ions on A Calixarene-bonded Silica Phase. Anal. Lett. 1993, 26, 153-162. [187] Healy, LO; McEnery, MM; McCharty, DG; Harris, SJ; Glennon, JD. Silica-Bonded Calixarenes in Chromatography: Enantioseparations on Molecular Basket Phases for Rapid Chiral Lc. Anal. Lett., 1998, 31 (9), 1543-1551. [188] Friebe, S; Gebauer, S; Krauss, GJ; Geormar, G; Krueger, J. HPLC on Calixarene Bonded Silica-Gels .1. Characterization and Applications of the p-tert-ButylCalix[4]arene Bonded Material. J. Chromatogr. Sci., 1995, 33 (6) 281-284. [189] Brindle, R; Albert, K; Harris, SJ; Tröltzsch, C; Horne, E; Glennon, JD. Silica-Bonded Calixarenes in Chromatography .1. Synthesis and Characterization by Solid-State NMR Spectroscopy. J. Chromatogr. A, 1996, 731 (1-2), 41-46. [190] Nechifor, AM; Philipse, AP; de Jong, F; van Duynhoven, JPM; Egberink, RJM; Reinhoudt, DN. Preparation and Properties of Organic Dispersions of Monodisperse Silica Receptor Colloids Grafted with Calixarene Derivatives or Alkyl Chains. Langmuir, 1996, 12 (16), 3844-3854. [191] Struck, O; van Duynhoven, JPM; Verboom W; Harkema, S; Reinhoudt, DN. Cavity Effect of Calix[4]arenes in Electrophilic Aromatic Substitution Reactions. Chem. Commun. 1996, 1517-1518. [192] Nabok, AV; Hassan, AK; Ray, AK; Omar, O; Kalchenko, VI. Study of Adsorption of Some Organic Molecules in Calix[4]resorcinolarene LB Films by Surface Plasmon Resonance. Sens. Actuators B, 1997, 45 (2), 115-121.

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Calixarene Based Sorbents for the Extraction of Ions and Neutral Molecules

333

[193] Yang, X; Johnson, S; Shi, J; Holesinger, T; Swanson, B. Polyelectrolyte and Molecular Host Ion Self-Assembly to Multilayer Thin Films: An Approach to Thin Film Chemical Sensors. Sens. Actuators B, 1997, 45 (2), 87-92. [194] Hassan, AK; Ray, AK; Nabok, AV; Davis, F. Spun Films of Novel Calix[4]resorcinarene Derivatives for Benzene Vapour Sensing. Sens. Actuators B, 2001, 77 (3) 638-641. [195] Li, X.; Zeng, Z.; Gao, S.; Li, H. Preparation and Characteristics of Sol–Gel-Coated Calix[4]arene Fiber for Solid-Phase Microextraction. Chromatography A, 2004, 1023, 15–25. [196] Li, X.; Zeng, Z.; Zhou, J. High thermal-stable sol–gel-coated calix[4]arene fiber for solid-phase microextraction of chlorophenols Anal. Chimica Acta 2004, 509, 27–37. [197] Wang, W.; Gong, S.; Cao, Q.; Chen, Y.; Li, X.; Zeng, Z. Solid-Phase Microextraction of Aromatic Amines with an Amide Bridged Calix[4]arene Coated Fiber. Chromatographia. 2005, 61, 75-80. [198] Katz, A; Costa, PD; Lam, ACP; Notestein, JM. The First Single-Step Immobilization of Calix[4]arene onto the Surface of Silica. Chem. Mater., 2002, 14, 3364-3368. [199] Suh, JK.; Kim, IW.; Chang, SH.; Kim, BE.; Ryu, JW.; Park, JH. Separation of Positional Isomers on a Calix[4]arene-methylsiloxane Polymer as Stationary Phase in Capillary GC. Bull. Korean Chem. Soc. 2001, 22, 409-412. [200] Neill, CO.; Lopez, A.; Esteves, S.; Hawkes FR.; Hawke, DL.; Wilcox, S. Azo dye degredation in an anaerobic–aerobic treatment system operating on simulated textile effluent, J. Appl. Microbiol. Biotechnol. 2000, 53, 249–254. [201] Razo-Flores, E.; Luijten, M.; Donlon, BA.; Lettinga, G.; Field, JA. Complete biodegradation azo dye azodisalicylate under anaerobic conditions, Environ. Sci. Technol. 1997, 31, 2098–2103. [202] Yilmaz, A.; Yilmaz, E.; Yilmaz, M.; Bartsch, RA. Removal of azo dyes from aqueous solutions using calix[4]arene and β-cyclodextrin Dyes and Pigments. 2007, 74, 54-59. [203] Ozmen, EY.; Sirit, A.; Yilmaz, M. A Calix[4]arene Oligomer and Two Betacyclodextrin Polymers: Synthesis and Sorption Studies of Azo Dyes J. Macro. Sci., Part A: Pure and Applied Chem. 2007, 44, 1–7. [204] Akceylan, E.; Bahadir, M.; Yilmaz, M.; Removal efficiency of a calix[4]arene-based polymer for water-soluble carcinogenic direct azo dyes and aromatic amines. J. Hazr. Matr. 2009, 162, 960–966. [205] Ozmen, EY.; Erdemir, S.; Yilmaz, M.; Bahadir, M. Removal of Carcinogenic Direct Azo Dyes from Aqueous Solutions Using Calix[n]arene Derivatives. Clean, 2007, 35, 612-616.

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 ©2009 Nova Science Publishers, Inc.

Chapter 9

THE MAGNETIC SORBENTS USED FOR DETOXIFICATION OF BLOOD

∗

N. P. Glukhoedov1, M. V. Kutushov 1, M. A. Pluzan 1, G. V. Stepanov 1∗, L. Kh. Komissarova 2, V. I. Filippov 2, L. A. Goncharov 2, F. S. Bayburtskiy 2† 1

Research Institute of Chemistry and Technology of Hetero-organic Compounds, Russian Federation, Moscow, Russia 2 N. M. Emanuel Institute of Biochemical Physics, Russian Academy of Science, Russian Federation, Moscow, Russia

ABSTRACT

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In given article use of magnetic sorbents for detoxification of blood has been investigated. Restored-iron, iron-carbon and iron-silica do not cause changes in erythrocyte's osmotic resistance and possess high sorption efficiency for substances of different molecular mass. These magnetic carriers can be recommended for extracorporeal blood detoxification of low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances.

Keywords: Absorptive capacity; sorption efficiency; erythrocyte; toxicity test (osmotic); heme protein; restored-iron; iron-silica; iron-carbon; surface modification; blood detoxification; barbiturates; bilirubin; blood purification.

∗

A version of this chapter was also published in Chemical and Biochemical Physics: New Frontiers, edited by G. E. Zaikov. It was submitted for appropriate modifications in an effort to encourage wider dissemination of research. ∗ E – mail: [email protected], [email protected]

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INTRODUCTION Magnetic carriers (MC) can be used in biochemistry and biotechnology for cell separation, immobilization of enzymes and other biologically active compounds [1,2]. The use of MC is particularly important for extracorporeal blood purification [3 – 5]. MC used for extracorporeal blood purification require a high absorptive capacity, should be selective for eliminated substances, should be hemocompatible and should have a high magnetic susceptibility so that they can be separated using a magnetic field intensity of not more than 1 T [5]. MC of iron-carbon and restored-iron types meet many of these demands but they are not hemocompatible. The encapsulation of magnetic particles is not favored as it is known [6] that the encapsulation of coal adsorbents with biocompatible polymers reduce the absorption of low molecular weight substances (MW 10,000 Da). Polystyrene microspheres usually used for the absorption of proteins or for covalent coupling of ligands are not intended for the sorption of low and middle molecular substances [7]. Our aim was to find a hemocompatible coating for magnetic particles, which on one hand did not reduce the sorption capacity of low and middle molecular substances, and which on the other hand promoted the adsorption of high molecular substances. We investigated different magnetic carriers consisting of iron-silica composites, iron-carbon, but also restorediron, which is a highly dispersed powder of metallic iron containing less than 10 % of iron oxides.

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MATERIALS AND METHODS MC of different types (restored-iron, iron-carbon and iron-silica) were all obtained using the same technology [8]. First, highly dispersed particles of restored-iron were fractionated at defined intervals of gas flow speeds (0.02 – 1.00 m / s) and a defined intensity of magnetic fields (10 – 10 3 A/m) in order to get fractions of particles sized 0.2 – 2 μm. The following thermal process was then carried out at 800 – 1000°C in a flow of inert gas, which contained either coal microparticles or silicon oxides. The composition of the studied MC is shown in Table 1. Their magnetic properties were studied with Faraday's magnetometer (Bruker) [5]. Measurements of the magnetic moment were performed at 20°C in a magnetizing field changing from 0 to 10 kOe. The analysis of the magnetization curves allowed the determination of the saturation magnetization (ISAT ) and made it possible to obtain the data necessary to predict the behavior of the particles in various fields. The magnetization of the particles reached saturation in a magnetic field of 1 – 2 kOe. The saturation magnetization for different types of MC are also given in Table 1. The particles with 90 % iron had an ISAT of up to 180 emu / g. Different types of MC (iron-carbon, iron-silica, restored-iron) had ISAT between 50 and 180 emu / g. The surface of restored-iron and iron-carbon particles was covered by human albumin or gelatin using Widder's method [9] in our modification [8,10]. The magnetic carrier's surface †

E – mail: [email protected], [email protected]

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The Magnetic Sorbents Used for Detoxification of Blood

337

was coated with albumin or gelatin by mixing a suspension of MC and albumin or gelatin using ultrasound. The suspensions were then heated to 120°C followed by cooling to room temperature (for albumin) and washing with water (for albumin and for gelatin). Surfacemodified particles were kept at 10 % concentration in distilled water at 2 – 4°C. Hemoglobin obtained from donor blood was used as high molecular weight substance. The heme proteins myoglobin, hemoglobin, methemoglobin and carboxyhemoglobin were received from the blood taken from patients with crush-syndrome, hemolysis and carbon oxide poisoning. Cyanocobalamin (Russia) and bilirubin (Lachema, Czech Rep.) were used as middle molecular weight substances. The barbiturates sodium thiopental, sodium hexenal and sodium phenobarbital were used as low molecular weight substances. Human albumin (Sigma, Germany) and gelatin (Russia) were used to coat the MC. The sorption efficiency of MC was determined as the ratio of the quantity of the adsorbed substance to its initial amount (w / w), expressed in % for a certain ratio (w / w) of adsorbent to substance. Optimal ratios of adsorbent to substance equal 15 – 20 for barbiturates, 20 – 25 for cyanocobalamin and bilirubin, and 40 – 50 for hemoglobin. The initial concentration of absorbed substances was 100 – 200 μg/ml. The substances were incubated for 1min with MC either in physiological solution or in donor plasma and donor blood at room temperature (pH 7.4). The concentration of substances in the solutions was measured by differential visual and UV-spectroscopy. Concentrations of substances in blood and plasma and adsorption of total plasma proteins was determined by thin-layer chromatography with a fluorescent label. Osmotic resistance of erythrocytes was studied by the method of HCl-hemolysis [10]. Table 1. Properties of the studied magnetic carriers (MC) Contents of MC (%) Type

Metallic iron

Iron oxides

Coal

Silica

Restored-iron Fe-coal Fe-silica

> 90 10 – 70 80 – 88

< 10 < 10 < 10

0 20 – 80 0

0 0 2 – 10

Saturation magnetizati on (emu / g) 175 – 180 50 – 120 140 – 150

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RESULTS AND DISCUSSION More than 50 patterns of different types of MC were studied. The results of sorption efficiency of the best patterns of MC to different molecular mass substances are represented in Tables 2 – 6. The sorption efficiency of MC for different barbiturates was identical, and the results shown are thus only for sodium phenobarbital. The highest sorption of 85.7 % for phenobarbital in physiological solution was reached by the ironsilica composite (see Table 2). It was also most effective for cyanocobalamin at 33.9 %. The modification of iron-carbon particles by gelatin did not change their sorption efficiency for phenobarbital and cyanocobalamin. The maximum sorption efficiency values of hemoglobin (more than 50 %) was reached by restored-iron, followed by iron-carbon modified with gelatin, and then the unmodified MC (less than 40 %). Table 3 demonstrates that iron-carbon composite, modified by gelatin or albumin absorbs large amounts of phenobarbital and hemoglobin in donor plasma. The sorption efficiency results of MC to bilirubin in physiological solution and

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plasma are interesting. Table 4 shows that iron-carbon composites modified by gelatin or albumin have higher sorption efficiencies for bilirubin than unmodified particles. Also, albumin coated MC have a higher sorption efficiency for bilirubin in plasma than particles coated with gelatin (59.7 % versus 39.3 %, respectively). Table 5 shows that the sorption efficiency of gelatin-modified restored-iron for heme proteins (myoglobin, hemoglobin and carboxyhemoglobin) in donor blood is rather high (52 – 84 %) and it is lower for methemoglobin (22 %). The initial concentration of myoglobin does not seem to influence the sorption efficiency of MC. Table 2. Sorption efficiency of magnetic carriers (MC) for substances of different molecular mass in physiological solution at pH 7.4 Sorption efficiency, average ± SD (%)

Type

Phenobarbital MW 232 Unmodifi ed

Restorediron Fe-carbon Fe-silica

38.3 ± 6.3 49.9 ± 6.8 85.7 ± 10.2

Cyancobalamin MW 1355 Gelatin Unmodifie d modifi ed

Gelatinmodifie d

40.4 ± 7.4 55.2 ± 7.0

9.0 ± 6.1 21.4 ± 5.3

Human hemoglobin MW 64.000 Gelatin Unmodi fied modifi ed

11,1 ± 3.4 23.2 ± 6.1

32.3 ± 7.1 37.6 ± 7.6 22.5 ± 5.8

33.9 ± 7.7

54.4 ± 8.2 52.7 ± 7.8

Table 3. Sorption efficiency of magnetic carriers (MC) in donor plasma at pH 7.4 Sorption efficiency, average ± SD (%)

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Type

Fecarbon Fesilica

Phenobarbital MW 232 Albumi nUnmodif ied modifie d 46.8 ± 43.1 ± 7.9 7.2 67.3 ± 8.4

Cyancobalamin MW 1355 Albumi nUnmodifi ed modifie d 15.7 ± 13.5 ± 4.1 5.8

Human hemoglobin MW 64.000 Albumi nUnmodifi ed modifie d 44.5 ± 39.4 ± 7.0 6.6

23.1 ± 4.3

11.9 ± 3.8

Table 4. Sorption efficiency of magnetic carriers (type Fe-carbon) for bilirubin (MW 584) Medium of incubation (pH 7.4)

Physiological solution Donor plasma

Sorption efficiency, average ± SD (%) Without modification

Gelatinmodified

Albuminmodified

29.0 ± 5.7 0

66.7 ± 7.4 34.3 ± 5.9

70.8 ± 8.6 59.2 ± 8.1

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The Magnetic Sorbents Used for Detoxification of Blood

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Table 5. Sorption efficiency for heme proteins of 2 mg of the gelatin-modified restored-iron MC in 10 ml of donor blood Concentration, average ± SD (%) Befor After 1000 ± 62.3 300 ± 22.0 640 ± 16.7 240 ± 19,8 280 ± 19.0 45.7 ± 4.1 40.6 ± 4.5 12.7 ± 1.30 27.5 ± 3.1 21.3 ± 0.9

Heme proteins

Myoglobin (ng / l) Hemoglobin (μg / l) Methemoglobin (%) Carboxyhemoglobin (%)

17.0 ± 3.9

Sorption (%) 70 62.5 83.8 60.7 22.5

8.0 ± 0.7

52.9

Table 6. Sorption efficiency of magnetic carriers (MC) for substances of different molecular mass in donor plasma at pH 7.4 Sorption efficiency, average ± SD (%) Substances

Phenobarbital Cyancobalamin

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Bilirubin Human hemoglobin

Fesilica 67.3 ± 8.4 23.1 ± 4.3 < 42 11.9 ± 3.8

Fe-carbon modified with gelatin

Fe-carbon modified with albumin

46.8 ± 7.9

43.1 ± 7.2

13.5 ± 4.1

15.7 ± 5.8

34.3 ± 5.9

59.2 ± 10.3

39.4 ± 7.0

44.5 ± 6.6

Changes in the erythrocytes' osmotic resistance were not observed. Adsorption of total plasma proteins on modified MC was lower than 12 %, but it was about 60 – 70 % on unmodified particles. Table 6 summarizes the results obtained of MC sorption efficiency to substances of different molecular mass in donor plasma. The sorption mechanism of low and middle molecular weight substances (phenobarbital and cyanocobalamin) on iron-carbon and restored-iron MC is apparently connected with absorption of molecules into the sorbent's pores. Iron-carbon composites have a more porous structure than restored-iron, therefore the sorption efficiency of iron-carbon MC is higher than that of restored-iron (see Table 2). The results show that the modification of the particle surface with gelatin or albumin does not interfere with this process. The high sorption efficiency of the iron-silica composite for phenobarbital is caused by the interaction of silica OH-groups with the barbiturate's molecules. High sorption efficiency of iron-carbon composite modified by albumin or gelatin to bilirubin in physiological solution (see Table 4) is probably connected to the formation of hydrogen bonds of bilirubin methyl-groups with carboxy-groups of albumin or gelatin [6]. Adsorption mechanism of hemoglobin and other heme proteins on the surface of MC modified by gelatin or albumin at pH 7.4 (see Table 5) can be explained by an electrostatic interaction of gelatin or albumin carboxy-groups with amino-groups of the heme proteins

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340

N. P. Glukhoedov, M. V. Kutushov, M. A. Pluzan et al.

[10]. Such electrostatic interactions are due to the differences in isoelectric points of heme proteins on one hand, and albumin or gelatin on the other.

SUMMARY The novel magnetic carriers of an iron-silica type iron-carbon or restored-iron composites modified by gelatin as well as the albumin do not cause changes in erythrocytes' osmotic resistance and no noticeable adsorption of total plasma proteins. The magnetic carriers have good magnetic characteristics and a high sorption efficiency for substances of different molecular mass. They can be recommended for extracorporeal blood detoxification for low (barbiturates), middle (bilirubin) and high (heme proteins) molecular weight substances.

REFERENCES Sharles S. O., Norman S., // J. Immunol. 73 (1984) 41. Safarik I., Safarikova M., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 24. [3] Stockmann H. B., Hiemstra C. A., Marquet R. I., Ijzermans J. N. // Ann. Surg. 231 (2000) 460. [4] Weber C., Falkenhagen D., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 371. [5] Komissarova L. Kh., Filippov V. I., Kutushov M. A., in: Hafeli U. (Editor), Scientific and Clinical Applications of Magnetic Carriers, Plenum Press, New York, 1997, p. 380. [6] Gorchakov V. D., Vladimirov V. G. Selective Hemosorbents, Moscow, Medicine, 1989. [7] Fishers R. C., Microsphere Selection Guide, 9025 Technology, March, 2000. [8] Komissorova L. Kh., Gluchoedov N. P., Kutushov M. V., Russian patent No. 2109522, 1998. [9] Widder K., Fluoret G., Senyei A. // J. Pharm Sci. 68 (1979) 79. [10] Komissarova L. Kh., Filippov V. I. // Izv. AN USSR, Ser. Biol. 6 (1988) 78.

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[1] [2]

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In: Sorbents: Properties, Materials and Applications Editor: Thomas P. Willis

ISBN: 978-1-60741-851-1 ©2009 Nova Science Publishers, Inc.

Chapter 10

SURFACE CONTROLLED REACTION KINETICS ON CALCIUM-BASED SORBENTS ∗

Jinsheng Wang1 and Siauw H. Ng2 1

CANMET Energy Technology Centre, Natural Resources Canada, 1 Haanel Dr., Ottawa, Ontario, K1A 1M1 Canada 2 National Centre for Upgrading Technology, 1 Oil Patch Drive, Suite A202, Devon, Alberta, T9G 1A8 Canada

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ABSTRACT CaO based sorbents are widely used in the electric power industry to capture sulphur released from fuels, such as in coal gasifiers, fluidized bed combustors, and flue gas desulphurization units. In recent years, using CaO based sorbents for capturing CO2 from coal combustors has also been actively studied. The capturing of the pollutants is a process of reactive sorption, and the effectiveness of the sorbents depends on the reactivity of CaO with the species to be sorbed. Despite the importance of the applications, the detailed reaction mechanisms are not well understood and the interpretations of the kinetic behavior are controversial. In the present study effort is made to seek some generalizations for the different reaction systems, with focus on the effects of physical and chemical changes of the sorbent surface on the reactivity and the observed kinetic behavior. Simplified mathematical models are developed to describe the sorption kinetics, and a simple method for data analysis and performance prediction is demonstrated.

NOTATION a c1 , c2 ∗

apparent activity of sorbent constants

A version of this chapter was also published in Chemical Reactions on Surfaces, edited by James I. Duncan and Artur B. Klein. It was submitted for appropriate modifications in an effort to encourage wider dissemination of research.

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f k k1 keff kS N t X Xmax (= k1/ τ ) XS

a parameter dependent on temperature, gas composition, pressure and particle size a rate coefficient a coefficient effective rate constant a constant number of carbonation/calcination cycles time conversion of the sorbent apparent maximum conversion in sulfation conversion of the surface layer

Greek letters

α β

a coefficient for converting XS to X a coefficient for activity decay

τ

a constant

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1. INTRODUCTION Coal fired power accounts for over 50% of the total power generation in the US. Millions of tons of coal are burnt every day. Coal typically contains 2 to 3 % sulfur. During burning of coal, the sulfur is released as sulfur dioxide and enters the atmosphere with the flue gas. The sulfur dioxide causes acid rains which damage plants, water and aquatic animals. Controlling SO2 emission is a major issue for coal based power generation. As a measure of the emission control, SO2 is commonly removed from the flue gas before the gas is discharged to the atmosphere. The removal techniques may be divided into two types: post-combustion and in-situ. The former uses SO2 absorption facilities to treat the postcombustion flue gas. The latter mainly works for fluidized bed combustion, where solid fuel, sorbent and inert particles are fluidized by high velocity air for enhancement of heat and mass transfer. SO2 is captured by the solid sorbent inside the combustors, thus eliminating the need for separate removal devices. Limestone is the most commonly used sorbent for the in-situ removal. Limestone is predominantly CaCO3. For sulfur removal the stone is crushed and injected into the combustor. At combustion temperature limestone decomposes to CaO and CO2: CaCO3 + heat = CaO + CO2

(1)

CaO then reacts with SO2 through the sulfation reaction CaO + SO2 + 1/2O2 = CaSO4

(2)

In this way, the sulfur is retained in the solid CaSO4 which remains with combustion ash and is easily separated from the flue gas.

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For gas-solid non-catalyzed reactions, adsorption of reactant gas molecules on the surface of the solids is the first step. The adsorbed molecules may react with surface groups of the solids, or dissociate into constituent groups or atoms as a result of their strong interactions with the atoms of the surface (Szekely et al., 1976). They may also react with other adsorbed molecules, or with gas phase molecules. The reaction systems are more complicated than heterogeneous catalytic systems because of the direct participation of the solids in the overall reactions. As the solids are consumed or subjected to chemical change, their structures change with time, making the analysis of the behavior more difficult. The complexity is well manifested in the sulfation of CaO. In spite of extensive studies for decades, the detailed mechanism of the sulfation is not clear at present. Several reaction routes have been proposed, such as (Moss, 1970; 1975) SO2 + 1/2O2 = SO3

(3-1)

CaO + SO3 = CaSO4

(3-2)

CaO + SO2 = CaSO3

(4-1)

CaSO3 + 1/2O2 = CaSO4

(4-2)

or (Allen and Hayhurst, 1996a, 1996b) 4CaSO3 = CaS+ 3CaSO4

(5-1)

CaS + 2O2 = CaSO4

(5-2)

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However, no conclusive evidence has been obtained so far. Like other gas – solid reaction systems, adsorption of gas molecules on the surface ought to be prerequisite. Even for the above simplified reaction schemes, a range of possibilities can be considered, for instance 2SO2 · S + O2 (g) = 2 SO3 · S

(6)

O2 (g) = 2O · S

(7)

SO2 · S + O · S = SO3 · S

(8)

CaO + SO3 · S = CaSO4

(9)

CaSO3 + O · S = CaSO4

(10)

2CaSO3 + O2(g) = 2CaSO4

(11)

where “· S” denotes adsorbed states, and “(g)” denotes gas phase. The sulfation system looks further complicated by the observation that the conversion of CaO to CaSO4 is usually below 50%, with an unreacted CaO core surrounded by a CaSO4 layer as illustrated in Figure 1. The

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Jinsheng Wang and Siauw H. Ng

incomplete conversion is generally attributed to the different molar volumes of CaO, its parent CaCO3 and its sulfation product CaSO4 (Anthony and Granatstein, 2001). The molar volume of CaO is smaller than that of CaCO3 (17 cm3/mol vs. 37 cm3/mol). This results in a porous structure of CaO following decompositfion of CaCO3 (Eq. 1).

Figure 1. Illustration of incomplete sulfation of a sorbent particle.

On the other hand, the sulfation product CaSO4 has a much larger molar volume (46 cm /mol), and the product layer is conceived to be compact and blocking the transport of the gas molecules to unreacted region by way of pore diffusion. Thus, diffusion of reacting species through the compact CaSO4 layer is required for the sulfation to proceed. The identities of the diffusing/reacting species are unclear. Whereas traditionally SO2 is 3

2−

considered to be a diffusant, Borgwardt et al. (1987) proposed that SO 4 2+

and O

2-

ions

2-

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diffuse through the CaSO4 layer, and Hsia et al. (1993) proposed that Ca and O diffuse outward and the sulphation occurs on the sorbent surface. In each case, surface process – be it adsorption, ionization or recombination - would be important even after the formation of the CaSO4 layer. Whereas the process looks complex and a range of plausible but unverified mechanisms exist, the major interest for practical sulfur removal operation is the rate of sulfation. In particular, knowledge on the time dependence of the sulfation conversion is essential to process design and control. The current discussion aims at presenting an easy way for analyzing the rate data and a simple formula for predicting the sulfation conversion or sulfur capture efficiency as a function of time.

2. SULFATION KINETICS OF CALCIUM OXIDE BASED SORBENT The general pattern of the sulfation kinetics can be seen from Figure 2. The conversion of CaO to CaSO4 is relatively fast in the beginning, but the rate decreases with increasing conversion level. After about one hour the conversion becomes very slow, and complete conversion does not seem to be achievable. Many mathematical models have been proposed to describe the sulfation behavior (Dennis and Hayhurst, 1986, 1990; Mattisson and Lyngfelt, 1998; Zevenhoven et al., 1998; Adánez et al., 2000; Suyadal et al., 1999, 2005). Most of the models take reactant diffusion through the sulphate product layer as rate-limiting (Adánez et al. 2000), and attempt to explain the observed kinetic behavior in terms of structural

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Surface Controlled Reaction Kinetics on Calcium-Based Sorbents

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properties of the sorbent such as pore size, density and active surface area. Whereas such models can give good interpretations of the observed behavior, they are generally quite complex and require numerical computations to obtain the time dependence of sulfation. By contrast, some empirical or semi-empirical models are simpler and more convenient for practical applications. Such models generally assume that the reactivity of the sorbent decreases linearly with conversion, in the way (Mattisson and Lyngfelt, 1998)

dX = k eff dt

(12-1)

and

k eff = k1 (1 −

X ) k1 / τ

(12-2)

where X is the conversion of the sorbent. t is time. keff is an effective rate constant. k1 and τ are constants. The above equation leads to

X = X max [1 − exp(−τ t )]

(13)

where Xmax= k1/ τ is the apparent maximum conversion. Mattisson and Lyngfelt (1998) proposed an exponentially decreasing reactivity

k eff = c1 exp(−c 2 X )

(14)

where c1 and c2 are constants. This leads to

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X = (1 / c 2 ) ln(c1c 2 t + 1)

(15)

Figure 2. Time dependence of conversion of CaO to CaSO4 in several sorbents. The data were reported by Lee and Georgakis (1981).

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However, no physical ground has been given for the decreasing rate constant. It will be shown in the present work that, by focusing on the change of the sorbent surface during the sulfation process, a simple expression for the time dependence of the conversion can be obtained. This expression not only provides insight to the sulfation behavior, but also gives a good description of the rate data for practical purposes. The surface change is perceived from another application of calcium based sorbent – capturing CO2 from burning coal.

3. CO2 SORBENT AND THE DECAY OF SORPTION ACTIVITY CO2 is the principal greenhouse gas associated with global warming, and coal-fired power plants are a major contributor to CO2 emission. A range of options for capturing CO2 from burning coal have been investigated. One of such options is in-situ capture of CO2 by CaO, via the carbonation reaction CaO + CO2 = CaCO3

(16)

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This reaction can occur below 900ºC at elevated pressures, and a pressurized fluidized bed combustor would suit this purpose (Wang et al., 2004; Abanades et al., 2005). The solid CaCO3 can be easily separated from the flue gas and decomposed in a calciner via the calcination reaction (Eq. 1) for regeneration of CaO and recovery of CO2. To obtain pure CO2, a smaller amount of coal is burnt with pure O2 in the calciner to provide the required heat. This results in nearly pure CO2, which joins the CO2 from decomposition of CaCO3 to form a CO2 stream for sequestraton underground or use in applications such as fertilizer production or enhanced oil recovery. The regenerated CaO is sent back to the combustor for subsequent taking up of CO2. The theoretical thermal efficiency of this process is the same as burning all of the fuel (combustion and calcination combined) in a single combustor, whereas recovery of CO2 is achieved. Another application of the carbonation/calcination cycle is in production of hydrogen, a potential fuel for the future. Hydrogen is typically produced from hydrocarbon feed stocks. Two important processes are the reforming and water gas shift reactions, which convert hydrocarbon gases and carbon monoxide into hydrogen in the presence of steam: CH4 + 2H2O = 4H2 + CO2

(17)

CO + H2O = CO2 + H2

(18)

The conversion to H2 through these reactions is limited by chemical equilibrium, and separation of H2 from a gas mixture and recycle of the unconverted reactants consume substantial amounts of energy. By adding solid CaO into the reactors, CO2 can be removed from the gas mixture through the carbonation reaction (Eq. 16). The overall reactions will be CH4 + 2H2O + CaO = 4H2 + CaCO3

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(17’)

Surface Controlled Reaction Kinetics on Calcium-Based Sorbents CO + H2O + CaO = H2 + CaCO3

347 (18’)

As a result, the equilibrium shifts toward the product side, enhancing the conversion of CH4 and CO to hydrogen. The CaCO3 is sent to a calciner to regenerate CaO and recover CO2 for use or sequestration.

Figure 3. Illustration of decreased carbonation conversion with increased number of carbonation/calcination cycles.

However, it has been found that the conversion of CaO to CaCO3 decreases with increasing cycles of carbonation/regeneration, as illustrated in Figure 3. A simple equation is able to describe the activity of the conversion as a function of the number of the carbonation/regeneration cycles (Wang and Anthony, 2005):

a N = a N −1 (1 − βa N −1 ) where a is the activity. N is the number of cycles.

(19)

β is a proportionality coefficient. To ease

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the calculations for large N, the equation can be written into

Δa = − βa 2 ΔN

(20)

which can be approximated by

da = − βa 2 dN for moderate changes of a . This leads to

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(21)

348

Jinsheng Wang and Siauw H. Ng

aN =

1

(22)

1 + βN

The validity of this equation was verified with available data for up to 90 carbonation and calcination cycles (Figure 4).

Figure 4. Validation of Eq. 22 with experimental data. The symbols represent the data reported by Curran et al.(1967), and the curve represents values predicted by the equation.

It is interesting to note that Eq. 9 is reminiscent of a known formula for deactivation of catalysts by sintering (a process by which the porosity of particles reduces at high temperature)

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a=

1 1 + βt

(23)

Hence, it suggests that sintering of the sorbent is the cause of the activity decay for carbonation. Decreased surface area, an indication of sintering, has also been observed in CaO sorbents following cyclic carbonation/calcination tests.

4. EFFECT OF DECAY OF SURFACE ACTIVITY ON SO2 SORPTION KINETICS The duration of the calcination operation was only a few minutes. If sintering occurs in such short time, prolonged exposure to high temperature, albeit lower than the tempeature for calcination, will also be likely to cause sintering. This would apply to sulfation of CaO

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Surface Controlled Reaction Kinetics on Calcium-Based Sorbents

349

particles. For in-situ removal of SO2, the particles are typically subjected to temperatures around 850ºC for hours - longer than the total time in the aforementioned cyclic carbonation/calcination tests. Moreover, the rate of sulfation is relatively slow. This could increase the impact of the decay of surface activity. In analogy with the heterogeneous reactions on catalysts, the previously discussed adsorption, reaction, ionization and recombination processes may all be considered to take place at some active sites only. Such sites are unstable and apt to be reduced by sintering (Wang and Anthony, 2007). When one of the processes is rate-limiting, the sulfation conversion would be dependent on the degree of sintering. Here an analytical expression is developed. Assuming the activity of the surface decreases as a result of sintering, and the sintering is dependent on time according to Eq. 23, the rate of conversion to CaSO4 may be given as (Wang et al., 2007)

dX = fa (t ) dt

(24)

where f is dependent on temperature, gas composition, pressure and particle size; a is the apparent activity of the sorbent which may depend on temperature and particle size. By incorporating Eq. 23 into Eq. 24 for the sorbent activity, the time dependence of the conversion is obtained as X

X = ∫ dX = ∫

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0

t

0

fdt f = ln(1 + βt ) 1 + βt β

(25)

Interestingly, this equation is very similar to the empirical formula Eq. 15. Sintering of limestones was observed in the temperature range of 650-800˚C and resulted in greatly reduced sulfidation (CaO + H2S = CaS + H2O) activity (De Diego et al., 1999). CaSO4 has a lower melting point (1450˚C) than that of CaO (about 2500ºC) (Iribarne et al., 1997). It is known that many metals and oxides begin to sinter at a temperature equal to about half the melting point in kelvin (the Tamman temperature), and surface diffusion of atoms can occur at still lower temperature (Heaton, 1996). The Tamman temperature for CaSO4 would be below 600˚C. Substantial sintering of CaSO4 on the sorbent particles is thus plausible around 850˚C. Another equation can be obtained by focusing on activity decay of unconverted sorbent surface, which is more convenient for evaluation of the time dependence of the conversion. Because of the larger molar volume of the CaSO4 product, the sulfation may proceed preferentially on the surface, until full coverage is reached. The conversion of the surface may be considered as dependent on the unconverted portion. By taking this dependence as linear, and the conversion rate as decreasing with conversion, one may write

dX S = k ( X S )(1 − X S ) f dt

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(26)

350

Jinsheng Wang and Siauw H. Ng

where XS stands for the conversion of a surface layer. k is a rate coefficient which decreases with increasing XS. For simplicity, this dependence is also taken as linear

k ( X S ) = k S (1 − X S )

(27)

where kS is a constant. This results in XS =

k S ft 1 + k S ft

(28)

Because the conversion of the surface layer only accounts for a fraction of the overall conversion in terms of the volume, one can write

X = αX S =

αk S ft 1 + k S ft

(α < 1)

(29)

The advantage of this formula is that a simple plot can be made to check its validity. By rearranging Eq. 29 into 1 1 1 = + X αk S ft α

(29’)

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it is clear that a plot of 1/X against 1/α will be linear if Eq. 29 holds. A few examples are given in Figures 5 and 6. They are taken for two different time scales – very short time in millisecond range and long time for hours. In both cases reasonable linear plots are obtained.

Figure 5. (Continued on next page.)

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Surface Controlled Reaction Kinetics on Calcium-Based Sorbents

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Figure 5. Sulfation conversion of sorbents in short time period. (a) Experimental data reported by Mahuli et al.(1997). (b) Plots of the data in terms of Eq. 29’.

Figure 6. Sulfation conversion of a limestone in the first 4 hours. (a) Experimental data obtained by Abanades et al.(2000). (b) Plot of the data in terms of Eq. 29’.

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Jinsheng Wang and Siauw H. Ng

It can be shown that Eqs. 25 and 29 are essentially the same in short period of time. When t is small, an approximation of the right hand side of Eq. 25 can be given

α ln(1 + k S ft ) ≈ α [k S ft −

The error is smaller than

(k S ft ) 2 ] 2

α (k S ft ) 3 3

(30)

. The result can be further approximated in the way

(k S ft ) 2 αk S ft α ' k ' ft ]≈ = α [k S ft − k ft 1 + k ' ft 2 1+ S 2

(31)

where k’ = kS/2 and α’ = 2α. Evidently, Eq. 31 has the same form as Eq. 29. Thus, the assumption of activity decay for the unconverted surface gives the same results. It can also be shown that Eq.13, the semi-empirical formula discussed earlier, is also identical to Eq. 29 in the initial stage. For small t and τ