Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics [1 ed.] 9781617286605, 9781607411697

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Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved. Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest Ebook

Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved. Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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FUNDAMENTALS AND APPLICATIONS OF BIOSORPTION ISOTHERMS, KINETICS AND THERMODYNAMICS

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Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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FUNDAMENTALS AND APPLICATIONS OF BIOSORPTION ISOTHERMS, KINETICS AND THERMODYNAMICS

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

AND

JIANLONG WANG EDITORS

Nova Science Publishers, Inc. New York

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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.

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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.

LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA Liu, Yu. Fundamentals and applications of biosorption isotherms, kinetics and thermodynamics / Yu Liu and Jianlong Wang. p. cm. Includes index. ,6%1H%RRN 1. Microbial biotechnology. 2. Adsorption (Biology) I. Wang, Jianlong. II. Title. TP248.27.M53L58 2009 660.6'2--dc22 2009006383

Published by Nova Science Publishers, Inc.    New York

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

CONTENTS Preface

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Chapter 1

vii Basic Microbiology: Microbial Structure and Function Jianlong Wang and Can Chen

1

Chapter 2

Biosorbents Can Chen and Jianlong Wang

29

Chapter 3

Biosorption Isotherms and Thermodynamics Liang Shen, Zhi-Wu Wang, Siqin Fang and Yu Liu

81

Chapter 4

Biosorption Kinetics Liang Shen, Yu Liu and Zhiwu Wang

119

Chapter 5

General Mechanisms of Biosorption Can Chen and Jianlong Wang

155

Chapter 6

Factors Influencing Biosorption Process Can Chen and Jianlong Wang

213

Chapter 7

Correlating Metal Ionic Characteristics with Biosorption Capacity Can Chen and Jianlong Wang

231

Biosorption of Heavy Metals by Aerobic Granules: An Innovative Approach Hui Xu and Yu Liu

257

Chapter 8

Index

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PREFACE Biosorption is an effective technology for the removal of organic and metallic elements, especially heavy metals from aqueous solution. Compared with conventional technologies for trace contaminant removal, such as chemical precipitation, evaporation, electroplating, adsorption and ion exchange, biosorption has advantages of high efficiency and low cost due to the economic biosorbent. Nowadays, a vast array of biomaterials have been tested as biosorbents including algae, fungi, yeast, wasted activated sludge, digested sludge, aerobic granules etc. Among these biosorbents, aerobic granules have more compact microbial structure than other loose bioflocs, so it is easier to be settled in the post treatment of biosorption. Biosorption indeed involves complex mechanisms of adsorption reaction, ion exchange reaction with functional groups on the cell surface, and surface complexation by extracellular polymeric substances. Thus far, intensive research has been dedicated to better understanding the mechanism of biosorption and its application in treating a wide variety of industrial wastewaters. Obviously, the basic research of biosorption has promoted this technology from laboratory-study all the way to the present pilot- and full-scale application, thus this book aims to provide all necessary basic knowledge of biosorption in terms of its fundamentals and main application. First of all, Chapters 1 and 2 introduce biosorbents. Chapter 1 briefly overviews biology and microbiology related to biosorption, which may help readers without microbiology background to catch up the following discussion quickly. Chapter 2 elaborates all types of biosorbents in detail, their properties and applications in biosorption processes. Considering the importance of biosorbent, development and selection of an appropriate biosorbent is a big challenge in the biosorption research. Chapter 3 looks into biosorption isotherms and thermodynamics, while Chapter 4 more focuses on biosorption kinetics. In Chapter 3, nearly all representative adsorption/biosorption isotherm equations are discussed with a special focus on theoretical derivation of the combined Langmuir-Freundlich isotherm equation, also known as the Sips isotherm. In Chapter 4, except for commonly used pseudo first-order and pseudo second-order rate equations, the more fundamental Langmuir kinetics is explored for understanding the theoretical origins of the empirical pseudo first- and second-order equations. Moreover, a general rate law equation is presented and applied to biosorption, which in turn reveals the potential uncertainty rooted in the fixed-order kinetic models. Some statistical methods for evaluation of biosorption models fitness are also presented at the end of Chapter 4. Both experimental observation and theoretical analysis presented in these two chapters point to a

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viii

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fact that the kinetic and equilibrium behaviors of biosorption are highly dependent on the initial adsorbate and biosorbent concentrations. Due to the extremely complex physical, chemical and biological natures of biosorbents, biosorption indeed involves highly complicated mechanisms that are often unknown in the most cases. In Chapter 5, some general biosorption mechanisms are elaborated and discussed, such as extracellular accumulation/precipitation, cell surface sorption/precipitation and intracellular accumulation, and instrumental technologies employed for the mechanism study are also reviewed. The focus of Chapter 6 is placed on factors influencing biosorption process. In this chapter, the important technical parameters of biosorption process besides biosorbents, such as properties of metal ions, pH, temperature, ionic strength, presence of anions and cations are all discussed in depth. Chapter 7 discusses biosorption capacity with consideration of metal ionic characteristics. In this chapter, methods based on qualitative structure activity relationships (QSARs) in metal toxicity assessment are employed to investigate the effect of metal ion characteristics on metal uptake capacity in biosorption. Chapter 7 seems to open a window for further exploring the metal biomass interaction by application QSAR in metal biosorption. Lastly, Chapter 8 presents a novel approach for metal biosorption by aerobic granules, and the more specific mechanisms of biosorption of heavy metals by aerobic granules are discussed in depth. Compared to conventional biosorbents in the form of suspended microbial flocs, aerobic granules have compact microbial structure and excellent settling ability. The settling velocity of aerobic granules is 5 to 8 times higher than that of microbial flocs, and aerobic granules can be completely separated out of the treated effluent by gravity within one minute. It appears from Chapter 8 that aerobic granule is an ideal biosorbent and the aerobic granule-based biosorption process would be an efficient and cost-effective technology for the removal of heavy metals from industrial wastewater streams. This book presents readers all the aspects of biosorption. The rising study of this technology in experiments and theories foresees its promising application in practical wastewater treatment. We sincerely hope that the publication of this book will provide a platform for the further development of this technology and promote its quick application in wastewater treatment industry. Yu Liu Nanyang Technological University Singapore Jianlong Wang Tsinghua Univeristy China

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In: Fundamentals and Applications of Biosorption… ISBN: 978-1-60741-169-7 Ed: Yu Liu and Jianlong Wang © 2009 Nova Science Publishers, Inc.

Chapter 1

BASIC MICROBIOLOGY: MICROBIAL STRUCTURE AND FUNCTION Jianlong Wang and Can Chen 1.1. OVERVIEW OF CELL STRUCTURE

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1.1.1. Prokaryotes and Eukaryotes A variety of reviews and books of microbiology were devoted to the microbial structure and function (Remacle, 1990; Baron, 1996; Urrutia, 1997; Madigan et al., 2000; Moat et al., 2002; Prescott et al., 2002; Talaro and Talaro, 2002; Tortora et al., 2004). Here we only supply some basic and brief introduction to cellular structure and function. Microbial cells have two fundamentally different types of cells — procaryotic and eucaryotic — and are distributed among several kingdoms or domains. Procaryotic cells have a much simpler and smaller structure than eucaryotic cells and lack a true membranedelimited nucleus. It generally lacks extensive, complex, internal membrane systems although with a plasma membrane. In contrast, eucaryotic cell have a membrane-enclosed nucleus and many membranous organelles. They are more complex morphologically and are usually larger than procaryotes. Algae, fungi, protozoa, higher plants, and animals are eucaryotic (Prescott et al., 2002). Prokaryotes are represented by Bacteria and Archaea. Most bacteria can be divided into gram-positive and gram-negative groups based on their cell wall structure and response to the Gram stain. Most bacteria and yeast are unicellular. Typical bacteria cells range in diameter from 0.5 to 1.0 μm, and some wider than 50 μm. Typical eucaryotic cells may be 2 μm to more than 200 μm in diameter. Apart from the aforementioned differences, procaryotes are simpler functionally in several ways than eucaryotic cells. Eucaryotic cells have mitosis and meiosis, and many complex eucaryotic processes which are absent in procaryotes: phagocytosis and pinocytosis, intracellular digestion, directed cytoplasmic streaming, ameboid movement, and others. The plasma membrane in prokaryotes performs many of the functions carried out by membranous organelles in eukaryotes.

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Figure 1.1 and table 1.1 show the comparison of procaryotic cell structure and eucaryotic cell structure. Despite the profound structural and functional differences between prokaryotes and eucaryotes, both cells are similar on the biochemical level. A typical cell of prokaryotes or eukaryotes includes four major components: cell wall, cell membrane, cytoplasm, and nuclear area.

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Figure 1.1. Comparison of procaryotic and eucaryotic cell structure. (a) The procaryote Bacillus megaterium (Magnification × 30 500). (b) The eucaryotic alga Chlamydomonas reinhardtii, a deflagellated cell. Note the large chloroplast with its pyrenoid body (Magnification × 30 000). (Prescott et al., 2002).

1.1.2. Cellular Structure (i) Cellular Wall Cell wall is a rigid outer layer of the cell membrane, which provides support and protection from osmotic lysis. Varying chemical composition of the cell wall differs from group to another cell. All fungi, and most bacteria and algae have cell walls. (ii) Cellular Membrane The cell membrane, or plasma membrane, or cytoplasmic membrane, is the critical permeability barrier, with a lipid and protein layer surrounding cytoplasm. It is the boundary between the cell and its environment when lacking cell walls. The membrane is the chief point of contact with the cell’s environment and thus is responsible for much of its relationship with the outside world. The exact proportions of protein and lipid in the cell membrane vary widely in different group of microorganisms. Eucaryotic plasma membranes usually have a lower proportion of protein than bacterial membranes. Cell membranes are about 5 to 10 nm thick, and only viewed under electron microscope. Lipids in membrane are structurally asymmetric with polar ends (hydrophilic) and nonpolar ends (hydrophobic), usually these asymmetric lipids are phospholipids. One major difference in chemical composition of membrane between eukaryotic and prokaryotic cells that that bacterial

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membranes, unlike eucaryotic membranes, lack sterols such as cholesterol. Sterols can make up from 5 to 20% of the total lipids of eukaryotic membranes. Sterols are rigid, planar molecules, whereas fatty acids are flexible serving to stabilize its structure and make it less flexible. However, bacterial membranes contain pentacyclic sterol-like molecules called hopanoids. A most widely accepted model for membrane structure is the fluid mosaic model, proposed by S. Jonathan Singer and Garth Nicholson. There are two types of membrane proteins: peripheral proteins and integral proteins. The former are loosely connected to the membrane and can be easily removed, soluble in aqueous solutions and make up about 20 to 30% of total membrane protein. The later compose the about 70 to 80% of membrane protein, and are not easily extracted from membranes and are insoluble in aqueous solutions when freed of lipids. The integral proteins are also asymmetric (Prescott et al., 2002).

(iii) Cytoplasm Cytoplasm, aqueous fluid of the cell, contains organelles, enzymes, chemicals, in which most cellular metabolic activity occur, e.g. ribosomes. Bacteria does not contain internal membrane-bound organelles, its interior appears morphologically simple. Ribosomes are small particles composed of protein and ribonucleic acid (RNA). Ribosomes are part of the translation apparatus, and synthesis of cell proteins takes place on these structures. Procaryotic cells occasionally contain inclusions consisting of storage material made up of compounds of carbon, nitrogen, sulfur, or phosphorus, formed when these nutrients are in excess. Algae have an additional type of organelle: chloroplast. Eucaryotic cells differ most obviously from procaryotic cells in having a variety of complex membranous organelles in the cytoplasmic matrix and the majority of their genetic material within membrane-delimited nuclei. Each organelle has a distinctive structure directly related to specific functions. Algae are eukaryotic microorganisms that carry out the process of photosynthesis. In these organisms, as well as in green plants, an additional type of organelle is found: the chloroplase. The chloroplast is green and is the site where chlorophyll is localized and where the light-gathering functions involved in photosynthesis occur. (iv) Nuclear Area Nuclear area includes the hereditary material, deoxyribonucleic acid (DNA). Most cells, but not bacteria, the DNA contained within a membrane. In bacteria, the genetic material is localized in a discrete region, the nucleoid, and is not separated from the surrounding cytoplasm by membranes. Prokaryotic cells do not possess a true nucleus, the function of the nucleus being carried out by a single molecule of DNA. The DNA molecule of the prokaryote is called a chromosome. The key difference between eukaryotic and prokaryotic cells is that eukaryotes contain true nuclei. In this chapter, we’ll mainly discuss three groups of biomass material related to metal biosorption: bacteria (gram-positive and gram-negative cells), fungi (filamentous fungi and yeast) and algae. The interface between the microbial cell and its external environment is the cell surface. It protects the cell interior from external hazards and maintains the integrity of the cell. The structure and composition of different cell surfaces can vary considerably, depending on the organism. Due to the importance of the cell surface, especially the cell wall for metal biosorption, the cell surface structures of three groups of microorganisms will be described in detail in term of biosorption.

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Jianlong Wang and Can Chen Table 1.1. Comparison between Procaryotic and Eucaryotic Cells

Property Size of Cell Membrane-enclosed Organelle Cytoplasm Chromosome (DNA)

Cell Division Sexual Reproduction Organization of Genetic Material True Membrane-bound Nucleus DNA Complexed with Histones Number of Chromosomes Introns in Genes Nucleolus

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Mitosis occurs Genetic Recombination Mitochondria Chloroplasts Plasma Membrane with sterols

Flagella

Endoplasmic Reticulum Golgi Apparatus Cell Walls

Procaryotes Typically 0.2-2.0 μm in diameter Absent No cytoskeleton or cytoplasmic streaming Single circular chromosome, lacks histones Binary fission No meiosis; transfer of DNA fragments only

Eucaryotes Typically 10-100 μm in diameter Present Cytoskeleton or cytoplasmic streaming Multiple linear chromosomes with histones arrangement Mitosis Involves meiosis

Absent No Onea Rare Absent. no nuclear membrane or nucleoli

Present Yes More than one Common Present. True nucleus, consisting of nuclear membrane and nucleoli Yes Meiosis and fusion of gametes Present Present Yes. sterols and carbohydrates that serve as receptors present Microscopic in size; membrane bound; usually 20 microtubules in 9 + 2 pattern. Complex, consist-ing multiple microtubules Present Present Chemically simpler and lacking peptidoglycan

No Partial, unidirectional transfer of DNA Absent Absent Usually nob. No carbohydrates and generally lacks sterols Submicrosopic in size; composed of one fiber, consisting of two protein building blocks Absent Absent Usually chemically complexd with peptidoglycanc

Differences in Simpler Organelles Ribosomes Smaller size (70 S)

Larger (80S) (except mitochondria and chloroplasts)

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Table 1.1 (Continued). Lysosomes and peroxisomes Microtubules Cytoskeleton Differentiation

Absent Absent or rare May be absent Rudimentary

Present Present Present Tissues and organs

a

Plasmids may provide additional genetic information. Only the mycoplasmas and methanotrophs (methane utilizers) contain sterols. The mycoplasmas cannot synthesize sterols and require them preformed. Many procaryotes contain hopanoids. c The mycoplasmas and Archaea do not have peptidoglycan cell walls. Adapted from Prescott et al. (2002) and Tortora et al. (2004) http://diverge.hunter. cuny.edu/~weigang/ Images/04-T02_Prok&Euka.jpg b

1.2. BACTERIA 1.2.1. Size and Shape

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Bacteria have simple morphology and most commonly encountered bacteria present in three basic shapes: spherical or ovoid (coccus), rod (bacillus, with a cylindrical shape), and spiral (spirillum) although there is a great variety of shapes due to differences in genetics and ecology (figure 1.2).

Figure 1.2. Bacterial Morphologies (Baron, 1996). http://gsbs.utmb.edu/microbook/ch002.htm by Milton R.J. Salton and Kwang-Shin Kim. Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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Bacteria vary in size as much as in shape. In many prokaryotes, the cells remain together in groups or clusters after division (pairs, chains, tetrads, clusters, etc.). Cocci or rods may occur in long chains. Typical bacteria cells range in diameter from 0.5 to 1.0 μm, some wider than 50 μm. The average size of the gram-negative organism, for example, Escherichia coli, often as typical size of bacteria cell, is about 1.1 to 1.5 μm wide by 2.0 to 6.0 μm long. The smallest bacteria are about 0.3 μm, and a few bacteria become fairly large, e.g. some spirochetes occasionally reach 500 μm in length, and the cyanobacterium Oscillatoria is about 7 μm in diameter. The average eucaryotic cell is 10 to 50 μm. Typical eukaryotic cells may be 2 μm to more than 200 μm in diameter. Cell size is an important characteristic for an organism. Small size of bacteria is very important because small size affects a number of cell biological properties. Small size of bacteria ensures rapid metabolic process.

1.2.2. Cell Structure

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Figure 1.3 showed a schematic representation of a “typical” bacterial cell (Escherichia coli), which contain cell wall, cell membrane and cytoplasmic matrix.

Figure 1.3. The relationship of the three layers of the cell envelope: cell membrane, cell wall and glycocalyx. (Talaro and Talaro, 2002).

The cytoplasm typically contains several constituents that are not membrane-enclosed: inclusion bodies, ribosomes, and the nucleoid with its genetic material. Some bacteria have special structure, such as flagella, S-layer. Microbiologists often call all the structures from

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the plasma membrane outward the envelope or cell envelope. This includes the wall and structures like capsules when present. Figure 1.4A and figure 1.4B supplied the schematic representation of a gram-positive and gram-positive bacterium.

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Figure 1.4. A. Schematic representation of a “typical” bacterial cell (Escherichia coli). Portions of the cell are enlarged to show further details. (Moat et al., 2002).

Figure 1.4.B. Schematic representation of a gram-positive bacterium. (Prescott et al., 2002).

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1.2.3. Cell Wall

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Main function of cell wall include: (1) strong walls give cells shape and protect them from osmotic lysis; (2) The wall can protect a cell from toxic substances (3) cell wall offers the site of action of several antibiotics. (4) cell wall is necessary for normal cell division. By Gram stain technique, the bacteria can be divided into two categories, i.e., the grampositive and gram-negative bacteria. The gram-positive bacteria stained purple, whereas gram-negative bacteria were colored pink or red. The surface of gram-negative cells is much more complex chemically and structurally than that of gram-positive cells. Because of the thicker peptidoglycan layer, the walls of gram-positive cells are stronger than those of gramnegative bacteria. The shape and strength of the cell wall is primarily dependent upon peptidoglycan, which is a rigid, porous, and amorphous material, the core of which is very similar in all bacteria. Unique features of almost all prokaryotic cells are cell wall peptidoglycan and the specific enzymes involved in its biosynthesis. The amount and exact composition of peptidoglycan only found in cell walls vary among the major bacterial groups. Peptidoglycan is a linear polymer of alternating units of two sugar derivatives, Nacetylglucosamine (NAG) and N-acetylmuramic acid (NAM) (figure 1.5).

Figure 1.5. Peptidoglycan Subunit Composition. The peptidoglycan subunit of Escherichia coli, most other gram-negative bacteria, and many gram-positive bacteria. NAG is N-acetylglucosamine. NAM is N-acetylmuramic acid (NAG with lactic acid attached by an ether linkage). The tetrapeptide side chain is composed of alternating D- and L-amino acids since meso-diaminopimelic acid is connected through its L-carbon. NAM and the tetrapeptide chain attached to it are shown in different shades of color for clarity. (Prescott et al., 2002).

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Figure 1.6 Peptidoglycan Cross-Links. (a) E. coli peptidoglycan with direct cross-linking, typical of many gram-negative bacteria. (b) Staphylococcus aureus peptidoglycan. S. aureus is a gram-positive bacterium. NAM is N-acetylmuramic acid. NAG is N-acetylglucosamine. Gly is glycine. Although the polysaccharide chains are drawn opposite each other for the sake of clarity, two chains lying side-byside may be linked together (see Figure 1.4). (Prescott et al., 2002)

Figure 1.7. Schematic diagram of peptidoglycan structure. A peptidoglycan segment showing the polysaccharide chains, tetrapeptide side chains, and peptide interbridges. (Prescott et al., 2002).

(I) Gram-Positive Cell Walls The gram-positive cell wall consists of a single 20 to 80 nm thick homogeneous peptidoglycan or murein layer lying outside the plasma membrane (figure 1.8A and 1.8B). This cell wall also contains large amounts of teichoic acids, polymers of glycerol or ribitol

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joined by phosphate groups. Peptidoglycan of a gram-postivie cell wall accounts for 40 to 90 % of the cell wall material, containing a peptide inter-bridge. This peptidoglycan core is usually between 20 and 40 layers thick, and adjacent glycan chains are cross linked through the aminoacid stems forming a highly resilient, three-dimensional macromolecule that surrounds the cells. Amino acids such as D-alanine or sugars like glucose are attached to the glycerol and ribitol groups. The teichoic acids are connected to either the peptidoglycan itself by a covalent bond with the six hydroxyl of N-acetylmuramic acid or to plasma membrane lipids (called lipoteichoic acids) (Prescott et al., 2002). Lipoteichoic acids, only present in gram-positive microorganisms—are synthesized at the membrane surface and may extend through the peptidoglycan layer to the outer surface, are polymers of amphiphitic glycophosphates with the lipophilic glycolipid and anchored in the cytoplasmic membrane. They are antigenic, cytotoxic and adhesins (e.g., Streptococcus pyogenes). ((Baron, 1996) http://gsbs.utmb.edu/microbook/ ch002.htm by Milton R.J. Salton and Kwang-Shin Kim).

Figure 1.8.A. Gram-Positive and Gram-Negative Cell Walls. The gram-positive envelope is from Bacillus licheniformis (left), and the gram-negative micrograph is of Aquaspirillum serpens (right). M; peptidoglycan or murein layer; OM, outer membrane; PM, plasma membrane; P, periplasmic space; W, gram-positive peptidoglycan wall. (Prescott et al., 2002).

Teichoic acids appear to extend to the surface of the peptidoglycan, and, because they are negatively charged, help give the gram-positive cell wall its negative charge. The teichuronic acids are free of phosphate and made up of hexuronic acid linear chains. The proportion of teichoic acids and teichuronic acids depends on the culture conditions, especially on the phosphate supply. The functions of these molecules are still unclear, but they may be important in maintaining the structure of the wall. Teichoic acids are not present in gramnegative bacteria. It is proved that the teichoic acids and teichuronic acids participate in metal tripping. Both the phosphoryl groups of the secondary polymers and the carboxyl groups of the peptide chains provide negatively charged sites in the gram-positive cell wall (Remacle, 1990;Urrutia, 1997; Moat et al., 2002; Prescott et al., 2002).

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Figure 1.8.B. Composition of the cell surfaces of gram-positive and gram-negative bacteria. Not all structures shown are found in all organisms. For example, M protein is only used to describe a structure in some of the streptococci. Also, not all organisms have flagella. (Moat et al., 2002).

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Wall teichoic acids are found only in certain Gram-positive bacteria (such as Bacillus spp), and their structures are illustrated in figure 1.9.

Figure 1.9. Structures of cell wall teichoic acids. (A) Ribitol teichoic acid with repeating units of 1,5phosphodiester linkages of D-ribitol and D-alanyl ester on position 2 and glycosyl substituents (R) on position 4. The glycosyl groups may abe N-acetylglucosaminyl (a or b) as in S. aureus or a-glucosyl as in B subtilis W23. (B) Glycerol teichoic acid with 1,3-phosphodiester linkages of glycerol repeating units (1,2-linkages in some species). In the glycerol teichoic acid structure shown, the polymer may be unsubstituted (R-H) or substituted (R-D-alanyl or glycosyl). ((Baron, 1996) http://gsbs.utmb.edu/micro book/ch002.htm by Milton R.J. Salton and Kwang-Shin Kim).

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Teichoic acids are polyol phosphate polymers, with either ribitol or glycerol linked by phosphodiester bonds. Substituent groups on the polyol chains can include D-alanine (ester linked), N-acetylglucosamine, N-acetylgalactosamine, and glucose. They are strongly antigenic. These highly negatively charged polymers of the bacterial wall can serve as a cation-sequestering mechanism.

(II) Gram-Negative Cell Walls The gram-negative cell wall is much more complex than the gram-positive cell, about 30 to 80 nm thick. It is a multilayered structure. It has a 2 to 7 nm peptidoglycan layer surrounded by a 7 to 8 nm thick outer membrane. The peptidoglycan is sandwiched between the plasma membrane and the outer membrane, which is composed of phospholipids, lipopolysaccharides, enzymes, and other proteins, including lipoproteins (figure 1.8A and 1.8B). The thin peptidoglycan layer next to the plasma membrane may constitute not more than 5 to 10% of the cell wall weight. In E. coli it is about 2 nm thick and contains only one or two layers or sheets of peptidoglycan. Only one type of the peptide bridge occurs between the glycan chains. The space between the outer membrane and the inner membrane is referred to as the periplasmic space, which is the translucent region where at several points by various enzymes and other proteins. The peptidoglycan is covalently bound to the outer membrane by lipoproteins. The outer membrane is composed of lipopolysaccharide (LPSs), phospholipids and proteins. A characteristic feature of Gram-negative bacteria is possession of various types of complex macromolecular lipopolysaccharide (LPS). LPSs are probably the most unusual constituents of the outer membrane. LPSs structure was illustrated in figure 1.10 and figure 1.11. LPSs contain both lipid and carbohydrate, and consist of three parts: (1) lipid A, (2) the core polysaccharide, and (3) the O side chain. The lipid A structure required for insertion in the outer leaflet of the outer membrane bilayer; a covalently attached core composed of 2keto-3deoxyoctonic acid (KDO), heptose, ethanolamine, N-acetylglucosamine, glucose, and galactose; and polysaccharide chains linked to the core. The polysaccharide chains constitute the O-antigens of the Gram-negative bacteria, and the individual monosaccharide constituents confer serologic specificity on these components. LPS and phospholipids help confer asymmetry to the outer membrane of the Gram-negative bacteria, with the hydrophilic polysaccharide chains outermost. Each LPS is held in the outer membrane by relatively weak cohesive forces (ionic and hydrophobic interactions) and can be dissociated from the cell surface with surface-active agents ((Baron, 1996) http://gsbs.utmb.edu/microbook/ch002.htm by Milton R.J. Salton and Kwang-Shin Kim)). The net negative charge of LPSs explains the negative surface charge of Gram-negative bacteria. The phosphate groups within LPSs and phospholipids have been proved to be the primary sites for metal interaction. However, only one of the carboxyl groups in LPSs is free to interact with metals (Remacle, 1990; Urrutia, 1997; Moat et al., 2002; Prescott et al., 2002).

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Figure 1.10. Lipopolysaccharide Structure. (a) The lipopolysaccharide from Salmonella. This slightly simplified diagram illustrates one form of the LPS. Abbreviations: Abe, abequose; Gal, galactose; Glc, glucose; GlcN, glucosamine; Hep, heptulose; KDO, 2-keto-3-deoxyoctonate; Man, mannose; NAG, Nacetylglucosamine; P, phosphate; Rha, L-rhamnose. Lipid A is buried in the outer membrane. (b) Molecular model of an Escherichia coli lipopolysaccharide. The lipid A and core polysaccharide are straight; the O side chain is bent at an angle in this model. (Prescott et al., 2002).

Figure 1.11. The three major, covalently linked regions that form the typical LPS. (Baron, 1996) http://gsbs.utmb.edu/microbook/ch002.htm by Milton R.J. Salton and Kwang-Shin Kim).

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1.2.4. Capsules Some bacterial cells produce a capsule or a slime layer above the bacterial cell wall (Figure 1.12).

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Figure 1.12. Capsules of Streptococcus pneumoniae. (Moat et al., 2002).

They are highly hydrated (>95% water) and loosely arranged polymers of carbohydrate and protein. Capsules are composed of polysaccharides (high molecular-weight polymers of carbohydrates), and a few consist of protein or polymers of amino acids called polypeptides (often formed from the D- rather than the L-isomer of an amino acid). The capsule of Streptococcus pneumoniae type III is composed of glucose and glucuronic acid in alternating β-1, 3- and β-1, 4- linkages (Moat et al., 2002):

Bacillus anthracis, the anthrax bacillus, produces a polypeptide capsule composed of Dglutamic acid subunits. Capsule may be thick or thin, rigid or flexbible, depending on specific organism. Several different terms can be found to describe the capsule layer, such as slime layer, glycocalyx (defined as the polysaccharide-containing material lying outside the cell), extra-cellular polysaccharide (EPS). Capsules polymers are usually acidic in nature although capsules can consist of neutral polysaccharide, charged polysaccharide or charged polypeptide. Capsule arrangement is important to metal binding (Urrutia, 1997; Madigan et al., 2000; Moat et al., 2002).

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1.2.5. S-Layers Many prokaryotes contain a cell surface layer composed of a two-dimensional array of protein, or glycoprotein, called S-layers or paracrystalline surface layer. S-layers have a crystalline appearance in p1, p2, p4, p6 symmetry, such as hexagonal (p6) and tetragonal (p4), depending on the number and structure of protein or glycoprotein subunits of which they are composed. Non-covalent interactions, such as hydrogen bonding, electrostatic attraction, and salt-bridging, are involved in the attachment between neighboring subunits and the underlying wall. Commonly, divalent metal cations contribute to the correct assembly of the structure. Metals can also be bound after assembly. S-layers are associated with LPSs of gram-negative or peptidoglycan of a gram-postivie cell (Urrutia, 1997; Madigan et al., 2000).

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1.3. FUNGI Microscopic fungi include yeasts with spherical budding cells and molds with elongate filamentous hyphae in mycelia. The molds are filamentous fungi, such as Penicillium, Aspergilis, etc. The body or vegetative structure of a fungus is called a thallus, which varies in complexity and size from the single-cell microscopic yeasts to multi-cellular molds. A single filament is called a hypha. Hyphae usually grow together, collectively called a mycelium. Classification of fungi was showed in table 1.2. Apart from of the Omycetes, which are phylogenetically distinct, the other groups of fungi are closely related. Yeasts are unicellular fungi—mainly ascomycetes. Fungi may be grouped into molds or yeasts based on the development of the thallus, which is the body or vegetative structure of a fungus. Yeasts are unicellular fungi. Yeasts reproduce either asexually by budding and transverse division or sexually through spore formation. A mold consists of long, branched, threadlike filaments of cells, the hyphae, that form a tangled mass called a mycelium. Hyphae may be either septate or coenocyticc. The mycelium can produce reproductive structures (Prescott et al., 2002). Table 1.2. Classification of fungi Group Ascomycetes

Common Name Sac fungi

Hyphae Septate

Typical Representative Neurospora, Saccharomyces, Morchella

Basidiomycetes

Septate

Amanita, Agaricus

Zygomycetes

Club fungi, mushroom Bread molds

Coenocytic

Mucor, Rhizopus

Oomycetes

Water molds

Coenocytic

Allomyces

Deuteromycetes

Fungi imperfecti

Septate

Penicillium, Aspergillus, Candida

Adapted from Madigan et al. (2000).

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c

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Figure 1.13. Hyphae. Drawings of (A) coenocytic hyphae and (B) hyphae divided into cells by septa. (C) Drawing of a multi-perforate septal wall structure. (Prescott et al., 2002).

Most fungi are filamentous. Hyphae structures are shown in figure 1.13. The hyphae are typically 5~10 μm wide but may vary from 0.5μm to 1.00 mm according to the species (Lester and Birkettn, 1999). The mycelium is composed of a complex mass of filaments or hyphae. The hyphae have walls which are composed of cellulose or chitin or both. A common cytoplasm exists throughout the hyphae. Thus fungi cellular organization has three types: (i) coenocytic, where the hypha contains a mass of multinucleate cytoplasm, also called as aseptate; (ii) septate with uninucleate protoplasts, where the hypha is divided by cross-walls or septa, each compartment containing a single nucleus; and (iii) septate with multinucleate protoplasts between the septa. In septate species there is a central pore in the septum connecting the cytoplasm of neighboring cells and permitting the migration of both cytoplasm and nuclei (Lester and Birkettn, 1999). The yeasts provide an example of a unicellular fungus. Generally yeast cells are larger than bacteria, vary considerably in size. Typical yeast cell is about 2.5 to 10 μm wide by 4.5 to 21 μm long. Yeast cells morphology are commonly spherical to oval shaped and will varied, depending on the yeast species, nutrition level, culture condition. The cells of most microscopic fungi grow in loose associations or colonies. Yeasts reproduce either asexually by budding and transverse division or sexually through spore formation. Each bud that separates can grow into a new yeast, and some group together to form colonies. Most yeast reproduced only as single cells, however some yeasts can form filaments under some conditions. Some yeasts exhibit sexual reproduction by a process called mating. The colonies of yeasts are much like those of bacteria because they have a soft, uniform texture and

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appearance. The most important commercial yeasts are the baker’s and brewer’s yeasts, which are member of the genus Saccharomyecs (Madigan et al., 2000). Baker’s and brewer’s yeasts are easily manipulable eukaryotic cells, thus are excellent models for the study of many important problems in eukaryotic biology. S. cerevieiae is a famous model eukaryote for scientific studies, and was the first eukaryote to have its genome completely sequenced. In general, yeast cells have a cell wall, cytoplasmic membrane, cytoplasm and inclusions, a single nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus, vacuoles, cytoskeleton, and glycocalyx. The yeasts have no flagella but do possess most of the other eucaryotic organelles. Typical yeast cell structure was showed in figure 1.14.

Figure 1.14. Diagrammatic drawing of a yeast cell showing typical morphology. For clarity, the plasma membrane has been drawn separated from the cell wall. In a living cell the plasma membrane adheres tightly to the cell wall (Prescott et al., 2002).

Saccharomyces cerevisiae is a species of budding yeast. "Saccharomyces" derives from Greek, and means "sugar mold". "cerevisiae" comes from Latin, and means "of beer". It is perhaps the most useful yeast owing to its use since ancient times in baking and brewing. It is believed that it was originally isolated from the skins of grapes (one can see the yeast as a component of the thin white film on the skins of some dark-colored fruits such as plums; it exists among the waxes of the cuticle). It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model prokaryote. It is the microorganism behind the most common type of fermentation. Saccharomyces cerevisiae cells are round to ovoid, 5–10 μm in diameter. It reproduces by a division process known as budding. The cell walls of the fungi and algae are rigid and provide structural support and shape, but they are different in chemical composition from procaryotic cell walls. Fungal cell walls are mainly 80-90% polysaccharide, with proteins, lipids, polyphosphates, and inorganic ions making up the wall-cementing matrix. Chitin is a common constituent of fungal cell walls. Chitin is a strong but flexible nitrogen-containing polysaccharide consisting of Nacetylglucosamine residues. Two layers were observed in ultra-structural studies of the fungal

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cell walls (figure 1.15): a thin outer layer consisting of mixed glycans (such as glucans, mannans, or galactans), and a thick inner mcirofibrillar layer of polysaccharide fibers composed of chitin or cellulose with chitin chains in parallel arrangement, sometimes of cellulose chains or in certain yeasts, noncellulosic gulcan (Remacle, 1990;Talaro and Talaro, 2002). The structures of cellulose, chitin, glucan, manna were showed in figure 1.16.

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Figure 1.15. Glycocalyx structure. Cross section through the tip of a fungal cell to show the general structure of the cell wall and other features. Top: Photomicrograph. (S, growing tip; CV, coated vesicles; G, Golgi apparatus; M, mitochondrion.) Bottom: The cell wall is a thick, rigid structure composed of complex layers of polysaccharides and proteins (Talaro and Talaro, 2002).

Figure 1.16. Structures of cellulose, chitin, glucan, manna.

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The cell membrane of eucaryotic cells is a thin, double-layered sheet composed of lipids such as phospholipids and sterols (averaging about 40% of membrane content) and protein molecules (averaging about 60%) (figure 1.17). Sterols are different from phospholipids in both structure and behavior.

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Figure 1.17. Schematic cell membrane structure (Talaro and Talaro, 2002).

Fluid mosaic model for membrane structure are widely accepted: a membrane is a continuous bilayer formed by lipids that are oriented with the polar lipid heads toward the outside and the nonpolar heads toward the center of the membrane. Embedded at numerous sites in this bilayer are various sized globular proteins. Some cell membranes are so thin—on the average, just 7 nm thick. Cytoplasmic membranes served as selectively permeable barriers in transport. Unlike procaryotes, eucaryotic cells also contain a number of individual membrane-bound organelles that are extensive enough to account for 60% to 80% of their volume (Prescott et al., 2002; Talaro and Talaro, 2002). The cytoplasm contains the organelles characteristic of eukaryotic organisms including mitochondria, ribosomes and an extensive endoplasmic reticulum. Vacuoles containing storage materials such as glycogen, lipids and volutin are also present. In a unicellular fungus such as the yeast, Saccharomyces spp. the protoplast is enclosed in a semi-permeable membrane, the plasma membrane, which is contained within a rigid cell wall. In filamentous species the protoplasm is concentrated in the tips of the young growing hyphae. The older hyphae are usually metabolically inactive and contain large vacuoles in their cytoplasm. The fungi all lack chlorophyll and are heterotrophic. A mycelium normally develops from the germination of a single reproductive cell or spore. Germination initially results in the production of a single long hypha which subsequently branches and ramifies to form a mass of hyphae which constitutes the mycelium.

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1.4. ALGAE

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Algae abound in nature in aquatic habitats, freshwater, marine and moist soil. Algae contain chlorophyll and carry out oxygenic photosynthesis. It should be noticed that algae are distinct from cyanobacteria, which are also oxygenic phototrophs, but are eubacteria (true bacteria), and are therefore evolutionarily distinct from algae. In biosorption, various algae were used for testing as metal biosorbents. The major groups of algae were listed in table 1.3, based on their type of pigments, cell wall, stored food materials, and body plan (Talaro and Talaro, 2002). Several characteristics are used to classify algae, including the nature of the chlorophyll(s), the cell wall chemistry, flagellation, form in which food or assimilatory products of photosynthesis are stored, cell morphology, habitat; reproductive structures; life history patterns, etc. The important differences between brown algae and other algae are in the storage products they utilize as well as in their cell wall chemistry, shown in table 1.3 (Madigan et al., 2000; Prescott et al., 2002; Davis et al., 2003). The ultra-structure of the algal cell was showed in figure 1.18. The algal cell is surrounded by a thin, rigid cell wall. In euglenoids, cell wall is absent. Some algae have an outer matrix lying outside the cell wall, similar to bacterial capsules. The nucleus has a typical nuclear envelope with pores; within the nucleus are a nucleolus, chromatin, and karyolymph. The chloroplasts have membrane-bound sacs called thylakoids that carry out the light reactions of photosynthesis. These organelles are embedded in the stroma where the dark reactions of carbon dioxide fixation take place. A dense proteinaceous area, the pyrenoid that is associated with synthesis and storage of starch may be present in the chloroplasts. Mitochondrial structure varies greatly in the algae. Some algae (euglenoids) have discoid cristae; some, lamellar cristae (green and red algae); and the remaining, (golden-brown and yellow- green, brown, and diatoms) have tubular cristae (Prescott et al., 2002).

Figure 1.18. Algal Morphology. Schematic drawing of a typical eucaryotic algal cell showing some of its organelles and other structures (Prescott et al., 2002).

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Table 1.3. properties of major groups of algae Group

Common name

Morphology

Pigments

Typical representative

Chrysophyta

Yellow-green and goldenbrown algae; diatoms)

Unicellular

Chlorophlls a and c

Navacul

Euglenophyt a

Euglenoids

Unicellular, photosynthetic euglenoid flagellates

Chlorophlls a and b

Euglena

Pyrrhophyta Charophyta Chlorophyta

Dinoflagellates Stoneworts Green algae

Phaeophyta

Brown algae

Rhodophyta

Red algae

Carbon reserve materials Lipids

Pramylon (β1,2-glucan)

Cell walls

Major habitats

Kindom

Many have two overlapping components made of silica No wall present

Freshwater, marine, soil

Protista (single cell or colonial; eucaryotic)

Freshwater, a few marine

Protista

Unicellular to leafy

Chlorophlls a and b

Chlamydomona s

Starch (α1,4-glucan)

Cellulose

Filamentousto leafy, occasionally massive and plantlike Unicellular, filamentous to leafy

Chlorophlls a and c, xanthophylls

Laminaria

Laninarin (β1,3-glucan), mannitol

Cellulose

Freshwater, soil, a few marine Marine

Chlorophlls a and d, phycocyanin, phycoerythrin

Polysiphonia

Floridean starch (α-1,4and α-1,6glucan), fluoridoside (glycerolgalactoside)

Cellulose

Marine

Adapted from Madigan et al. (2000) and Prescott et al. (2002).

Protista Protista Protista

Plantae (multicellul ar; eukaryotic) Plantae

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Algae cell wall show considerable variation in their structure and chemistry. The cell wall contains a network of cellulose fibril, and usually modified by the addition of other polysaccharides such as pectin (highly hydrated polygalacturonic acid containing small amounts of the hexose rhamnose), xylans, mannans, alginic acids, or fucinic acid. Sometimes chitin also occurs in the algae cell wall. Algae cell walls contain pores about 3-5 nm wide to allow pass only low molecular-weight substances such as water, inorganic ions, gases and other small nutrient substances for metabolism and growth. It is usually made of a multilayered microfibrillar framework, generally consisting of cellulose and intersperse with amorphous material (Madigan et al., 2000). The cellulose can be replaced by xylan in the Chlorophyta and Rhodophyta in addition to mannan in the Chlorophyta. The Phaeophyta algal mainly contain alginic acid or alginate (the salt of alginic acid) with a smaller amount of sulfated polysaccharide (fucoidan). The Rhodophyta contains a number of sulfated galactans. Both the Phaeophyta and Rhodophyta are potentially excellent heavy metal biosorbents, because two divisions contain the largest amount of amorphous embedding matrix polysaccharides and their well-known metal binding ability (Davis et al., 2003). The Chlorophyta or green algae are an extremely varied division. They have chlorophylls a and b along with specific carotenoids, and store carbohydrates as starch. Many have cell walls of cellulose. They can present in unicellular, colonial, filamentous, membranous or sheet-like, and tubular types. Green algae are associated with the land plants and have mitochondria with lamellar cristae (Prescott et al., 2002). Most Rhodophyta or red algae are filamentous and multicellular. The stored food is the carbohydrate called floridean starch composed of α-1,4 and α-1,6 linked glucose residues. The cell walls of most red algae include a rigid inner part composed of microfibrils and a mucilaginous matrix. The matrix is composed of sulfated polymers of galactose called agar, funori, porphysan, and carrageenan, which are responsible for flexible, slippery texture of the red algae. Agar is used extensively in the laboratory as a culture medium component. Many red algae also deposit calcium carbonate in their cell walls and play an important role in building coral reefs (Prescott et al., 2002). The Phaeophyta or brown algae have been proved most effective biosobent for metals based on statistical review among those algae tested in biosorption (Romera et al., 2006). Davis et al. (2003) summarized the characteristics of brown algae and other algae in a review paper. The cellular structure and biochemistry were introduced in detail, including cellular structure, storage polysaccharides, cell wall and extracellular polysaccharides, extracellular polysaccharides (fucoidan and alginic acid). Among thirteen orders in the Phaeophyta; however, only Laminariales and Fucales are important from the point of view of biosorption (Davis et al., 2003). Laminariales, also called as ‘‘kelps’’, have many commercial uses (e.g. water holding property for frozen foods, syrups, and frozen deserts; gelling property for instant puddings and dessert gels, or even explosives; emulsifying properties for polishes; stabilizing properties in ceramics, welding rods and cleaners). The well-known algal genus Sargassum belong to the order Fucales, and have shown good metal capacity (Davis et al., 2003). Brown algae are multicellular and occur almost exclusively in the sea. Most of the conspicuous seaweeds that are brown to olive green in color are assigned to this division. The main storage product is laminarin, similar to chrysolaminarin in structure. The algal cell wall, similar to the fungal cell wall in structure, is made of multilayered microfibrillar framework, generally consisting of cellulose and interspersed with amorphous material. The algal cell wall is complex, and even more than ten layers can be found in certain

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algal cell wall. The microfibrils can be organized in parallel or randomly. The amorphous embedding matrix consist of glycoproteins. The cellulous accounted for 90% in the algal cell wall. The algal cells covered by mucilaginous layers bind metal due to the presence of uronic acids (Remacle, 1990). Figure 1.19 showed the cell wall structure of brown algae. The cell wall of algae is composed of at least two different layers. The innermost layer consists of a microfibrillar skeleton, and the outer layer is an amorphous embedding matrix, which does not penetrate the fibers, but rather is attached to this layer via hydrogen bonds. The inner layer of brown algae is mainly comprised of the uncharged cellulose polymer (β-1,4-linked unbranched glucan; figure 1.20a). Two other fibrillar molecules, xylan (principally β-1,3-linked D-xylose) and mannan (β-1,4-linked linked D-mannose) occur in the red and green algae (figure 1.20b,c). Alginate contributes to the strength and flexibility to the cell wall of brown algae. Cellulose remains the principal structural component even if alginate occurs in the inner layer. Fucoidan is present not only in the matrix but also within the inner cell wall.

Figure 1.19. Cell wall structure in the brown algae (Davis et al., 2003).

Structures of algal cellulose, xylan, manna, fucoidan and alginate were illustrated in figures 1.20 and 1.21. The molecular structure of cellulose as a carbohydrate polymer comprises of repeating β-D-glucopyranose units, which are covalently linked through acetal functions between the OH group of the C4 and C1 carbon atoms (β-1,4-glucan). Cellulose is a large, linear-chain polymer with a large number of hydroxyl groups (three per anhydroglucose (AGU) unit) and present in the preferred 4C1 conformation. To accommodate the preferred bond angles, every second AGU unit is rotated 180° in the plane. The length of the polymeric cellulose chain depends on the number of constituent AGU units (degree of polymerisation, DP) and varies with the origin and treatment of the cellulose raw material. Cellulose has a ribbon shape allowing it to twist and bend in the direction out of the plane, thus making the molecule moderately flexible. There is a relatively strong interaction between neighboring cellulose molecules in dry fibres due to the presence of the hydroxyl (– OH) groups, which stick out from the chain and form intermolecular hydrogen bonds. Regenerated fibres from cellulose contain 250–500 repeating units per chain. Cellulose is hydrophilicity, chirality and degradability. Chemical reactivity is largely due to the high donor reactivity of the OH groups (O'Connell et al., 2008).

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Figure 1.20. The fibrillar molecules of algal cell walls. (a) Algal cellulose, a β-1,4-linked unbranched glucan, of the brown algae; (b) structural units present in xylan from the red algae, both β-1,3- and β1,4-linked forms have been isolated; (c) mannan, a β-1,4-linked D-mannose from the red algae; (d) The structure of fucoidan, a branched polysaccharide sulfate ester with l-fucose building blocks as the major component with predominantly α -1,2-linkages (Davis et al., 2003).

Figure 1.21. Alginate structural data: (a) alginate monomers (M vs.G); (b) the alginate polymer; (c) chain sequences of the alginate polymer (Davis et al., 2003).

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1.5. CHEMICAL FUNCTIONAL GROUPS RELATED TO THE BIOSORPTION According to the metal classification of Pearson (1963) as well as Nieboer and Richardson (1980), metal affinity for ligands was supposed and illustrated in table 1.4 (Remacle, 1990). The symbol R represents an alkyl radical such as CH2–, CH3CH2–, etc. Class A metal ions preferred to bind the ligands of I through oxygen. Class B metal ions show high affinity for III types of ligands, but also form strong binding with the ligands with II types of ligands. Borderline metal ions could bind these three types of ligands with different preferences. According to the Hard and Soft Acid Base Principle (HSAB principle), hard ions which bind F- strongly, such as Na+, Ca2+, Mg2+ could form stable bonds with OH-, HPO42-, CO32+, R–COO- and =C=O, which are oxygen-containing ligands. Contrast to hard ions, soft ions, heavy metal ions, such as Hg2+ and Pb2+ form strong bond with CN-. R–S-, –SH-, NH2- and imidazol, which are groups containing nitrogen and sulfur atoms. Borderline or intermediate metal ions, such as Zn2+ and Co2+ are less toxic. Hard ions mainly show ionic nature of binding, whereas soft ions binding exhibit a more covalent degree (Pearson, 1963;Nieboer and Richardson, 1980; Remacle, 1990). Metal biosorption by biomass mainly depend on the components on the cell especially through cell surface and the spatial structure of the cell wall. Peptidoglycan, teichoic acids and lipoteichoic acids are all important chemical components of bacteria surface structures. Various polysaccharides, including cellulose, chitin, alginate, glycan, etc. in fungi or algae cell walls have been proved to play a very important role in metal binding. Various proteins are also proved to involve in metal binding by certain biomass. Some functional groups have been found to bind metal ions, especially carboxyl group. There is some evidence to confirm the O, N, S, or P containing groups participate directly in certain metals. More information could refer to Chapter 4. Table 1.5 offers a representative functional groups and classes of organic compounds in biomass. The symbol R is shorthand for residue, and its placement in a formula indicates that what is attached at that site varies from one compound to another (Talaro and Talaro, 2002). Table 1.4. Ligands present in biological systems and three class of metal

I: Ligands prefered by Class A II: Other important ligands III: Ligands prefered by Class B:

Ligands F-, O2-, OH-, H2O, CO32-, SO4-, ROSO3-, NO3-, HPO42-, PO43-, ROH, RCOO-, C=O, ROR Cl-, Br-, N3-, NO2-, SO32-, NH3, N2, RNH2, R2NH, R3N, =N-, CO-N-R, O2, O2-,O22H-, I-, R-, CN-, CO, S2-, RS-, R2S, R3As

Metal class Class A: Li, Be, Na, Mg, K, Ca, Sc, Rb, Sr, Y, Cs, Ba, La, Fr, Ra, Ac, Al, Lanthanides, Actinides Borederline ions: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Cd, In, Sn, Sb, As Class B: Rh, Pd, Ag, Lr, Pt, Au, Hg, Tl, Pb, Bi

Adapted from Pearson (1963), Nieboer and Richardson (1980) and Remacle (1990).

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Table 1.5. The representative functional groups and classes of organic compounds in biomass

Adapted from Talaro and Talaro (2002).

ACKNOWLEDGMENTS The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 50830302; 50808111; 50278045), China Postdoctoral Science Foundation funded project (Grant No. 20080430350), special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (Grant No. 08K05ESPCT) and the Basic Research Fund of Tsinghua University (Grant No. JC2002054), to carry out the relevant research works.

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REFERENCES

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Baron S., Medical Microbiology. 4th ed. Galveston, U.S.A: The University of Texas Medical Branch; 1996. Davis T. A., Volesky B., Mucci A., Water Res. 37(2003) 4311-4330. Lester J. N., Birkettn J. W.. Microbiology and chemistry for environmental scientists and engineers. London, UK: Spon Press; 1999. Madigan M. T., Martinko J. M., Parker J., Brock biology of microorganisms. 9th ed ed. Upper Saddle River, NJ: Pearson Prentice Hall; 2000. Moat A. G., Foster J. W., Spector M. P., Microbial physiology. 4th ed. New York: WileyLiss, Inc.; 2002. Nieboer E., Richardson D. H. S., Environ. Pollut. Ser. B 1 (1980) 3-26. O'Connell D. W., Birkinshaw C., O'Dwyer T. F., Bioresour. Technol. 9(2008) 6709-6724. Pearson R. G., J. Am. Chem. Soc. 85 (1963) 3533-3539. Prescott L. M., Harley J. P., Klein D. A., Microbiology. Fifth ed: McGraw-Hill Science/Engineering/Math; 2002. Remacle J., In: Biosorption of heavy metals. Edited by Volesky B. Boca Raton: CRC Press; 1990. Romera E., Gonzalez F., Ballester A., Blazquez M. L., Munoz J. A., Crit. Rev. Biotechnol. 26(2006) 223-235. Talaro K. P., Talaro A., Foundations in Microbiology. 4th ed. Blacklick, Ohio, U.S.A.: McGraw-Hill College; 2002. Tortora G. J., Funke B. R., Case C, L., Microbiology: An Introduction. 8th ed. San Francisco: The Benjamin/Cummings Publishing Company, Inc.; 2004. Urrutia M. M., In: Biosorbents for Metal Ions. Edited by Wase J, Forster C. London, UK: CRC Press; 1997.

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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In: Fundamentals and Applications of Biosorption… ISBN: 978-1-60741-169-7 Ed: Yu Liu and Jianlong Wang © 2009 Nova Science Publishers, Inc.

Chapter 2

BIOSORBENTS Can Chen and Jianlong Wang

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2.1. TYPES OF BIOSORBENTS The capability of some microorganisms to accumulate metallic elements have been observed, and numerous research papers have been published from toxicological points of view at first, but these were concerned with the accumulation due to the active metabolism of living cells, the effects of metal ions on the metabolic activities of the microbial cell and the consequences of accumulation on the food chain (Volesky, 1987). However, further researches have revealed that inactive/dead microbial biomass can passively bind metal ions via various physicochemical mechanisms. With this new findings, research on biosorption became active, with numerous biosorbents of different origins being proposed for the removal of pollutants, such as metals and dyes. Researchers have understood and explained that biosorption depends not only on the type or chemical composition of the biomass, but also on the external physicochemical factors and solution chemistry. The mechanisms responsible for biosorption have been studied, they may be one or combination of ion exchange, complexation, coordination, adsorption, electrostatic interaction, chelation and microprecipitation (Vegliò and Beolchini, 1997; Volesky, 1990 ;Vijayaraghavan and Yun, 2008). Strong biosorbent behavior of certain types of microbial toward metallic ions is a function of the chemical makeup of the microbial cells of which it consists. It is necessary to emphasize that this type of active biomass consists of dead and metabolically inactive cells. This aspect is particularly important when it comes to the process application, whereby new biosorbents represent “chemicals” capable of sequestering a relatively large amount of the metal (Volesky and Holan, 1995). A large quantity of materials has been tested as biosorbents for the removal of metals or organics extensively. The tested biosorbents basically come under the following categories: bacteria (e.g. Bacillus subtillis), fungi (e.g. Rhizopus arrhizus), yeast (e.g. S. cerevisae), algae, industrial wastes (e.g., S. cerevisae waste microbes from fermentation and food

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Can Chen and Jianlong Wang

industry), agricultural wastes (e.g. corn core) and other polysaccharide materials, etc. (Vijayaraghavan and Yun, 2008). Those tested biomasses have been reported to bind a variety of heavy metals to different extents (Gupta et al., 2000). Some potential biomaterials with high metal binding capacity have been identified in part. Some types of biosorbents binding and collecting the majority of heavy metals with no specific priority, while others can even be specific for certain types of metals (Volesky and Holan, 1995). The role of some groups of micro-organisms has been well reviewed, such as algae, bacteria, fungal, yeast, etc. Volesky and Holan (1995) have presented an exhaustive list of microbes and their metal-binding capacities. From the published reviews and other related references, potent biosorbent materials among easily available biomass types are from all three groups: algae, fungi, and bacteria, the former two perhaps giving broader choices. Waste material or byproduct biomass from largescale fermentation processes is the source of the raw materials for the new family of biosorbents conveniently. In particular, some waste mycelia available in large quantities indicate an interesting potential of these biomass types in the collection and removal of heavy metals. Some of this work has been reviewed during past ten years (Kapoor and Viraraghavan, 1995; Wang and Chen, 2006). Seaweeds from the oceans produced in copious quantities are another inexpensive source of biomass. The research group led by Volesky contributed a lot on marine algae, especially brown alage such Sargassum seaweed (Davis et al., 2003c). Abundant natural materials, particularly of cellulosic nature, have been suggested as potential biosorbents for heavy metals. For economic reasons, other low-cost biosorbents are of interest recently, such as agricultural wastes. Kratochvil and Volesky (1998) pointed out that the first major challenge for the biosorption field was to select the most promising types of biomass from an extremely large pool of readily available and inexpensive biomaterials. Although many biological materials bind heavy metals, only those with sufficiently high metal-binding capacity and selectivity for heavy metals are suitable for use in a full-scale biosorption process. Although this task is not complete, a large number of biomass types have been tested for their metal binding capability under various conditions, and a summary of metal-biosorption results has been published. One major challenge in the biosorption field is to continue to search for and select readily available and inexpensive biomaterials (Kratochvil and Volesky, 1998). Tedious experimental screening of selected readily available types of biomass is still the basis for discovering new biosorbents when the phenomenon of metal biosorption was not better understood. Although this task is rather large, a large number of biomass types have been tested for their metal binding capability under various conditions, and a summary of metal-biosorption results has been published. The published work on testing and value the performance of biosorbents offered a good basis for looking for new and potentially feasible metal biosorbents. In this section, the performance of various biosorbents was reviewed based on the large quantity of published references. In the following sections, bacteria, filamentous fungi and yeast, marine algae among the various biosorbents were introduced. Tables 2.1-2.7 summarize most of the more consistent attempts to identify metal-sorbing biomass types according to several groups of biosorbents. Because of the different criteria used by the authors in searching for suitable material, the results of these studies varied widely, and had been reported in different units and in many different ways, which often make quantitative comparison impossible. Some used easily available biomass types, others specially isolated strains, and some processed the raw

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Biosorbents

biomass to a certain degree to improve its biosorption application properties. It should be noted that comparing results from different sources involves standardizing the different ways in which the sorption capacity may be expressed. However, these tables could offer valuable information on biosorption performance (Volesky and Holan, 1995). According to the statistic review on biosorption (Romera et al., 2006), algae have been less used as biosorbent material than other kinds of biomass, especially fungi and bacteria (15.31% in the former case and 84.69% in the second).

2.2. BACTERIA Bacteria are the most abundant and versatile of the microorganism and constitute a significant fraction of the entire living terrestrial biomass of about 1018 g (Mann, 1990). Early 1980 some microorganisms were known to accumulate metallic elements with high capacity (Vijayaraghavan and Yun, 2008). Some marine microorganisms enriched Pb and Cd by factors of 1.7×105 and 1.0×105 respectively, relative to the aqueous solute concentration of these elements in ocean waters (Mann, 1990). Bacteria were used as biosorbents because of their small size, their ubiquity, their ability to grow under controlled conditions, and their resilience to a wide range of environmental situations (Urrutia, 1997). Bacteria species such as Bacillus, Pseudomonas, Streptomyces, Escherichia, Micrococcus, etc, have been tested for uptake metals or organics. Table 2.1 summarizes some of the important results of metal biosorption using bacterial biomasses, mainly according to the references of (Ahluwalia and Goyal, 2007, Vijayaraghavan and Yun, 2008). Table 2.1 also provides basic information to evaluate the possibility of using bacterial biomass for the uptake of metal ions.

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Table 2.1. Bacterial biomass used for metal removal metal

Bacteria species

Operating conditions: pH Temp(°C) Other information

Pb Pb

Bacillus sp. Bacillus firmus

3.0 25 M=2 g l-1, teq=2 h

Pb

Corynebacterium glutamicum Enterobacter sp. Pseudomonas aeruginosa Pseudomonas aeruginosa Pseudomonas putida Pseudomonas putida Streptomyces rimosus a

5.0 20±2 M=5 g l-1, teq=2 h

Pb Pb Pb Pb Pb Pb

5.0 25 teq=24 h 5.5 NA M=1–2 g l-1; teq=24 h 5 50 M=200 g l-1 5.5 25 M=1 g l-1, teq=24 h 6.5 NA NA NA NA M=3 g l-1; teq=3 h

Metal uptake (mg/g) 92.3 (E) 467

References

567.7 (E) 50.9 (L) 79.5 (L)

(Tunali et al., 2006) (Salehizadeh and Shojaosadati, 2003) (Choi and Yun, 2004) (Lu et al., 2006) (Chang et al., 1997)

0.7 (L)

(Lin and Lai, 2006)

270.4 (L) 56.2 (L)

(Uslu and Tanyol, 2006) (Pardo et al., 2003)

135.0 (L)

(Selatnia et al., 2004c)

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Can Chen and Jianlong Wang Table 2.1. (Continued).

metal

Bacteria species

Zn

Streptomyces rimosus Bacillus firmus

Zn Zn

Metal uptake (mg/g) 30 418 133.0 (L) 6.9 (L)

5.0 30 M=1 g l-1; teq=24 h 7.5 20 M=3 g l-1

17.7 (L)

(Chen et al., 2005)

30.0 (L)

(Mameri et al., 1999)

7.5 20 M=3 g/l

80.0 (L)

(Mameri et al., 1999)

5.5 28±3 M=2 g/l, teq=0.5 h 6.0 25 M=0.2 g l-1, teq=2 h 6.0 40 M=300 g l-1; teq=2 h

21.3 (E)

(Puranik and Paknikar, 1997) (Celaya et al., 2000)

Cu Cu

Bacillus sp. Bacillus subtilis

5.0 25 M=2 g l-1, teq=2 h 5 25 M=0.5 g l-1, teq=1 h

16.3 (E) 20.8 (L)

Cu Cu

Enterobacter sp. Micrococcus luteus Pseudomonas aeruginosa Pseudomonas cepacia Pseudomonas putida Pseudomonas putida Pseudomonas putida Pseudomonas stutzeri Sphaerotilus natans

5.0 25 teq=24 h 5 25 M=0.5 g l-1, teq=1 h

32.5 (L) 33.5 (L)

5.0 NA M=1–2 g l-1; teq=24 h 7 30 NA

23.1 (L) 65.3 (L)

6.0 NA NA

6.6 (L)

5.5 30 M=1 g l-1, teq=24 h 4.5 30 M=1 g l-1; teq=24 h 5 25 M=0.5 g l-1, teq=1 h

96.9 (L) 15.8 (L) 22.9 (L) 60 (E)

Zn Zn Zn Zn Zn

Cu Cu Cu Cu Cu Cu Cu

(Mameri et al., 1999)

6.5 30 M=0.2 g l-1, teq=1 h 7.0 NA NA

Cu

Zn

References

(Salehizadeh and Shojaosadati, 2003) (Incharoensakdi and Kitjaharn, 2002) (Pardo et al., 2003)

Aphanothece halophytica Pseudomonas putida Pseudomonas putida Streptomyces rimosus Streptomyces rimosus a Streptoverticillium cinnamoneum a Thiobacillus ferrooxidans a Thiobacillus ferrooxidans a Bacillus firmus

Zn

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Operating conditions: pH Temp(°C) Other information

6 NA M=3 g l-1; teq=0.5 h

82.6 (L) 172.4 (L) 381

(Liu et al., 2004) (Salehizadeh and Shojaosadati, 2003) (Tunali et al., 2006) (Nakajima et al., 2001) (Lu et al., 2006) (Nakajima et al., 2001) (Chang et al., 1997) (Savvaidis et al., 2003) (Pardo et al., 2003) (Uslu and Tanyol, 2006) (Chen et al., 2005) (Nakajima et al., 2001) (Beolchini et al., 2006)

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Biosorbents Table 2.1. (Continued). Metal

Bacteria species

Cu

Cd

Sphaerotilus natans b Streptomyces coelicolor Thiobacillus ferrooxidans a Ochrobactrum anthropi Sphingomonas paucimobilis Aeromonas caviae

Cd

Enterobacter sp.

6.0 25 teq=24 h

Cd

Pseudomonas aeruginosa Pseudomonas putida Pseudomonas sp.

6.0 NA M=1–2 g/l; teq=24 h 6.0 NA NA

Cu Cu Cd Cd

Cd Cd

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Cd

Cr(IV)

Staphylococcus xylosus Streptomyces pimprina a Streptomyces rimosus a Streptomyces rimosus a Bacillus coagulans Bacillus megaterium Zoogloea ramigera

Cr(IV)

Aeromonas caviae

Cr(IV)

Bacillus coagulans

Cr(IV)

Bacillus licheniformis Bacillus megaterium

Cd Cd Fe(III) Cr(IV) Cr(IV)

Cr(IV)

Operating conditions: pH Temp(°C) Other information 5.5 30 NA

Metal uptake (mg/g) 5.4 (L)

5.0 25 M=1 g l-1; teq=8 h

66.7 (L) 39.84 (L) --

5.0 40 M=300 g l-1; teq=2 h

7.0 20 M=1 g l-1; teq=2 h

7.0 NA M=1 g l-1, teq=1.5 h 6.0 NA M=1 g l-1, teq=1.5 h 5.0 NA teq=1 h 8.0 NA M=3 g l-1 NA NA M=3 g l-1; teq=4 h

155.3 (L) 46.2 (L) 42.4 (L) 8.0 (L) 278.0 (L) 250.0 (L) 30.4 (L) 64.9 (L) 122.0 (L) 39.9 30.7 2

2.5 20 M=0.5 g l-1; teq=2 h 2.5 28±3 M=2 g l-1, teq=1 h 2.5 50 M=1 g l-1, teq=2 h 2.5 28±3 M=2 g l-1, teq=1 h

284.4 (L) 39.9 (E) 69.4 (L) 30.7 (E)

References

(Beolchini et al., 2006) (Ozturk et al., 2004) (Liu et al., 2004) (Ozdemir et al., 2003) (Tangaromsuk et al., 2002) (Loukidou et al., 2004) (Lu et al., 2006) (Chang et al., 1997) (Pardo et al., 2003) (Ziagova et al., 2007) (Ziagova et al., 2007) (Puranik et al., 1995) (Selatnia et al., 2004a) (Selatnia et al., 2004b) (Srinath et al., 2002) (Srinath et al., 2002) (Nourbakhsh et al., 1994) (Loukidou et al., 2004) (Srinath et al., 2002) (Zhou et al., 2007) (Srinath et al., 2002)

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Can Chen and Jianlong Wang Table 2.1. (Continued).

Metal

Bacteria species

Cr(IV)

Bacillus thuringiensis Pseudomonas sp.

Cr(IV) Cr(IV) Fe Ni

Pd

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Pt

Pt U U U U U U U U U

Staphylococcus xylosus Bacillus biomass Bacillus thuringiensis Streptomyces rimosus a Desulfovibrio desulfuricans Desulfovibrio fructosivorans Desulfovibrio vulgaris Desulfovibrio desulfuricans Desulfovibrio fructosivorans Desulfovibrio vulgaris Arthrobacter nicotianae Bacillus licheniformis Bacillus megaterium Bacillus subtilis Corynebacterium equi Corynebacterium glutamicum Micrococcus luteus Nocardia erythropolis Zoogloea ramigera

Operating conditions: pH Temp(°C) Other information 2.0 25 M=1 g l-1

Metal uptake (mg/g) 83.3 (L)

4.0 NA M=1 g l-1, teq=1.5 h 1.0 NA M=1 g l-1, teq=1.5 h

95.0 (L)

6 35 M=1 g l-1, teq=8 h

45.9 (L)

6.5 NA M=3 g l-1, teq=2 h 2.0 30 M=0.15 g l-1, teq=4 d 2.0 30 M=0.15 g l-1, teq=4 d 2.0 30 M=0.15 g l-1, teq=4 d 2.0 30 M=0.15 g l-1, teq=4 d 2.0 30 M=0.15 g l-1, teq=4 d 2.0 30 M=0.15 g l-1, teq=4 d 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h

32.6 (L)

143.0 (L)

128.2 (L) 119.8 (L) 106.3 (L) 62.5 (L) 32.3 (L) 40.1 (L) 68.8 (E) 45.9 (E) 37.8 (E) 52.4 (E) 21.4 (E) 5.9 (E) 38.8 (E) 51.2 (E) 49.7 (E)

References

(Sahin and Ozturk, 2005) (Ziagova et al., 2007) (Ziagova et al., 2007) (Volesky and Holan, 1995) (Ozturk, 2007) (Selatnia et al., 2004d) (de Vargas et al., 2004) (de Vargas et al., 2004) (de Vargas et al., 2004) (de Vargas et al., 2004) (de Vargas et al., 2004) (de Vargas et al., 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004)

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Biosorbents Table 2.1. (Continued). Metal

Bacteria species

Th

Pseudomonas fluorescens Arthrobacter nicotianae Bacillus licheniformis Bacillus megaterium Bacillus subtilis

Th Th Th Th Th Th Th Th

Corynebacterium equi Corynebacterium glutamicum Micrococcus luteus Zoogloea ramigera

Operating conditions: pH Temp(°C) Other information

3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h 3.5 30 M=0.15 g l-1, teq=1 h

Metal uptake (mg/g) 15 75.9 (E) 66.1 (E) 74.0 (E) 71.9 (E) 46.9 (E) 36.2 (E) 77.0 (E) 67.8 (E)

References

(Ahluwalia and Goyal, 2007) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004) (Nakajima and Tsuruta, 2004)

a

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metal uptake is not necessarily maximum. E=experimental uptake; L=uptake predicted by the Langmuir model; M=biomass dosage, teq=equilibrium time, NA=not available; a=Chemically modified; b=Immobilized.

Bacteria may either possess the capacity for biosorption of many elements or, alternatively, depending on the species, may be element specific. It is likely that, in the future, microorganism will be tailored for a specific element of groups of elements, using recombinant DNA technology which is based on genetic modification using endorestrictive nucleases (Mann, 1990).

2.3. FUNGI Although fungi are a large and diverse group of eukaryotic microorganisms, three groups of fungi have major practical importance: the molds, yeasts and mushrooms. Filamentous fungi and yeasts have been observed in many instances to bind metallic elements. Fungi are ubiquitous in natural environments and important in industrial processes. A range of morphologies are found from unicellular yeasts to polymorphic and filamentous fungi, many of which have complex macroscopic fruiting bodies. Their most important roles are as decomposers of organic material, with concomitant nutrient cycling, as pathogens and symbionts of animals and plants, and as spoilage organisms of natural and synthetic materials, e.g. wood, paint, leather, food and fabrics. They are also utilized as producers of

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Can Chen and Jianlong Wang

economically important substances, e.g. ethanol, citric acid, antibiotics, polysaccharides, enzymes and vitamins (Gadd, 1993). The importance of metallic ions to fungal and yeast metabolism has been known for a long time (Gadd, 1993). The presence of heavy metals affects the metabolic activities of fungal and yeast cultures, and can affect commercial fermentation processes, which created interest in relating the behavior of fungi to the presence of heavy metals. Then results from such studies led to a concept of using fungi and yeasts for the removal of toxic metals (such as lead and cadmium) from wastewater and recovery of precious metals (such as gold and silver) from process waters (Kapoor and Viraraghavan, 1997b). Both living and dead fungal cells possess a remarkable ability for taking up toxic and precious metals. In biosorption, the molds and yeast are of interests and many researches are reported and reviewed. The molds are filamentous fungi. The yeasts are unicellular fungi and most of them are classified with the Ascomycetes. The most important commercial yeasts are the baker’s and brewer’s yeasts, which are members of the genus saccharomyces. The original habitats of these yeasts were undoubtedly fruits and fruit juices , but the commercial yeasts of today are probably quite different from wild strains because they have been greatly improved through the years by careful selection and genetic manipulation eukaryotic cells, and they are thus excellent models for the study of many important problems in eukaryotic biology. Yeast cells are much larger than bacterial cells and can be distinguished microscopically from bacteria by their size and by the obvious presence of internal cell structures, such as the nucleus (Madigan et al., 1997). Fungi and yeasts are easy to grow, produce high yields of biomass and can be manipulated genetically and morphologically. The fungal organisms are widely used in a variety of large-scale industrial fermentation processes. For example, strains of Aspergillus are used in the production of ferrichrome, kojic acid, gallic acid, itaconic acid, citric acid and enzymes like amylases, glucose isomerase, pectinase, lipases and glucanases; while Saccharomyces cerevisiae is used in the food and beverage industries. The biomass can be cheaply and easily procured in rather substantial quantities, also as a byproduct from the established industrial fermentation processes, for the biosorption of heavy metals and radio nuclides, which made the fungi of primary interest as a raw material serving as a basis for formulation suitable biosorobents. The use of biomass as an adsorbent for heavy-metal pollution control can generate revenue for industries presently wasting the biomass and at the same time ease the burden of disposal costs associated with the waste biomass produced. Alternatively, the biomass can also be grown using unsophisticated fermentation techniques and inexpensive growth media (Kapoor and Viraraghavan, 1995). It is not a priority from the economic point of view to use the waste byproduct biomass, but the fungal cultures are also amenable to genetic and morpholocial manipulations which may result in better raw biosrobents material (Volesky, 1990). Thus, this section reviews the removal of heavy metals and radio nuclides by filamentous fungi (Aspergillus sp., Mucor sp., Rhizopus sp. and Penicillium sp.) and yeast (Saccharomyces spp.) from aqueous solutions.

2.3.1. Yeast – Saccharomyces Cerevisiae The yeast biomass may be used successfully as biosorption material for removal of Ag, Au, Cd, Co, Cr, Cu, Ni, Pb, U, Th, Zn from aqueous solution. Yeasts of genera

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Biosorbents

37

Saccharomyces, Candida, Pichia are efficient biosorbents of metals. Most of yeasts can sorb a wide range of metals or be strictly specific in respect of only one metal. Saccharomyces cerevisiae as biosorbents is of special interest (Podgorskii et al., 2004).

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2.3.1.1. Advantages of S. Cerevisiae as Biosorbents in Metal Biosorption S. cerevisiae is the cheapest industrial microbe due to the industrialization production at large scale. Sources of S. cerevisiae include various food and beverage industries. The yeast can be easily grown using unsophisticated fermentation techniques and inexpensive growth media (Kapoor and Viraraghavan 1995) and can produce high yields of the biomass. Moreover, S. cerevisiae as a by-product is easier to be obtained from fermentation industry in comparison to other types of waste microbial biomass. Microbes used in enzyme industry and pharmaceutical industry are usually involved in secret of their products, which makes them are reluctant to supply the waste biomass from their companies. The supply of S. cerevisiae as waste raw material is basically stable. S. cerevisiae is generally regarded as safe. Therefore, biosorbents made from S. cerevisiae can be easily accepted by the public when applied practically. S. cerevisiae, is also an ideal model organism to identify the machniasm of biosorption in metal ion removal, especially to investigate the interaction of metal-microbe at molecular level. Peregol and Howell (1997) reported that the use of yeasts as model systems is particualr attractive because of the ease of genetic manipulation and the availability of the complete S.cerevisiae genomcic sequence. In fact, S. cerevisiae, as a model system in biology, has been explored fully in molecular biology (Zhou 2002). Knowledge accumulated on the molecular biology of the yeast is very helpful to identify the molecular machniasm of biosorption in metal ion removal not only for itself but also for plants in phytoremidiaton and mammals (Eide, 1997, 1998). At the same time, S. cerevisiae can be easily manipulated genetically and morphologically, which is helpful to make engineering yeast appropriate for various purpose of metal removal. 2.3.1.2. Forms of S. Cerevisiae Used for Biosorption S. cerevisiae in different forms has been studied for different purposes of research. For example, living cell/dead cell (Kapoor and Virraghavan, 1995), intact cell/deactivated cell, immobilized cell/free cell (Veglio and Beolchini, 1997), raw material/ pretreated cell by physico-chemical process, wild type/mutatnt cell, flocculent / non-flocullent cell (Marques et al., 1999), engineered /nonengieered cell, lab culture/waste industrial cell, and cells from different industries producing different product ( Park et al., 2003). By comparing studies of different forms of the yeast, one can obtain useful information for understanding mechanism of metal uptake by S cerevsiae. For instance, by examining and comparing the responses of vacuole-deficient mutants and wild type of S. cerevisiae to several toxic metals, Ramsay and Gadd (1997) found that vacuole-deficient strains are more sensitive to Zn,Mn,Co,Ni with a largely decreased capacity to accumulate these metals than wild type, but no change for Cu or Cd. The results confirmed the essential role of vacuole in detoxification for Zn, Mn, Co, Ni, but not for Cu and Cd. Immobilization technique is one of the key elements for the practical application of biosorption, especially by dead biomass. Various kinds of immobilized S. cerevisiae have been studied with different surpport materials, which can be used in practical biosorption (Veglio and Beolchini, 1997). Park et al. (2003) compared two strains of S. cerevisiae in biosorpiton of cadmium. One strain ATCC 834 used for the production of l-phenylacetyl carbinol (l-PAC) and another strain ATCC

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Can Chen and Jianlong Wang

24858 for ethanol production. They found that the thicker mannan layer and the larger specific surface layer seemed to bestow a larger cadmium uptake capacity on the strain S. cerevisiae ATCC 834. Free cells appear to be unsuitable in practical application largly due to solid/liquid separation. However, Veglio and Beolchini (1997) pointed out that investigation of the performance of free cells for metal uptake can offer us fundamental information about the equilibrium of the biosorption process, which is useful for application. Meanwhile, flocculating cell has been suggested to be used for biosorption attempting to overcome the separation problem of free cells (Soares et al., 2002). To employ living or non-living cells in biosorpiton are in arguing or ambiguity (Suh and Kim, 2000). Early researches on biosorption of heavy metal ions began with living cells. However, dead cells have been found to have the same or even higher uptake capacity of metal ionss camparing with living cells. Meanwhile, dead cells can overcome some limits of using living cells: nutruition demand, sensitivity to extremes of pH or high metal ion concentration, etc. Therefore, biosorption studies involving dead/pretreated biomass were dominated the literatures in 1980s-90s (Malik, 2004). However, the limitations of the industrial application of biosorption with immobilized dead cells have been realized from some pilot plants of biosorption. For example, the cost for producing the required biosorbents with waste biomass was too expensive by immobilized techniques and by various pretreatment processes. Process of regeneration and re-use on-line is complex and very expensive. The co-existed ions and organic matters of solution made matters even more difficult and more complex for real effulents. Hybrid biotechnologies, including biosorption, bioprecipitation, bioaccumulation by using living cells, even with physico-chemical process, are suggested in recent years (Tsezo, 2001; Malik, 2004). As for S. cerevisiae, dead or living cells are the same important in biosorption studies today. As a waste microbial biomass from fermentation, study on dead cells of the yeast is also dominant and necessary. In exploring mechanism of metal uptake, especially metal-microbes interactions, living cells of S. cerevisiae must have been used inevitably for specific research at molecular level. Each aspect should not be neglected.

2.3.1.3. Biosorptive Capacity of S. Cerevisiae A number of literatures have proved that S. cerevisiae can remove toxic metals, recover precious and clean radionuclides from aqueous solutions to various extents (table 2.2). Recovery of light metals, such as aluminium by S. cerevisiae, is also reported (Schott and Gardner, 1997). Brady et al. (1994) proved that the hot alkali treated yeast cells of S. cerevisiae was capable of accumulating a wide range of heavy metal cations (Fe3+, Cu2+, Cr3+, Hg2+, Pb2+, Cd2+, Co2+, Ag+, Ni2+, and Fe2+). A part of typical metals studied in S. cerevisiae biosorption is listed in table 2.2. Lead, cadmium, copper, zinc, chromium, nickel, silver and uranium, etc. are paid more attention than cobalt, molybdenum, iron, magnese, radium, selenium, lanthanid, precious metals, etc. It should be noted that S.cerevisiae can distinguish different metal species based on their toxicity, such as selenium species (Se(IV) and Se(VI)), antimony species (Sb(III) and Sb(V)) and mercury species (CH3Hg and Hg(II)). This kind of property of S.cerevisiae makes it useful not only for metal bioremediation and removal or recovery, but also for analytical measurement (Madrid et al., 1995; Madrid and Camara, 1997; Perez-Corona et al., 1997).

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Biosorbents

39

Table 2.2. Some studies of metal ions biosorption by S. cerevisiae Metal class Toxic metals

Metal Pb Cu Zn Cd

Precious metals

Hg Co Ni Cr As Pd Pt Au Ag

Metal class Radionuclides

Metal U,Pu,Am,Ce;Cs,Sr 241 Am Sr

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U

Light metal

Se,Sb U，Se，Sr，Ce， Cs Al

References (Suh et al., 1999, Ozer and Ozer, 2003, Goksungur et al., 2005) (Bakkaloglu et al., 1998, Wang, 2002a) (Bakkaloglu et al., 1998) (Park et al., 2003, Vasudevan et al., 2003, Goksungur et al., 2005) (Al-Saraj et al., 1999) (Al-Saraj et al., 1999) (Bakkaloglu et al., 1998, Ozer and Ozer, 2003) (Ferraz et al., 2004) (Nguyen-nhu and Knoops, 2002) (Liu et al., 2003, Xie et al., 2003a) (Xie et al., 2003b) (Karamushka and Gadd, 1999, Lin et al., 2005) (Simmons and Singleton, 1996, Bustard and McHale, 1998) References (Kedari et al., 2001) (Liu et al., 2002) (Avery and Tobin, 1992) (Riordan et al., 1997, Nakajima, 2001, Popa et al., 2003) (Perez-Corona et al., 1997) (Kapoor and Viraraghavan, 1997b) (Schott and Gardner, 1997)

The determination of the metal uptake (q) by the biosorbent is often based on the equilibrium state of sorption system. The sorption uptake rate, q, is usually expressed in milligrams of metal sorbed per gram of the (dry) sorbent (the basis for engineering process mass balance calculations), or mmol g-1 or meq g-1 (when stoichiometry and/or mechanism are considered) material (Kratochvil and Volesky 1998). Metal ion uptake by S. cerevisiae was reported in substantial literatures. Table 2.3 presents some data on the biosorptive capacities of the yeast (in various forms) for different metal ions reported in part of literatures. Based on data presented in table 2.2, the magnitude order of metal uptake capacity by S. cerevisiae can be estimated as the followings: for Lead, biosorptive capacity by S. cerevisiae is in the order of 2-3, above tenth and less than 300 mg Pb g-1 dry weight biomass; for copper, in the order of 1-2, less than 20 mg Cu g-1 dry weight yeast; For zinc, in the order of 1-2, usually less than 30 mg Zn g-1 dry weight; For Cadmium, in the order of 2-3, usually above 10 but less than 100 mg Cd g-1 dry mass; For mercury, in the order of 2; For chromium and nickel, usually in the order of 1, seldom more than 40 mg/g dry mass; for precious metals , such as Ag, Pt, Pd, in the oreder of 2, around 50 mg g-1 dry weight yeast. Biosorptive capacity of radionuclide urimium by S. cerevisiae is usually between 150-300 mg U g-1 dry

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Can Chen and Jianlong Wang

weight biomass. It should be noted that comparing results from different literatures involves standardizing the different ways the sorption capacity may be expressed. At the same time, uptake, q, should be compared in almost the same equilibrium concentration of metal in solution for the purpose of evaluating performance of the biomaterial (Kratochviland Volesky, 1998). In particular, there is no standard measurement of dry weight of biomass, i.e. no standard of dry temperature and dry hours when drying biomass. Park et al. (2003) obtained the dry-cell weight by drying cells at 70°C until the weight of the cells became constant. Liu et al. (2002a) measured the dry weight of S. cerevisiae after drying in a stove for 2 hours at 100-120°C to calculate the adsorption capacities. Özer and Özer (2003) dired the yeast at 100ºC for 24 h. Rapoport and Muter (1995) determined dry weight by drying the sample at 105°C until the constant weight was achieved. Obvoiusly, the numberic value of dry weight of biomass obtained in different drying conditions is sure to be different. Hence, attention should be paid to these conditions when reading literatures. Table 2.3. Metal biosorption by S. cerevisiae (mg metal g-1 dry weight biomass) Metal

Source or form

Pb Pb

Pb Pb

Free cells Immobilized cells in a sol-gel matrix Whiskey distillery spent wash, lyophilized Lab cultivated, then dried at 100°C Ethanol treated waste baker yeast

Cu

Adapted and growing cells

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Pb

Cu Cu Cu Cu Cu Zn Zn2+ Zn Zn Zn Zn

2+

Cd

Waste yeast from fermentation industry and then autoclaved at 120°C Free cells Whiskey distillery spent wash lyophilized Immobilized cells on sepiolite Waste yeast from brewery, formaldehyde cross-linked cells in column bioreactors Waste yeast from fermentation industry and then autoclaved at 120°C Free cells Immobilized cells in a sol-gel matrix Whiskey distillery spent wash, lyophilized Immobilized cells on sepiolite Formaldehyde cross-linked cells in column bioreactors Deactivated protonated yeast from yeast co.

Biosorption capacity a 79.2 41.9 189 270.3 17.5 2.04-9.05

References Al-Saraj et al. 1999 Al-Saraj et al. 1999 Bustard and McHale 1998 Özer and Özer 2003 Goksungur etal.2005 Donmez and Aksu, 1999

4.93

Bakkaloglu et al. 1998

6.4

Al-Saraj et al. 1999 Bustard and McHale 1998 Bag et al., 1999a

5.7 4.7 8.1

Zhao and Duncan, 1997

3.45-1.95

Bakkaloglu et al. 1998

23.4 35.3

Al-Saraj et al. 1999 Al-Saraj et al. 1999 Bustard and McHale 1998 Bag et al., 1999a Zhao and Duncan, 1997

16.9 8.37 7.1 9.91-86.3

Vasudevan et al. 2003a

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41

Biosorbents Cd Cd Cd Cd Cd Cd

35.5-58.4

Park et al., 2003

14.3-20.0

Park et al., 2003

10.9 15.6

Bag et al., 1999a Goksungur et al. 2005

14

Zhao and Duncan, 1997

70

Volesky et al., 1993

Hg2+

Free cells

64.2

Co2+

Free cells Waste yeast from fermentation industry and then autoclaved at 120°C Free cells Lab cultivated, then dried at 100°C Deactivated protonated yeast from yeast co. oven at 80°C for 24 h Lab cultivated, dehydrated at 30°C, 15% of cell humidity; 80.5% of the viability As a by-product from brewery, formaldehyde cross-linked cells in fixed-bed column Lab cultivated, then dried at 100°C Whiskey distillery spent wash, lyophilized Immobilized cells of waste yeast Whiskey distillery spent wash lyophilized Industrial strain, then lab cultivated and freeze-dried Lab cultivated, free cell Whiskey distillery spent wash lyophilized Beer yeast 8.75 mmol UO22+/g yeast washed and unwashed non-viable spent yeast from a company in Greece

9.9

Al-Saraj et al. 1999; Madrid et al. 1995 Al-Saraj et al., 1999

1.47

Bakkaloglu et al.1998

8 46.3

Al-Saraj et al.1999 Özer and Özer 2003 Padmavathy et al., 2003

Ni Ni Ni Ni Cr

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

Free cell suspended in solution Lab culture Free cell suspended in solution Lab culture Immobilized cells on sepiolite Ethanol treated waste baker’s yeast Waste yeast from brewery, formaldehyde cross-linked cells in column bioreactors Non-living and resting cells from aerobic culture

Fe Pd2+ Ag Ag 241

Am

U U

U Th

11.4 - 5.5

Rapoport and Muter, 1995

6.3

Zhao and Duncan, 1998

32.6

2082.5 c

Özer and Özer 2003 Bustard and McHale 1998 Xie et al 2003a Bustard and McHale 1998 Simmons and Singleton1996 Liu et al., 2002 Bustard and McHale 1998 Popa et al. 2003

360-150

Riordan et al. 1997

150 63

Tsezos, 1997 Tsezos, 1997

16.8 40.6 59 41.7 7.45-1880.0 b 180

a

metal uptake is not necessarily maximum. unit: μg U g-1. c the value calculated by the data 8.75 mmol UO22+ g-1 yeast from Popa et al. (2003). b

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Can Chen and Jianlong Wang

2.3.1.4. Selectivity and Competitive Biosorption by S. Cerevisiae To determine which metal ions have high affinity with S. cerevisiae’s, it is necessary to compare the biosorptive capacity of different metal ions in the same experimental conditions. Also, it has been found that metal biosorption by S. cerevisia is selective and, in some cases, competitive. Some relevant work has been launched (table 2.4). However, limited information is availale on the competitive sorption of metal ions on fungal biomass (Kapoor and Viraraghavan, 1997a), including the yeast of S. cerevisia. In principle, S. cerevisiae has high affinity for uranium, lead and mercury than copper, nickel or other metal ions. Table 2.4. Comparison of the biosorptive capacity of metal ions (unit: mg/g) Comparitive results Pb(II(270.3)>Ni(II)(46.3)>Cr(VI)(32.6)

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Hg2+(55.76)>Zn2+(30.27)>Pb2+(24)>Cd2+( 20.91)>Co2+(14.50)=Ni2+(13.50)>Cu2+(4. 45)

Remark Mono solute biosorption system, comparison based on Langmiur equation Mono solute biosorption system, based on the same experimental condition

References Özer and Özer 2003 Al-Saraj et al. 1999

Pb(189)>U(180)>Ag(59)>Zn（16.9>=Fe （16.8>Cu（5.7）mg/g

Mono solute biosorpiton system based on Langmiur equation

Bustard and McHale 1998

Cd2+(14.0)>Cu2+(8.0)=Zn2+(7.1)

Mono solute biosorption system, based on the same experimental condition

Zhao and Duncan 1997

Cu(7.01)>Cd(5.50)=Zn(5.01)

Mono solute biosorpiton system based on Langmiur equation

Lu and Wilkins, 1996

Pb2+（60.24）>Cd2+（31.75） More than 95% sorption of UO22+, Pu4+, Am3+ and Ce3+, while sorption of Cs+ and Sr2+ were negligible Cu2+ was significantly affected by nonflocculent yeast, Cd2+was slightly affected by both Cu2+and Pb2+,and pb2+ removal was not affencted by

Mono solute biosorpiton system based on Langmiur equation Mono solute biosorpiton system based on the similar experimental conditions Two- or three-metal sorption systems (Cu,Pb or Cr), results were compared with one-solute system

Goksungur et al. 2005 Kedari et al., 2001 Marques et al., 1999

2.3.2. Filamentous Fungi This section reviews the removal of heavy metals and radio nuclides by fungi (Aspergillus spp., Mucor spp., Rhizopus spp. and Penicillium spp.) from aqueous solutions. Different species of Penicillium, under some circumstances also of Aspergillus, have been reported as good biosorbents of metals. The genus Rhizopus, such as R. arrhizus and R. javanicus, has been discovered to owe the relatively good-sequestering properties (Volesky,

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Biosorbents

1990). Table 2.5 summarizes some of the important results of metal biosorption using fungal and yeast biomasses.

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Table 2.5. Biosorption by fungal biomass Species of fungi A. niger, M. rouxii, R. arrhizus (Living cells)

Metal Au, Ag

Penicillium sp. (Living cells)

Cu, Zn, Cd, Au, Pb

Penicillium, Aspergillus, Trichoderma, Rhizopus, Mucor Saccharomyces Fusarium (Living cells) Penicillium, Rhizopus, Saccharomyces (Living cells) Phanerochaete chryosporium (Living cells)

U, Sr, Cs Cd, Pb, Cu

References Kapoor and Viraraghavan, 1997b Kapoor and Viraraghavan, 1997b Kapoor and Viraraghavan, 1997b Kapoor and Viraraghavan, 1997b Day et al., 2001

2.3.2.1. Penicillium Penicillium can remove a variety of heavy metals from aqueous solutions, such as Cu, Au, Zn, Cd, Mn, U, Th, see (table 2.6). Penicillium italicum (Mendil et al., 2008), Penicillium spinulosum, Penicillium oxalicum (Svecova et al., 2006) Penicillium austurianum (Awofolu et al., 2006), Penicillium verrucosum (Cabuk et al., 2005), Penicillium purpurogenum (Say et al., 2003a), Penicillium canescens (Say et al., 2003b), Penicillium griseofulvum (Shah et al., 1999), Penicillium austurianum (Rostami and Joodaki, 2002), Penicillium chrysogenum, etc. were reported to adsorb various metals. For example, Penicillium chrysogenum, can extract gold from a cyanide solution. However, the biosorption capacity was not encouraging (Vieira and Volesky, 2000). Penicillium spinulosum was reported to remove Cu, Au, Zn, Cd, Mn (Kapoor and Viraraghavan, 1995). Among those Penicillium sp., Penicillium chrysogenum was studied more. The Penicillium chrysogenum, a semi-known strains Hyphomycetes gang door Hyphomycetes Head (Cong stems Species) CONG stems Branch Penicillium spores of fungi. Classified asymmetry Penicillium group, cashmere-like Penicillium Asian group, the middle Penicillium chrysogenum and it is typical of penicillin-producing bacteria. Fungi smooth surface, long-150-350 µm, a width of 3 to 3.5 µm, 2-3 branches, brush sticks asymmetry, ranging from the length of the vice sticks, based on the growing stems and small stems. Small stems 4 to 6 rounds of Health, on the middle conidia chain. Conidia oval, (2-4) μm × (2.8 ~ 3.5) µm, the surface smooth. Bacteria grows faster, round, tight cashmere-like or slightly tempered, blue and green (white edge), a radial grooving on the surface, often yellowcolored droplets exudative. Bright yellow colony back to a dark brown, and yellow-soluble spread to the medium; widely distributed in the air, soil and organic matter on Biodeterioration. Penicillinu is the famous production bacteria also produce glucose acid, citric acid or glucose oxidase (http://www.chemyq.com/En/xz/xz4/39623ajqia.htm). P. chrysogenum exhibited preferential sorption orders Pb2+ > Cu2+ > Zn2+ > Cd2+ > Ni2+ > Co2+ (Puranik and Paknikar, 1999). Nonliving Penicillium chrysogenum: Pb2+ > Cd2+ > Cu2+ > Zn2+ > As3+. Penicillium canescens exhibited the same sorption orders: Pb2+ > Cd2+ > Hg2+ > As3+ for non-competitive conditions or competitive conditions. In non-competitive

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Can Chen and Jianlong Wang

conditions, metal uptake of Penicillium canescens were 26.4 mg g-1 for As(III), 54.8 mg g-1 for Hg(II), 102.7 mg g-1 for Cd(II) and 213.2 mg g-1 for Pb(II), respectively. However, competitive adsorption capacities of the heavy metal ions were 2.0 mg/g for As(III), 5.8 mg/g for Hg(II), 11.7 mg g-1 for Cd(II) and 32.1 mg g-1 for Pb(II), respectively, at a 50 mg l-1 initial concentration of the metal ions. The species Pencillium biosorption seems to be only sorbing well of uranium and lead (Volesky and Holan, 1995). However, some other reports regarded the genera Rhizopus and Penicillium have already been studied as potential biomass for the removal of heavy metals from aqueous solutions (Kapoor et al., 1999).

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Table 2.6. Biosorption of heavy metals by Penicillium sp Biosorption capacity (mg -) 102.7 213.2 54.8 26.4 11, 9, 116 56 39

References

Species

Metal

Penicillium canescens Penicillium canescens Penicillium canescens Penicillium canescens Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum (surface imprinted) Penicillium chrysogenum (waste biomass) Penicillium chrysogenum Penicillium chrysogenum (modified) Penicillium chrysogenum (modified) Penicillium chrysogenum (modified) Penicillium chrysogenum (modified) Penicillium chrysogenum (modified) Penicillium chrysogenum (raw) Penicillium chrysogenum (raw) Penicillium chrysogenum (raw) Penicillium chrysogenum (Alkaline pretreatment) Penicillium chrysogenum (Alkaline pretreatment) Penicillium chrysogenum (Alkaline pretreatment) Penicillium chrysogenum

Cd(II) Pb(II) Hg(II) As(III) Cd, Cu, Pb Cd Cd Th Zn Ni

6.5 82.5

Say et al., 2003b Say et al., 2003b Say et al., 2003b Say et al., 2003b Niu et al., 1993 Holan and Volesky, 1995 Fourest et al., 1994 Gadd and White, 1992 Niu et al., 1993 Su et al., 2006

Ni

56.2

Su et al., 2006

Cr(VI) Cd

-210.2

Park et al., 2005 Deng and Ting, 2005b

Cu

108.3

Deng and Ting, 2005b

Pb

204

Deng and Ting, 2005a

Ni

55

Deng and Ting, 2005a

Ni

260

Tan et al., 2004

Cr(III)

18.6

Tan and Cheng, 2003

Ni

13.2

Tan and Cheng, 2003

Zn

6.8

Tan and Cheng, 2003

Cr(III)

27.2

Tan and Cheng, 2003

Ni

19.2

Tan and Cheng, 2003

Zn

25.5

Tan and Cheng, 2003

Cd

56

Holan and Volesky, 1995

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Biosorbents Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium chrysogenum Penicillium digitatum Penicillium digitatum Penicillium griseofulvum (immobilized) Penicillium griseofulvum (free)

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Penicillium italicum

Pb, Cd, Zn, Cu Pb Th Th Pb U Ni, Zn, Cd, Pb Cd, Pb Cu Cu

96, 21.5, 13, 11.7

Skowronski et al., 2001

116 150 142 116 70

Niu et al., 1993 Veglio and Beolchini, 1997 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995

3.5, 5.5 20.47

Veglio and Beolchini, 1997 Shah et al., 1999

1.51

Shah et al., 1999

Penicillium italicum Penicillium italicum Penicillium notatum

Cu, Th, Zn Cu Zn Cu

Ahluwalia and Goyal, 2007 0.4-2 0.2 80

Penicillium notatum

Zn

23

Penicillium notatum

Cd

5.0

Penicillium janthinellum

U

52.7

Penicillium purpurogenum Penicillium purpurogenum Penicillium purpurogenum Penicillium purpurogenum Penicillium purpurogenum Penicillium simplicissimum Penicillium spinulosum (Non-growing) Penicillium spinulosum (Growing, midlinear phase) Penicillium spinulosum (Non-growing) Penicillium spinulosum (Growing, lag period) Penicillium spinulosum (Non-growing) Penicillium spinulosum (Growing, midlinear phase) Penicillium spinulosum Penicillium sp.

Cr(VI) Cd(II) Pb(II) Hg(II) As(III) Pb, Cu Cd

36.5 110.4 252.8 70.4 35.6 298.01, 207.68 1.5

Cd

0.4

Cu

2.4

Cu

3.6

Zn

1.3

Zn

0.2

Cd Al, Sn, Pb

84.5 50, 60, 5.0

Ahluwalia and Goyal, 2007 Ahluwalia and Goyal, 2007 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Say et al., 2004 Say et al., 2003a Say et al., 2003a Say et al., 2003a Say et al., 2003a Xu et al., 2008 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan, 1995 Gabriel et al., 1996 Kapoor and Viraraghavan, 1995

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Can Chen and Jianlong Wang

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Table 2.6. (Continued). Species

Metal

Penicillium sp.

U

Biosorption capacity (mg -) 1.4

Penicillium spp.

Pb

6.0

Penicillium spp.

Cu

3

Penicillium spp.

Cd

3

Penicillium spp.

U

165

Penicillium spp.

Sr

75

Penicillium sp.

Nd

178

References Kapoor and Viraraghavan, 1995 Kapoor and Viraraghavan,1997b Kapoor and Viraraghavan, 1997b Kapoor and Viraraghavan, 1997b Kapoor and Viraraghavan, 1997b (Kapoor and Viraraghavan, 1997b Palmieri et al., 2000)

2.3.2.2. Aspergillus According to Bapat et al. (2003), Aspergillus niger is an important microorganism in biotechnological applications. It has been used to produce extracellular enzymes such as glucoamylas, pectinase, acidic lipase, feruloyl esterase, and xylanase and organic acids such as gluconic acid and citric acid. Citric acid and several A. niger produced enzymes are considered GRAS (generally regarded as safe) by the United States Food and Drug Administration. In addition, A. niger is used in biotransformations of ferrulic acid, progesterone, diperpenoid, isosteviol, terpene, linaloo, gereniol, nirol, and citral. In the last two decades, A. niger has been developed as an important transformation host to overexpress food enzymes. A. niger is also ecologically important in biodegradation of toxic chemicals such as hexadecane, waste treatment of beet molasses and olive mill waste, and bioconversion of wastewater sludge. Biomass of A. niger is used to remove hazardous heavy metals such as cadmium, lead, chromium, and copper from aqueous solution. As it produces organic acids, A. niger is used in bioleaching to extract metals from mining ores. Table 2.7 shows that various metal ions could be removal by A. niger. Fungus Aspergillus niger 405 showed a good affinity for binding of Cu2+, Zn2+ and Ni2+ ions in single, while in multi-component solution it occurred only for copper and zinc (Filipovic-Kovacevic et al., 2000). The adsorption densities for various metal ions could be arranged as Ca> Cr (III) > Ni > Fe > Cr (VI). A waste fungal biomass containing killed cells of Aspergillus niger was efficiently used in the removal of toxic metal ions such as nickel, calcium, iron and chromium from aqueous solutions (Natarajan et al., 1999). Non-living waste biomass consisting of Aspergillus niger attached to wheat bran was used as a biosorbent for the removal of copper and zinc from aqueous solutions. Copper and zinc uptake by the biomass obeyed Langmuir isotherms. The binding capacity of the biomass for copper was found to be higher than that for zinc. The metal uptake, expressed in milligrams per gram of biomass, was found to be a function of: the initial metal concentration (with the uptake decreasing with increasing initial concentration), the biomass loading (with the uptake decreasing with increasing biomass loading) and pH (with the uptake increasing with increasing pH in the range of 1.5 and 6.0).

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Biosorbents

The metal uptake was significantly affected in the presence of a co-ion. The uptake of copper by the biomass decreased in the presence of zinc and vice versa. The decrease in metal uptake was dependent on the concentrations of metals in the two-component aqueous solutions. The effect of copper on zinc uptake was more pronounced than the effect of zinc on copper uptake (Modak et al., 1996).

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Table 2.7. Biosorption of heavy metals by Aspergillus sp. References

Cu, Pb

Biosorption capacity (mg g-1) 28.7, 32.6

Cu, Pb

25.5, 28.9

Dursun, 2003

Cu, Pb 241Am 241Am

15.6, 34.4 7.2-142.4 MBq/g 5.2-106.5 MBq/g 93

Dursun et al., 2003a Yang et al., 2004 Yang et al., 2004

Species

Metal

Aspergillus niger (pretreated with NaOH) Aspergillus niger (pretreated with NaOH) Aspergillus niger (growing) Aspergillus niger (spore) Aspergillus niger (hyphae) Aspergillus niger Aspergillus niger

Pb Hg2+, CH3Hg+

Aspergillus niger Aspergillus niger Aspergillus niger

Cr(VI), Fe(III) Cu(II) Cd

Aspergillus niger Aspergillus niger Aspergillus niger Aspergillus niger

Cd Ni Ni Ph, Cd, Ni and Cr

Aspergillus niger Aspergillus niger Aspergillus niger Aspergillus niger

Cu, Zn Fe(II), Fe(III) Cu, Zn, Fe, Ni, Cd Cu2+, Zn2+, Ni2+, Cr(VI) Free Cd and complexed Cd Ni, Ca, Fe, Cr Tc, U, Am, Ce, Cs, Eu, Pa, Sb Pb, Cd, Cu, Ni Pb, Cd, Cu, Ni

Aspergillus niger Aspergillus niger Aspergillus niger Aspergillus niger (live) Aspergillus niger (NaOH pretreated) Aspergillus niger

Aspergillus niger Aspergillus niger (attached to wheat bran)

Cyano-metal complexes (Au, Ag. Cu, Fe, Zn) Pb, Cd, Cu Cu, Zn

9.53

2.25, 1.31, 0.75, 1.75 7.24, 3.43, 2.66, 0.96

Dursun, 2006

Spanelova et al., 2003 Karunasagar et al., 2003 Goyal et al., 2003 Dursun et al., 2003b Basumajumdar et al., 2003 Barros et al., 2003 Rajendran et al., 2002 Magyarosy et al., 2002 Bhattacharyya et al., 2002 Price et al., 2001 Bag et al., 2001 Bag et al., 1999b Filipovic-Kovacevic et al., 2000 Rosa et al., 1999 Natarajan et al., 1999 Lyalikova-Medvedeva and Khijniak, 1999 Kapoor et al., 1999 Kapoor et al., 1999 Gomes et al., 1999

Kapoor and Viraraghavan, 1997c Modak et al., 1996

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Table 2.7. Biosorption of heavy metals by Aspergillus sp. (Continued) Metal

Aspergillus niger Aspergillus niger Aspergillus niger Aspergillus carbonarius

Cd2+, Cu2+, Zn2+, Ni2+, Co2+ Ag Th Cu, Cr

Aspergillus flavus Aspergillus flavus

U, Th Au, Ag, Cu

Aspergillus fumigatus

U

Aspergillus fumigatus

Au, Ag, Cu

Aspergillus nidulans Aspergillus terreus (mycelial waste) Aspergillus terreus Aspergillus terreus (immobilized in polyurethane foam) Aspergillus terreus Rhizopus arrhizus Rhizopus nigricans

Zn Cu

160-180

Akthar et al., 1995 Gadd and White, 1992 Alasheh and Duvnjak, 1995 Hafez et al., 1997 Gomes and Linardi, 1996 Bhainsa and D'Souza, 1999 Gomes and Linardi, 1996 Zhou, 1999 Gulati et al., 2002

Cd Fe, Cr, Ni

164.5, 96.5, 19.6

Massaccesi et al., 2002 Dias et al., 2002

Aspergillus awamori Aspergillus oryzae Mucor rouxii (pretreatment with detergent and alkali chemicals) R. arrhizus Rhizopus arrhizus white-rot fungus Trametes versicolor

Cu Th Li+, Ag+, Pb2+, Cd2+, Ni2+, Zn2+, Cu2+, Sr2+, Fe2+, Fe3+, Al3+ Cu Cu, Cd, Zn

Biosorption capacity (mg g-1)

References

Species

224

Tsekova et al., 2000 Vianna et al., 2000

Pb2+, Cd2+, Ni2+, Zn2+

Cu(II) Ph, Cd, Ni and Cr Cd

Gulati et al., 1999 Gadd and White, 1992 Kogej and Pavko, 2001

Yan and Viraraghavan, 2000

10.76 Live: 102.3 ± 3.2 Dead: 120.6 ± 3.8

Arica et al., 2001

2.3.2.3. White Rot Fungi A white rot fungus species Lentinus sajorcaju biomass was entrapped into alginate gel via a liquid curing method in the presence of Ca(II) ions. The maximum experimental biosorption capacities for entrapped live and dead fungal mycelia of L. sajurcaju were found to be 104.8±2.7 mg Cd(II) g-1 and 123.5±4.3 mg Cd(II) g-1, respectively (Bayramoglu et al., 2002).

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2.3.3. Selectivity and Competitive Biosorption by Fungi Native fungal biomass of fungi Absidia orchidis, Penicillium chrysogenum, Rhizopus arrhizus, Rhizopus nigricans, and modified spruce sawdust (Picea engelmanii) sequestered metals in the following decreasing preference: Pb > Cd > Ni (Holan and Volesky, 1995). Penicillium canescens in competitive or noncompetitive conditions exhibited the same preferential order: Pb(II) > Cd(II) > Hg(II) > As(III). Non-competitive conditions were 26.4 mg g-1 for As(III), 54.8 mg g-1 for Hg(II), 102.7 mg g-1 for Cd(II) and 213.2 mg g-1 for Pb(II), respectively. competitive adsorption capacities of the heavy metal ions were 2.0 mg g-1 for As(III), 5.8 mg g-1 for Hg(II), 11.7 mg g-1 for Cd(II) and 32.1 mg g-1 for Pb(II), respectively, at a 50 mg l-1 initial concentration of the metal ions (Say et al., 2003b). Sag (2001) compared the biosorption performance of heavy metal ions on various free and immobilized fungal cells in different reactor systems. Although the results from the different authors cannot be compared directly, some qualitative conclusion can be draw from those data: Cd>Co>Cr>Au≈Cu>Fe>Ni>Th>U>Pb>Hg>Zn. Aspergillus seems to sorbing well Au, Co, Th, Zn. Penicillium is also excellent biosorbent for Cd, Fe, Pb, Th, U, Zn. As can be seen in table 2.1, Cu(II) is one of the most studied metal ions due to its biological functions: it is an essential micronutrient for most living organisms but is toxic. Cu(II) is one of the most studied metal ions due to its biological functions: it is an essential micronutrient for most living organisms but is toxic when in excess. A wide variety of free-immobilized, treateduntreated fungal biomasses has been used for Cu biosorption in different reactor systems and a wide range of capacities for Cu ions has been observed with the uptake capacity from 1.015 mmol g-1 for Ganoderma lucidum to 0.012 mmol g-1 for A. oryzae. The Cu(II) biosorption capacities of R. arrhizus obtained in batch stirred tank reactor (BSTR), continuous-flow stirred-tank contactor (CFST), batch stirred-tank reactors in series (BSTRS) (when three reactor was used in series), packed column (or fixed bed) reactor (PCR) at exactly same operating conditions have been found to be 0.301, 0.353, 0.738, 0.754 mmol g-1, respectively (Sag, 2001).

2.3.4. Comparison among Fungi and Yeast and Other Biomaterials Table 2.8 represents a part of comparative results of metal uptake capacity between S.cerevisiae and other biomaterials. Bakkaloglu et al. (1998) coveres the comparison of various types of waste biomass including bacteria (S. rimosus), yeast (S. cerevisiae), fungi (P. chrysogenum), activated sludge as well as marine algae (F. vesiculosus and A. nodosum) for zinc, copper and nickel ions removal effieciency in the biosorption, sedimentation and desorption stages. The results showed that S. cerecisiae has the mediocre efficiency for oneor multi- metal biosorpiton systems. By comparing the index qmax of Langmiur equation with seven types of waste biomass for the example of lead ion, Kogej and Pavko (2001) indicated that lead uptake capacity of S. cerevisiae is in the middle in comparison with other six biomaterials. Vianna et al. (2000) studied the capability for the adsorption of Cu, Cd and Zn by three kinds of waste biomass from fermentation industries, that is, Bacillus lentus, Aspergillus oryzae and S. cerevisiae. The results showed that protonated B. lentus had the highest sorption capacity for Cu and Cd, followed by protonated A. oryzae and S. cerevisiae biomass. Donmez and Aksu (1999) studied the copper ion bioaccumulation by adapted and

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growing cells of S. cerevisiae, Kluyceromyces marxianus, Schizosaccharomyces pombe and Candida sp. They found that the biosorptive uptake for Cu2+ decreaed in the following order: S. cerevisiae（7.11）>K. Marxianus（6.44）>Candida sp.（4.80）> S. pombe（1.27）. However, the researchers suggested that Candida sp. and K. marxianus have been found to be more efficient than S. cerevisiae and S. pombe in heavy metal resistance and Cu(II) bioaccumulation at higher copper(II) concentrations. Compared with the excellent biosorbent of fungi Rhizopus for lead, cadmium, copper, zinc, and uranium, the common yeast S. cerevisiae is regarded as a 'mediocre' metal biosorbent (Volesky, 1994). The metal removal capacity of cadmium by S. cerevisiae was observed to be higher in comparison with adsorbents such as aluminum oxide, activated carbon, and activated charcoal (Kapoor and Viraraghavan, 1997b). In spite of the mediocre metal uptake capacity comparing with other fungi biomaterials, S. cerevisiae is a unique biomaterial in biosorpiton research and application. It has long been and continues to be paid much attention. The metal uptake capacity of Cr(VI) is found to decrease in the order R. nigricans > R. arrhizus > A. oryzae > A. niger (Bai and Abraham, 1998). Table 2.8. Comparison of different biomterials with S. cerevisiae Metal 2+

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Zn

Biosorptive capacity（mg metal g-1 dry weight biomass) A.nodosum(25.6)>P.chrysogenum>(19.2)>F.vesiculosus(17.3)> Activated sludge(9.7)>S.rimosus(6.63)>S.cerevisiae(3.45)

References Bakkaloglu et al., 1998

Cu2+

S.rimosus(9.07)>P.chrysogenum(8.62)>F.vesiculosus(7.37)>Act ivated sluge(5.54)>S.cerevisiae(4.93)>A.nodosum(4.89)

Bakkaloglu et al. 1998

Ni2+

F.vesiculosus(2.85)>S.rimosus(1.63)>S.cerevisiae (1.47)>A.nodosum(1.11)

Bakkaloglu et al. 1998

Pb2+ Cd2+ or Cu2+ Cu2+

Phanerochaete chrysosporium(419.4)> R.nigricans(403.2) > M.Purpurea(279.5) > S.cerevisiae(211.2)> A.terreus(201.1)> M.inyoensis(159.2)>Streptomyces clavulgerus(140.2) Protonated biomass: Bacillus lentus (≈30)> Aspergillus oryzae > S. cerevisiae (< 5) Growing cells: S. cerevisiae（7.11）>K. Marxianus（6.44） >Candida sp.（4.80）> S. pombe（1.27）

Kogej and Pavko, 2001 Vianna et al., 2000 Donmez and Aksu, 1999

Three by-products of fermentations containing Bacillus lentus, Aspergillus oryzae or Saccharomyces cerevisiae biomass were tested for the capacity to absorb Cu, Cd and Zn. The composition of the three biomasses was first determined and showed high contents of ashes in both B. lentus and A. oryzae biomass and high amounts of lipids in the bacterial biomass. Metal ion binding experiments were performed by contact of 0.1 g of biomass (protonated for all the metal tests and not protonated only for the Cd test) with 50 ml of solutions containing each of the metals in the concentration range from 10 to 500 mg ml-1, at pH 4.5, 3.5 and 2.5. The final metal ion concentrations were determined using a plasma absorption spectrometer, and the metal removal levels for isotherm plots were determined using the Langmuir model. The results showed that B. lentus protonated biomass had the best sorption capacity for Cu and Cd, followed by protonated A. oryzae and S. cerevisiae biomass. The sorption of Zn was

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low for all tested biomasses, as also was the binding of all metals at acidic pH (2.5 and 3.5). A significant increase in Cd sorption was obtained using non-protonated biomass from B. lentus and A. oryzae (Vianna et al., 2000). Table 2.9 offered some information of metal affinity by the same biomass, Penicillium canescens as an example. Table 2.9. Biosorption capacities of metal ions by Penicillium canescens (unit: mg g-1) Comparitive results Hg2+(55.76)>Zn2+(30.27)>Pb2+(24)>Cd2+( 20.91)>Co2+(14.50)=Ni2+(13.50)>Cu2+(4.4 5) Pb(189)>U(180)>Ag(59)>Zn（16.9>=Fe （16.8>Cu（5.7）mg/g Cd2+(14.0)>Cu2+(8.0)=Zn2+(7.1) Cu(7.01)>Cd(5.50)=Zn(5.01) Pb2+（60.24）>Cd2+（31.75）

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More than 95% sorption of UO22+, Pu4+, Am3+ and Ce3+, while sorption of Cs+ and Sr2+ were negligible Cu2+ was significantly affected by nonflocculent yeast, cd2+was slightly affected by both Cu2+and Pb2+,and pb2+ removal was not affencted by

Remark Mono solute biosorption system, based on the same experimental condition Mono solute biosorpiton system based on Langmiur equation Mono solute biosorption system, based on the same experimental condition Mono solute biosorpiton system based on Langmiur equation Mono solute biosorpiton system based on Langmiur equation Mono solute biosorpiton system based on the similar experimental conditions Two- or three-metal sorption systems (Cu,Pb or Cr), results were compared with one-solute system

References Al-Saraj et al. 1999 Bustard and McHale 1998 Zhao and Duncan 1997 Lu and Wilkins 1996 Goksungur et al. 2005 Kedari et al. 2001 Marques et al. 1999

2.4. MARINE ALGAE 2.4.1. Introduction to Microbiology of Algae According to Madigan et al. (1997), algae have been extensively studied due to their ubiquitous occurrence in nature. The term algae refer to a large and diverse assemblage of eukaryotic organisms that contain chlorophyll and carry out oxygenic photosynthesis. Algae should not be confused with cyanobacteria, which are also oxygenic phototrophs but which are bacteria and thus evolutionarily quite distinct from algae. Although most algae are of microscopic size and hence are clearly microorganisms, a number of forms are macroscopic, some seaweeds growing to over 100 ft in length (Madigan et al., 1997). Algae are unicellular of colonial, the latter occurring as aggregates of cells. When the cells are arranged end to end, the alga is said to be filamentous. Among the filamentous forms, both unbranched filaments and more intricate branched filamentous forms occur. Most algae contain chlorophyll and are thus green in color. However, a few kinds of common algae are note green but appear brown or red because in addition to chlorophyll, other pigments such as carotenoids are present that mask the green color. Algae cells contain one or more chloroplasts, membranous structures that house the photosynthetic pigments.

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Several characteristics are used to classify algae, including the nature of the chlorophyll(s) present, the carbon reserve polymers produced, the cell wall structure, and the type of motility. All algae contain chlorophyll a. Some, however, also contain other chlorophylls that differ in minor ways from chlorophylls a. The presence of these additional chlorophylls is characteristic of particular algal groups.. The distribution of chlorophylls and other photosynthetic pigments in algae was summarized by Madigan et al. (1997). The algal group includes Chlorophyta (green algae), Euglenophyta (euglenoids, also considered with the protozoa), Chrysophyta (golden-brown algae, diatoms), Phaeophyta (brown alage), Pyrrophyta (dino-flagellates), Rhodophyta (red algae). One of the key characteristics used in the classification of algal groups is the nature of the reserve polymer synthesized as a result of photosynthesis. Algae of the division Chlorophyta produce starch (z-1,4-glucose) in a form very similar to that of higher plants. By contrast, algae of other groups produce o variety of reserve substances, some polymeric and some as free monomers. Cell walls of algae. Algae show considerable diversity in the structure and chemistry of their cell walls. In many cases the cell wall is composed of a network of cellulose fibrils, but it is usually modified by the addition of other polysaccharides such as pectin (highly hydrated polygalacturonic acid containing small amounts of the hexose rhamnose), xylans, mannans, alginic acids or fucinic acid. In some algae, the wall is additionally strengthened by the deposition of calcium carbonate; these forms are often called “calcareous” or “coralline” (corallike) algae. Sometimes chitin, a polymer of N-acetylglucosamine, is also present in the cell wall. In euglenoids a cell wall is absent. In diatioms, the cell wall is composed of silica, to which protein and polysaccharide are added. Even after the diatom dies and the organic materials have disappeared, the external structure remains, showing that the siliceous component is indeed responsible for the rigidity of the cell. Because of the extreme resistant decay of these diatom frustules, they remain intact for long periods of tine and constitute some of the best algal fossils ever found. Algal cell walls are freely permeable to lowmolecular-weight constituents such as water, ions, gases, and other nutrients. Their cell walls are essentially impermeable, however, to larger molecules or to macromolecules. Algal cell walls contain pores 3-5 nm wide, which are sufficiently small to pass molecules of a molecular weight of about 15,000 or less. Thus, although animal cells can eat particulate mater, a process called phagocytosis, phagocytic activities are impossible in algae; particles large enough to be phagocytized never reach the cytoplasmic membrane because they are unable to penetrate the cell wall. Cell walls are more complex in algae than in fungi or bacteria, and three group algae of brown, red and green algae are of interest, and need to be differentiated in those three evolutionary pathways (Kuyicak and Volesky, 1990; Rincon et al., 2005). The cell walls of brown algae (Phaeophyta) generally contain three components: cellulose, the structural support; alginic acid, a polymer of mannuronic and guluronic acids (M and G) and the corresponding salts of sodium, potassium, magnesium and calcium; and sulphated polysaccharides (fucoidan matrix). Red algae (Rhodophyta) also contain cellulose, but their interest in connection with biosorption lies in the presence of sulphated polysaccharides made of galactanes (agar and carragenates). Green algae (Chlorophyta) are mainly cellulose, and a high percentage of the cell wall are proteins bonded to polysaccharides to form glycoproteins (Romera et al., 2006).

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2.4.2. Algae Used for Biosorption Algae are of special interest in the search for and development of new biosorbents materials due to their high sorption uptake and their ready availability in practically unlimited quantities in the seas and oceans (Kuyicak and Volesky, 1990; Rincon et al., 2005). However, according to Romera et al. (2006), there are few publications on biosorption with algae as compared to those using other biomass (mainly fungi and bacteria), and the number is still lower for multi metallic systems. The topic is relatively novel, with exponential growth of interest throughout the scientific community in the last few years. From the published literatures, brown algae among the three groups of algae (red, green, brown algae) received the most attention. Higher uptake capacities have been found for brown algae than for red and green algae (Brinza et al., 2007). The reason seems to be that they offer better sorption uptake than red or green algae (Romera et al., 2006). Researchers have employed mainly brown algae treated in various different ways to improve their sorption uptake (Romera et al., 2006). Volesky research group is such a group and published many references on brown algae biosorption characteristics, especially the brown algae of Sargassum sp. (Davis et al., 2003a; Davis et al., 2003b; Davis et al., 2003c; Volesky et al., 2003; Yun and Volesky, 2003; Davis et al., 2004; Diniz and Volesky, 2005). A review of the biochemistry of heavy metal biosorption by brown algae was published (Davis et al., 2003c). Brinza et al. (2007) reviewed some marine micro and macro algal speicies as biosorbents for heavy metal ions. The micro algal mentioned in the review include Chlamydomonas reinhardtii, Chlorella salina, Chlorella sorokiniana, Chlorella vulgaris, Chlorella miniata, Chlorococcum sp., Cyclotella cryptica, Lyngbya taylorii, Phaeodactylum tricornutum, Porphyridium purpureum, Scenedesmus abundans, Scenedesmus quadricauda, Scenedesmus subspicatus, Spirogyra sp., Spirulina platensis, Stichococcus bacillaris, Stigeoclonium tenue. The macro algal mentioned in the review include Ascophyllum nodosum, Ascophyllum sp., Cladophora crispata, Cladophora fascicularis, Codium fragile, Colpomenia sinuosa, Corallina officinalis, Ecklonia sp., Fucus vesiculosus, Fucus ceranoides, Fucus serratus, Fucus spiralis, Gracilaria fischeri, Gracilaria sp. , Fucus spiralis, Gracilaria fischeri, Gracilaria sp., Jania rubrens, Laminaria digitata, Laminaria japonica, Laurencia obtuse Padina pavonia, Padina sp., Palmaria palmata, Petalonia fascia, Pilayella littoralis, Porphyra columbina, Sargassum asperifolium, Sargassum hemiphyllum, Sargassum hystrix, Sargassum natans, Sargassum sp., Sargassum sp., Sargassum vulgaris, Sargassum kjellmanianum, Turbinaria conoides, Ulva fascia, Ulva reticulata, Ulva sp. Those algae were reported to be able to adsorb one or more heavy metal ions of K, Mg, Ca, Fe, Sr, Co, Cu, Mn, Ni, V, Zn, As, Cd, Mo, Pb, Se, Al with good metal uptake capacity (Brinza et al., 2007). Chojnacka et al. (2005) reported the biosorption performance of Cr3+, Cd2+ and Cu2+ ions by blue-green algae Spirulina sp. Nayak et al. (2003) studied the bio-sorption of heavy and toxic radionuclides by three genera of algae from different taxonomic groups, including Hg-197, Tl-198, Tl-199, Tl-200, Tl-201, Pb-199, Pb-200, Pb-201, Bi-204 and Po-204, Po-205 radionuclides. Thirty freez-dried strains of algae were examined to uptake of cadmium, lead, nickel, and zinc from aqueous solution (Klimmek et al., 2001). The screening batch adsorption experiments were carried out with one initial concentration for each metal. The initial concentrations where the surface of C. vulgaris was saturated with the particular metal were selected for the screening. The use of saturating conditions for a screening investigation was

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necessary because the uptake capacities otherwise would not be comparable. The initial concentrations for the screening investigations were determined with 400 mg l-1 for lead and 100 mg l-1 for the other three metals. The maximum capacities (qmax) according to the Langmuir Model were used to screen those 30 algae. A wide range of the values of qmax between the different strains of algae and between the four metals can be observed. The results were shown in the table. According to the refrence (Klimmek et al., 2001), table 2.10 offered the qmax for 30 algae strains.

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Table 2.10. The maximum biosorption capacities (qmax) for 30 algae strains (Unit: mmol g-1) Biomass S. hofmani L. taylorii A. densus K. spiculiformis V. dichotoma C. kessleri M. species N. parmeloides S. maxima C. vulgaris G. longicauda R. spiculiforme A. hantzschii S. platensis P. tricornutum M. aeroginosa P. purpureum T. species G. verrucosa C. species A. cylindrica S. laxissima G. planctonica Biomass S. species P. species A. africanum E. magnus D. salina A. inaequealis D. bioculata a

Pb (0.4)a 0.85 0.84 0.8 0.71 0.7 0.55 0.54 0.5 0.49 0.46 0.44 0.4 0.39 0.38 0.36 0.35 0.33 0.3 0.24 0.23 0.22 0.22 0.21 Pb (0.4)a 0.19 0.19 0.18 0.16 0.1 0.1 0.02

Cd (0.1) 0.33 0.32 0.24 0.34 0.28 0.24 0.25 0.23 0.27 0.29 0.27 0.25 0.27 0.29 0.23 0.23 0.18 0.13 0.15 0.2 0.14 0.22 0.06 Cd (0.1) 0.24 0.17 0.17 0.09 0.07 0.08 0.05

Ni (0.1) 0.17 0.43 0.26 0.28 0.37 0.12 0.2 0.22 0.12 0.31 0.2 0.26 0.25 0.4 0.19 0.21 0.2 0.26 0.13 0.17 0.14 0.13 0.11 Ni (0.1) 0.09 0.18 0.15 0.12 0.06 0.12 0.05

Zn (0.1) 0.37 0.37 0.23 0.42 0.42 0.14 0.24 0.24 0.23 0.18 0.28 0.25 0.11 0.27 0.37 0.23 0.25 0.19 0.24 0.16 0.1 0.11 0.18 Zn (0.1) 0.07 0.36 0.11 0.17 0.06 0.1 0.04

In parentheses is the initial concentration of the particular metal.

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The cyanophyceae Lyngbya taylorii exhibited high uptake capacities for the four metals (qmax: mmol g-1): Pb (1.47), Ni (0.65), Zn (0.49) and Cd (0.37). The modified biosorbent of L. taylorli by phosphorylation improved the metal binding abilities and achieved the values of qmax: Pb (3.08), Ni (2.79), Zn (2.60) and Cd (2.52). The selectivity remained quite similar to the unmodified algae (Klimmek et al., 2001). Based on the statistical analysis using biosorption data of 37 different algae (20 brown algae, 9 red algae and 8 green algae) from 214 references collected, a statistical review of biosorption of algae as dead biomass were given by Romeral et al. (2006). The available data of maximum sorption uptake (qmax) and biomass-metal affinity (b) of the Langmuir equation for Cd2+, Cu2+, Ni2+, Pb2+ and Zn2+ were listed in the review. Brown algae stand out as very good biosorbents of heavy metals. The information available in connection with multimetallic systems is very poor. Alage achieve values of qmax were close to 1 mmol g-1 for copper and lead and smaller for the other metals. Metal recovery performance was worse for nickel and zinc, but the number of samples for zinc was very small. Algae present a high affinity for Pb. Lead is followed by cadmium, copper, nickel and zinc, all of which present very similar values. The best performer for metal biosorption by brown algae is lead (Romera et al., 2006). Based on the some reviews and relevant articles, some values of sorption uptake were listed as the following table 2.11. In the review by Romera et al. (2006), they found that the best results were obtained with brown algae, followed by green algae, and red algae with the lower average sorption capacity. Baran et al. (2005) also reported that the maximum sorption capacities of Halimeda tuna, Sargassum vulgare, Pterocladia capillacea, Hypnea musciformis, Laurencia papillosa for Cr6+ were determined as 2.3, 33.0, 6.6, 4.7 and 5.3 mg/g, respectively. The results showed that Sargassum vulgare was suitable for removing chromium from aqueous solution. Five different brown seaweeds, Bifurcaria bifurcata, Saccorhiza polyschides, Ascophyllum nodosum, Laminaria ochroleuca and Pelvetia caniculata were studied and their ability to remove cadmium from aqueous solution ranged from 64 to 95 mg g-1 (Lodeiro et al., 2005). Taking Cu(II) as an example, the uptake capacity (qmax) of Cu (II) by various algal species were (qmax: mmol Cu g-1) according to the review (Brinza et al., 2007): Ascophyllum nodosum (Brown algae: 0.99), Caulerpa lentillifera (Green macroalgae: 0.13), Chlorella vulgaris (Green microalgae: 0.67, 1.40), Durvillaea potatorum (Brown algae: 1.30), Ecklonia radiate (Brown algae: 1.11), Glacillaria sp. (Red macroalgae: 0.59), Padina sp. (Brown algae: 0.80, 1.14), Sargassum filipendula (Brown algae: 0.98), Sargassum fluitans (Brown macroalgae: 0.80, 0.96), Sargassum sp.(Brown algae: 0.99, 1.48), Sargassum vulgare (Brown algae: 0.93). Spirulina sp., (Blue green algae: 0.004), Ulothrix zonata (Green macroalgae: 2.77), Ulva sp. (Green macroalgae: 0.75). The results were not able to be compared directly due to the data from the various authors’ reports. Murphy et al. (2007) also studied several dried biomass of the marine macroalgae Fucus spiralis and Fucus uesiculosus (brown), Ulva spp. (comprising Ulva linza, Ulva compressa and Ulva intestinalis) and Ulva lactuca (green), Palmaria palmata and Polysiphonia lanosa (red) in terms of their Cu(II) biosorption performance (Murphy et al., 2007). Ulva spp. Performed extremely efficiently in sequestering copper ions (0.326 mmol/g), maybe due to its high uronic acid content.

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Table 2.11. Sorption parameters in monometallic systems for unpretreated algal biomass Algae Ascophyllum nodosum (B) Ascophyllum nodosum Ascophyllum nodosum Chaetomorha linum (G) Chlorella miniata (G) Chlorella miniata Chlorella vulgaris (G) Chlorella vulgaris Chlorella vulgaris Chlorella vulgaris Chlorella vulgaris Chlorella vulgaris Cladophora glomerata (G) Chondrus crispus (R) Chondrus crispus Codium fragile (G) Codium taylori (G) Codium taylori Corallina officinalis (R) Fucus vesiculosus (B) Fucus vesiculosus Fucus vesiculosus Galaxaura marginata (R) Galaxaura marginata Gracilaria corticata (R) Gracilaria edulis (R) Gracilaria Salicornia (R) Padina sp.(B) Padina gymnospora (B) Padina gymnospora Padina tetrastomatica (B) Padina tetrastomatica Polysiphonia violacea (R) Porphira columbina (R) Sargassum sp. (B) Sargassum sp. Sargassum sp. Sargassum baccularia (B) Sargassum fluitans (B) Sargassum fluitans Sargassum hystrix (B) Sargassum natans (B)

Metal ion Cd Ni Pb Cd Cu Ni Cd Ni Zn Cr6+ Cu Fe3+ Pb Ni Pb Cd Ni Pb Cd Cd Ni Pb Ni Pb Pb Cd Cd Cd Ni Pb Pb Cd Pb Cd Cd Cr6+ Cu Cd Ni Pb Pb Cd

qmax (mmol g-1) 0.338~1.913 1.346~2.316 1.313~2.307 0.48 0.366 0.237 0.30 0.205~1.017 0.37 0.534~1.525 0.254~0.758 0.439 0.355 0.443 0.941 0.0827 0.099 1.815 0.2642 0.649 0.392 1.105~2.896 0.187 0.121 0.2017~0.2605 0.24 0.16 0.53 0.170 0.314 1.049 0.53 0.4923 0.4048 1.40 1.30~1.3257 1.08 0.74 0.409 1.594 1.3755 1.174

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Biosorbents Sargassum natans Sargassum natans Sargassum siliquosum (M) Sargassum vulgare (M) Sargassum vulgare Scenedesmus obliquus (G) Scenedesmus obliquus Scenedesmus obliquus Ulva lactuca (G) Undaria pinnatifida (B)

Ni Pb Cd Ni Pb Cu Ni Cr6+ Pb Pb

0.409 1.1487~1.221 0.73 0.085 1.100 0.524 0.5145 1.131 0.61 1.945

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(B): Brown alga, (G): Green alga, (R): Red alga.

Zhou et al. (1998) found that Spirulina platensis had the highest capacity for Cd, followed by Nannochloropsis oculata, Phaeodactylum tricornutum, Platymonas cordifolia and Chaetoceros minutissimus among those five microalgae tested. Lee et al. (2000) compared chromate adsorption capacities of 48 species of red, brown, or green marine algae from the east coast of Korea. A red marine alga, Pachymeniopsis sp was identified as a highly chromate-selective biosorbent with high adsorption capacity of 225 mg g-1. The alga also showed high selectivity for chromate and its adsorption capacity for other heavy metal ions such as cadmium and manganese was relatively low. According to Matsunaga et al. (1999), twenty four strains out of 191 marine microalgal strains exhibited cadmium (Cd) resistance. They were tested for their Cd removal ability in growth media containing 50 mu M Cd. Six strains out of 19 green algae and one out of five cyanobacteria removed more than 10% of total Cd from the medium. The marine green alga Chlorella sp. NKG16014 showed the highest removal of Cd 48.7% of total. Cd removal by NKG16014 was further quantitatively evaluated by measuring the amount of cell adsorption and intracellular accumulation. After 12 days incubation, 67% of the removed Cd was accumulated intracellularly and 25% of the Cd removed was adsorbed on the algal cell surface. The maximum Cd adsorption was estimated to be 37.0 mg Cd/g using the Langmuir sorption model. The Cd removal by freeze-dried NKG16014 cells also determined. Cd was more quickly adsorbed by dried cells than that by living cells, with a qmax of 91.0 mg Cd g-1. The metal uptakes by the nonliving, dried marine brown algae decreased in the following sequence: U. pinnatifida>H. fusiformis>S. fulvellum (Nayak et al., 2003). Algae affinity and selectivity for metal ions were of interest. The microalgae Chlamydomonas reinhardtii show the affinity order for algal biomass was Pb(II) > Hg(II) > Cd(II). The maximum biosorption capacities of microalgae for Hg(II), Cd(II) and Pb(II) ions were 72.2 ± 0.67, 42.6 ± 0.54 and 96.3 ± 0.86 mg g-1 dry biomass, respectively (Tuzun et al., 2005). The affinity of metals for the red algae Palmaria palmata was found to decrease in the order: Pb2+ > Co2+ > Cu2+ > Ni2+ (Prasher et al., 2004). The selectivity of four ions was related as: Ca>Mg>Cd>K for Laminaria sp.; Cd>Ca>Mg>K for Durvillaea sp.; Ca>Cd>K>Mg for Ecklonia sp.; Mg>Cd>K>Ca for Hormosira sp. And by ion exchange model: Ca>Mg>Cd>K for Laminaria sp.; Cd>Mg>Ca>K for Durvillaea sp.; Ca>Cd>K>Mg for Ecklonia sp.; Mg>Cd>K>Ca for Hormosira sp (figuera et al., 2000). Sheng et al., (2004) have determined the general affinity sequence for Padina sp. as being:Pb>Cu>Cd>Zn>Ni and for Sargassum sp.: Pd>Zn>Cd>Cu>Ni. due to the possibility of metal recovery. According to

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the reference (Romera et al., 2006), table 2.12 offered the average qmax values for each metal in monometallic systems by algae. Table 2.12. Average qmax values (mmol g-1 biomass) for each metal in monometallic systems without treatment Metal ions Cd Ni Zn Cu Pb

Brown 0.930 0.865 0.676 1.017 1.239

Red 0.260 0.272

Green 0.598 0.515 0.370 0.504 0.813

0.651

Average value 0.812 0.734 0.213 0.909 1.127

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From Romera et al. (2006).

The biomass of non-living, dried marine brown algae U. pinnatifida, H. fusiformis, and S. fulvellum harvested in the sea near Cheju Island, Korea were studied for their sorption ability of copper, zinc, and lead. The metal uptakes by biosorbent materials decreased in the following sequence: U. pinnatifida>H. fusiformis>S. fulvellum. The maximum metal uptake values of U. pinnatifida for Cu2+, Pb2+, and Zn2+ in the single metal solution are 2.58, 2.6, and 2.08 meq g-1 in the range of pHs 5.3-4.4, respectively. The metal uptakes by biosorbent materials in the mixed metal solution decreased greatly in comparison to each metal uptake in the single metal solution (Lee et al., 2002). Batch equilibrium sorption experiments were used for screening for cost-effective marine algal biomass harvested from the Gulf of Persian. Biosorption of lead by eight brown, green and red marine algae was investigated. Three species of brown algae, namely Sargassum hystrix, S. natans and Padina pavonia, removed lead most efficiently from aqueous solution, respectively (Jalali et al., 2002). Rincon et al. (2005) compared brown algae and other sorbents with results as the followings (table 2.13). Table 2.13. Values of qmax (mmol g-1) for different sorbents Sorbents Natural zeolite Activated charcoal powder Pseudomonas aeruginosa (bacteria) Rhizopus arrhizus (fungus) Activated charcoal granular Ion exchange resin Fucus vesiculosus

Cu --0.29 0.25 0.03 0.97

Pb 0.18 0.10 0.33 0.50 0.15 1.37 1.04

Cr ---0.27 0..07 0.59 1.12

Ni ------0.08

2.5. EFFECT OF PRE-TREATMENT ON BIOSORPTION As the biosorption process involves mainly cell surface sequesteration, cell wall modification can greatly alter the binding of metal ions. A number of methods have been

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employed for cell wall modification of microbial cells in order to enhance the metal binding capacity of biomass and to elucidate the mechanism of biosorption. The biomass could be given several physical and chemical treatments to tailor the metalbinding properties of biomass to specific requirements. The physical treatments include heating/boiling, freezing/thawing, drying and lyophilization. The various chemical treatments used for biomass modification include washing the biomass with detergents, cross-linking with organic solvents, and alkali or acid treatment. The pretreatments have been suggested to modify the surface characteristics/ groups either by removing or masking the groups or by exposing more metal-binding sites 34 (Vieira and Volesky, 2000). Yeast cells killed by extreme chemical and physical conditions may also show very different properties for metal accumulating compared with the original yeast (Lu and Wilkins, 1996). Now various pretreatment methods were reported to deal with the yeast cells of S. cerevisiae. Physical methods include vacuum and freeze-drying, boiling or heat, autoclaving, mechanical disruption. Chemical methods include treatment with various organic and inorganic compounds, such as acid and caustic, methanol, formaldehyde, etc. Those methods are found to improve metal biosorption to some extent. Alkali treatment of fungal has been shown to increase significantly the metal uptake capacity, whereas acid treatment of biomass almost has no influence on metal biosorption (Kapoor and Viraraghavan, 1995; Wang, 2002a). Due to the important role of cell wall for metal biosorption by non-viable cells, metal biosorption may be enhanced by heat or chemical sterilization or by crushing. Thus degraded cells would offer a larger available surface area and expose the intracellular components and more surface binding sites because of the destruction of the cell membranes (Errasquin and Vazquez, 2003). The biosorption of cadmium and lead ions from synthetic aqueous solutions using yeast biomass was investigated (Goksungur et al., 2005).The waste baker’s yeast cells were treated by caustic, ethanol and heat methods, and the highest metal uptake values for Ca2+ and Pb2+ were obtained by ethanol treated yeast cells. However, Suh and Kim (2000) gave the different results on pretreatment. The equilibrium uptake capacity of lead (mg Pb2+/ g cell dry weight) decreased in the order: original cell (260) >5 times autoclaved cell for 15 min (150) > grinded cell after drying (100) > autoclaved cell for 5 min (30). Brown alga Fucus vesiculosus for copper, cadmium, lead and nickel removal was investigated. Metal sorption yields were modified using different kinds of pretreatment reagents: HCl, CaCl2, formaldehyde, Na2CO3 and NaOH. The Langmuir isotherm was applied to both the non-treated and all treated biomass tests. Calcium chloride was the only chemical that improved the maximum sorption capacity of the biomass (Rincon et al., 2005). Pretreatment of Mucor rouxii biomass on bioadsorption of Pb2+, Cd2+, Ni2+ and Zn2+ with detergent and alkali chemicals such as NaOH, Na2CO3, and NaHCO3 were investigated (Yan and Viraraghavan, 2000). Different alkaline treatments were also studied ( 1M NaOH/ 20 ℃/ 24 h and 10M NaOH/ 107 ℃/ 6 h) (Spanelova et al., 2003). The effect of pretreatment of Aspergillus niger biomass on biosorption of lead, cadmium, copper and nickel was studied. Pretreatment of live A. niger biomass using sodium hydroxide, formaldehyde, dimethyl sulphoxide and detergent resulted in significant improvements in biosorption of lead, cadmium and copper in comparison with live A. niger cells. Pretreatment

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of A. niger reduced biosorption of nickel as compared to live cells (Kapoor and Viraraghavan, 1998). Some modifications can be introduced either during the growth of a microorganism or in the pregrown biomass because the condition in which micro-organisms grow affects its cell components or surface phenol type which in turn affects its biosorption potential (Vianna et al., 2000). Variations in growth conditions possibly bring about changes in composition of the cell surface thereby affecting metal biosorption characteristics of the biomass (Mehta and Gaur, 2005). Some work has been done on the effect of culture conditions of cells on their biosorptive capacity, such as the effect of glucose, cysteine, glucose, ammonium sulphate, phosphate, ammonium chloride, C-, N-, P-, S-, Mg- and K-limited conditions could refer to Chapter 3.7.

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2.6. IMMOBILIZED BIOMASS FOR BIOREACTORS AND REGENERATION/REUSE For industrial application of biosorption, it is important to utilize an appropriate immobilization technique to prepare commertial biosorbents which retain the ability of microbial biomass to sorb metal(s) during the continuous industrial process. The free microbial cells generally are basically small particles, with low density, poor mechanical strength and little rigidity, which may come up with the solid–liquid separation problems, possible biomass swelling, inability to regenerate/reuse and development of high pressure drop in the column mode in real application. Excessive hydrostatic pressures are required to generate suitable flow rates in a fixed or expanded bed reactor. High pressures can cause disintegration of free biomass. These problems can be avoided by the use of immobilized cell systems. The immobilization of the biomass in solid structures would create a material with the right size, mechanical strength, rigidity and porosity necessary for use in practical processes. The immobilized materials can be used in a manner similar to ion exchange resins and activated carbons such as adsorption-desorption cycels (recovery of the adsorbed metal, reactivated and re-use of the biomass) (Veglio and Beolchini, 1997). The authors introduce the immobilization biotechnology in a book which could be refered to (Wang, 2002b). Immobilization technique is one of the key elements for the practical application of biosorption, especially by dead biomass. Various kinds of immobilized S. cerevisiae have been studied with different surpport materials, which can be used in practical biosorption (Veglio and Beolchini, 1997). A number of matrices have been employed for immobilization of cells. Important immobilization matrices used in biosorbent immobilization include sodium or calcium alginate, polysulfone, polyacrylamide, polyurethane, silica (Vijayaraghavan and Yun, 2008). The polymeric matrix determines the mechanical strength and chemical resistance of the final biosorbent particle to be utilized for successive sorption–desorption cycles so it is very important to choose the immobilization matrix. Fluidized beds of Ca-entrapped cells of Chlorella vulgaris and Spirulina platensis were successfully used to recover gold from a simulated gold-bearing process solution containing AuCl4, CuCl2, FeCl2 and ZnCl2 (Vieira and Volesky, 2000). P maltophilia cells immobilized

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with polyacrylamide gel also have a high ability for gold biosorption. The gold adsorbed on the immobilized cells is easily desorbed with 0.1 M thiourea solution. The immobilized P maltophilia cells can be used repeatedly in biosorption-desorption cycles (Tsuruta, 2004). Basidiospores of P. chryosporium were immobilized into Ca-alginate beads via entrapment for the removal of Hg(II) and Cd(II) ions from aqueous solution in the concentrations range of 30~500 mg l-1. The alginate-fungus beads could be regenerated using 10 mM HCl, up to 97% recovery. The biosorbents were reused in three biosorptiondesorption cycles with negligible decrease in biosorption capacity (Kacar et al., 2002). Another important matrix is silica. The silica immobilized product is mechanically strong and exhibits excellent flow characterstics. Trametes versicolor mycelia were immobilized in carboxymethylcellulose, CMC, beads via entrapment, and the bead containing immobilized fungus spores were incubated at 30 degreesC for 3 days to attain uniform growth on the bead surface. After incubation, the live and heat inactivated immobilized fungus on the CMC beads were used for the biosorption of Cu2+, Pb2+ and Zn2+ ions. Plain CMC beads were used as a control system. The maximum biosorption capacities for both immobilized live and heat inactivated Trametes versicolor were 1.51 and 1.84 mmol Cu2+, 0.85 and 1.11 mmol Pb2+ and 1.33 and 1.67 mmol Zn2+ per g of dry biosorbents, respectively. The CMC beads with the immobilized fungus can be regenerated using 10 mM HCl, with up to 97% recovery of the metal ions; the biosorbents reused up to five biosorption-desorption cycles without any major loss in the biosorption capacity (Bayramoglu et al., 2003). The complete biosorption process for metal removal include sorption followed by desorption, i.e., to concentrate the solute. Biotechnological exploitatation of biosorption technology for removal of heavy metal(s) depends on the efficiency of the regeneration of biosorbent after metal desorption. It is important to regenerate the biosorbents especially the biomass preparation/generation is costly. Therefore non-destructive recovery by mild and cheap desorbing agents is desirable for regeneration of biomass for use in multiple cycles. Appropriate elutants are necessary to attain the above aid, which strongly depends on the type of biosorbent and the mechanism of biosorption. Also, the elutant must be (i) non-damaging to the biomass, (ii) less costly, (iii) environmental friendly and (iv) effective (Vijayaraghavan and Yun, 2008). Acidic and alkaline condition were used for desorption. The eluants such as CaCl2 with HCl, HCl with EDTA, NaOH were reported (Vijayaraghavan and Yun, 2008). Desorption data showed that nearly 99% of the Cr(VI) adsorbed on Mucor hiemalis could be desorbed using 0.1N NaOH. Study with the cyclic use of a batch of M. hiemalis repeatedly after desorption, showed that it retain its activity up to five sorption and desorption cycles (Tewari et al., 2005). Desorbent of nitric acid showed high elution efficiency and preservation of biosorptive properties for heavy metal ions (Cr3+, Cd2+, Cu2+) by blue-green algae Spirulina sp (Chojnacka et al., 2005). In a number of studies, the biomass has been immobilized using inert solid supports as biofilms. These inert matrices include polyvinyl chloride, ZirFon R membrane, glass, metal sheets, plastics, uneven surfaces e.g. wood shavings, clay, sand, crushed rocks and porous materials like foams and sponges. The efficiency of desorption is often expressed by the S/L ratio, i.e. solid to liquid ratio. The solid represents the solid sorbent (mg dry wt) and the liquid represents the amount of eluant applied (in ml). High values of S/L are desirable for complete elution and to make the process more economica. Sometimes metal-selective elution is desirable and dependent on

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metal sequesteration mechanism. Dilute mineral acids, EDTA, carbonates and bicarbonates, NH4OH, KHCO3, KCN have been used in various studies to remove metal(s) from the loaded biomass (Vieira and Volesky, 2000). Less attention has been paid to the regeneration ability of the biosorbent, so more relavant work is necessary for future biosorption application. Immobilization probably bring about at least two practical problems: mass transfer limitations and additional process costs (Vijayaraghavan and Yun, 2008). As we pointed out that the limitations of the industrial application of biosorption with immobilized dead cells have been realized from some pilot plants of biosorption. For example, the cost for producing the required biosorbents with waste biomass was too expensive by immobilized techniques and by various pre-treatment processes. Process of regeneration and re-use on-line is complex and very expensive. The co-existed ions and organic matters of solution made matters even more difficult and more complex for real effluents (Wang and Chen, 2006). When developing the immobilization and regeneration technololgy in biosorption application, the amentioned problems should be considered. Figure 2.1 showed the process of preparing different types of microbial biomass into usable biosorbents.

Figure 2.1. Schematic diagram of processing different types of microbial biomass into usable biosorption materials. (Vieira and Volesky, 2000).

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2.7. BIOSORBENT SELECTION AND ASSESSMENT How to select the suitable bisorbents among a large quantity of biomass tested? Availability and economy is a major factor to be taken into account to select biomass for clean-up purposes (Vieira and Volesky, 2000). Correct assessment of the metal-binding capacity of some types of biomass is very important. How to value the sorption performance by a certain biosorbent? How to evaluate the experimental results on biosorption as they have been reported throughout recent literature by authors from different backgrounds? The research group by Volesky discussed the related question in some references (Volesky and Holan, 1995, Kratochvil and Volesky, 1998). Two types of investigations could help to examine a solid-liquid sorption system: (a) equilibrium batch sorption tests and (b) dynamic continuous-flow sorption studies. The Langmuir model and Freundlich model are two widely accepted equilibrium adsorption isotherm models for single solute systems used in the literature. Langmuir

qe =

qmaxbCe 1 + bCe

(2.1)

Freundlich 1/ n

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qe = K F Ce

(2.2)

where qmax is the maximum sorption capacity corresponding to complete monolayer coverage (mmol g-1), Ce is (mmol l-1) the equilibrium solute concentration, and b is the equilibrium constant related to the energy of sorption (or “affinity”) (l mmol-1), KF and n are the Freundlich constants related to the adsorption capacity and intensity of the biosorbent, respectively. Both models do not reflect any mechanisms of sorbate uptake and can hardly have a meaningful physical interpretation in biosorption. (Volesky and Holan, 1995) pointed out that the results from both empirical models cannot be extrapolated, and no predictive conclusions can be drawn for systems operating under different conditions. Both simple basic models also do not incorporate the effects of any external variable environmental factors although capable of describing many biosorption isotherms in most cases. The mechanistic conclusions from the good fit of the models alone should be avoided. Moreover, biosorption isotherms may exhibit an irregular pattern due to the complex nature of both the biomaterials and its varied multiple active sites, as well as the complex solution chemistry of some metallic compounds (Kapoor and Viraraghavan, 1995; Volesky and Holan, 1995; Kim et al., 1998). The evaluation of sorption systems based on the classical sorption isotherm derived from equilibrium batch contact experiments carried out under the same environmental conditions (e.g. pH, temperature, ionic strength). A quantitative comparison of two different sorption systems can only be done at the same equilibrium (final, residual) concentration. Thus comparison at low equilibrium concentration Cf (e.g. 10 mg l-1) and another at high

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equilibrium concentration Cf (e.g. 200 mg l-1) are made in some biosorption screens (figure 2.2). Biosorption performance in terms of uptake showed be judged at the same (selected: e.g. 10 and/or 200 mg l-1) equilibrium (final) metal concentration. Comparisons of qmax are also useful. Langmuir isotherm model incorporates two easily interpretable constants: qmax and b. Low values of b are reflected in the steep initial slope of a sorption isotherm, indicating a desirable high affinity. Thus, for ‘good’ sorbents in general, one is looking for a high qmax and a steep initial sorption isotherm slope (i.e. low b) (Kratochvil and Volesky, 1998). Any other comparison carries an inherent error. The comparison of sorbent performance based on ‘% removal’ (percent of metal removal) is an often-used criterion encountered in the literature. However, it it does not indicate the concentration range, and could lead to outright misleading conclusions on the relative sorption performance (Kratochvil and Volesky, 1998). They also strengthened that,

Figure 2.2. Comparison the performance of two biosorbents (Kratochvil and Volesky, 1998).

“Even if all experimental parameters are given, this criterion can only result in a qualitative, and relative comparison (better or worse performance) that is adequate only for material screening purposes. Any figures given are essentially misleading because they lead to inadvertent and erroneous comparative calculations. The presence of other ions in solution can complicate the evaluation of the sorption system to a large degree, depending on the way the new solute species interact with the sorbent and with the original one. Knowledge of these aspects may not be readily available. Appropriate and meaningful evaluation of a sorbent system with three or more metallic ions becomes very complicated, if not impossible for all practical purposes.” ‘% removal’ can only serve the purpose of crude orientation, such as a qualitative comparison, often used for quick and very approximate screening of (bio)sorbent materials (Kratochvil and Volesky, 1998). To obtain the laboratory equilibrium sorption data, enough time must be allowed for the sorption system to reach equilibrium. A simple preliminary sorption kinetics test will establish the exposure time necessary for the given sorbent particles to reach the equilibrium state (characterized by unchanging sorbate concentration in the solution) by using time-based analyses (Volesky and Holan, 1995).

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Evaluation of equilibrium sorption performance needs to be supplemented by processoriented studies of its kinetics and eventually by dynamic continuous-flow tests. The rate of the sorption metal uptake, together with the hydrodynamic parameters, determines the size of the contact equipment. Those key process parameters could be used for comparative, process design, and scale-up purposes (Volesky and Holan, 1995). Several reviews on the state art of equilibrium models and kinetics models can be refered to (Veglio and Beolchini, 1997; Kratochvil and Volesky, 1998; Volesky, 2003; Gavrilescu, 2004). In his book entitled “sorption and biosorption”, Volesky (http://www. Biosorption.mcgill.ca) also offered a detailed introduction to biosorption equlibrium and kinetics, e.g. single-sorbate isotherms, multi sorbate sorption equilibrium (multi-compontet Langmiur models considering electrostatic binding, the effect of pH, surface complex model, Donnan model considering ionic strength, Wilson model for ion exchange etc), Biosorption batch dynamics (mass transfer model for biosorption rate), dynamic continuous-flow reactor/contactor systems modeling of column performance including equlibrium column model, mass transfer model and derivation of mass transfer model to evaluate column sorption performance. Kinetics studies and dynamic continuous-flow investigations, offering information on the rate of the sorption metal uptake, together with the hydrodynamic parameters, are very important for biosoprtion process design (Volesky and Holan, 1995). However, biosorption kinetics studies are insufficient according to literature published so far.

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2.8. DEVELOPMENT OF NOVEL BIOSORBENTS Routinely lots of biosorbents, such as bacteria, fungi and algae are discovered and distinguished by trial and experiments. Some easily available biomass in their native state or after simple processing were tested for their biosorption performance, in particular bio-waste generated as a by-product of large-scale industrial fermentation, olive mill solid residues, activated sludge from sewage treatment plants, biosolids, aquatic macrophytes, and other plant derived materials (Ahluwalia and Goyal, 2007). As above-mentioined, chemically modification methods could increasing/activating the binding sites on the biomass surface including pretreatment, binding site enhancement, binding site modification and polymerization (Vijayaraghavan and Yun, 2008). For example, the grafting of long polymer chains onto the biomass surface via direct grafting or polymerization of a monomer could introduce functional groups onto the biomass surface. Deng and Ting (2005b) modiefied Penicillium chrysogenum by graft polymerization of acrylic acid (AAc) on the surface of ozone-pretreated biomass. The sorption capacity for copper and cadmium increased significantly as a large number of carboxyl groups were present on the biomass surface, especially when the carboxylic acid group was converted to carboxylate ions using NaOH. Another method of making novel biosorbents is genetic engineering technology which has the potential to improve or redesign microorganisms, so enhance the selectivity as well as the accumulating properties of the cells.

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Many genes on metal uptake or detoxification or tolerance have been identified (Rosen, 2002). For example, the S. cerevisiae Arr4p plays an important role in metal ions (As3+, As5+, Co2+, Cr3+, Cu2+ , VO 43− ) tolerance (Shen et al., 2003). Higher organisms produce cysteine-rich peptides such as glutathione (GSH), phytochelatins (PCs) and metallothioneins (MTs) which could bind metal ions (Cd, Cu, Hg etc), usually occurring in the animal kingdom, plants, eukaryotic microorganisms or some prokaryotes.). MT, a specific metal-binding protein, can be induced by many substances, including heavy metal ions, such as Cd, Cu, Hg, Co, Zn etc (Vijver et al., 2004). However, MT in the yeast of S.cerevisiae can only be induced by Cu, hence called Cu-MT. MT has been paid much attention recently because of the potential application in meta removal. In addition to MT, other cellular thiols influencing the sensitivity to toxic metals include glutathione (GSH), phytochelatins (≡ cadystins (γ-Glu-Cys)nGly), labile sulfide (Perego and Howell, 1997, Gharieb and Gadd, 2004). Tripeptide glutathione (GSH) is a typical low molecular weight cellular thiol and function as a storage form of endogenous sulphur and nitrogen as well as detoxification of metal ions. GSH in S.cerevisiae may account for 1% of the cell dry weight (Gharieb and Gadd, 2004). Based on the understanding of metal uptake mechanism, engineered technology, including the cell surface display technology have been reported to improve the performance of biomass in metal removal from solution (Kuroda et al., 2002, Bae et al., 2003, Kuroda and Ueda, 2003). Kuroda et al. (2002) have constructed a cell surface-engineered yeast S.cerevisiae which displays histidine hexa-peptide, the engineered yeast can chelate copper ion, and possesses the property of the self-aggregation, which indicated the potential application for bioremediation of heavy metal pollution. Express MTs or PCs on the cell surface could dramatically increases whole-cell accumulation of metal ions. According to Bae et al. (2003) the metalloregulatory protein MerR, which exhibits high affinity and selectivity toward mercury, was exploited for the construction of microbial biosorbents specific for mercury removal. Whole-cell sorbents were constructed with MerR genetically engineered onto the surface of Escherichia coli cells by using an ice nucleation protein anchor. The presence of surface-exposed MerR on the engineered strains enabled sixfold higher Hg2+ biosorption than that found in the wild-type JM109 cells. Hg2+ binding via MerR was very specific, with no observable decline even in the presence of 100-fold excess Cd2+ and Zn2+. The Hg2+ binding property of the whole-cell sorbents was also insensitive to different ionic strengths, pH, and the presence of metal chelators. Bae et al. (2003) suggested that microbial biosorbents overexpressing metalloregulatory proteins may be used similarly for the cleanup of other important heavy metals. An attractive alternative strategy is to develop organisms harboring synthetic genes encoding protein analogs of PCs with the general structure (Glu-Cys)nGly (ECs) (Bae et al., 2000). A gene fusion system consisting of the signal sequence and the first nine amino acids of lipoprotein (Lpp) joined to a transmembrane domain from outer membrane protein A (OmpA) has been used successfully to anchor a variety of proteins and enzymes onto the cell surface (Richins et al., 1997). Bae et al. (2000) constructed the recombinant E. coli strains that anchor and display functional synthetic phytochelatins ranging from 8–20 cysteines (EC8, EC11, and EC20) onto the cell surface using this Lpp-OmpA fusion system. Synthetic genes encoding for several metal-chelating phytochelatin analogs (Glu-Cys)(n)Gly (EC8 (n = 8), EC11 (n = 11), and EC20 (n = 20) were synthesized by Bae et al. (2000), linked to a lppompA fusion gene, and displayed on the surface of E. coli. For comparison, EC20 was also

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expressed periplasmically as a fusion with the maltose-binding protein (MBP-EC20). Purified MBP-EC20 was shown to accumulate more Cd2+ per peptide than typical mammalian metallothioneins with a stoichiometry of 10 Cd2+/peptide. Cells displaying synthetic phytochelatins exhibited chain-length dependent increase in metal accumulation. For example, 18 nmoles of Cd2+ mg-1 dry cells were accumulated by cells displaying EC8, whereas cells exhibiting EC20 accumulated a maximum of 60 nmoles of Cd2+ mg-1 dry cells. Moreover, cells with surface-expressed EC20 accumulated twice the amount of Cd2+ as cells expressing EC20 periplasmically. The ability to genetically engineer ECs with precisely defined chain length could provide an attractive strategy for developing high-affinity bioadsorbents suitable for heavy metal removal (Bae et al., 2000). Molecular breeding of yeast with higher metal-adsorption capacity was investigated by expression of histidine-repeat insertion in the protein anchored to the cell wall (KambeHonjoh et al., 2000).

2.9. COMMERCIAL APPLICATIONS

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2.9.1. Several Attempts of the Biosorption Commercialization Some commercial biosorbents were reported. In the early 1980s, the first patents appeared claiming the use of specific microbial biomass types as biosorbents for wastewater treatment (Tsezos, 2001). In the early 1990s, other biomaterials were developed and commercialized, including AlgaSORB™, AMT-BIOCLAIM™ (MRA), Bio-fix, etc., prepared by immobilization technology (Volesky, 1990;Garnham, 1997;Veglio and Beolchini, 1997). The immobilization of the microbial biomass seems indispensable for biosorption application, and also can make use of traditional chemical engineering reactor configurations, such as upflow or downflow packed bed reactors, fluidized bed reactors. In the early 1990s, three enterprises in North America were mentioned in developing the biosorption system: B. V. SORBEX, Inc. in Montreal, Canada, have produced a series of biosorbents based on different types biomaterial, including the algae Sargassum natans, Ascophyllum nodosum, Halimeda opuntia, Palmyra pamata, Chondrus crispus and Chlorella vulgaris. The biosorbent was effective over a range of pH values and solution conditions, and can biosorb a wide range of metals. The metal biosorption are not affected by calcium or magnesium, as well as are not affected by organics and can be regenerated easily (Volesky, 1990). Advance Mineral Technologies Inc. In Golden, Colorado, developed a broad-range metal removal biosorbent based on Bacillus sp, but it stopped in late 1988 (Volesky, 1990). AlgaSORB™ was produced by Bio-recovery Systems Inc. in Las Cruces, New Mexico. The biosorbent based on immobilised Chlorella (a freshwater alga) in silica or polyacrylamide gels. It can efficiently remove metal ions from dilute solution of 1 to 100 mg/L, thus may reduce the concentration to below 1 mg/L or lower. The heavy metal biosorption was not affected by light metals such as Ca and Mg. The biosorbent resembles an ion-exchange resin and can undergo more than 100 biosorption-desorption cycles (Kuyucak, 1990; Garnham, 1997).

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AMT-BIOCLAIM™ (Visa Tech Ltd), which comprises of Bacillus subtilis, treated using strong caustic solution, washed with water, and immobilized as porous balls onto polyethyleneimine and glutaraldehyde efficiently removes metal (Brierley, 1990;Garnham, 1997;Veglio and Beolchini, 1997;Vijayaraghavan and Yun, 2008). Brierley (Brierley, 1990) introduced the production and application of this kind of Bacillus-based biosorbent. AMTBIOCLAIM™ based on Bacillus biomass can accumulate 2.90 mmol Pb g-1, 2.39 mmol Cu g1 , 2.09 mmol Zn g-1, 1.90 mmol Cd g-1 or 0.8 mmol Ag g-1 metal cations with high efficient of more than 99% from dilute solutions (Kuyucak, 1990). It is non-selective and metal(s) can be stripped using H2SO4, NaOH or complexing agents and the granules can be regenerated for repeated use (Gupta et al., 2000). AMT-BIOCLAIMTM is able to accumulate gold, cadmium and zinc from cyanide solutions and is therefore suitable to metal-finishing operations (Atkinson et al., 1998). The biosorbent BIO-FIX is made up of a variety of biomasses, including Sphagnum peat moss, algae, yeast, bacteria, and/or aquatic flora immobilized in high density polysulfone. This biosorbent is selective for toxic heavy metals over that of alkaline earth metals (Vijayaraghavan and Yun, 2008). U. S. Bureau of Mines (Golden, Colorado) produced the granular Bio-fix, which has been tested extensively for the treatment of acid mine waste (Garnham, 1997). It is said Zn binding to the biosorbent BIO-FIX is about 4-fold higher than the ion exchange resins. The metal affinity followed Al3+ > Cd2+ > Zn2+ > Mn2+ and a much lower affinity for Mg2+ and Ca2+. Metal(s) can be eluted using HCl or HNO3 and the biosorbent can be used for more than 120 extraction–elution cycles (Gupta et al., 2000). The type of these system employed is dependent on the amount of flow to be processed, its composition, its continuity, and the regeneration conditions. From the process of application point of view, the design and operation of the biosorption are similar to the established technologies of ion exchagnse or activated carbon adsorption. In these systems, pre-treatment of a liquor may be required in some cases, depending on the suspended-solids removal prior to biosorption (Volesky, 1990). All the commercial biosorption enterprises, including both Bio-recovery Systems and B. V. Sorbex offer small “canisters” as flow-through fixed-bed systems, as well as large-scale fluidised-bed, pulsed-bed systems, multielement large-scale treatment schemes capable of handling flows in excess of 100 m3/day (Volesky, 1990). It is said the fluidized-bed contactors would offer optimum removal process using large amount of MRA, 79 kg of MRA to treat wastewater in 3.8 to 30 L per minute (Kuyucak, 1990). The performance of the several biosorbents were summarized by Volesky (1990), the major features are high versatility for wide-range of operate condition, metal selectivity and not affect by alkaline earth common light metal, no concentration dependence (good for ≤10 ppm or ≥100 ppm), high tolerance for organics, and convenient and effective regeneration. Immobilized Rhizopus arrhizus biomass was tested for recovery of uranium from an ore biolecha solution (Veglio and Beolchini, 1997). Two other commercialized biosorbents include ‘MetaGeneR’ and “RAHCO Bio-Beads” are effective to remove metal from electroplating or mining waste streams. Information relating to their industrial application is still limited although the extensive laboratory and field trials were carried out on them (Atkinson et al., 1998). Metal uptake by synthetic or biosynthetic chemicals was reported. Mercury-binding synthetic biosorbent was called VitrokeleTM 573. The biosorbent is an insoluble composition comprising Hg-binding groups in particular cysteine, convalently fixed to the surface of a

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suitable insoluble carrier. The basic formula of the group is carrier-R-Cys, where Cys is a cysteine redidue, and R is a hydrocarbon chain. The variation and synthesis were introduced in the (Huber et al., 1990). The batch and column tests demonstrate that mercury was efficiently removed from solutions containing high concentration of sulfate and chloride. V573 could be reused over multiple cycles (Huber et al., 1990). Another VitrokeleTM product was the iron-binding synthetic biosorbent. The common groups binding iron are hydroxamates and phenolate-catecholates, usually found in siderouphore. The catecholate type VitrokeleTM was tested in a column containing 600 μM radioactive iron, cobalt, sodium and cadmium. The result showed that the VitrokeleTM showed good affinity for Fe, poor affinity for Co and no affinity for Na or Cd. Comparing with the performance of commercial ion exchangers using artificial seawater, the VitrokeleTM to remove trace amounts of iron in the presence of high concentration of other cations was not interfered by other cations and was not saturated quickly (Huber et al., 1990). According to Wase et al. (1997), attempts of full-scale metal and organic removal from industrial wastewater mainly focused on the biosorbent of peat during the past 20 years (calculated from the year of 1997). Some peat on-site wastewater treatment systems were operation in Maine, Alaska, Canada, and Ireland for ion removal. The peat was regarded utilizable and disposable. With the emphasis toward using readily renewable biosorbents, peat-involving system become much more engineered an much more specific, such as membrane-media extraction process developed by Harrison Western Environmental Services Inc. of Lakewood, Colorado. The process use peat moss capsules and is able to effectively treat As, Cd, Pb, Ni, Se and other metals from several type of wastewater, including electroplating rinse water, pulp and paper mill discharge, municipal wastewater and acid mine drainage. Meeting the renewable demand, another alternative is to take a pure component in a load-regeneration cycle system. The cellulosic sago waste was more effective than peat in Pb removal (Wase et al., 1997). Peat was regarded as the most successful and the rigorously scrutinised biosorbent in its natural state or in a modified form. Designs for large-scale peat-sorption processes are also available for application. However, the supplies of peat are finite, and probably not the best biomaterial resource for commercialization aim. Thus, the development of other forms of biosorption is essential (Forster and Wase, 1997;Wase et al., 1997). Three types biomass of algae, fungi and wastes were suggested as potential biosorbents basis materials after predicting the future for biosorption application (Forster and Wase, 1997).

2.9.2. Application Feasibility and Considerations Despite those attempts of biosorption application or commercialization, Tsezos (2001) as well as Volesky and Naja (2005) pointed out that attempts have failed to obtain successful commercial application in the market. Obviously, biosorption application meet with the great difficulties, although the biosorption seems have the following advantages: (1) versatility and flexibility for a vide range of applications; (2) robustness; (3) selectivity for heavy metals over alkaline earth metals; (4) ability to reduce metal concentration to very low level such as drinking water standards in some cases; (5) cost-effectiveness against alternative processes (Garnham, 1997).

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Volesky and Naja (2005) analyzed the feasibility of biosorption process in detail and are optimistic on the biosorption future on a stage-wise approach. Assessment of the competing technologies (precipitation, reverse osmosis, ion Exchange, bio-reduction), assessment of the market size, as well as assessment of costs of new biosorbents should be considered with highest priority at the early stage in assessment of the commercial potential and feasibility of application of the new technology based on the family of new biosorbent products (Volesky and Naja, 2005). After analysis, Volesky and coworkers proposed the following views: (1) Huge markets already exist for cheap biosorbents, because a large amount of heavy metal is released into waters from various polluting industries, and because ion exchange is expensive. (2) The partnership approach is advisable for demand of innovative process ventures, i.e., a solid capitalization. Identification of potential synergies and partners appears critical considering biosorption as a direct competitor of ion exchange. A handful of huge transnational companies controlling the ion exchange resin market are difficult in operative decision making. Dynamic consulting companies are not capital-rich entities although in an excellent position to acquire and push new process technologies into the marketplace. Pioneering and propagation of innovative biosorption process is not appealing mining and ore processing companies although they appear to be excellent “clients” for innovative clean-up technologies. The above mentioned aspects make biosorption to a wide industrial application difficult despite of its excellent performance from the R&D angle. (3) Biosorption to treat the simulated AMD liquid waste, ready for demonstration tests, as an example, was introduced. In view of Volesky and coworkers, the enormous potential of application for biosorption and its strong economic and technical advantages open considerable market opportunities that can actually be quantified through a responsible market analysis (Volesky and Naja, 2005). Kuyucak (1990) discussed the feasibility of biosorbents application. Metal situation, the cost biosorbents, the capacity and selectivity, the fate of exhausted biosorbent are all should be considered. The author compared biosorption with the several existing technology, including evaporation and reverse osmosis techniques, memabrane processes, precipitation and classification techniques, activated carbon and ion exchange resin. The biosorpton exhibited some extraordinary properties as follows: (1) selective at low metal concentration; (2) low affinity for Ca and Mg; (3) effective over the broad range conditions, including pH (3 to 9), temperature (4 to 90°C); (4) meet the regulation; (5) low capital investment and low operation cost; (6) Converting pollutant metals to a metal product thus eliminated the cost and liability of toxic sludge. However, the fate of exhausted biosorbent in fact remains relatively unanswered(Vijayaraghavan and Yun, 2008). Precipitation and electrowinning procedures were supposed to re recover metals from concentrated solutions. However, the final disposal of the material should be addressed. Landfill or incineration still have their problems (Vijayaraghavan and Yun, 2008). Atkinson et al. (1998) think that the feasibility of a potential biosorben for inorganics removal from industrial effluents should be considered. The biosorption needs to effectively compete both on a cost and performance basis with existing methods before industry will accept and implement it. These factors include: (i) the effluent characteristics, such as volume, type of contaminant and competitive ions, solution chemistry, pH and temperature adjustment; (ii) biomass characteristics, such as availability, mechanical stability, capacities, efficiencies and metal selectivity of the biosorbent, ease of recovery and regenerative properties of the biomass, contaminant specificity and reaction kinetics, and immunity from interference by other effluent components or operating conditions; (iii) process

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characteristics, such as capital and operating costs, economic and performance equivalence to existing chemical and physical processes, batch/continuous and land space requirements. In fact, proper and cheap immobilization techniques are vital for biosorption application, deciding the design and type of process to be employed (batch/continuous). Kapoor and Viraraghavan (1997) proposed several factors affecting the application of a biosorbent in practice: (i) the biosorptive capacity; (ii) the availability of the biosorbent; (iii) the cost of the biosorbent; (iv) the ease of regeneration and subsequent use of the biosorbent; and (v) the ease with which the biosorbent can be used in various reactor configurations. Vijayaraghavan and Yun (2008) also offered some important features required for the successful application of biosorption technology to real situations include. Kratochvil and Volesky (1998) strengthened and pointed out that the limited understanding of the metal biosorpiton mechanisms has hindered the application of biosorption. Selection of industrial effluents for pilot testing has remained largely intuitive. Therefore, exploring the mechanism of metal uptake by dead biomass was a real challenge for the field of biosorption . Cost is a major factor of biosorbent systems in application. The overall economics of the biosorbent was influenced mainly by the cost of procuring/ growing the biomass and the cost of immobilization process. The cost of commercialized biosorbents must be considerably lower in cost than ion-exchange resins, activated carbon and other agents. Bulk production costs of specifically cultured algae and fungi are in the order of £2000-£10000 per ton. The commercially supplied, dried seaweed cost in the order of £200-£300 per ton. Waste biomass including agricultural wastes will be expected considerable cheaper than this (Edyvean et al., 1997). Kuyucak (1990) discussed the cost of biosorbents and the ceonomc assessment of biosorption process. Harvesting and drying are the major costs from marine algal biomass types. Usually the immobilization of biomass is simple and inexpensive, thus the source of raw biomass was the final cost of a biosorbent. The regeneration, kinetics, bioosorption performance, etc. are all important factors on the cost of a biosorbent process. Although the full costs of an algal-based biosorption metal recovery system are not well documented, Garnham (1997) described some authors’ work on the costs assessment. The cost assessment of two biosorption processes, alkaline precipitation and ion-exchange for treating electroplating waste (a total metal concentration including nickel, cadmium, chromium and zinc was 60 mg l-1) with a flow rate of 50000 gallons per day, five days a week (1 gallon= 4.5 l). It was found that the capital equipment price included metal removal, biosorbent regeneration and metal recovery systems. AMT-Bioclaim process based on Bacillus subtilis exhibited a 50% saving over alkaline precipitation and a 28% saving over ion-exchange. The cost of the Bio-fix process (partially based on algal biomass) was compared with lime precipitation. The result showed that the costs of both the processes were similar per 1000 gallons of waste treated, but the recovered metals from the biofix could offer some income (Garnham, 1997). Some pilot installations and a few commercial scale units constructed in the USA and in Canada, not only confirmed the applicability of biosorption as the basis for recovery process, but also helped people to realize the limitations of the industrial application of biosorption. There is the absence of a reliable supply of waste microbial biomass suitable for biosorption applications. Fermentation industry was reluctant or unable to secure a steady supply of waste microbial biomass as the inexpensive raw material. The cost for producing the required biomass for the sole purpose of transforming this biomass into biosorbents was shown to be

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too expensive. Furthermore, the immobilized biomass distribution, regeneration, recycling and re-use made the above issues even more complex and more difficult (Tsezos, 2001). Faced with the great difficulties of biosorption application, some authors proposed some suggestions. Volesky and Naja (2005) think that the failure of the process commercialization is due to mainly non-technical pitfalls involved in commercialization of technological innovations. As solid capitalization is required for innovative process ventures, partnership approach is perhaps advisable. However, the choice of partners appears critical. Malik (2004) advised to use growing microbes as a feasible alternate to pure biosorptive removal of metal contaminants from complex industrial effluents. Tsezos (2001) suggested a hybrid technologies either intra-biotechnological or inter-technologica, making use of a combination of various processes, including biosorption. Biosorption is a desirable component in the design of flow sheets because the biosorption can effectively sequester dissolved metals out of dilute complex solutions in high efficiency and rapid intrinsic kinetics. These characteristics make biosorption an ideal candidate for the treatment of high volume low concentration complex waste waters (Tsezos, 2001). Biosorption appear to be suitable as secondary or polishing applications for metal removal from dilute waste streams, which would be competitive with ion-exchange resin based on final cost-beneficial analysis (Edyvean et al., 1997). They think the greatest use for biosorption may be in modular system for small companies, e.g for specific treatment. In one word, there is a lot of work to do for biosorption application in real effluent.

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2.10. OPPORTUNITY OF BIOSORPTION RESEARCH A large amount of researches on metal biosorption have been published to elucidate the principles of this effective metal-concentration phenomenon during the past 30 years. Biosorption is regarded as a potential cost-effective biotechnology for the treatment high volume low concentration complex waste waters containing heavy metal(s) (Wang and Chen, 2006). Some efficient natural biosorbents have been identified that require little modification in their preparation. There have been few investigations examining the compatibility of the biosorbent for real industrial effluents. However, several attempts of engineering scale-up of the biosorption process or commercialization of the process based on experience from conventional sorption operations so far have not been successful. The biosorption has not been applied as yet while it seems that biosorption could hardly have any competition in many types of large-scale environmental metal removal applications (Volesky and Naja, 2005).

2.11. CHALLENGES OF BIOSORPTION RESEARCH Heavy metal removal by biosorption is extensively investigated during last several decades (Gadd, 2009). Numerous references have been published focusing on different aspects of heavy metal biosorption during past decades. These researches, to a certain degree, provided a better understanding of metal biosorption. More information on biosorption is required, and there will be more research or application attempts in future. Biosorption is

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basically at lab-scale in spite of its development for tenth years. That mechanism is not fully understood (Kratochvil and Volesky, 1998), and the inert shortcomings of biosorption technology are the two major factors to limit biosorption application (Tsezos, 2001). Moreover the difficulty of innovative environmental technologies into markets is also a factor which should be considered in attempts of biosorption application (Volesky and Naja, 2005). From R&D angle, according to published references, the biosorption field has to meet three major challenges. First, it is necessary to continue to search for and select the most promising types of biomass from an extremely large pool of readily available and inexpensive biomaterials (Kratochvil and Volesky, 1998). Second, mechanism of metal biosorption is understood to a limited extent. It is necessary to identify the mechanism of metal uptake by biosorbents and understood microbe-metal interaction. Third, biosorpiton process is basically in the stage of laboratory-scale study. Application of biosorption is in great difficulties and almost a failure in attempt of practicing biosorpiton process (Tsezos, 2001). Great efforts have to be taken to improve biosorption process of dead or living cells, including immobilization of biomaterials, improvement of regeneration and re-use, optimization of biosorption process et al.

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2.12. SELECTION OF BIOMATERIALS A whole family of very cheap biosorbent materials based on natural or waste biomass constitutes the basis for the biosorption application in treatment of metal-bearing industrial effluents. Now a large number of biomass types have been tested for their metal binding capability under various conditions, and some species are identified as excellent biomass. However, to screen and select the most promising biomass with sufficiently high metalbinding capacity and selectivity for heavy metals are suitable for use in a full-scale biosorption process, the first major challenge in the biosorption field, is being continued (Kratochvil and Volesky, 1998). The study of the biomass sources and costs are particularly important, and will allow a measurement of the economic performance of the process. The primary significant difference between the biosorption and ion exchange processes is the low cost of the biosorbent. For this reason, the study of the biomass sources and costs are particularly important (Volesky and Naja, 2005).

ACKNOWLEDGMENTS The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 50830302; 50808111; 50278045), China Postdoctoral Science Foundation funded project (Grant No. 20080430350), special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (Grant No. 08K05ESPCT) and the Basic Research Fund of Tsinghua University (Grant No. JC2002054), to carry out the relevant research works.

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REFERENCES Ahluwalia S. S., Goyal D., Bioresour. Technol. 98(2007) 2243-2257. Akthar N., Sastry S., Mohan M., Biotechnol. Lett. 17(1995) 551-556. Al-Saraj M., Abdel-Latif M. S., El-Nahal I., Baraka R., J. Non-Cryst. Solids. 248(1999) 137140. Alasheh S., Duvnjak Z., Biotechnol. Progr. 11(1995) 638-642. Arica M. Y., Kacar Y., Genc O., Bioresour. Technol. 80(2001) 121-129. Atkinson B. W., Bux F., Kasan H. C., Water SA. 24(1998)129-135. Avery S. V., Tobin J. M., Appl. Environ. Microbiol. 58(1992) 3883-3389. Awofolu O. R., Okonkwo J. O., Roux-Van Der Merwe R., Badenhorst J., Jordaan E., Electronic J. Biotechnol. 9(2006) 340-348. Bae W., Chen W., Mulchandani A., Mehra R. K., Biotechnol. Bioeng. 70(2000) 518-524. Bae W., Wu C. H., Kostal J., Mulchandani A., Chen W., Appl. Environ. Microbiol. 69(2003) 3176-3180. Bag H., Lale M., Turker A. R., Fresenius J. Anal. Chem. 363(1999a) 224-230. Bag H., Turker A. R., Lale M., Anal. Sci. 15(1999b) 1251-1256. Bag H., Turker A. R., Tunceli A., Lale M., Anal. Sci.17(2001) 901-904. Bai R. S., Abraham T. E., J. Sci. Indus. Res. 57(1998) 821-824. Bakkaloglu I., Butter T. J., Evison L. M., Holland F. S., Hancock I. C., Water Sci. Technol. 38(1998) 269-277. Bapat P. M., Kundu S., Wangikar P. P., Biotechnol. Progr. 19(2003) 1683-1688. Baran A., Baysal S. H., Sukatar A., J. Environ. Biol. 26(2005) 329-333. Barros L. M., Macedo G. R., Duarte M. M. L., Silva E. P., Lobato A., Brazilian J. Chem. Eng. 20(2003) 229-239. Basumajumdar A., Pal T. K., Bhattacharyya S., J. Indian Chem. Soc. 80(2003) 899-902. Bayramoglu G., Bektas S., Arica M. Y., J. Hazard. Mater. 101(2003) 285-300. Bayramoglu G., Denizli A., Bektas S., Arica M. Y., Microchem. J. 72(2002) 63-76. Beolchini F., Pagnanelli R., Toro L., Veglio F., Water Res. 40(2006) 144-152. Bhainsa K. C., D'Souza S. F., Biotechnol. Tech. 13(1999) 695-699. Bhattacharyya S., Pal T. K., Basumajumdar A., Banik A. K., J. Indian Chem. Soc. 79(2002) 747-750. Brady D., Stoll A., Duncan J. R., Environ. Technol. 15(1994) 429-438. Brierley J. A. Production and application of a Bacillus-based product for use in metals biosorption, CRC press, 1990. Brinza L., Dring M. J., Gavrilescu M., Environ. Eng. Manage. J. 6(2007) 237-251. Bustard M., McHale A. P., Bioprocess Eng. 19(1998) 351-353. Cabuk A., Ilhan S., Filik C., Caliskan F., Turkish J. Biology. 2005;29(1):23-28. Celaya R. J., Noriega J. A., Yeomans J. H., Ortega LJ, Ruiz-Manriquez A., Bioprocess Eng. 22(2000) 539-542. Chang J. S., Law R., Chang C. C., Water Res. 31(1997) 1651-1658. Chen X. C., Wang Y. P., Lin Q., Shi J. Y., Wu W. X., Chen Y. X.., Colloids Surf., B 46(2005) 101-107. Choi S. B., Yun Y. S., Biotechnol. Lett. 26(2004) 331-336. Chojnacka K., Chojnacki A., Gorecka H., Chemosphere 59(2005) 75-84.

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Davis T. A., Ali F. E., Giannitti E., Volesky B., Mucci A., Water Qual. Res. J. Can. 39(2004) 183-189. Davis T. A., Llanes F., Volesky B., Diaz-Pulido G., McCook L., Mucci A., Appl. Biochem. Biotechnol. 110(2003a) 75-90. Davis T. A., Llanes F., Volesky B., Mucci A., Environ. Sci. Technol. 37(2003b) 261-267. Davis T. A., Volesky B., Mucci A., Water Res. 37(2003c) 4311-4330. Day R., Denizli A., Arica M. Y., Bioresour. Technol. 76(2001) 67-70. de Vargas I., Macaskie L. E., Guibal E., J. Chem. Technol. Biotechnol. 79(2004) 49-56. Deng S. B., Ting Y. P., Water Res. 39(2005a) 2167-2177. Deng S. B., Ting Y. P., Langmuir. 21(2005b) 5940-5948. Dias M. A., Lacerda I. C. A., Pimentel P. F., de Castro H. F., Rosa C. A., Lett. Appl. Microbiol. 34(2002) 46-50. Diniz V., Volesky B., Water Res. 39(2005) 239-247. Donmez G., Aksu Z., Process Biochem. 35(1999) 135-142. Dursun A.Y., Fresenius Environmental Bulletin. 12(2003) 1315-1322. Dursun A.Y., Biochem. Eng. J. 28(2006) 187-195. Dursun A.Y, Uslu G., Cuci Y., Aksu Z., Process Biochem. 38(2003a) 1647-1651. Dursun A. Y., Uslu G., Tepe O., Cuci Y., Ekiz H. I., Biochem. Eng. J. 15(2003b) 87-92. Edyvean R. G. J., Williams C. J., Wilson M. W., Aderhold D., Biosorption using unusual biomasses, CRC Press 1997. Errasquin E. L., Vazquez C., Chemosphere 50(2003) 137-143. Ferraz A. I., Tavares T., Teixeira J. A., Chem. Eng. J. 105(2004) 11-20. Filipovic-Kovacevic Z., Sipos L., Briski F., Food Technol. Biotechnol. 38(2000) 211-216. Forster C. F., Wase D. A. J., Biosorption: The future. In: Biosorbents for Metal Ions, CRC Press 1997. Fourest E., Canal C., Roux J. C., Fems Microbiol. Rev. 14 (1994) 325-332. Gabriel J., Vosahlo J., Baldrian P., Biotechnol. Tech. 10(1996) 345-348. Gadd G. M., New Phytologist. 124(1993) 25-60. Gadd G. M., White C., J. Chem. Technol. Biotechnol. 55(1992) 39-44. Gadd G. M., J. Chem. Technol. Biotechnol. 84(2009) 13-28. Garnham G. W., The use of algae as metal biosorbents, CRC Press, 1997. Gavrilescu M., Eng. Life Sci. 4(2004) 219-32. Gharieb M. M., Gadd G. M., Biometals. 17(2004) 183-188. Goksungur Y., Uren S., Guvenc U., Bioresour. Technol. 96(2005) 103-109. Gomes N. C. M., Figueira M. M., Camargos E. R. S., Mendonca-Hagler L. C. S., Dias J. C. T., Linardi V. R., Biotechnol. Lett. 21(1999) 487-490. Gomes N. C. M., Linardi V. R., Revista De Microbiologia. 27(1996) 218-222. Goyal N., Jain S. C, Banerjee U. C., Adv. Environ. Res. 7(2003) 311-319. Gulati R., Saxena R. K., Gupta R., Curr. Sci. 77(1999) 1359-1360. Gulati R., Saxena R. K., Gupta R., World J. Microbiol. Biotechnol. 18(2002) 397-401. Gupta R., Ahuja P., Khan S., Saxena R. K., Mohapatra H., Curr. Sci. 78(2000) 967-973. Gupta R., Ahuja P., Khan S., Curr. Sci. 78(2000) 967-973. Hafez N., AbdelRazek A. S., Hafez M. B., J. Chem. Technol. Biotechnol. 68(1997) 19-22. Holan Z. R., Volesky B., Appl. Biochem. Biotechnol. 53(1995) 133-146. Huber A. L., Holbein B. E., Kidby D. K., Metal uptake by synthetic and biosynthetic chemicals, CRC press, 1990.

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

76

Can Chen and Jianlong Wang

Incharoensakdi A., Kitjaharn P., Curr. Microbiol. 45(2002) 261-264. Jalali R., Ghafourian H, Asef Y., Davarpanah S. J., Sepehr S., J. Hazard. Mater. 92(2002) 253-262. Kacar Y., Arpa C., Tan S., Denizli A., Genc O., Arica M. Y., Process Biochem. 37(2002) 601-610. Kambe-Honjoh H., Ohsumi K., Shimoi H., Nakajima H., Kitamoto K., J. Gen. Appl. Microbiol. 46(2000) 113-117. Kapoor A., Viraraghavan T., Fungi as biosorbents, CRC Press, 1997. Kapoor A., Viraraghavan T., Bioresour. Technol. 53(1995) 195-206. Kapoor A., Viraraghavan T., Dordrecht: Kluwer Academic Publ; 1997a. Kapoor A., Viraraghavan T., In: Biosorbents for Metal Ions. Edited by Wase J, Forster C. London, UK: CRC Press; 1997b. Kapoor A., Viraraghavan T., Bioresour. Technol. 61(1997c) 221-227. Kapoor A., Viraraghavan T., Bioresour. Technol. 63(1998) 109-113. Kapoor A., Viraraghavan T., Cullimore D. R., Bioresour. Technol. 70(1999) 95-104. Karamushka V. I., Gadd G. M., Biometals. 12(1999) 289-294. Karunasagar D., Arunachalam J., Rashmi K., Latha J. N. L., Mohan P.M., World J. Microbiol. Biotechnol. 19(2003) 291-295. Kedari C. S., Das S.K., Ghosh S., World J. Microbiol. Biotechnol. 17(2001) 789-793. Kim Y. H., Park J. Y., Yoo Y. J., Korean J. Chem. Eng. 15(1998) 157-163. Klimmek S., Stan H. J., Wilke A., Bunke G., Buchholz R., Environ. Sci. Technol. 35(2001) 4283-4288. Kogej A., Pavko A., World J. Microbiol. Biotechnol. 17(2001) 677-685. Kratochvil D., Volesky B., Trends In Biotechnol. 16(1998) 291-300. Kuroda K., Ueda M., Appl. Microbiol. Biot. 63(2003) 182-186. Kuroda K., Ueda M., Shibasaki S., Tanaka A., Appl. Microbiol. Biot. 59(2002) 259-264. Kuyicak N., Volesky B., In: Biosorption of Heavy Metals. Edited by Volesky B. Florida: CRC press; 1990. Kuyucak N., Feasibility of biosorobents application, CRC press, 1990. Lee D. C., Park C. J., Yang J. E., Jeong Y. H., Rhee H. I., S Appl. Microbiol. Biot. 54(2000) 597-600. Lee M. G., Lim J. H., Kam S. K., Korean J. Chem. Eng. 19(2002) 277-284. Lin C. C., Lai Y. T ., J. Hazard. Mater. 137(2006) 99-105. Lin Z. Y., Wu J. M., Xue R., Yang Y., Spectroc Acta Pt A-Molec Biomolec. Spectr. 61(2005) 761-765. Liu H. L., Chen B. Y., Lan Y. W., Cheng Y. C., Chem. Eng. J. 97(2004) 195-201. Liu N., Luo S. H., Yang Y. Y., Zhang T. M., Jin J. N., Liao J. L., J. Radioanal. Nucl. Chem. 252(2002) 187-191. Liu Y. Y., Du T. S.., Chen P., Tang D. L., Ni Z. J., Gu P. Y., Fu J. K., Chem. J. Chinese Univ. 2003;24(12):2248-2251. Lodeiro P., Cordero B., Barriada J. L., Herrero R., de Vicente M. E. S., Bioresource Technol. 96(2005) 1796-1803. Loukidou M. X., Karapantsios T. D., Zouboulis A. I., Matis K. A., J. Chem. Technol. Biotechnol. 79(2004) 711-719. Lu W. B., Shi J. J., Wang C. H., Chang J. S., J. Hazard. Mater. 134(2006) 80-6. Lu Y. M., Wilkins E., J. Hazard. Mater. 49(1996) 165-179.

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

Biosorbents

77

Lyalikova-Medvedeva N. N., Khijniak T. V., In: Biohydrometallurgy And The Environment Toward The Mining of The 21st Century, Pt B 1999. Amsterdam: Elsevier Science Publ B V; 1999. Madigan M. T., Martinko J. M., Parker J., Brock biology of microorganisms. 8th ed ed. Upper Saddle River, NJ: Prentice Hall; 1997. Madrid Y., Cabrera C., Perezcorona T., Camara C., Anal. Chem. 67(1995) 750-754. Madrid Y., Camara C., Trac-Trend Anal. Chem. 16 (1997) 36-44. Magyarosy A., Laidlaw R. D., Kilaas R., Echer C., Clark D. S., Keasling J. D., Appl. Microbiol. Biot. 59(2002) 382-388. Malik A., Environ. Int. 30(2004) 261-278. Mameri N., Boudries N., Addour L., Belhocine D., Lounici H., Grib H., Pauss A., Water Res. 33(1999) 1347-1354. Mann H., In: Biosorption of Heavy Metals. Edited by Volesky B. Boca Raton: CRC press; 1990. Marques P. A., Pinheiro H. M., Teixeira J. A., Rosa M. F., Desalination. 124(1999) 137-144. Massaccesi G., Romero M. C., Cazau M. C., Bucsinszky A. M., World J. Microbiol. Biotechnol. 18(2002) 817-820. Matsunaga T., Takeyama H., Nakao T., Yamazawa A., J. Biotechnol. 70(1999) 33-38. Mehta S. K., Gaur J. P., Crit. Rev. Biotechnol. 25(2005) 113-152. Mendil D., Tuzen M., Soylak M., J. Hazard. Mater. 152(2008) 1171-1178. Modak J. M., Natarajan K.A., Saha B., Minerals and Metallurgical Processing. 13(1996) 5257. Murphy V., Hughes H., McLoughlin P., Water Res. 41(2007) 731-740. Nakajima A., J Radioanal. Nucl. Chem. 247(2001) 347-350. Nakajima A., Tsuruta T., J. Radioanal. Nucl. Chem. 260(2004) 13-18. Nakajima A., Yasuda M., Yokoyama H., Ohya-Nishiguchi H., Kamada H., World J. Microbiol. Biotechnol. 17(2001) 343-347. Natarajan K. A., Subramanian S., Modak J. M., In: Biohydrometallurgy and The Environment Toward The Mining of The 21st Century, Pt B 1999. Amsterdam: Elsevier Science Publ B V; 1999. Nayak D., Lahiri S., Mukhopadhyay A., Pal R., J. Radioanal. Nucl. Chem. 256(2003) 535539. Nguyen-nhu N. T., Knoops B., Toxicol. Lett. 135(2002) 219-228. Niu H., Xu X. S., Wang J. H., Volesky B., Biotechnol. Bioeng. 42(1993) 785-787. Nourbakhsh M., Sag Y., Ozer D., Aksu Z., Kutsal T., Caglar A., Process Biochem. 29(1994) 1-5. Ozdemir G., Ozturk T., Ceyhan N., Isler R., Cosar T., Bioresour. Technol. 90(2003) 71-74. Ozer A., Ozer D., J. Hazard. Mater. 100(2003) 219-229. Ozturk A., J. Hazard. Mater. 147(2007) 518-523. Ozturk A., Artan T., Ayar A., Colloid Surf B-Biointerfaces. 34(2004) 105-111. Padmavathy V., Vasudevan P., Dhingra S. C., Process Biochem. 38(2003) 1389-1395. Palmieri M. C., Garcia O., Melnikov P., Process Biochem. 36(2000) 441-444. Pardo R., Herguedas M., Barrado E., Vega M., Anal. Bioanal. Chem. 376(2003) 26-32. Park D., Yun Y. S., Park J. M., Process Biochem. 40(2005) 2559-2565. Park J. K., Lee J. W., Jung J. Y., Enzyme Microb. Technol. 33(2003) 371-8. Perego P., Howell S. B., Toxicol. Appl. Pharm. 147(1997) 312-318.

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

78

Can Chen and Jianlong Wang

Perez-Corona T., Madrid Y., Camara C., Anal. Chem. Acta. 345(1997) 249-255. Podgorskii V. S., Kasatkina T P., Lozovaia O. G., Mikrobiol. Z 66(2004) 91-103. Popa K., Cecal A., Drochioiu G., Pui A., Humelnicu D., Nukleonika. 48(2003) 121-125. Prasher S. O., Beaugeard M., Hawari J., Bera P., Patel R. M., Kim S. H., Environ. Technol. 25(2004) 1097-1106. Price M. S., Classen J. J., Payne G. A., Bioresour. Technol. 77(2001) 41-49. Puranik P. R., Chabukswar N. S., Paknikar K. M., Appl. Microbiol. Biot. 43(1995) 11181121. Puranik P. R., Paknikar K. M., J. Biotechnol. 55(1997) 113-124. Puranik P. R., Paknikar K. M., Bioresour. Technol. 70(1999) 269-276. Rajendran P., Ashokkumar B., Muthukrishnan J., Gunasekaran P., Appl. Biochem. Biotechnol. 102 (2002) 201-206. Rapoport A. I., Muter O. A., Process Biochem. 30(1995) 145-149. Richins R. D., Kaneva I., Mulchandani A., Chen W., Nat. Biotechnol. 15(1997) 984-987. Rincon J., Gonzalez F., Ballester A., Blazquez M. L., Munoz J. A., J. Chem. Technol. Biotechnol. 80(2005) 1403-1407. Riordan C., Bustard M., Putt R., McHale A. P., Biotechnol. Lett. 19(1997) 385-387. Romera E., Gonzalez F., Ballester A., Blazquez M. L., Munoz J. A., Crit. Rev. Biotechnol. 26(2006) 223-235. Rosa L. H., Pimentel P. F., Figueira M. M., Mendonca-Hagler L. C. S., Gomes N. C. M., In: Biohydrometallurgy and The Environment Toward The Mining of The 21st Century, Pt B 1999. Amsterdam: Elsevier Science Publ B V; 1999. Rosen B. P., Comp. Biochem. Physiol. A-Mol Integr. Physiol. 133(2002) 689-693. Rostami K., Joodaki M. R., Chem. Eng. J. 89(2002) 239-252. Sag Y., Sep. Purif. Methods. 30 (2001) 1-48. Sahin Y., Ozturk A., Process Biochem. 40(2005) 1895-1901. Salehizadeh H., Shojaosadati S. A., Water Res.37(2003) 4231-4235. Savvaidis I., Hughes M. N., Poole R. K., World J. Microbiol. Biotechnol. 19(2003) 117-121. Say R., Yilmaz N., Denizli A., Sep. Sci. Technol. 38(2003a) 2039-2053. Say R., Yilmaz N., Denizli A., Eng. Life Sci. 4(2004) 276-280. Say R., Yimaz N., Denizli A., Adsorpt. Sci. Technol. 21(2003b) 643-650. Schott E. J., Gardner R. C., Mol. Gen. Genet. 254(1997) 63-72. Selatnia A., Bakhti M. Z., Madani A., Kertous L., Mansouri Y., Hydrometallurgy 75(2004a) 11-24. Selatnia A., Boukazoula A., Kechid N., Bakhti M. Z., Chergui A., Process Biochem. 39(2004b) 1643-1651. Selatnia A., Boukazoula A., Kechid N., Bakhti M. Z., Chergui A., Kerchich Y., Biochem. Eng. J. 19(2004c) 127-135. Selatnia A., Madani A., Bakhti M. Z., Kertous L., Mansouri Y., Yous R., Miner. Eng. 2004d;17(7-8) 903-11. Shah M. P., Vora S. B., Dave S. R., In: Biohydrometallurgy and The Environment Toward The Mining Of The 21st Century, Pt B 1999. Amsterdam: Elsevier Science Publ B V; 1999. Shen J., Hsu C. M., Kang B. K., Rosen B. P., Bhattacharjee H., Biometals. 16(2003) 369-378. Sheng P. X., Ting Y. P., Chen J. P., Hong L., J. Colloid Interface Sci. 275(2001) 131-141. Simmons P., Singleton I., Appl. Microbiol. Biot. 45(1996) 278-285.

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79

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Skowronski T., Pirszel J., Pawlik-Skowronska B., Water Qual. Res. J. Can. 36(2001) 793803. Spanelova M., Machovic V., Brezina M., Cent. Eur. J. Chem. 1(2003) 192-200. Srinath T., Verma T., Ramteke P. W., Garg S. K., Chemosphere. 48(2002) 427-435. Su H. J., Zhao Y., Li J., Tan T. W., Process Biochem. 41(2006) 1422-1426. Suh J. H., Kim D. S., Bioprocess Eng. 23(2000) 327-329. Suh J. H., Yun J. W., Kim D. S., Bioprocess Eng. 21(1999) 1-4. Svecova L., Spanelova M., Kubal M., Guibal E., Sep. Purif. Technol. 52(2006) 142-153. Tan T. W., Cheng P., Appl. Biochem. Biotechnol. 104(2003) 119-128. Tan T. W., Hu B., Su H. J., Enzyme Microb. Technol. 35(2004) 508-513. Tangaromsuk J., Pokethitiyook P., Kruatrachue M., Upatham E. S., Bioresour. Technol. 85(2002) 103-105. Tewari N., Vasudevan P., Guha B. K., Biochem. Eng. J. 23(2005) 185-192. Thomas R. A. P., Macaskie L. E., Environ. Sci. Technol. 30(1996) 2371-2375. Tsekova K. V., Marinov P. G., Tzekova A. N., Folia Microbiologica. 45(2000) 217-220. Tsezos M., Hydrometallurgy 59(2001) 241-243. Tsezos M., In: Biosorbents for Metal Ions. Edited by Wase J, Forster C. London, UK: CRC Press; 1997. Tsuruta T., J. Gen. Appl. Microbiol. 50(2004) 221-228. Tunali S., Cabuk A., Akar T., Chem. Eng. J. 115(2006) 203-211. Tuzun I., Bayramoglu G., Yalcin E., Basaran G., Celik G., Arica M. Y., J. Environ. Manage. 77(2005) 85-92. Urrutia M. M., In: Biosorbents for Metal Ions. Edited by Wase J, Forster C. London, UK: CRC Press; 1997. Uslu G., Tanyol M., J. Hazard. Mater. 135(2006) 87-93. Vasudevan P., Padmavathy V., Dhingra S. C., Bioresour. Technol. 89(2003) 281-287. Veglio F., Beolchini F., Hydrometallurgy 44(1997) 301-316. Vianna L. N. L., Andrade M. C., Nicoli J. R., World J. Microbiol. Biotechnol. 16(2000) 437440. Vieira R. H. S. F., Volesky B., Int. Microbiol. 3(2000) 17-24. Vijayaraghavan K., Yun Y. S., Biotechnol. Adv. 26(2008) 266-291. Vijver M. G., Van Gestel C. A. M., Lanno R. P., Van Straalen N. M., Peijnenburg W., Environ. Sci. Technol. 38(2004) 4705-4712. Volesky B., In: Biosorption of Heavy Metals. Edited by Volesky B. Florida: CRC press; 1990. Volesky B., FEMS Microbiol. Rev. 14(1994) 291-302. Volesky B., Hydrometallurgy. 71(2003) 179-190. Volesky B., Holan Z. R., Biotechnol. Progr. 11(1995) 235-250. Volesky B., May H., Holan Z. R., Biotechnol. Bioeng. 41(1993) 826-829. Volesky B., Weber J., Park J. M., Water Res. 37(2003) 297-306. Volesky B., Removal and recovery of heavy metals by biosorption, CRC press, 1990. Volesky B., Naja G., Biosorption: Application Strategies. 16th Internat. Biotechnol. Symp. Compress Co., 2005. Wang J. L., Beijing: Sci. Press; 2002b. Wang J. L., Chen C., Biotechnol. Adv. 24(2006) 427-451.

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Wang J. L., Process Biochem. 37(2002a) 847-850. Wase D. A. J., Forster C. F., Ho Y. S., Low-cost biosorbents: Batch processes, CRC Press, 1997. Xie D., Liu Y. Y., Wu C. L., Fu J. K., Xue R., Microbiology. 30(2003a) 29-34. Xie D. D., Liu Y. Y., Wu C. L., Chen P., Fu J. K., J. Xiamen Univ. 42(2003b) 800-804. Xu X. Q., Li X. M., Yang Q., Liao D. X., Zeng G. M., B Acta Scientiae Circumstantiae 28(2008) 95 - 100. Yan G. Y., Viraraghavan T., E. Water SA. 26(2000) 119-123. Yang Y. Y., Liu N., Luo S. Z., Liao J. L., Jin J. N., Zhang T. M., Jin J. N., Liao J. L., J. Radioanal. Nucl. Chem. 260(2004) 659-663. Yun Y. S., Volesky B., Environ. Sci. Technol. 37(2003) 3601-3608. Zhao M., Duncan J. R., Biotechnol. Lett. 19(1997) 953-955. Zhao M., Duncan J. R., Biotechnol. Lett. 20(1998) 603-606. Zhou J. L., Appl. Microbiol. Biot. 51(1999) 686-693. Zhou J. L., Huang P. L., Lin R.G., Environ. Pollut. 101(1998) 67-75. Zhou M., Liu Y. G., Zeng G. M., Li X., Xu W. H., Fan T., World J. Microbiol. Biotechnol. 23(2007) 43-48. Ziagova M., Dimitriadis G., Aslanidou D., Papaioannou X., Tzannetaki E. L., LiakopoulouKyriakides M., Bioresour. Technol. 98(2007) 2859-2865.

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In: Fundamentals and Applications of Biosorption… ISBN: 978-1-60741-169-7 Ed: Yu Liu and Jianlong Wang © 2009 Nova Science Publishers, Inc.

Chapter 3

BIOSORPTION ISOTHERMS AND THERMODYNAMICS Liang Shen, Zhiwu Wang, Siqin Fang and Yu Liu

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3.1. INTRODUCTION Equilibrium and thermodynamic analyses of adsorption/biosorption are the fundamental studies to evaluate the adsorption capacity and tendency of an adsorbent. A variety of different isotherm equations have been developed, some of which have a theoretical basis and some being of a more empirical nature. This chapter attempts to offer insights into adsorption/biosorption isotherms and thermodynamics that have been commonly employed. It should be pointed out that this chapter is partially extended from the review by Liu and Liu (2008).

3.2. LANGMUIR ISOTHERM EQUATION Langmuir (1918) theoretically examined the adsorption of gases on solid surfaces, and considered sorption as a chemical phenomenon. Basically, the Langmuir isotherm equation has a hyperbolic form:

q e = q max

K L Ce 1 + K L Ce

(3.1)

in which qe is adsorption capacity by weight at equilibrium, qmax is the theoretical maximum adsorption capacity by weight, and KL represents the equilibrium constant of adsorption reaction with a unit of l mol-1, while Ce is molar concentration of adsorbate in solution at equilibrium (mol l-1). The Langmuir isotherm is developed with the following assumptions: (i) there is a finite number of binding sites which are homogeneously distributed over the adsorbent; (ii) these binding sites have the same affinity for adsorption of a single molecular

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layer; (iii) there is no interaction between adsorbed molecules, and (iv) adsorption is reversible. When the rate of adsorption of molecules onto the surface is the same as the rate of desorption of molecules from the surface, the equilibrium is reached. The rate at which adsorption proceeds is proportional to the driving force, which is the difference between the amount adsorbed at a particular concentration and the amount that can be adsorbed at that concentration. At the equilibrium concentration, this difference is zero (Metcalf & Eddy, 2003). The Langmuir isotherm equation has been most frequently applied in equilibrium study of biosorption, and a typical plot of Equation 3.1 is shown in figure 3.1. It needs to emphasize that the Langmuir isotherm offers no insights into the mechanism of biosorption. So far, two approaches have been developed for derivation of the Langmuir isotherm.

Figure 3.1. A typical plot of the Langmuir isotherm.

3.2.1. Equilibrium Approach for Derivation of Langmuir Isotherm Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

According to Langmuir (1918), adsorption process can be depicted as follows: A + B ↔ A-B

(3.2)

in which A represents free adsorptive molecules, B is vacant sites and AB is the occupied sites. The equation for the equilibrium constant (KL) for Equation 3.2 is written as

KL =

Sites occupied (Vaccant sites) (molar concentration of solute at equilibrium)

(3.3)

Equation 3.3 can be translated to the following expression:

KL =

θe (1 - θe )Ce

(3.4)

in which θe is the fraction of the surface covered at equilibrium, Ce is molar concentration of solute in solution at equilibrium. For biosorption, θe is defined by Equation 3.5:

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

Biosorption Isotherms and Thermodynamics

θe =

qe q max

83

(3.5)

Replacing θe in Equation 3.4 by Equation 3.5 yields

q e = q max

K L Ce 1 + K L Ce

(3.6)

which is the same as Equation 3.1, the so-called Langmuir isotherm.

3.2.2. Kinetic Approach for Derivation of Langmuir Isotherm In Equation 3.2, ka represents adsorption rate constant and kd is desorption rate constant. The proportion of the surface occupied by solute (θt) at time t is defined as

θt =

qt q max

(3.7)

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in which qt is adsorption capacity at time t. The adsorption and desorption rates in Equation 3.2 can be expressed as ra=kaCt(1-θt)

(3.8)

rd=kdθt

(3.9)

In the development of the Langmuir isotherm, it has been assumed that for Equation 3.2, the forward adsorption rate is first order with respect to of Ct and (1-θt) respectively, and the desorption follows the first order regarding the sites occupied (θt). Thus, the overall rate equation can be expressed as follows:

dθ t = ra − rd = k a C t (1 − θ t ) − k dθ t dt

(3.10)

When biosorption reaches its equilibrium, dθt/dt=0 becomes zero and Equation 3.10 reduces to

k a Ce (1 − θ e ) − k d θ e = 0

(3.11)

Inserting Equation 3.5 into Equation 3.11 leads to Equation 3.1 or Equation 3.6, the Langmuir isotherm.

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3.2.3. Some Consideration on Use of Langmuir Kinetics As shown above, in a strict theoretical sense, the equilibrium concentration of adsorbate in the Langmuir isotherm must be expressed in its molar concentration (mol l-1). However, as noted by Liu (2006), in the literature of biosdsorption study, volumetric concentration (mg l-1) of adsorbate at equilibrium has been commonly used in the Langmuir isotherm equation. To convert adsorbate concentration from molar concentration to corresponding volumetric concentration, Liu (2006) proposed that both numerator and denominator of Equation 3.6 should be multiplied by the molar weight of adsorbate, MA (g mol-1):

q e = qmax

K L Ce M A 1000K L C v = qmax M A + K L Ce M A M A + 1000K LC v

(3.12)

in which Cv=1000CeMA is volumetric concentration of solute in mg l-1. Equation 3.12 can be rewritten to

1000K L Cv K 'LC v MA q e = q max = q max 1000K L 1 + KL' C v 1+ Cv MA

(3.13)

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Equation 3.13 reveals that if the volumetric concentration of solute is used in the Langmuir isotherm, the Langmuir equilibrium constant is given by

K 'L =

1000K L MA

(3.14)

It should be emphasized that in Equation 3.14, KL has a unit of l mol-1, whereas the unit '

of K L is l mg-1.

3.3. FREUNDLICH ISOTHERM EQUATION Freundlich (1907) proposed an empirical isotherm equation: F q e = k FC1/n e

(3.15)

in which kF and nF are Freundlich constants. As the Freundlich isotherm equation is exponential, it can only be reasonably applied in the low to intermediate concentration ranges. Figure 3.2 shows a simulation plot of the Freundlich isotherm at given kF and 1/nF.

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Similar to the Langmuir isotherm equation, Equation 3.15 has also been widely employed in the field of biosorption research. Different from the Langmuir isotherm, the Freundlich isotherm has been considered empirical. In a special case where 1/nF is equal to unity, Equation 3.15 reduces to a linear isotherm which is valid only at very low adsorbate concentration:

q e = k FCe

(3.16)

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Otake et al. (2004) attempted to correlate the Freundlich constants with molecular properties of adsorbate and adsorbent involved in adsorption system, and they found that the Freundlich constant 1/nF is correlated with total highest occupied molecular orbital electron density of adsorbate and adsorbent. It was also found that the value of kF/n would be related to the molecular orbital energy between adsorbent surfaces and adsorbate molecules. Figure 3.2 shows plots of the Freundlich isotherm at a fixed kF of 1.5, but 1/nF varies from 0.5 to 2. It can be seen that at 1/nF1, qe tends to increase sharply with increasing Ce, and in this case, use of the Langmuir isotherm is appropriate.

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Figure 3.2. Simulating plots of the Freundlich isotherm at a fixed kF of 1.5. a: 1/nF=0.5; b: 1/nF=1; c: 1/nF=2.

Silva da Rocha et al. (1997) looked into the possible theoretical origin of the empirical Freundlich isotherm from the aspect of statistical mechanics underlying the theory of heterogeneous surface. The following is a brief description of their approach. In this approach, the exponential distribution for the site energy frequency distribution N(Q) and the Langmuir local coverage θ(Q) are expressed as follows:

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θ(Q) =

b0Cexp(Q RT ) 1 + b0Cexp(Q RT)

N(Q) = αexp( − mQ RT )

(3.17)

3.18)

in which m and b0 are constants, R is the universal gas constant, T is the absolute temperature, and α is a normalization constant =m/RT. In the above expression, Q represents the difference between the adsorption energies of the solute and the solvent for a given site. The relative monolayer coverage of the entire surface (θT) is related to N(Q) and θ(Q) through the following formula:

θT = ∫ N(Q)θ(Q)dQ (3.19) Inserting Equations 3.17 and 3.18 into Equation 3.19 gives

θT = ∫

∞

0

exp(−mQ / RT)b 0αC exp(Q / RT)dQ 1 + b0 C exp(Q / RT)

Equation 3.20 can be rearranged to the following formula by letting x=exp(Q/RT):

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(3.20)

Biosorption Isotherms and Thermodynamics

θT = mb0 C ∫

∞

1

x − m dx 1 + b 0 Cx

87

(3.21)

By applying the principle of integration by parts, the general integrated form of Equation 3.21 is given by

θT =

K (b0C) m (i − 1)!(b0C)i −1 K!(b C)! 1 x K − m dx − mb 0C∑ +mb0C K 0 K K +1 ∫ i sin(mπ) /(mπ) i =1 (1 + b 0 C) ∏ ( j − m) ∏ ( j − m) 0 (1 + b0Cx) j =1

j =1

(3.22)

At small C, only the first term in Equation 3.22 is dominant over the others, thus Equation 3.22 reduces to

θT ≈

(b 0 C) m sin(mπ) /(mπ)

(3.23)

Furthermore, if m is also very small, then sin(mπ)/(mπ) should be very close to unity, and Equation 3.23 becomes the famous Freundlich isotherm:

θ T ≈ (b0 ) m Cm

(3.24)

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The comparison of Equation 3.24 with Equation 3.15 reveals that

k F = (b0 ) m and 1/n F = m

(3.25)

It should be pointed out that in the approach by Silva da Rocha et al. (1997), m is limited to the range 0 to 1, i.e. 0>βθt, Equation 4.22 is reduced to

dθ t = k a C0 - (k a C0 + k d )θ t dt

(4.23)

Integration of Equation 4.23 leads to

⎛ θ ⎞ ln⎜⎜1 − t ⎟⎟ = − k1' t ⎝ θe ⎠ '

in which k1 is rate constant and is given by

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(4.24)

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k1' = C0 k a + k d

(4.25) '

Equation 4.25 clearly shows that k1 is linearly related to initial adsorbate concentration in solution. It is known that

θt qt = θe qe

(4.26)

Thus, Equation 4.24 can be rewritten to

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⎛ q ⎞ ln⎜⎜1 − t ⎟⎟ = −k1' t ⎝ qe ⎠

(4.27)

Equation 4.27 indeed is the integrated form of the pseudo first-order equation. As concluded by Azizian (2004), “the sorption process obeys pseudo first-order kinetics at high initial concentration of solute”. To a great extent, such conclusion is still debatable. It should be realized that an important assumption indeed is hidden in Equation 4.18, i.e., the adsorption was assumed to be the first order with respect to the concentration of adsorbate (Ct) and available adsorption sites (1-θt), respectively, while desorption was assumed to be a first order regarding the sites occupied (θt). These seem to imply that the overall kinetic order of reversible adsorption process is restricted to a range of 1 to 2. More importantly, the reaction orders of forward and reverse reactions (Equation 4.18) can not be simply preset to 1 unless the complex mechanisms of adsorption process are known. In fact, a fundamental challenge in chemical kinetics is the determination of the reaction order from experimental data. It is well known that the rate law is closely related to the reaction mechanism, and the reaction stoichiometry does not determine the reaction order except in the special case of an elementary reaction (IUPAC, 1997). As shown in Azizian’s approach, Equation 4.24 or Equation 4.26 is obtained by assuming C0>>βθt. However, under such a circumstance, Equation 4.20 would become C=C0. This implies that the pseudo first-order equation (Equation 4.24 or Equation 4.27) derived by Azizian (2004) would be valid only for a pure solution system, which is not common in adsorption study. Thus, it is apparent that the Azizian’s approach for derivation of the pseudo first-order kinetic equation for adsorption would be still debatable. Equation 4.22 is the basic equation in Azizian’s approach, and it can be rearranged as follows:

dθ t = k aβθ 2t − (k a C0 + k aβ + k d )θ t + k a C0 dt

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(4.28)

125

Biosorption Kinetics 2

As 0 nitrate (53 mg/g) > chloride (21 mg/g). Zn2+ sorption and uptake characterization of an exopolysaccharide- mutant of EPSsynthesizing cyanobacterium Nostoc spongiaeforme were investigated (Singh et al., 2003). Exposure of the biomass to Zn2+ transformed the strain into white debris. However, a few mutant strain survived (designated as Zn-20). The parent strain retained almost 88% of the total EPS synthesized, the rest being released into the ambient medium, while for Zn-20, the EPS retained approximated to 74%. Zn2+ uptake of the mutant was still 5-fold higher than that of the parent strain, although the Zn2+-sensitivity of the mutant was comparable with that of the parent (LD50, 7 muM). Both the strains showed insignificant difference in Zn2+ sorption onto their isolated EPS. The mutant was characterized by having higher cell carbohydrate content (642.8 μg mg-1 dry wt.) than its parent (513.6 μg mg-1 dry wt.). The X-ray diffraction pattern revealed Zn2+ deposition on EPS from the parent mainly as zinc hypophosphite monohydrate [Zn(H2PO2)2.H2O], whereas there was a lack of distinct peaks in similar samples from Zn-20, thus confirming the amorphous nature. There was participation in Zn2+ binding of only COO-, N=O, NO2, SO2 groups in the parent while participation of P-O and C=O groups in the mutant EPS was evident in IR spectra. The observations suggest that the mutant could be deployed to achieve sustained EPS synthesis, its release and metal sorption/desorption in repeated cycles (Singh et al., 2003). Liu and Fang (2002) investigated the electrostatic binding sites of EPS were characterized according to the titration data using linear programming analysis. Test results indicated that the possible corresponding functional groups were carboxyl, carboxyl/phosphoric, phosphoric, amine/phenolic, and hydroxyl for EPS from a hydrogenproducing sludge (HPS). For EPS from a sulfate-reducing biofilm (SRB), the possible corresponding functional groups were similar plus a sulfhydryl group. Kazy et al. (2002) investigated extracellular polysaccharides of a copper-sensitive (Cu-s) and a copper-resistant (Cu-r) Pseudomonas aeruginosa strain in terms of their production,

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chemical nature and response towards copper exposure. The resistant strain synthesized the considerably higher extent of EPS (4.78 mg mg-1 cell dry wt.) than its sensitive counterpart (2.78 mg mg-1 dry wt.). FTIR-spectroscopy and gas chromatography revealed that both the polymers were acidic in nature, containing alginate as the major component along with various neutral- and amino-sugars. Acid content in the Cu-r EPS (480.54 mg g-1) was greater than that in the Cu-s EPS (442.0 mg g-1). Presence of Cu2+ in the growth medium caused a dramatic stimulation (approximately 4-fold) in EPS synthesis by the Cu-r strain, while in a similar condition, the Cu-s failed to exhibit such response. Cu2+ binding capacity of the resistant strain EPS (320 mg g-1 EPS) was higher than that of the sensitive type (270 mg g-1). The aromatic hydrocarbon-degrading bacterium, Pseudomonas putida G7, produces exopolymers. (Kachlany et al., 2001) proved that the released extracellular polysaccharide (EPS) contained the monosaccharides, glucose, rhamnose, ribose, N-acetylgalactosamine and glucuronic acid. The structural and chemical properties of the P. putida EPS described contribute to understanding of the mechanisms of toxic metal binding by this well-known Proteo bacterium. The biofilm for removal of the heavy metals (Cu2+, Pb2+, and Ni2+) in wastewater were investigated by Jang et al. (2001). A series of batch adsorption tests to estimate the biofilm capacity for removal of the heavy metals (Cu2+, Pb2+, and Ni2+) in wastewater were carried out. The metal sorption results were fitted to the Freundlich isotherm model to compare their sorption capacity. The change of the composition of EPSs (extracellular polymeric substances) was simultaneously represented by the ratio of carbohydrate to protein (C/P) when the biofilm was exposed to the heavy metals. EPS composed of slime loosely bound to the cell and capsular materials was extracted by the four general extraction methods including regular centrifugation, regular centrifugation with formaldehyde, EDTA extraction and steam extraction. Although the various extraction methods showed different results, CIP ratio of biofilm exposed to copper and lead metal ions was generally lower than that of control. Guine et al. (2006) also proved that a dominant role of extracellular polymeric substances in Zn2+ retention processes, although Zn2+ binding to inner cell components cannot be excluded when Zn2+ sorption to three gram-negative bacteria, Cuprialvidus metallidurans CH34, Pseudomonas putida ATCC112633, and Escherichia coli K12DH5 alpha. Suh et al. (1999b) investigated the effect of EPS on Pb2+ removal by a polymorphic fungus Aureobasidium pullulan. Pb2+ only accumulated on the surface of the intact cells of A. pullulans due to the existence of EPS, whereas Pb2+ penetrated into the inner cellular parts of the EPS-extracted cells of A. pullulans. The longer the storage time of cells, the higher the uptake capacity of Pb2+ by intact cells due to increase of the mount of excrete EPS. More than 90% of Pb2+ removal based on maximal Pb2+ accumulation amount was due to excreted EPS. The biosorptive capacity of Pb2+ by the EPS-extracted cells was much less than that of the intact cells and remained constant irrespective of storage time. Suh et al. (1998b) discovered that initial rate of Pb2+ uptake by live cells of S. cerevisiae is lower than that of dead cells, while in the case of A. pullulans, both the capacity and the initial rate of Pb2+ accumulation in the live cells is higher than those in the dead cells due to the presence of EPS of live A. pullulans. Roles of EPS on metal removal in biosorption system is usually neglected or ignored especially in the case of fungi and yeast. Among limited studies on metal removal by EPS, most pertain to the EPS extracted from intact organism cells, but not the EPS in living cells. Although conspicuous extracellular layers is mainly associated with bacterial cells, whether

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the yeast of S.cerevisiae excrete EPS is unclear. Suh et al. (1998b) implied that the strain of S. cerevisiae used in their experiment did not excrete EPS. However, flocculent strain of S. cerevisiae has been suggested to be used in metal biosorption due to higher uptake capacity of metal ions than that of non-flocculent strain and other unique traits (Soares et al. 2002). The mechanism of flocculation is believed to be related to a specific protein on the surface of cell wall, i.e. lectin. Proteins on the surface of the yeast cells could be extracted by EDTA. With respect to that feature, lectin seems to be taken as a kind of EPS. Flocculation of the yeast may vary significantly even disappear under certain conditions.

5.4. CELL SURFACE SORPTION/PRECIPITATION Cell wall tends to be the first cellular structure to contact with the ions of metal ions excluding possible existing extracelluar layer mainly related to bacterial cells. Two basic mechanisms of metal uptake by cell wall are: stoichiometric interaction between functional groups of cell wall composition, including phosphate, carboxyl, amine as well as phosphodiester; and physicochemical inorganic deposition via adsorption or inorganic precipitation. Now complexation, ion exchange, adsorption (by electrostatic interaction or Val force), inorganic microprecipitation, oxidation and/or reduction have been proposed to explain the metal uptake by organism (Volesky, 1990a).

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5.4.1. Ion Exchange Ion-exchange is an important concept in biosorption, because it explains many of the observations made during heavy metal uptake experiments (Davis et al., 2003b). Many evidences accumulated have proved the existence of ion exchange mechanism in metal ion removal in biosorption system (Veglio and Beolchini, 1997; Schneider et al., 2001). It was universally reported that the enhanced release of ions (Ca2+, K+, Mg2+or Na+) from the biomass materials (fungi or algae or bacteria) when reacted with heavy metal ion bearing aqueous solution rather than heavy metal-free solution, which confirmed that ion-exchange takes place between metals when binding to biomass. The release of cellular cation ions (K+, Mg2+, Ca2+ or Na+) from the biomaterial cells and/or pH variation were observed by many authors during heavy metal ion uptake by biomaterials (Avery and Tobin, 1993; Brady and Duncan, 1994b; Meunier et al., 2003; Chen and Wang, 2007). For example, Meunier et al. (2003) found that pH increase and potassium, calcium, magnesium and sodium release from the cocoa shells in contacting aquatic solution with or without heavy metal ions. The release of cellular metal ions (K+, Mg2+, Ca2+, etc.) were also reported during the biosorption of Pb2+ (Suh et al., 1999) and Cu2+ (Brady and Duncan, 1994b) by S. cerevisiae. The increase in the pH value of biosorption system was also observed during the biosorption of Ag+ and Ni2+ by Rhizopus arrhizus (Tsezos et al., 1995), and Cu2+, Cd2+ and Pb2+ by waste brewery biomass (Marques et al., 2000). Calcium or potassium ion exchange with adsorbed metal ion was usually considered to be one of the metal uptake mechanisms (Avery and Tobin, 1993; Reddad et al., 2002). Water fern Azolla showed a high affinity for Sr2+ from polluted solution, involving ion exchange

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with Na+, K+, Mg2+ and Ca2+. The biosorption of Sr2+ was optimal at neutral and high pHs, but lower at acidic pH, due to a competition between Sr2+ and H+ ions on the cation binding groups of Azolla (Cohen-Shoel et al., 2002). Suh et al. (1999) suggested cation exchange played an important role in Pb2+ accumulation by the yeast of Saccharomyces cerevisiae when accumulation sites were in inner cellular parts rather than EPS. K+ and Na+ release were not found during Pb2+ accumulation by Aureobasidium pullulans. Ni2+ was nearly removed through the mechanism of ion exchange by sugar pulp (Reddad et al., 2002). Latha et al. (2005) also found metal (Co2+, Cu2+, Ni2+) binding to the cell wall of the fungi Neurospora crassa result in the release of proportional quantities of Ca2+ and Mg2+. The rapid release suggests that these physiologically essential cations appear to be wall bound rather than emerging from the intracellular pool. Calcium was the predominant ion to be displaced and was two to four fold more than magnesium ions. Rapid release of 70% of cellular K+, followed by a slower release of approximately 60% of cellular Mg2+, but little loss of Ca2+, was observed in Cu2+ accumulation by S. cerevisiae (Brady and Duncan, 1994c), indicating the existence of ion exchange mechanism. According to Vasudevan et al. (2002), biosorption of monovalent ions, such as Na+ and K+ by deactivated protonated cells of S.cerevisiae was accompanied by H+ release, whereas biosorption of divalent ions, such as Ca2+ and Mg2+ were sorbed not only by proton displacement, but also by additional mode, which was not accompanied by release of H+. The total maximum biosorptive capacity of divalent ions was higher than that of the monovalent ions. Ca2+, Mg2+ or H+ release were also observed in biosorpiton process of heavy metal ions (Sr2+, Mn2+, Zn2+, Cd2+, Cu2+, Ti+) by living, non metabolizing cells of S.cerevisiae, which also confirmed the existing of ion exchange. Exploring the cation changes of the biosorption system is evidently helpful to understand metal biosorption mechanism. In our lab, the phenomena of the release of cellular metal ions (K+, Mg2+, Na+, Ca2+) and pH change in aqueous solution during Zn2+, Pb2+ or Ag+ uptake by the cells of S. cerevisiae were described in detail. Some of the results were published (Chen and Wang, 2007, 2008). In our lab, the cations release during the biosorption of zinc ion by the intact cells of Saccharomyces cerevisiae was investigated (Chen and Wang, 2007). Saccharomyces cerevisiae was obtained from the Institute of Microbiology, Chinese Academy of Sciences. The initial concentration of the zinc ion varied at the range of 0.08~0.8 mmol l-1 and the initial pH was natural, about 5.65. The experimental results showed that the zinc uptake was 74.8~654.8 μmol/g when the sorbent concentration was about 1 g l-1. A large quantity of K+, Mg2+, Ca2+ and Na+ were observed to release rapidly from the biomass in zinc uptake systems in a few minutes (figure 5.2A). pH increased rapidly also. The higher equilibrium metal concentration (or higher initial metal ion concentration) resulted in the lower final (equilibrium) pH value. The pH increase range was 1.28 (initial Zn2+ concentration was 0.08 mmol l-1), 0.74 (0.4 mmol l-1), 0.55 (0.8 mmol l-1) for the intact cells, respectively. The presence of Zn ions reduced the H+ uptake by the yeast cells or cause H+ release from the biomass. Brady and Tobin (1995) found that freeze dried R. arrhizus cells released H+ during adsorbing Zn and Pb ions. H+ displacement implied that Zn2+ exhibited a certain degree of covalent binding with the biomass. Obviously, zinc ion promoted the biomass to release more cations such as K+, Mg2+ and Na+ shown in figure 5.2B taking Mg2+ as an example. Usually the release of K+, Mg2+, Na+ and Ca2+ from biosorbents in binding heavy metal ions was regarded as an indicator of the mechanism of ion exchange for heavy

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metal binding (Reddad et al., 2002). The result here indicated that ion exchange played role in zinc uptake. Ion exchange of K+, Mg2+, Na+ or Ca2+ with Zn2+ during sorption indicated that a certain degree of ionic binding interaction between Zn2+ and the biomass.

0.6

-1

qt (mmol g )

0.5

K Zn Mg Na Ca

0.4 0.3 0.2 0.1 0.0 0

10

20 time (h)

30

40

30

40

a

-1

C0=0.08 mmol L -1

C0=0.4 mmol L

0.08

-1

C0=0.8 mmol L

0.06 0.04 0.02

2+

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-1

Mg release (mmol g )

0.10

0.00 0

10

20 time (h)

b Figure 5.2. (A) K+, Mg2+, Ca2+ and Na+ release during zinc uptake (initial pH=5.65, C0=0.4 mmol l-1, live cells: 1 g l-1); (B) Zinc ions promote the intact cells release more cations (Mg2+ as an example).

The similar conclusions could be drawn for the dry dead cells of S. cerevisiae, from the local beer industry as a waste. Batch tests were performed using un-buffered solution at initial pH of 4, and using 1 g l-1 of the biomass concentration. The values of pH were not controlled during metal uptake. Initial metal concentration of 0.5 mmol l-1 was selected for kinetic studies with the contact time less than 21 h. Initial metal concentration of 0.08-3.0 mmol l-1 were chosen for isotherm studies. The kinetics of K+, Mg2+, Na+, Ca2+ release and the tested ion (Zn2+, Pb2+ or Ag+) uptake could be described very well by the pseudo second-order

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equation. Generally, metal uptake (Zn2+, Pb2+ and Ag+) was found to take place rapidly, whereby almost 80% uptake occurred within the first five minutes of exposure. For four cation ions, initial rate decreased in the order: K+>Mg2+>Na+>Ca2+. The equilibrium data of Zn2+, Pb2+, Ag+ uptake followed Langmuir adsorption isotherms much better than the Freundlich model. However, both Langmuir and Freundlich models did not described the cation release isotherms well. The maximum uptake capacities of Zn2+, Pb2+and Ag+ (qmax) were determined from the Langmuir model and found to be 0.522 mmol g-1, 0.574 mmol g-1, 0.329 mmol g-1, respectively. The relationship between cation release (K+, Mg2+, Ca2+ and Na+) from the dry dead cells of S. cerevisiae, and metal uptake (Zn2+, Pb2+ or Ag+) were also studied in our lab. The contact of the biomass with aquatic solution containing Zn2+ (Zn-Bio system), Pb2+(Pb-Bio system) or Ag+(Ag-Bio system) or free metal solutions (“Bio”) resulted in instant release of cellular K+, Mg2+ Ca2+ and Na+ ions and resulted in pH increase, which reflected the intrinsic ability of the cells. However, the presence of metal ions would promote the cells to release more cations especially Mg2+ and Ca2+ (figure 5.3), and inhibit the cells to decrease absorbing H+ from the solution. For different systems, including Zn2+, Pb2+, Ag+ uptake system and the bio control system without any metal ion, the quantity and the magnitude of released K+, Mg2+, Na+ or Ca2+ in different systems were basically similar: K+, highest about 0.6-0.8 mmol g-1, then for Mg2+ about 0.06-0.1 mmol g-1, for Na+ about 0.013-0.019 mmol g-1 and for Ca2+ about 0.001-0.04 mmol g-1. It was reasonable to conclude that Ca2+ and/or Mg2+ release was responsible for part of Zn uptake in our study although the absolute K+ release quantity was the largest among four cellular cations. On the basis of mequivalent/g unit, equilibrium uptake capacity for Zn2+ was near to the total amount of cation released (Mg2++Ca2+ + K+ + Na+) (in meq g-1). However, equilibrium uptake capacity for Pb2+ was much larger than the total released. The equilibrium uptake capacity for Ag+ was much less than the total released. Displacement of H+ and cation (K+, Mg2+, Ca2+ or Na+) release simultaneously in binding 2+ Zn , Pb2+ or Ag+ further confirmed that both covalent binding and ion exchange played roles in Zn2+, Pb2+and Ag+ uptake. Ion exchange mechanism was not the sole mechanism in metal ion removal. The role of ion exchange became less important at higher metal ion concentration. Ion exchange played minor role in Zn and Pb removal, but ion exchange was responsible for 75% Ag+ removal. pH value increase in the overall kinetic studies and isotherm studies, and K+, Mg2+, Ca2+and Na+ release was caused by the cells itself, independent of the existing metal ion, species and viabilities of the cells. The metal ion could promote the cells to release more cations and decrease the extent of pH increase. The ratio of the total amount of Mg2+ plus Ca2+ to the corresponding zinc ion uptake at equilibrium statement, expressed as j, declined sharply and intended to level off when zinc equilibrium concentration increased to 0.44 mmol l-1 with the range of initial concentration of 0.1~3.0 mmol l-1 (figure 5.4 D). Therefore, the role of ion exchange decreased in high initial (or equilibrium) concentration of metal ions. The result indicated that ion exchange existed but not sole in zinc biosorption and other mechanisms may play more important role in zinc uptake. Ion exchange of Ca2+ and Mg2+ with Zn2+ during sorption indicated that a certain degree of ionic binding interaction between Zn and the biomass.

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Figure 5.3. Comparison of release of K+, Mg2+, Ca2+, Na+ among Zn, Pb, Ag biosorption system and bio control system C0=0.5 mmol l-1，dry biomass was 1g l-1).

Figure 5.4. Relationship of metal uptake and the corresponding cellular cation release at equilibrium conditions: (A) Zn2+, (B) Pb2+, (C) Ag+, (D) the ratio of the amount of Mg2+ plus Ca2+ to ion uptake.

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Is ion exchange the main mechanism in metal biosorption removal? Brady and Tobin (1995) found that the total ions displaced (H++Mg2++Ca2+) accounted for only a small portion of the metal ions taken up in biosorption of metal ions (Sr2+, Mn2+, Zn2+, Cd2+, Cu2+, Pb2+) by freeze-dried Rhizopus arrhizus, indicating that ion exchange is neither the sole nor the main mechanism for metal biosorption by fungi. However, Davis et al. (2003) believed the ion exchange was the main mechanism for metal ions uptake by brown algae. In particular, they thought the term ion-exchange was rather an umbrella term to describe the experimental observations, probably the precise binding mechanism range from physical binding (i.e. electrostatic or London–van der Waals forces) to chemical binding (i.e. ionic and covalent). Therefore, the definition of ion exchange should be clear before discussing the importance of its role in biosorption.

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5.4.2. Complexation Complexation was observed to involve in metal removal (Veglio and Beolchini, 1997). Complexation with functional groups, for example hydroxyl (–CHOH), carboxyl (-COOH), phosphoryl (–PO4H3), amine (-NH2) or sulfhydryl (-SH), on the surface of various biomass was regarded as possible biosorption mechanisms for metal uptake by the biomass. According to Davis et al.(2003b), complexation or coordination, may be electrostatic or covalent, was defined as combination of cations (often called as central atom) with molecules or anions containing free electron pairs (bases, often called as the ligand(s). A multidentate ligand contains more than one ligand atom which can be responsible for combining the metal cation(s). Avery and Tobin (1993) applied the hard-and-soft principle of acids and bases to explore the interactions of metal ions-cells of living, non metabolizing S.cerevisiae for metabolismindependent biosorption. The displacement of Ca2+, Mg2+ or H+ was observed in biosorption process. The release of Ca2+ and Mg2+ (indicating ionic bonding of the metal) and H+ displacement (indicating covalent bonding of the metal) seemed to be markedly dependent on the metal concentration. Brady and Tobin (1995) observed that Ca2+ and Mg2+ were released for each test ions, whereas H+ displacement for the borderline test ions only. They concluded that hard metal Sr2+ was only due to ionic binding and the borderline ions (Mn2+, Zn2+, Cd2+, Cu2+, Pb2+ ) exhibited a significant degree of covalent binding. A lot of researches on roles of separated cell part and it’s composition on metal removal were carried out in1990s. Brady and Duncan (1994a) found that the blocking of amino, carboxyl, or hydroxyl groups of the isolated cell walls from the yeast S. cerevisiae reduced the uptake capacity of Cu2+, indicating these groups play a role in the binding of Cu2+, and implying both the protein and the carbohydrate fractions of the cell walls are involved in heavy metal cation binding. We also confirmed the carboxyl and amino group in the cell wall played important role in Cu2+ removal by the waste yeast cells of S.cerevisiae modified by methanol and formaldehyde (Wang, 2002). Brady et al. (1994c) obtained partially purified products (glucan, mannan, and chitin, respectively) from isolated cells walls of the yeast S. cerevisiae by chemical enzymatic methods. Metal biosorption by the isolated components revealed that each component accumulated greater quantities of the cations than the intact cell wall. The yeast cell wall without the protein component removed by pronase decreased the metal accumulation by 29.5%, indicating that protein is involved in heavy metal removal,

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such as cobalt, copper and cadmium. The data also showed that the outer mannan-protein layer of the yeast cell wall is more important than the inner glucan-chitin layer in heavy metal cation accumulation. Simmons and Singleton (1996) also confirmed the sulphydryl groups of these amino acid residues as major metal-binding components of the protein. However they pointed out that isolated cell wall contributed little for Ag+ removal in comparison to the whole cells. Bacterial cell surface components are the major factors responsible for pathogenesis and bioremediation. In particular, the surface of a gram-negative bacterium cell has a variety of components compared to that of a gram-positive cell. Oh et al. (2002) isolated an isogenic mutant of Bradyrhizobium japonicum, which exhibited altered cell surface characteristics, including an increased hydrophobicity. They investigated the involvement of lipopolysaccharide of Bradyrhizobium japonicum in metal binding. Polyacrylamide gel electrophoretic analysis of the lipopolysaccharide (LPS) in the mutant demonstrated that the Opolysaccharide part was completely absent. Meanwhile, a gel permeation chromatographic analysis of the exopolysaccharide (EPS) in the mutant demonstrated that it was unaltered. Since LPSs are known to have several anion groups that interact with various cation groups and metal ions, the mutant provided an opportunity to examine the direct role of LPS in metal binding by B. Japonicum. Using atomic absorption spectrophotometry, it was clearly demonstrated that LPS was involved in metal binding. The binding capacity of the LPS mutant to various metal ions (Cd2+, Cu2+, Pb2+, and Zn2+) was 50-70% lower than that of the wild-type strain. Also, through an EPS analysis and desorption experiment, it was found that EPS and centrifugal force had no effect oil the metal binding. Accordingly, it would appear that LPS molecules on B. japonicum effect the properties, which precipitate more distinctly metal-rich mineral phase (Oh et al., 2002). In fact, bacterial walls cells are flexible, whose composition reflects that of the external rather than that of the cytoplasm in order to maintain electro-neutrality (Urrutia, 1997). Most metal binding occurs after initial metal complexation and neutralisation of the chemically active site on bacteria. Binding to the bacteria cell walls might involve at least a two-step mechanism: the first step is the stoichiometric interaction of metal with reactive chemical groups, followed by a second stage in which those same sites nucleate the deposition of more metal as a chemical precipitate, which results in the development of fine-grained minerals. Therefore, metal retention ability by bacterial walls goes further than their adsorption capacity due to the cell surface mineral nucleation. Differences in metal binding characteristics of the EPS and cell wall of bacteria was noticed by Urrutia (1997). The cell wall peptidoglycan is cross-linked by covalent bonds with anionic carboxylate residues are held in an almost rigid orientation due to the turgor of the wall (in live cells). However, capsule polymers are not, and they are highly hydrated and are better able to adapt to the coordination sphere of a particular metal (Urrutia, 1997). Different algae such as Ascophyllum nodosum and Fucus vesiculosus respond in practically the same way to different metals. Both algae have cell walls containing polysaccharides with a high sorption uptake due to the presence of ligands like phosphoryl, −SO32−, R-NH2, R2-NH, and mainly –COO− groups. In addition, sulfate groups at other carbons could assist in forming covalent bonds between adjacent chains of fucoidans and other sulfated polysaccharides (Romera et al., 2006).

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Volesky and Holan (1995) strengthened that the presence of some functional groups in biomass does not guarantee their accessibility for sorption heavy metals, perhaps due to steric, conformational, or other barriers At least two types of binding sites on the cell surface were identified. One is a highaffinity biding sites and the other a low-affinity sites. Heavy metals bind high affinity surface ligand first, followed by lower affinity surface groups. It was true for some bacteria and fugal, such as Pseudomonas fluorescens, Klebsiella pneumoniae, Rhizopus arrhizus, Penicillium chrysogenum, etc (Brady and Tobin, 1995; Urrutia, 1997; Sarret et al., 1998). The investigation of the binding mechanisms of Zn and Pb to Penicillium chrysogenum cell walls have revealed that Zn and Pb bind to the predominant phosphoryl (approximate to 95%) and minor carboxyl groups (approximate to 5%) with a reversed affinity. Zn is predominantly complexed to four PO4 groups in a tetrahedral configuration at low (7.6 × 10-3 mmol/g) to high (0.15 mmol/g) Zn concentration and additionally to COOH groups at total saturation of reactive sites (0.22 mmol/g). In contrast, carboxyl complexes of Pb (≡(COO)n-Pb) are formed at low Pb concentration (5.6 × 10-3 mmol g-1), and their formation is followed by ≡(PO4)n-Pb complexes at higher complexation rate. The structural models in figure 5.5 would be an idealized representation of the average structure of Zn complexes in the Penicillium chrysogenum cell wall. Figure 5.5 clearly showed that Zn is predominantly complexed to phosphoryl groups from low to high concentration and additionally to carboxyl groups near saturation of the reactive surface sites. The above molecular analysis results by extended X-ray absorption fine structure (EXAFS) technique accorded with the relevant isotherms. The Pb isotherm exhibits two plateaus, which correspond to the successive saturation of COOH and PO4 sites, whereas the Zn isotherm has a single-site Langmuir shape because low affinity minor ≡(COO)n-Zn complexes formed at high metal concentration are masked by more abundant ≡(PO4)4-Zn complexes, which readily form. Urrutia (1997) discussed the controversy regarding use of adsorption isotherms to describe meta-microbial interactions. Some authors think adsorption isotherms could describe metal-binding process to microbial surface, but this approach may not be adequate when precipitation of metals occurs. However, others think that the Langmuir model could explain their data even in presence of precipitation. Now improvements of modeling research allow better a description on biosorption on heterogeneous systems (Urrutia, 1997). By X-ray diffraction, synchrotron-based X-ray microfluorescence, and powder- and micro-extended X-ray absorption fine structure (EXAFS) spectroscopy with principal component analysis and linear combination fits, the research on an organic topsoil contaminated by Zn2+ revealed that Zn2+ was found to be predominantly speciated as Zn2+organic matter complexes (similar to45%), outer-sphere complexes (similar to20%), Zn2+sorbed phosphate (similar to10%), and Zn2+-sorbed iron oxyhydroxides (similar to10%), although Zn2+ primary minerals (franklinite, sphalerite, and willemite) are still present (similar to15% of total Zn2+) in the bulk soil (Sarret et al., 2004). Now more and more references use EXAFS to explore the local structure of the adsorbed metal in biomass. More information can be refer to the section of 5.5.6 in this chapter.

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Figure 5.5. Structural representation of possible ≡(PO4)n-Zn and ≡(COO)n-Zn complexes existing in P. chrysogenum cell walls following equilibration of aqueous Zn (Sarret et al., 1998).

5.4.3. Precipitation and Redox Reaction Precipitation and redox reaction in cell surface are also reported by many researchers. A series of experiments has been carried out to explore the mechanism of precious metal ions removal by the dead cells of yeast of S.cerevisiae by using various modern instrumental tools and surface technology. The results showed that the precious metal ions, such as Pd2+ (Liu et al., 2003; Xie et al., 2003a), Pt4+(Xie et al., 2003b), Au3+(Lin et al., 2005), Ag+ and Rh3+ (Lin et al., 2001), were unexceptionally bound to the cell wall of the yeast and then in-situ reduced into the corresponding metal particle. Taking Au3+ as an example, Lin et al. (2005) studied the mechanism of Au3+ biosorption by utilizing XRD, FTIR and XPS techniques, the results demonstrated that the Au3+ bound on the cell wall of the biomass had been reduced into Au0, where Au3+ binding sites may be the hydroxyl and the carboxylate anions, and the aldehyde group of the reducing sugars serving as the electron donor.

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Discrete particles containing Ag were found at or near the cell wall of both gram-positive and gram-negative bacteria, so does gold containing particles localized in Sargassum natans cells (Vieira and Volesky, 2000). Uranium and thorium were found to be accumulated in a dense layer around the surface of Aspergillus flavus cells (Hafez et al., 1997). Magyarosy et al. (2002) proved that Ni removed by a strain of Aspergillus niger from the broth was localized in the cell walls and also inside the cell in the form of small rectangular crystals. X-ray and electron diffraction analysis confirmed that these crystals were nickel oxalate dihydrate. Experiments with non-growing, live fungal biomass showed that nickel removal was not due to biosorption alone and energy metabolism is essential for the metal removal. The precipitates containing Zn2+, Pb2+ or Ag+ were observed to present on the surface of S. cerevisiae after those metal contacted with the yeast (figure 5.6).

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a

b

Figure 5.6. Back-scattered electron scanning microscopy of S. cerevisiae after contact with Pb2+ (a: Magnification × 2500) and Ag+ (b: Magnification × 10000). Obvious precipitate containing Pb2+ or Ag+ occurred.

Although Rhizopus sp. strain showed the highest uptake capacity of Ni among filamentous fungi strains tested (Rhizopus sp., Penicillium sp. Aspergillus sp., Trichoderma sp., Byschoclamyss sp., and Mucor sp.), no Ni deposits were observed on the cell wall of Rhizopus sp, but rather a homogeneous accumulation was seen on the cell surface (Mogollon et al., 1998). Biosorption often depends on multi mechanisms. Kratochvil et al. (1998) thought that the maximum uptake of Cr(VI) by protonated Sargassum biomass at pH 2 was due to simultaneous anion exchange and the reduction of Cr(VI) to Cr(III). Park et al. (2005) also proved that the mechanism of Cr(VI) removal by the dead fungal biomass of Aspergillus niger was a redox reaction making Cr(VI) to Cr(III) by XPS technique. Based on the mechanism of reduction of Cr(VI) at pH 0.1 absorption length). Fluorescence or electron yield mode is suggested when a good transmission sample cannot be made. Fluorescence detection is preferred for dilute samples (say, < 0.1 absorption length). The detector center is positioned along the x-ray polarization vector because scattered radiation is minimum there. Particle size effects of XAS sample are important in fluorescence as well as transmission mode. Particles prepared should be considerably smaller than one absorption length of their material. Use thin sample in fluorescence mode, if possible, considering electron yield detection. No matter how to measure μ(E), the following steps to reduce the XAS data to χ(k) begin the data analysis and modeling (http://cars9.uchicago.edu/xafs/ NSLS_EDCA/Sept2002/): 1. Convert measured intensities to μ(E). 2. Subtract a smooth pre-edge function, to get rid of any instrumental background, and absorption from other edges. 3. Normalize μ(E) to go from 0 to 1, so that it represents the absorption of 1 x-ray. 4. Remove a smooth post-edge background function to approximate μ0(E) to isolate the XAS χ. 5. Identify the threshold energy E0, and convert from E to k space. 6. Weight the XAS χ(k) and Fourier transform from k to R space. Once the EXAFS have been extracted and k weighted, they can be fitted to ideal crystal structures using an initio calculating programs to get the fitting parameters: inter atomic distance R, coordination number N, and the relative mean square displacement around the

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equilibrium bond length, or the Debye–Waller factor (σ2) of each coordination shell. The most commonly used commercial ab initio calculator is FEFF (Parsons et al., 2002). According to standard procedures and methods, XAS spectra are able to be processed and analyzed data analysis using EXAFSPAK written by Dr Graham George of SSRL(Kelly et al., 2002), WinXAS (Ressler, 1998), IFEFFIT (Webb, 2005), FEFF and FEFFIT (Newville et al., 1995), EXCURV98 (Fomina et al., 2007), or Cerius2 EXAFS program (Chen and Wang, 2008). Figure 5.24B shows that the EXAFS data are isolated from the absorption spectrum by subtracting the ionization energy, E0, removal of a smooth background, and normalization of the oscillations to the edge step (the difference in absorbance just before and just after the edge). The data are displayed as a function of the wave-vector k (proportional to the square root of the difference between the X-ray energy and E0). In k-space each scatterer contributes a damped sine wave to the total EXAFS, with a frequency which depends on the absorber– scatterer distance and an intensity which depends on the atomic number of the scatterer. The damping is affected by thermal oscillations along the absorber–scatterer axis. Thus, the observed EXAFS spectrum is an interference pattern of the contributions from all the surrounding scatterers (figure 5.24B). Taking a Fourier transform of the EXAFS spectrum gives peaks corresponding to the different frequencies, yielding an approximate radial distribution function showing ‘shells’ of scatterers (i.e. groups of scatterers at a similar distance) around the absorber atom (figure 5.24C). This can be used to build up a model of distribution of scatterers surrounding the absorber. The EXAFS spectrum is analysed by calculating a spectrum based on the model of the absorber coordination site using various possible scatterers and refining parameters in the model (distances, damping factors) to minimize a least squares residual, giving the best fit to the experimental data.

Figure 5.24. Diagram illustrating X-ray absorption spectroscopy. A. The Cu K-edge X-ray absorption spectrum of copper phosphate. B. The Cu K-edge EXAFS spectrum of copper phosphate. The oscillations are displayed as a function of k, the wave-vector, and the amplitude (normalized to the size of the edge-step) is multiplied by k3, in order to enhance the features at high k (high energy). C. The Fourier transform of the EXAFS spectrum of copper phosphate. The major peak is due to the four nearest neighbor oxygen atoms around the copper, at a distance of 1.95 Å. The smaller peak is due to a combination of two copper atoms at 2.98 Å and three phosphorus atoms at 3.15 Å. (Fomina et al., 2007).

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Sarret et al. (1998) studied the binding mechanisms of Zn2+ and Pb2+ to Penicillium chrysogenum cell walls by solution chemistry and extended X-ray absorption fine structure (EXAFS). The results showed that Zn2+ and Pb2+ bind to the predominant phosphoryl (approximate to 95%) and minor carboxyl groups (approximate to 5%) with a reversed affinity. The difference in complexation affinity by reactive PO43- and COOH- groups observed by EXAFS provides a molecular level explanation for the differences in Pb2+ and Zn2+ isotherms. Using XAS, Fomina et al. (2007) found that oxygen ligands (phosphate, carboxylate) played a major role in toxic metal (Zn2+, Cu2+, Pb2+) coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized toxic metals. Coordination of toxic metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium. In this reference, the authors offered plentiful information of Cu2+ K-edge EXAFS parameters, Zn2+ K-edge EXAFS parameters and Pb L(III)-edge EXAFS parameters, such as atomic distance R, coordination number N, Debye–Waller factor (σ2) on Cu2+, Zn2+ and Pb2+ on fungus, and some models of copper, and lead coordination within fungal biomass were suggested. The models of lead coordination within fungal biomass are illustrated in figure 5.25.

Figure 5.25. Models of lead coordination within fungal biomass. a: Model of phosphate coordination of lead accumulated within biomass of a variety of mycorrhizal and saprotrophic fungi (e.g. H. ericae, P. involutus, S. bovinus, S. collimitus) grown in the presence of pyromorphite. b: A model for carboxylate coordination of lead accumulated by A. niger grown on PbO and nitrate-containing AP1 agar medium with outer shells also fitting a metal element (Met) such as iron or nickel. (Fomina et al., 2007).

EXAFS is less sensitive to metals bound to matrixes composed of light elements such as organic matter and to metals present as outer-sphere surface complexes. To obtain the EXAFS spectra of pure species, one can combine powder-EXAFS on bulk sample with chemical treatments or use micro-focused EXAFS (μEXAFS) spectroscopy combining the principal component analysis (PCA) (Sarret et al., 2004).

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5.6.8. XPS X-ray photoelectron spectroscopy (XPS) for chemical analysis is a relatively new technique for determination of binding energy of electrons in atoms/molecules which depends on distribution of valence charges and thus gives information about the oxidation state of an atom/ion (Vieira and Volesky, 2000). Figueira et al. (1999) using XPS observed that iron was present in two oxidation states, when brown seaweed Sargassum fluitans was exposed to Fe2+, while only Fe(III) was present when the biomass was exposed to ferric irons. In both Fe (II) and Fe(III) exposed samples, XPS indicated iron complexation with sulfate groups in the biomass (Figueira et al., 1999).

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5.6.9. NMR Magnetic resonance spectroscopy (NMR: nuclear magnetic resonance) is a nondestructive technique to observe environmentally relevant processes with both spatial and temporal resolution. Nestle (2002) reviewed on heavy metal immobilization in biosorbents and mineral matrices. The prominent advantage of NMR-techniques over most other experimental methods is their non-invasive nature with high spatial (several 10 μm routinely) and temporal (several min) resolution. NMR has long wavelength, magnetic fields and RF waves can intrude into extended objects regardless of their optical transparency and without notable scattering effects. Magnetic resonance imaging (MRI) experiments is a laboratory method and thus better available for time-dependent studies than over synchrotron-based Xray tomography (which offers even better sensitivity and spatial resolution). Nestle introduced NMR studies on alginate-based biosorbents (algal and yeast) to adsorb the heavy metal salts (chlorides, nitrates and sulfates ) of Cu2+, VO2+, Zn2+, Ba2+, Ce3+, Pr3+, Nd3+, Sm3+, Gd3+, Yb3+). The results showed that there is a pronounced difference in the binding behavior for divalent heavy metals (e.g., Cu2+) and trivalent ions such as rare earths (and perhaps actinoids, too) (figure 5.26). Wingender (1999) also pointed out that the technique has several advantages for the investigation of polysaccharides. First, sample is still available for subsequent measurement because NMR is non-destructive. Second, NMR spectroscopy is the ease of determining the signals in the anomeric region. Third, NMR can easily control certain chemical derivatization and degradations. Non-imaging NMR studies also can provide valuable information on ion exchange and immobilization of heavy metal ions in solid materials, but it need to carefully design experimental conditions (Nestle, 2002). 113 Cd-NMR technique has been employed to investigate Cd-biomass interaction. 113CdNMR spectra were measured in solution for a series of adducts between the extracellular organic matter (EOM) of the green alga Selenastrum capricornutum and cadmium(II). NMR results showed that a carbohydrate type coordination. With synchronous fluorescence measurements, structurally different binding sites, such as humic-like also existed (Grassi and Mingazzini, 2001).

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Figure 5.26. (A) Typical NMR image contrast in an experiment on a tube-shaped Ca2+-alginate sample in exchange with paramagnetic divalent ions (e.g., Cu2+). The diagram in the lower part demonstrates the origin of the image contrast due to the concentration-dependent change of both the transverse and longitudinal relaxation time. The dotted grey lines stretching from various zones of the sample to the diagram are to show the relationship between image contrast and Cu2+ concentration. B)–D) Snapshots from a measurement with 1 mM Cu2+ and a 2%w/v alginate tube. The images were taken B) after 10 min Cu2+ exposition, C) after 270 min and D) after 17 h. The acquisition of the individual images took about 8 min each. The bright bars in the images correspond to a length of 1 mm. (Nestle, 2002).

Xia and Rayson (2002) used 113Cd-NMR technique to investigate the binding of Cd2+ to various biologically generated materials including several strains of algae (Chlorella pyrenoidosa, Bryopsis spp., Cladophora spp., and Entiomorpha spp.), the fragments of cultured Datura innoxia cells, organic peat, sphagnum peat, freeze dried roots and stems of cattail plants (Typha latifolia), freeze dried leaves, roots and stems of mature and young tumble weed (Salsola spp.), and pecan shells. A soluble component of each of these materials (with the exception of the C pyrenoidosa, the sphagnum peat, and the immobilized D. innoxia materials) was observed to coordinate with the Cd2+ ions in solution. The dominant chemical moiety involved in binding Cd2+ was found to be carboxylates. Chemical moieties containing nitrogen, sulfur and phosphorous were eliminated as significant sources of Cd2+ binding under the solution conditions investigated. 1 H-NMR study of Na alginates extracted from Sargassum spp. in relation to metal biosorption was carried out by (Davis et al., 2003a). 27Al-NMR, 19F-NMR, 13C-NMR were also reported. 13C-NMR has the potential to study EPS compounds in situ (Wingender et al., 1999; Bi et al., 2001). More details about the basic principles of NMR and MRI can be found elsewhere (Lens and Hemminga, 1998; Blumich, 2000).

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5.6.10. CLSM Confocal laser scanning microscopy is a non-destructive, three-dimensional, optical sectioning of fully hydrated, living biofilm systems. Wingender et al. (1999) thought that CLSM may be the most versatile microscopic instrument for biofilm investigation, and they introduced the CLSM approach to study biofilm (mainly EPS, polysaccharides, proteins, nucleic acids), and physicochemical characterization of EPS matrix, including charge distribution, hydrophobicity/hydrophilicity within films, permeability, three-dimensional imaging, etc.

ACKNOWLEDGMENTS The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 50830302; 50808111; 50278045), China Postdoctoral Science Foundation funded project (Grant No. 20080430350), special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (Grant No. 08K05ESPCT) and the Basic Research Fund of Tsinghua University (Grant No. JC2002054), to carry out the relevant research works.

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REFERENCES Ahimou F., Denis F. A., Touhami A., Dufrêne Y. F., Langmuir. 18(2002) 9937-9941. Arai T., Ikemoto T., Hokura A., Terada, Y., Kunito, T., Tanabe, S., Nakai, I., Environ. Sci. Technol. 38(2004) 6468-6474. Avery S. V., Tobin J. M., Appl. Environ. Microbiol. 58(1992) 3883-3889. Avery S. V., Tobin J. M., Appl. Environ. Microbiol. 59(1993) 2851-2856. Beech I B., Cheung C. W. S., Int. Biodeterior. Biodegrad.. 35(1995) 59-72. Bi S. P., Yang X. D., Zhang F. P., Wang X. L., Zou G. W., J. Anal. Chem, 370 (2001) 984996. Blumich B., NMR imaging of materials / Bernhard Blumich. Oxford: Clarendon Press; 2000. Bonthrone K. M., Basnakova G, Lin F, Macaskie L. E., Nat. Biotechnol. 14(1996) 635-638. Boyanov M. I., Kelly S. D., Kemner K. M., Bunker B.A., Fein J.B., Fowle D.A., Geochim. Cosmochim. Acta. 67(2003) 3299-3311. Brady D., Duncan J. R., Enzyme Microb. Technol. 16(1994a) 633-638. Brady D., Duncan J. R., Biotechnol Lett. 16(1994b) 543-548. Brady D., Duncan J. R., Biotechnol Lett. 16(1994c) 543-548. Brady D., Glaum D., Duncan J. R., Lett. Appl. Microbiol. 18(1994a) 245-250. Brady D., Stoll A., Duncan J. R., Environ. Technol. 15(1994b) 429-438. Brady D., Stoll A. D., Starke L., Duncan, J.R., Biotechnol. Bioeng. 44(1994c) 297-302. Brady J. M., Tobin J. M., Enzyme Microb. Technol. 17(1995) 791-796. Brassard P., Kramer J. R., Collins P. V., Environ. Sci. Technol. 24(1990) 195-201. Brown M. J., Lester J. N., Water Res. 16(1982) 1539-1548.

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Chan J., Merrifield M. E., Soldatov A. V., Stillman M. J., Inorg. Chem. 44(2005) 4923-4933. Chang D., Fukushi K., Gosh S., Water Environ. Res. 67 (1995) 822-827. Chen C., Wang J. L., Biomed. Environ. Sci. 20 (2007) 478-482. Chen C., Wang J. L., Appl. Microbiol. Biotechnol. 79(2008) 293-299. Cho D. H., Yoo M. Y., Kim E. Y., J. Microbiol. Biotechnol. 14(2004) 250-255. Cohen-Shoel N., Ilzycer D., Gilath I., Tel-Or E., Water Air Soil Pollut. 135(2002) 195-205. Comte S., Guibaud G., Baudu M., Enzyme Microb. Technol. 38(2006) 246-252. Cox J. S., Smith D. S., Warren L. A., Ferris F.G., Environ. Sci. Technol. 33(1999) 4514-4521. Das S. K., Das A. R., Guha A. K., Environ. Sci. Technol. 41 (2007) 8281-8287. Daughney C. J., Fein J. B., J. Colloid Interface Sci. 198(1998) 53-77. Daughney C. J., Fein J. B., Yee N., Chem. Geol. 144(1998) 161-176. Davis T. A., Llanes F., Volesky B., Diaz-Pulido G., McCook L., Mucci A., Appl. Biochem. Biotechnol. 110(2003a) 75-90. Davis T. A., Volesky B., Mucci A., Water Res. 37(2003b) 4311-4330. Deng S. B., Ting Y. P., Water Res. 39(2005) 2167-2177. Eide D., Curr. Opin. Cell Biol. 9(1997) 573-577. Eide D. J., Annu. Rev. Nutr. 18 (1998) 441-469. Eide D. J., In: Advances in Microbial Physiology, Vol 43. London: ACADEMIC PRESS LTD; 2000. Fein J. B., Daughney C. J., Yee N., Davis, T. A., Geochim. Cosmochim. Acta. 61(1997) 33193328. Ferraz A. I., Tavares T., Teixeira J. A., Chem. Eng. J. 105(2004) 11-20. Figueira M. M., Volesky B., Mathieu H. J., Environ. Sci. Technol. 33(1999) 1840-1846. Flemming H. C., Wingender J., Water Sci. Technol. 43(2001) 9-16. Fomina M., Charnock J., Bowen A. D., Gadd, G.. M., Environ. Microbiol. 9 (2007) 308-321. Foster L. J. R., Moy Y. P., Rogers P. L., Biotechnol. Lett. 22(2000) 1757-1760. Fourest E., Volesky B., Environ. Sci. Technol. 30(1996) 277-282. Freire-Nordi C. S., Vieira A. A. H., Nascimento O. R., Process Biochem. 40(2005) 22152224. Fukushi K., Kato S., Antsuki T., Omura T., Water Sci. Technol. 44(2001) 453-459. Gavrilescu M., Eng. Life Sci. 4(2004) 219-232. Geesey G. G., Jang L., In: Metal Ions and Bacteria. Edited by Beveridge TJ, Doyle RJ. New York: John Wiley and Sons; 1989. Gharieb M. M., Gadd G. M., Biometals. 11(1998) 101-106. Gharieb M. M., Gadd G. M., Biometals. 17(2004) 183-188. Gomes N. C. M., Rosa C. A., Pimentel P. F., Mendonça-Hagler, L.C.S., Braz. J. Microbiol. 33(2002) 62-66. Goyal N., Jain S. C., Banerjee U. C., Adv. Environ. Res. 7(2003) 311-319. Grassi M., Mingazzini M., Environ. Sci. Technol. 35(2001) 4271-4276. Guibaud G., Comte S., Bordas F., Dupuy S., Baudu M., Chemosphere 59(2005) 629-638. Guine V., Spadini L., Sarret G., Muris M., Delolme C., Gaudet J., Martins J., Environ. Sci. Technol. 40(2006) 1806-1813. Hafez N., AbdelRazek A. S., Hafez M. B., J. Chem. Technol. Biotechnol. 68(1997) 19-22. Harada M., Okada T., Anal. Sci. 17(2001) 233-235. Hung C. C., Santschi P. H., Gillow J. B., Carbohydr. Polym. 61(2005) 141-147. Jang A., Kim S. M., Kim S. Y., Lee S. G., Kim I. S., Water Sci. Technol. 43(2001) 41-48.

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

General Mechanisms of Biosorption

209

Kachlany S. C., Levery S. B., Kim J. S., Rheus, B.L., Lion, L.W., Ghiorse, W.C., Environ. Microbiol. 3(2001) 774-784. Kang S. Y., Lee J. U., Kim K. W.. In: On The Convergence Of Bio-Information-, Environmental-, Energy-, Space- And Nano-Technologies, Pts 1 And 2. Zurich-Uetikon: Trans Tech Publications Ltd; 2005. Kazy S. K., Das S. K., Sar P., J. Ind. Microbiol. Biotechnol. 33(2006) 773-783. Kazy S. K., Sar P., Singh S. P., Sen A.K., D’Souza S.F., World J. Microbiol. Biotechnol. 18(2002) 583-588. Kelly R. A., Andrews J. C., DeWitt J. G., Microchem. J. 71(2002) 231-245. Klaus T., Joerger R., Olsson E., Granqvist, C. G., Proc. Natl. Acad. Sci. U. S. A. 96(1999) 13611-13614. Latha J. N. L., Rashmi K., Mohan P. M., Can. J. Microbiol. 51(2005) 1021-1026. Lawrence J. R., Swerhone G. D. W., Kwong Y. T. J., Can. J. Microbiol. 44(1998) 825-832. Lens P. N. L., Hemminga M. A., Biodegradation 9(1998) 393-409. Lin Z. Y., Fu J. K., Wu J. M., Liu Y. Y., Cheng H., Acta Phys-Chim Sin. 2001, 17(5) 477480. Lin Z. Y., Wu J. M., Xue R., Yang Y., Spectroc. Acta Pt A-Molec. Biomolec. Spectr. 61(2005) 761-765. Liu H., Fang H. H. P., Biotechnol. Bioeng. 80(2002) 806-811. Liu Y., Lam M. C., Fang H. H. P., Water Sci. Technol. 43(2001) 59-66. Liu Y. Y., Du T. S., Chen P., Tang D. L., Ni Z. M., Gu P. Y., Fu J. K., Chem. J. Chin. Univ.. 24(2003) 2248-2251. Lovley D. R., Coates J. D., Curr. Opin. Biotechnol. 8(1997) 285-289. Macaskie L. E., Bonthrone K. M., Yong P., Goddard D. T., Microbiology-(UK). 146 (2000) 1855-1867. Madrid Y., Cabrera C., Perezcorona T., Camara C., Anal. Chem. 67(1995) 750-754. Madrid Y., Camara C., Trac-Trends In Anal. Chem. 16(1997) 36-44. Magyarosy A., Laidlaw R. D., Kilaas R., Echer C., Clark D. S., Keasling J. D., Appl. Microbiol. Biotechnol. 59(2002) 382-388. Mandal D., Bolander M. E., Mukhopadhyay D., Sarkar G., Mukherjee P., Appl. Microbiol. Biotechnol. 69(2006) 485-492. Marques P., Rosa M. F., Bioprocess Eng. 23(2000) 135-141. Merroun M. L., Ben Chekroun K., Arias J. M., Gonzalez-Munoz, M. T., Chemosphere. 52(2003) 113-120. Meunier N., Blais J. F., Tyagi R. D., J. Environ. Eng. Sci. 2(2003) 1-8. Meyer A., Wallis F. M., Water Sa. 1997, 23(2) 187-192. Mogollon L., Rodriguez R., Larrota W., Raminez N., Torres R.. Appl. Biochem. Biotechnol. 70 (1998) 593-601. Mukherjee P., Ahmad A., Mandal D., Senapati S., Sainkar S. R., Khan M. I., Ramani R., Parischa R., Nano Lett. 1(2001) 515-519. Murphy V., Hughes H., McLoughlin P., Water Res. 41(2007) 731-740. Naeem A., Woertz J. R., Fein J. B., Environ. Sci. Technol. 40(2006) 5724-5729. Naja G., Mustin C., Berthelin J., Volesky, B., Berthelin, J., J. Colloid Interface Sci. 292(2005a) 537-543. Naja G., Mustin C., Volesky B., Berthelin J., Water Res. 39(2005b) 579-588. Nakajima A., Water Res. 36(2002) 2091-2097.

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

210

Can Chen and Jianlong Wang

Nestle N., Rev. Environ. Sci. Biotechnol. 1(2002) 215-225. Neu T. R., Lawrence J. R.. In: Microbial extracellular polymeric substances: characterization, structures and function. Edited by Wingender J, Neu TR, Flemming H-C. Berlin Heidelberg New York: Springer-Verlag; 1999. Newville M., Ravel B., Haskel D., Rehr J. J., Stern E. A., Yacoby Y., Physica. B-Condensed Matter. 208(1995) 154-156. Oh E. T., Yun H. S., Heo T. R., Hoh S.C., Oh K.H., So J.S., J. Microbiol. Biotechnol. 12(2002) 296-300. Ohnuki T., Aoyagi H., Kitatsujia Y., Mohammad S., J. Environ. Radioact. 77(2004) 339-353. Oliver B G., Cosgrove E. G., Water Res. 8 (1974) 869-874. Ozdemir G., Ceyhan N., Manav E., World J. Microbiol. Biotechnol. 21(2005a) 163-167. Ozdemir G., Ceyhan N., Manav E., Bioresour. Technol. 96(2005b) 1677-1682. Ozer A., Ozer D., Ekiz H. I., Adsorpt-J. Int. Adsorpt. Soc. 10(2004) 317-326. Padmavathy V., Vasudevan P., Dhingra S. C., Process Biochem. 38(2003) 1389-1395. Pagnanelli F., Veglio F., Toro L., Chemosphere 54(2004) 905-915. Pan J. H., Ge X. P., Liu R. X., Tang H. X., Colloid Surf. B-Biointerfaces 52(2006) 89-95. Paner E. T., Udan M. L. D.. In: European Symposium on Environmental Biotechnology, Eseb 2004. Lisse: A A Balkema Publishers; 2004. Park D., Yun Y. S., Jo J. H., Park J. M., Water Res. 39(2005) 533-540. Parsons J. G., Aldrich M. V., Gardea-Torresdey J. L., Appl. Spectrosc. Rev. 37(2002) 187222. Perego P., Howell S. B.. Toxicol. Appl. Pharmacol. 147(1997) 312-318. Pirog T. P., Microbiology. 66(1997) 284-288. Pokrovsky O. S., Pokrovski G. S., Gelabert A, Schott J., Boudou A., Environ. Sci. Technol. 39(2005) 4490-4498. Popa K., Cecal A., Humelnicu D., Caraus I., Draghici C.L., Cent. Eur. J. Chem. 2(2004) 434445. Portnoy M. E., Schmidt P. J., Rogers R. S., Culotta V. C., Mol Genet Genomics. 265(2001) 873-882. Pulsawat W., Leksawasdi N., Rogers P. L., Foster L.J.R., Biotechnol. Lett. 25(2003) 12671270. Ramsay L. M., Gadd G. M., FEMS Microbiol. Lett. 152(1997) 293-298. Reddad Z., Gerente C., Andres Y., Le Cloirec P., Environ. Sci. Technol. 36(2002) 2067-2073. Ressler T., J. Synchrot Radiat. 5 (1998) 118-122. Richert L., Golubic S., Le Guedes R., Herve A., Payri C., Curr. Microbiol. 51(2005) 379-384. Romera E., Gonzalez F., Ballester A., Blázquez M., Munoz J., Crit. Rev. Biotechnol. 26(2006) 223-235. Romero-Gonzalez M. E., Williams C. J., Gardiner P. H. E., Gurman, S.J., Habesh, S., Environ. Sci. Technol. 2003, 37(18) 4163-4169. Rosen B. P., Comp. BioChem. Physiol. A-Mol. Integr. Physiol. 133(2002) 689-693. Rudd T., Sterrit R. M., Lester J. N., J. Water Pollut Contr. Fed. 56 (1984) 1260–1268. Sarret G., Balesdent J., Bouziri L., Garnier J.M., Marcus M.A., Geoffroy N., Panfili F., Environ. Sci. Technol. 38(2004) 2792-2801. Sarret G., Manceau A., Spadini L., Roux J. C., Soldo Y., Eybert- Berard L.. Methonnex J.J.. Environ. Sci. Technol. 32(1998) 1648-1655. Savvaidis I., Hughes M. N., Poole R. K., Antonie Van Leeuwenhoek 84(2003) 99-107.

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General Mechanisms of Biosorption

211

Sawalha M. F., Peralta-Videa J. R., Saupe G. B., Dokken, K.M., Gardea-Torresdey, J.L., Chemosphere 66(2007) 1424-1430. Schlekat C. E., Decho A. W., Chandler G. T., Environ. Toxicol. Chem. 17(1998) 1867-1874. Schneider I A. H., Rubio J., Smith R. W., Int J. Miner Process. 62(2001) 111-120. Simmons P., Singleton I., Appl. Microbiol. Biotechnol. 45(1996) 278-285. Singaravelu G., Arockiamary J. S., Kumar V. G., Govindaraju K., Colloid Surf. BBiointerfaces 57(2007) 97-101. Singh N., Asthana R. K., Singh S. P., World J. Microbiol. Biotechnol. 19(2003) 851-857. Singh S., Rai B. N., Rai L. C., Process Biochem. 36(2001) 1205-1213. Smith D. S., Kramer J. R., Environ. Int. 25(1999) 307-314. Sobeck D. C., Higgins M. J., Water Res. 36(2002) 527-538. Suh J. H., Kim D. S., Yun J. W., Song S. K., Biotechnol. Lett. 20(1998) 153-156. Suh J. H., Yun J. W., Kim D. S., Bioprocess Engineering. 21(1999) 383-387. Tewari N., Vasudevan P., Guha B. K., Biochem. Eng. J. 23(2005) 185-192. Texier A. C., Andres Y., Illemassene M., Le Cloirec P., Environ. Sci. Technol. 34(2000) 610615. Tian Y., Int. J. Environ. Pollut. 32(2008) 78-89. Tsezos M.. In: Biosorbents for Metal Ions. Edited by Wase J, Forster C. London, UK: CRC Press; 1997. Tsezos M., Remoudaki E., Angelatou V., Int. Biodeterior. Biodegrad. 35(1995) 129-153. Urrutia M. M.. In: Biosorbents for Metal Ions. Edited by Wase J., Forster C. London, UK: CRC Press; 1997. Vasudevan P., Padmavathy V., Dhingra S. C., Bioresour. Technol. 82(2002) 285-289. Vasudevan P., Padmavathy V., Dhingra S. C., Bioresour. Technol. 89(2003) 281-287. Veglio F., Beolchini F., Hydrometallurgy. 44(1997) 301-316. Vieira R. H. S. F., Volesky B., Int. Microbiol. 3(2000) 17-24. Vijver M. G., Van Gestel C. A. M., Lanno R. P., van Straalen N.M., Peijnenburg W.J.G.M., Environ. Sci. Technol. 38(2004) 4705-4712. Volesky B., In: Biosorption of Heavy Metals. Edited by Volesky B. Florida: CRC press; 1990a. Volesky B., In: Biosorption of Heavy Metals. Edited by Volesky B. Boca Raton: CRC press; 1990b. Volesky B., Holan Z. R., Biotechnol. Progr. 11(1995) 235-250. Wang B. J., Yang H. F., Chongqing Environ. Sci.. 18(1996) 35-39. Wang J. L., Process Biochem. 37(2002) 847-850. Webb S. M., Physica. Scripta. T T115 (2005) 1011-1014. Webb S. M., Gaillard J. F., Jackson B. E., Stahl D. A., J. Synchrot. Radiat. 8 (2001) 943-945. White C., Gadd G. M., Sci. Total Environ. 176(1995) 107-115. White C., Wilkinson S. C., Gadd G. M., Int. Biodeterior. Biodegrad. 35(1995) 17-40. Wingender J., Neu T. R., Flemming H. C., Berlin Heidelberg New York: Springer-Verlag; 1999. Wright C. J., Armstrong I., Surf. Interface Anal. 38(2006) 1419-1428. Xia H. Y., Rayson G. D., Adv. Environ. Res. 7(2002) 157-167. Xie D. D., Liu Y. Y., Wu C. L., Fu J. K., Xue R., Gu P. Y., Microbiology. 30(2003a) 29-34. Xie D. D., Liu Y. Y., Wu C. L., Chen P., Fu J. K., J. Xiamen Univ. 42(2003b) 800-804.

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Yee N., Fein J. B., Geomicrobiol. J. 20(2003) 43-60. Zhang D. Y., Wang J. L., Pan X. L., J. Hazard. Mater. 138(2006) 589-593. Zhao L. M., Schaefer D., Xu H. X., Modi S. J., LaCourse W.R., Marten M.R., Biotechnol. Progr. 21(2005) 292-299.

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In: Fundamentals and Applications of Biosorption… ISBN: 978-1-60741-169-7 Ed: Yu Liu and Jianlong Wang © 2009 Nova Science Publishers, Inc.

Chapter 6

FACTORS INFLUENCING BIOSORPTION PROCESS Can Chen and Jianlong Wang

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6.1. INTRODUCTION Biosorption process is mainly influenced by three kinds of factors: properties of metal ions (radius of ion, valence, etc.), environmental conditions (such as pH, temperature, contact time, co-ions in solution, initial concentration of metal ion and biomass, availability of metal ions and micro-nutrients etc.), as well as the cell status (such as cell species, cell age) and cultural conditions (carbon source, nutrient supply, composition of growth media, etc.). The understanding of the effects of nutritional and environmental factors on the quality of microbial biomass could enable the propagation of desirable types of organisms on cheap nutrients and in a form suitable for direct application.

6.2. PROPERTIES OF METAL IONS Pearson (1963) classified metallic ions according to a “hardness scale” defined by their binding strength with F- and I- based on thermodynamic and not on kinetic considerations. Nierboer and Ruchardson (1980) proposed a refined classification of metal ions for biological systems considering the electro-negativity, charge and ionic radius of metal ions in determining their relativeness. Hard metal ions, such as Na+, K+, Ca2+, Mg2+ , are usually nontoxic and often essential macronutrients for microbial growth, they bind preferentially to oxygen-containing (hard) ligands, such as OH-, HPO42-, CO32-, R-COO-, and =C=O, whereas soft metal ions, such as Hg2+, Cd2+ and Pb2+, which often display greater toxicity, form stable bonds with nitrogen- or sulfur-containing (soft) ligands, such as CN-, R-S-, -SH-, NH2-, and imidazol. Borderline or intermediate metal ions are less toxic and can even be detected in certain bio-molecules where they assist in mediating specific biochemical reactions, e.g., Zn2+, Cu2+ and Co2+ (Avery and Tobin, 1993). Tobin et al. (1984) reported that biosorption of

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metal ions by Rhizopus arrhizus was linearly influenced by the ionic radius, but independent of the ionic charge or electrostatic strength. Based on the hard-and-soft principle of acids and bases, Avery and Tobin (1993) investigated the metal adsorption characteristics for metabolism-independent uptake of the metal ions, including Sr2+, Mn2+, Zn2+,Cu2+, Cd2+, Ti2+ by S. cerevisiae. The results proved that the complex characteristics of microbial metal uptake correlate well with and can be accounted for using the hard and soft acid base principles (HSAB principle). The HSAB principle is not a theory but a statement of experimental facts (Pearson, 1963). Biosorption of metals ions such as Sr2+, Mn2+, Zn2+,Cu2+, Cd2+ and Pb2+ by freeze-dried Rhizopus arrhizus is observed to be related to their covalent index (Xm2r), where Xm is electro-negativity and r is the ionic radius (Brady and Tobin, 1995). The greater the covalent index value of metal ion is, the greater is potential to form covalent bonds with biological ligands. However, it is still difficult to explore the effect of metal ion properties. In the chapter 10, The QSARs (qualitative structure activity relationships) used in metal toxicity assessment was introduced and applied to investigate the effect of metal ion characteristics on metal biosorption capacity. The method not only offered a new way and idea to explore the metal biomass interaction by applying QSAR in metal biosorption, but also can predict metal biosorption capacity.

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6.3. INFLUENCE OF PH For biosorption of heavy metal ions, pH is one of the most important environmental factors. The pH value of solution strongly influences not only site dissociation of the biomass’s surface, but also the solution chemistry of the heavy metal ions: hydrolysis, complexation by organic and/or inorganic ligands, redox reactions, precipitation, the speciation and the biosorption availability of the heavy metal ions (Esposito et al., 2002; Wang, 2002). It seems that the optimum pH is slightly acid to around neutral (pH = 4~7) for the majority of biosorbents, regardless of bacteria, fungi, yeast or algae. Results published so far indicate that biosorptive capacity of metal cations increases with increasing pH of the sorption system, but not in liner increase (figure 6.1), which illustrated the biosorption of Zn2+ and Pb2+ by the waste biomass of S. cerevisiae from a local brewery in China (unpublished data). On the other hand, too high pH values which can cause precipitation of metal complexes should be avoided during biosorption process. At higher solution pH, the solubility of metal ion may decrease leading to precipitation, which may complicate the sorption process. The general explanation for pH effect on biosorption is that protons would compete for the same active binding sites on the biomass cell wall thus reducing the amount of metal ion adsorbed at low pH (high proton concentration). Low pH would change the cell surface charge from negative to positive, and inhibits the approach of positive metal ions to biomass surface (Garnham, 1997; Wang and Chen, 2006).

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Correlating Metal Ionic Characteristics with Biosorption Capacity

0.4

Pb Ag Co Cu

0.3 q (mmol/g)

215

0.2 0.1 0.0 2

4

6

8

initial pH

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Figure 6.1. Effect of initial pH on biosorption of Zn2+, Pb2+, Co2+ and Ag+ by S. cerevisiae (initial metal ion was 1.0 mmol l-1, 3 h, cells was 2 g l-1).

It has been reported that optimal pH value is 5~9 for copper by S. cerevsiae, and 4~5 for uranium. Of course, optimal pH exists for different metal ions in a special biosorption system. Mapolel and Torto (2004) found that uptake of Cd2+, Cr3+, Cr6+, Cu2+, Pb2+ and Zn2+ is dependent on pH. All metal ions studied exhibited an optimal pH greater than pH 5. Optimal pH for Cd and Pb uptake is up to pH 5.8, while for Cr (III) and Pb is 5.2, substantially and subsequently decreased as the pH increased. The researchers explained that at low pH, the affinity for the binding site on yeast by the proton is much greater than that of the metal ion (H+ >> M2+), as compared with that at higher pH where M2+>> H+. Vianna et al. (2000) reached the similar conclusion on pH that metal cations uptake strongly depend on pH value: uptake capacity for Cu, Cd and Zn at pH 4.5 by Bacillus lentus, Aspergillus oryzae or Saccharomyces cerevisiae biomass is far higher than at pH 2.5 and pH 3.5. Electrostatic attraction to negatively charged functional groups may be one of the specific uptake mechanisms, and the most important group at pH 4.5 would be the phosphate. The other two main active molecular groups are carboxyl and sulfate. Marques et al. (2000) studied the pH effects (i.e. initial pH and of pH shift and control) on the removal of Cu2+, Cd2+ and Pb2+ from un-buffered aqueous solution by non-viable S.cerevisiae (brewery waste biomass) in detail. A shift in the medium pH from 4.5-5.0 (optimum pH range) to a final value in the 7.0-8.0 range was observed. They suggested different removal mechanisms for each cation: Cu2+ was removed by both the metal sorption and precipitation due to the pH shift occurred during the process, while Cd2+ removal was completely dependent on this pH shift. Pb2+ was totally and quickly removed by precipitation in the presence of the yeast suspension at pH4.5. Ozer and Ozer (2003) found that optimal pH value for Pb(II) and Ni(II) ions uptake is 5.0. At lower pH, cell wall ligands were closely associated with the hydronium ions [H3O+] and restricted the approach of metal cations as a result of the repulsive force. At higher pH, e.g. 5.0, divalent positive ions are suitable to interact with negatively charged groups in biomass. On the other hand, the outer layer of the cell wall of S. cerevisiae consists of a coating protein, which can cause a charge by dissociation of ionizable side groups of the constituent amino

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acids. The ionic state of ligands such as carboxyl, phosphate, imidazole and amino groups will promote reaction with the positively charged metal ions. For bacterial biomass, pH 3 to 6 has been found favorable for metal ion biosorption, regarding to the negatively charged carboxyl groups (pKa = 3–5),which are responsible for the binding metal cations via ion exchange mechanism (Vijayaraghavan and Yun, 2008). It is reported that Al3+, Cu2+, Pb2+, Cr3+, Cd2+, Ni2+, Co2+, Zn2+, Fe3+, Be2+, UO22+ are tightly bound at pH>5 by algae and can be desorbed at pH7.0), at least four times more chromium uptake occurred to the modified cells than that to unmodified cells (Bingol et al., 2004). This kind of modification on the yeast may offer a way to utilize the biomass at high pH to remove metal anions. Some controversy or inconsistent conclusions on pH effect on a certain metal ions by a certain biomass were also noted. For example, biosorption of Ag+ by S. cerevisiae is dependent on pH, as shown in figure 6.1. However, the biosorption of Ag+, Hg2+ or AuCl4was independent of pH (Garnham, 1997). Mehta and Gaur (2005) also pointed out that great variability in optimum pH for sorption of a particular metal ion by different algal species, and the authors owe this variability to the differences in chemical composition of cell surface of various algal species.

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Obviously, the solution pH influences chemical speciation of metal ions in solution, thus affects availability of metal ions for binding onto biomass. Decrease in pH of the solution generally increases the concentration of free metal ions. pH also regulates the metal-ligand complex in solution. Such inorganic or organic ligands include HCO3-, CO32-, Cl-, SO42- , HS-, acetic acid, oxalic acid, amino acids, etc., are for metal binding (Mehta and Gaur, 2005). The explanation of the pH shift in biosorption process and pH effect is helpful to identify the mechanisms of metal uptake. Jones and Gadd (1990) discussed the pH effects on ion transport into the yeast cells at molecular level. More efforts should be devoted to this problem.

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6.4. TEMPERATURE EFFECT Temperature can affect the biosorption of metal ions, but to a limited extent under a certain range of temperature, indicating that ion exchange mechanism exists in biosorption process to some extent because ion exchange is almost not influenced by temperature. Operation of biomass is usually not at high temperature because it will increase the operational cost (Wang, 2002). Generally, the effect of temperature was not as pronounced as that of pH. Temperature (5-40°C) had minor effect on the level of Cu2+, Co2+ or Cd2+ accumulation by free cells of S. cerevisiae (Brady and Duncan 1994b). Mehta et al. (2002) also could not observe a pronounced effect of temperature on algae Chlorella vulgaris binding of Cu and Ni. The different effect of temperature （10°C, 20°C, 30°C, 40°C）on a certain metal species (Zn2+, Ag+, Cu2+, Co2+) bisorption by S. cerevisiae were observed, as illustrated in Figure 6.2 (unpublished). The results showed that little effect on Zn2+, Ag+ or Cu2+ sorption capacity in low equilibrium concentration of metal ions. However, the variation of temperature effect on sorption of Ag+, Cu2+ and Zn2+ were noticed on high equilibrium concentration of metal ions (usually higher than 0.4~0.5 mmol l-1). For Co2+ ， high temperature of 40°C exhibited the lowest uptake capacity when equilibrium concentration of Co2+ was lower than 0.4 mmol l-1. However, higher temperature was favorable for Co2+ uptake by the yeast when equilibrium concentration of Co2+ was higher than 0.4 mmol l-1. According to the thermodynamic equations (Ho and Ofomaja, 2006; Uslu and Tanyol, 2006), the thermodynamic parameters, such as Gibbs free energy change (ΔG0), the enthalpy change (ΔH0), and the entropy change (ΔS0) were calculated (data not shown). Gibbs free energy change, ΔG0, is an indication of spontaneity of a chemical reaction and therefore is an important criterion for spontaneity. The results showed that biosorption process was spontaneous with high preference of the metal ions tested, Zn2+, Ag+, Cu2+ or Co2+, onto the waste yeast cells, due to the negative values of Gibbs free energy change for these metal ions, -19.17~-23.97 kJ mol-1. The enthalpy change (ΔH0) was also negative, for Cu2+ (-2.40 kJ mol1 ), Zn2+ (-2.82 kJ mol-1) and Co2+ (-9.90 kJ/mol), indicating that the biosorption reaction of Cu2+, Zn2+ or Co2+ with the waste yeast cells was exothermic. However, the positive value of ΔH0 for Ag+ (3.38 kJ mol-1) confirmed that the endothermic nature of biosorption to the waste yeast cells, and also indicated the possible strong interaction between Ag+ and the waste yeast cells. The positive values of the entropy change (ΔS0) for the all tested metal ions indicated the increased randomness at the solid/liquid interface during the biosorption of Ag+, Cu2+,

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Zn2+ or Co2+ onto the waste yeast cells (data not shown). The positive ΔS0 also reflected the affinity of the yeast cells to the metal ions tested and suggested some structural changes in Ag+, Cu2+, Zn2+ or Co2+ and the yeast cells. Many references on metal ion biosorotion showed the negative values of ΔG0 and positive values of ΔS0, such as the biosorption of lead(II) and copper(II) ions onto Pseudomonas putida (Uslu and Tanyol, 2006), cadmium on coconut copra meal (Ho and Ofomaja, 2006).

Figure 6.2. Effect of temperature on biosorption of Zn2+, Cu2+, Co2+ and Ag+ by S. cerevisiae (initial metal ion was 1.0 mmol l-1, 3 h, cells was 2 g l-1, initial pH was 4.0).

Adsorption processes are normally exothermic, and biosorption capacity usually increased with decreasing temperature (Kapoor and Viraraghavan, 1997). In the range of 15~40°C, the maximum equilibrium biosorption for Pb(II), Ni(II) and Cr(VI) ions by the inactive S. cerevisiae was found to be at 25°C. The decrease of the capacity at higher temperatures between 25~40°C revealed that the processes of biosorption for these metal ions by S. cerevisia are exothermic. This decrease at higher temperatures may be due to the damage of active binding sites in the biomass (Ozer and Ozer, 2003). However，Goyal et al. (2003) found that the metal uptake of Cr (VI) by S. cerevisiae increased with increasing temperature in the range of 25~45°C. The authors explained that higher temperature would lead to increase higher affinity of sites for metal ions or binding sites on the yeast. The energy of the system facilitated Cr (VI) attachment on the cell surface to some extent. When the

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temperature is too high, there is a decrease in metal sorption due to distortion of some sites of the cell surface available for metal biosorption. Also, Zhao and Duncan (1998) have found that regeneration of the saturated yeast (immobilized S. cerevisiae by formaldehyde) is satisfying at 4°C by the combination of reduction and desorption using formaldehyde and HNO3, whereas it is not at room temperatures with the same procedure, reflecting the thermochemical effect on binding of the metal to yeast biomass. Heavy metal sorption capacity by Sargassum sp. slightly decreased with increasing the temperature (20~55ºC) based on some relevant researches (Brinza et al., 2007). Other references also reported that temperature exhibits little effect on biosorption (Garnham, 1997). Metha and Gaur (2005), however, also noticed that the contrasting results have been obtained regarding the effect of temperature on sorption of heavy metals by algae. Some researchers observed that metal uptake capacity increased with increase in temperature, which probably suggests that metal biosorption by biomass is an endothermic process. It is said that higher temperature enhances the number of active sites involved in metal sorption or higher affinity of sites for metal ion. However, exothermic nature of metal ion sorption by algae was also reported.

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6.5. IONIC STRENGTH EFFECT Ionic strength plays an important role in metal ion uptake by biomass as reported in many references. Some researchers think that apart from the pH value, another important parameter in biosorption is the ionic strength (Schiewer and Wong, 2000). Generally, metal uptake capacity increased with decreasing ionic strength due to the competition for the functional groups on biomass between metal ions and other ions at a fixed pH. As Chen reported (Chen et al., 1997), Cu2+ removal efficiency by calcium alginate beads increases with decreasing ionic strength, when the ionic strength of the solution was adjusted to 0.005, 0.05, and 0.5 M by adding appropriate amounts of sodium perchlorate. Sodium is common in many wastewaters and usually high Na concentrations lead to high ionic strengths which reduced the amount of heavy metal ions bound for competition effects (Schiewer and Volesky, 1997a; 1997b; Schiewer and Wong, 2000). The amount of Pb2+ adsorbed by marine algae Dunaliella tertiolecta increased at low salinity values and 43% more lead is adsorbed at low salinities than at seawater salinity. The difference may be due to competition of sites on the algae for metal ions such as Mg2+ and Ca2+ (Santana-Casiano et al., 1995). However, ionic strength effect on metal biosorption exhibited more complex particularly considering pH. The ionic strength can influence metal accumulation by affecting the activities of the metal ions in solution, as well as the surface charge and double-layer capacitance of the hydrated cells (Santana-Casiano et al., 1995). Figure 6.3 shows the effect of the ionic strength (I=0, 0.002, 0.02, 0.2 mol NaNO3 l-1) on Zn2+ and Pb2+ biosorption in different initial pH (4, 5, 6) by the waste yeast (unpublished). Here, the ionic strength of 0.2 mol l-1 was used to simulate many typical wastewater (Beolchini et al., 2006).

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Figure 6.3. Influence of ionic strength on Zn2+ (left) and Pb2+ (right) biosorption by the waste yeast in different initial pH (C0-=0.16 mmol l-1, 3 h, the cells was 2 g l-1).

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It appears from figure 6.3A that Zn2+ biosorption decreased with increase of I, apart from the point of I was 0 at pH6. Without considering this point, the amount of Zn2+ uptake by the biomass was negatively correlated to the square root of I at pH4, pH5 or pH6, and the corresponding linear equation was:

q = 0.0444-0.0456 I1/2 (R2=0.992, pH=4),

(6.1)

q = 0.0433-0.035 I1/2 (R2=0.958, pH=5),

(6.2)

q = 0.0414-0.0195 I1/2 (R2=0.995, pH=6).

(6.3)

The increase of pH value in the biosystem also decreased with the square root of I (data not shown), which further indicated that the certain degree of competition of Na+ with Zn2+ for binding site on the biomass. Sodium competed with metal ions for electrostatic binding to biomass active sites (Schiewer and Wong, 2000). However, the removal efficiency of Zn2+ basically remained between 48~53% when the ionic strength I was between 0~0.02 mol l-1. Only I was as high as 0.2 mol l-1, the ionic strength exited obvious influence and decreased Zn2+ uptake with the removal efficiency of Zn2+ of only 29~38%. According to the statistic analysis by the software of excel 2003, the coefficient of variability for Zn2+ uptake caused by the difference of ionic strength was 24.8% at pH4, 19.1% at pH5, 10.7% at pH6. However, the coefficient of variability for Zn2+ uptake caused by the difference of initial pH was 14.5% at I= 0 mol l-1, 2.2% at I=0.002 mol l-1, 2.2% at I= 0.02 mol l-1, 16.2% at I=0.2 mol l-1. The above values demonstrated that the influence of ionic strength on Zn2+ uptake was bigger than that of pH in our study at low initial pH (such as pH4). Reversely, the influence of pH on Zn2+ uptake was bigger than that of ionic strength at low (I= 0 mol l-1) or high ionic strength (I=0.2 mol l-1).The interaction of pH-ionic strength occurred, which was also observed in Cu2+ biosorption by a gram-negative bacterium Sphaerotilus natans. Cu2+ uptake decreased by ionic strength was explained by ionic strength (interact with ion-exchange sites) over a pH-depending metal binding (complexation) due to site dissociation especially at low pH of 4 (Beolchini et al., 2006). According to a reference (Schiewer and Wong, 2000), the effect of Na+ is more pronounced regarding the uptake of weakly bound metals such as Zn2+ or Ni2+

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than those strongly bound metals such as Cu2+ less affected by the ionic strength. The effect of ionic strength can be explained as the result of competition of Na+ with the heavy metals for electrostatic binding to the biomass as sodium was typical hard ion. From the above result, Zn2+ as a borderline ion indeed showed a certain degree of electrostatic binding and covalent binding to the biomass. Ionic strength seemed not exited obvious influence on Pb2+ uptake, shown in the figure 6.3B. At initial pH of 4, the removal efficiency for Pb2+ was among 35.5~39.0% in 0~ 0.2 mol l-1, less than 5% in four ionic strength. Zhou et al. (2004) reported the ionic strength (≤0.1 mmol NaCl l-1) do not make any considerable influence on Pb2+ (280 mg l-1) uptake by cellulose/chitin at initial pH of 5. According to the statistic analysis by the software of excel 2003, the coefficient of variability for Pb2+ uptake caused by the difference of ionic strength was 5.7% at pH4, 41.4% at pH5, 52.7% at pH6. However, the coefficient of variability for Pb2+ uptake caused by the difference of initial pH was 108.5% at I= 0 mol l-1, 72.5% at I=0.002 mol l-1, 76.3% at I= 0.02 mol/L, 79.05% at I=0.2 mol l-1. The above values demonstrated that the influence of ionic strength on Pb2+ uptake was much less than that of pH in our study. Pb2+ was a soft ion. Na+ was a typical hard ion and would not compete directly with the soft ions for covalent binding with the biomass (Schiewer and Wong, 2000). Under the different initial pH, the influence of ionic strength on Pb2+ uptake was different according to the figure 6.3B. At low pH of 4, Na+ seemed promoted Pb2+ uptake, whereas at high pH6, Pb2+ uptake decreased with increase of ionic strength. At high pH of 6, Pb2+ uptake and the removal efficiency of Pb2+ decreased greatly compared with that of pH of 4 and 6. At initial pH of 6, the removal efficiency of Pb2+ decreased to 5~17% from 35~39% at initial pH 4 or 5. Pb2+ was easily precipitated (Volesky and Holan, 1995; Marques et al., 2000). The scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX) had evidenced a large precipitation occurred on the surface of the waste yeast cells after contact with Pb2+ (data not shown). It is also noticed that Pb2+ uptake at I=0 was lower than that of I >0 at the pH 4, 5, or 6, which could by caused by a larger degree of precipitation or less binding site at I=0 for Pb2+ uptake. It needs to be further explored. Some references reported that apparent site density of the cell surface increased with increasing salt (such as Na+) concentration (Andrade et al., 2005; Borrok and Fein, 2005). High ionic strength possibly could possibly lead to cell disruption (Andrade et al., 2005). The different influence of ionic strength at different pH was reported to relate to partial cell disruption (Beolchini et al., 2006). Ionic strength can also influence the aqueous phase equilibrium in metal sorption studies (Mark et al., 2006). Schiewer and Wong (2000) investigated the ionic strength effects in biosorption of metal (Cu2+ and Ni2+) by four marine algae, i.e. green alga Ulva fascia and the brown seaweeds Sargassum hemiphyllum, Petalonia fascia, and Colpomenia sinuosa using pH titrations at different ionic strengths. The results showed that the decrease of proton binding with increasing ionic strength and pH as well as the increase of Cu2+ and Ni2+ binding with increasing pH and decreasing ionic strength could be described by the Donnan model in conjunction with an ion exchange biosorption isotherm. In all four types of biomass a pronounced effect of ionic strength was observed. Ionic strength did not influence the number of acidic groups titrated, it strongly affected apparent pKa values of the acidic groups titrated (i.e., the log of the proton binding constant). At high ionic strength the average pKa value was 3.8, i.e., 2 units lower than at low ionic strength (0.1 g biomass, no NaNO3 added). This means that the apparent proton binding constant changed in average by a factor of 100.

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Electrostatic effects could explain this kind of the effect of ionic strength: at high ionic strength Na balances most of the negative charges in the biomass whereas at low ionic strength an electrostatic attraction of protons leads to intraparticle concentrations that are higher than the bulk proton concentration. This higher intraparticle concentration leads to an increased amount of protons covalently bound to the binding sites, i.e., to an apparently higher binding constant (Schiewer and Wong, 2000). Schiewer and Volesky (1997a; 1997b) also investigated the effect of ionic strength and electrostatic effects in biosorption of divalent metal ions and protons by brown algae Sargassum biomass. A combined Donnan-Biosorption-Isotherm equation was derived to predict was possible to predict the effect of pH, ionic strength, and Ca2+ concentration on Cd2+ binding by Sargassum. The effect of ionic strength on the adsorption of H+, Cd2+, Pb2+, and Cu2+ by two grampositive bacteria Bacillus subtilis and Bacillus licheniformis in 0.01 or 0.1 M NaNO3 was investigated. A surface complexation model was evaluated. The results showed that the stability constants between the metal tested and the distinct functional groups on the bacterial cell walls vary substantially but systematically between the two bacterial species at the two different ionic (Daughney and Fein, 1998). Naeem et al. (2006) reported that ionic strength exerts no significant or consistent effect on Pb2+ adsorption onto the cell walls of S. cerevisiae. For Cd2+ and Zn2+, adsorption capacity increased with decreasing ionic strength in general, but this relationship does not hold under all conditions studied. For example, little significant difference in Zn2+ removal in 0.1 and 0.01 M electrolytes above pH 6.5, or between the 0.01 and the 0.001 M ionic strength below pH 6 were observed. The lgK values for each metal-functional group complex studied here exhibit no systematic dependence on ionic strength. Thus the authors suggested a nonelectrostatic surface complexation model with four discrete surface organic acid functional group types, which ignores ionic strength effects on metal adsorption onto the fungal cell wall, provides a reasonable fit to the observed adsorption behavior over the ionic strength range of 0.001-0.1 M.

6.6. PRESENCE OF ANIONS AND CATIONS Real industrial effluent usually contains various ionic components, including metal cations and anions. Studies indicated that cations and anions additional to the ions of interest have a generally detrimental impact on metal accumulation (Suh and Kim, 2000). One metal ion uptake capacity is often interfered and reduced by co-ions including other metal ions and anions presenting in solution, with the gross uptake capacity of all metals in solutions retains almost unchangeable. Biosorption of metal on certain fungal strains has been found to be both selective and, in some cases, competitive (Kapoor and Viraraghavan, 1997). The nature of biosorption on biomass is complex, and any general conclusion on biosorption should be drawn in extreme caution. Now limited information is available on the competition in metal biosorption between metals interested and other components on algae or fungi comparisoan with that of one-metal system (Kapoor and Viraraghavan, 1997; Romera et al., 2006). In the review on algae biosortion by Romera et al. (2006), 90% of the total 214 references collected was

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related to monometallic systems, and the remaining 10% was about multi-metallic systems. Ledin (2000) also reviewed metal ion accumulation by bacteria, fungi and algae in the presence of other ions, and some contrasting results were obtained with regard to the effect of other cations. Sag (2001) summarized the competitive metal biosorption by fungal cells and antagonistic-synergistic interactions. Following are some other examples on effect of other cations in biosorption. Competition effect occurred in a mixture of solution containing lead and chromium during the uptake process by flocculating brewer's yeast (Ferraz and Teixeira, 1999). The cells of S. cerevisiae seems to have more affinity, higher selectivity and uptake capacity to Pb (II) than to Cr (III) from aqueous solutions. Goksungur et al. (2005) observed that the competitive biosorption capacities of the ethanol treated yeast for all metal ions of Pb2+, Cu2+ and Cd2+ were lower than non-competitive conditions. The decreased metal uptake in competitive conditions was thought to be a response to increased competition between like charged species for binding sites of the ethanol treated yeast cells. The order of the sorption capacity was found as Pb2+ >Cu2+ >Cd2+ for both pH 4.0 and 5.0. Pb2+ accumulation by S.cerevisiae was seriously inhibited by Hg2+. Uptake capacity of 2+ Pb decreased ( from 0.22 to 0.02 mmol Pb2+ g-1 cell dry weigh by the presence of Hg2+),but the total amount of accumulated metals was not changed (Suh and Kim, 2000). Goyal et al. (2003) also found that the biosorptive capacity of Cr(VI) ion by dried S. cerevisiae at the end of 24 h was significantly reduced by lower concentration of Fe(III), whereas this concentration of Fe (III) did not appreciably affect the ultimate uptake of Cr(VI) by S. equisimilis and A. niger. As for radionuclides, some co-ions seem to have limited influence on the uptake of certain radionuclides. No significant differences on 241Am adsorption by S. cerevisiae were observed in solutions containing Au3+ or Ag+, even 2000 times above 241Am concentration (Liu et al., 2002). Similar results were obtained by Das et al.(2002). Accumulation of longlived radionuclides such as 233U, 239Pu, 241Am by immobilized S. cerevisiae was observed to have no significant differences in presence of the cationic impurities such as Al3+, Be2+, Cd2+, Cr3+, Fe2+, Mn2+, Pb2+, Ce2+, Dy2+, Eu2+, Gd2+ and Sm2+. However, The uranium uptake by R. arrhizus or A. niger was reduced in presence of Zn and Fe (Kapoor and Viraraghavan, 1997). Al3+, but not Na+, K+, Ca2+, Cl-, SO42- or NO3- ions affected the accumulation La2+, Eu2+ and Yb2+ to Pseudomonas aeruginosa (Texier et al., 1999). Light metal ions, such as Ca2+, Na+, K+, are present in quantity in real industrial wastewater. The experiment data have shown that those light metal ions have little effect on metal biosorption, which indicates that the affinity of the yeast for those light metal ions is far less than for heavy metal ions. Those alkali metal ions and alkaline earth metals were not absorbed by the yeast possibly because they lack the ability to form complexes with the various ligand groups present on the fungal surface (Kapoor and Viraraghavan, 1997). However, Mehta and Gaur (2005) thought that light ions exist in most industrial effluents and they greatly affect metal sorption potential of biosorbents. Reduction of metal uptake in the presence of light metals is attributed to competition for cellular binding sites, or precipitation or complexation by carbonates, bicarbonates or hydroxides of Ca2+ and Mg2+. High concentrations of salts like NaCl in solution also decrease the rate of metal sorption just aforementioned high ionic strength could depress the metal uptake. Mehta and Gaur (2005) also found that little effect on metal removal by some biomass reported, for example, inhibitory effect of Ca2+ and K+ on Cd2+ sorption by lyophilized Chlamydomonas reingardtii did not occur. Ca2+ exhibited negative or

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positive effect on metal uptake, maybe due to altered cell wall structure in the presence of bivalent ions (Ledin, 2000). The inhibitory effect of other cations on interested metal uptake could be explained in terms of competition between ions for the same metal binding sites on biomass. Studies of this effect lead to construction of selectivity of biosorption series. The selectivity order various with biomass species (Garnham, 1997; Kapoor and Viraraghavan, 1997). Al3+ ≈Ag+ > Cu2+> Cd2+> Ni2+> Pb2+> Zn2+= Co2+> Cr3+ by microalga Chlorella vulgaria, and Cu2+ >Sr2+ > Zn2+ >Mg2+ >Na+ by mcaroalga Vaucheria was reported (Garnham, 1997). Tobin (1984) reported the similar order for the metal uptake affinity of Rhizopus arrhizu: UO22+> Cr3+> Pb2+> Ag+> Ba2+> La3+> Zn2+> Hg2+> Cd2+> Cu2+> Mn2+> Na+, K+, Rb+, Cs+. When using sugar beet pulp as biosorbent, Pb2+> Cu2+> Zn2+> Cd2+> Ni2+ was observed (Reddad et al., 2002). The selectivity in biosorption can be explained by biding sites on algae having preference for hard or soft ions, i.e. HSAB principle. In fact, Ledin (2000) reviewed the metal selectivity of biomass. The presence of anions also affects the biosorption of metal ions. Biosorption capacity reduced in the presence of ethylenediamine tetraacetate (EDTA), sulphate, chloride, phosphate, carbonate, glutamate, citrate and pyrophosphate (Kapoor and Viraraghavan, 1997). The anions in solution may form complex with the metal ions which would reduced metal biosorption uptake severely. When the stability constants of metal-anion complexes are higher than stability constants for metal biosorption sites on the cell surface, the metal uptake by biomass could be severely reduced. EDTA has been found considerably inhibited biosorption of Cu2+, La2+, U6+, Ag+, Cd2+ and Pb2+. Pulsawat et al. (2003) reported the anions effects on biosorption of Mn(II) by extracellular polymeric substance (EPS) from Rhizobium etli. The results showed that maximum manganese specific adsorptions (qmax) decreased in the sequence: sulphate (62 mg Mn g-1 EPS) > nitrate (53 mg g-1) > chloride (21 mg g-1). It was suggested to consider anion effect during metal uptake because it is usually neglected but is important in providing more practical and comparable data between different biosorbent systems. However, Das et al. (2002) found that anionic impurities, such as Cl-, NO3-, SO42-, C2O42- and CH3COO-, do not show any adverse effect on Pu4+ sorption, while the presence of PO34- reduces its sorption by the yeast of S. cerevisiae (The effect of anions was studied separately up to 0.5 mol l-1 of their individual concentrations). Garnham (1997) also think that anionic concentration rarely affect the metal biosorption by algae. Nowadays only limited information is available on the competition on fungal biosorption. More efforts need to be put into competitive study for two-or multi-metal ions biosorption system by utilizing multi parameters mathematic model (Sag, 2001; Wang, 2002; Romera et al., 2006).

6.7. OTHER FACTORS 6.7.1. Contact Time Usually, heavy metal biosorption by passive mode is a rapid process and often reaches equilibrium within several hours (Kapoor and Viraraghavan, 1997). The immobilized cells of S. cerevisiaes for Pu2+, Am2+ and Ce2+ reached equilibrium within 60 minutes. In the case of

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U6+, equilibrium attained in 100 minutes (Das et al., 2002). The biosorption of metals such as copper, zinc, lead and uranium by non-growing cells of S. cerevisiae reaches equilibrium within several hours (Kapoor and Viraraghavan, 1997). Usually during a certain range of time, higher uptake capacity and removal efficiency of metal ions by biomass are obtained with longer contact time. However, in practice of the biosorption, it is necessary to decide the optimum contact time considering the efficiency of desorption and regeneration of the biomass. Sorption time for Cr(III) by S. cerevisiae from a brewery company was optimized in the sorption–desorption process, the result showed that a 30 min sorption period was the best option to ensure metal removal from solution and good recovery from biosorbent (Ferraz et al., 2004). The biosorption uptake of metals discussed in a substantial of references was mainly due to the passive mode. However, Malik (2004) pointed out that short biosorption studies have low possibility to observe and appreciate the delayed intracellular accumulation and hence, most of such studies conclude with the surface adsorption of the metal. However, the studies, monitoring metal removal by growing cells, often realize the metabolically linked intracellular accumulation. Recent studies have proved that in spite of low apparent growth rate, growing cells are able to remove metal ions continuously through internal detoxification mechanisms (Malik, 2004). The active mode can contribute significantly to metal ion removal for yeast (Kapoor and Viraraghavan, 1997). It is meaningful to carry out researches on application of growing cells of the yeast in bioremediation. In a word, equilibrium time of active cells of the yeast in solution should be paid much attention.

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6.7.2. Cell Culture Conditions Composition of cultural medium, nutrient level, growth rate and illumination greatly influence metal sorption by living cells. Variations in growth conditions possibly bring about changes in composition of the cell surface thereby affecting metal biosorption characteristics of the biomass (Mehta and Gaur, 2005). Glucose is a widely common used carbon source and also acts as an important source of energy. For biosorption of living cells, glucose and other trace elements added into biosorption system will enhance the growth of living cells, which could facilitate metal biosorption. Some researches were carried out on the role of glucose in metal ion biosorption. Stoll and Duncan (1996) investigated the uptake of Cu2+, Cr6+ Cd2+, Ni2+ and Zn2+ from electroplating effluent by living cells of S. cerevisiae. The results showed that pretreatment of the yeast cells with glucose increased the amount of metal removed, whilst direct addition of glucose to the yeast-effluent solution had no effect on the amount of metal accumulated. Avery and Tobin (1992) reported a little different result. Glucose was added to the living yeast cells solution just 5 min before the addition of Sr2+, the presence of glucose resulted in a stimulation of Sr2+ uptake due to metabolism-dependent intracellular Sr2+ accumulation, mainly in vacuole. Mapolelo and Torto (2004) also reported that the pretreatment of the S.cerevisiae by using 10-20 mM glucose increased 30-40% removal efficiency for Cd2+, Cr3+, Cu2+, Pb2+ and Zn2+, but by using 60 mM glucose decreased the almost 50% removal for Cr6+. The mechanism of Cr6+ uptake may differ from other metal ions. Higher uptake of Cr (III) may be related to the glucose tolerance factor (GTF), a cationic Cr3+ complex of lower molecular weight consisting of Cr3+, nicotinic acid, and the amino acids glycine, glutamic

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acid and cysteine. It is believed that GTF is mainly connected with carbohydrate metabolism by yeast cells. Carbohydrate metabolism by S.cerevisiae, requiring Cr (III) as a component of GTF, contributed to such a high uptake of Cr (III) in the presence of glucose (Mapolelo and Torto, 2004). In order to compare S. cerevisiae with other yeast cells, Gomes et al. (2002) investigated five strains of Rhodotorula mucilaginosa for accumulating free and complexed silver ion by metabolism-dependent and independent processes. Silver dicyanide (Ag(CN)2-) uptake was strictly glucose dependent. Ag+ uptake by both live and dead biomass was studied. Glucose addition decreased the Ag+ uptake rate of living UFMG - Y02, Y27, and Y35 cells by 16 to 25%, while an improved uptake rate of Ag+ (115% and 13%, respectively) by strains CBS 316 and UFMG-Y01 was observed. It seems that the role of glucose addition depends on the type of strains and the status of metal ions (free or complex) even for the same biomass and for the same metal ions. A strain of Trichoderma atroviride, isolated from sewage sludge, was found to be capable of surviving at high concentrations of heavy metal ions (copper, zinc and cadmium). Lopez Errasquin and Vazquez (2003) found that when the mycelia were transferred to medium without dextrose, T. atroviride was capable of uptaking more metal ion than in the presence of dextrose. The lowest uptake of metal ions in the presence of glucose, and the highest values of metals removal were achieved for autolysed mycelia (Lopez and Vazquez, 2003). The researchers proposed two possible and alternative explanations for the above results. Firstly, an active detoxification process would occur with the presence of an abundant source of carbon such as glucose, thereby reducing the amount of metal ion in the cell. Secondly, no carbon source available will trigger the cell autolysis. Cell autolysis will not only increase surface area of the autolysed cell wall, but also lead to exposure of intracellular binding sites of the biomass, thus providing access to additional negatively charged binding sites in addition to those present on the surface of the fungal cells. Therefore, physical binding of metal ions by cell surfaces rather than an active process is main uptake mechanism, in which, fungal cell wall plays an important role in metal biosorption. Chojnacka et al. (2004) also found that decrease in initial glucose concentration favored synthesis of cells, hence elevating cations biosorption uptake by microalgae Spirulina sp. For Chryseomonas sp. MGF-48, a bacterium isolated from electroplating effluent, uranium uptake by washed bacterial cells (198.2 mg g-1 dry weight, under starvation conditions for 16h) was reduced by the addition of glucose but remained higher than (156.5 mg g-1) as observed for cells not subject to starvation (151 mg g-1) (Malekzadeh et al., 2002). Uranium uptake in the presence of selected carbohydrates decreased as follows: xylose > arabinose > mannose > maltose > glucose. Other compositions of cultural medium also affect the metal uptake. Goyal et al. (2003) found that supplement of cysteine, glucose, ammonium sulfate, phosphate and ammonium chloride in fermentation media for the growth of S. cerevisiae increased the Cr(VI) uptake. The best recovery of Cr(VI) was obtained when the cells grow in cysteine-supplemented medium, followed by glucose-, phosphate-, ammonium sulphate-, and ammonium chloriderich media. Different nutrients clearly led to different functional groups in the corresponding cell surface. Cysteine inserts –S and –N ligands, glucose C-ligands, ammonium N-ligands and phosphates P-ligands (Engl and Kunz, 1995). Of all of these, cysteine-rich media gave the highest adsorption capacity. Simmons and Singleton (1996) obtained similar results. Addition of L-cysteine into the growth medium increased silver biosorption capacity, protein and

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sulphydryl group content of the freez-dried and viable yeast cells, although increase the concentration of L-cysteine (from 1 to 5 mM) decreased the cell numbers of the medium in comparison to the control without L-cysteine. Precipitates on exposed cells to silver ion were analyzed by TEM with X-ray microanalysis, the peak occurring due to silver or sulphur, indicating that the silver ion may have bound to a sulphur-containing molecule and precipitated around it. Dostaleka et al. (2004) investigated biosorption of Cd2+, Cu2+ and Ag+ ions by C-, N-, P-, S-, Mg2+- and K+-limited cells of S. cerevisiae. The binding capacity of yeast cells for cadmium ions decreased in the order: K-limited ≥ Mg-limited ＞ C-limited ＞N-limited ＞Slimited＞P-limited. For Ag+ ions: P-limited＞K-limited＞C-limited ≥ N-limited ＞ Mglimited＞S-limited. For copper ion: K-limited＞Mg-limited ≥ C-limited＞N-limited ＞Plimited＞S-limited.

ACKNOWLEDGMENTS The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 50830302; 50808111; 50278045), China Postdoctoral Science Foundation funded project (Grant No. 20080430350), special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (Grant No. 08K05ESPCT) and the Basic Research Fund of Tsinghua University (Grant No. JC2002054), to carry out the relevant research works.

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REFERENCES Aksu Z., Gulen H., Process Biochem. 38 (2002) 161-173. Andrade A. D., Rollemberg M. C. E., Nobrega J. A., Process Biochem. 40(2005) 1931-1936. Avery S. V., Tobin J. M., Appl. Environ. Microbiol. 58(1992) 3883-3889. Avery S. V., Tobin J. M., Appl. Environ. Microbiol. 59(1993) 2851-2856. Azizian S., J. Colloid Interface Sci. 276 (2004) 47-52. Banerjee K., Cheremisinoff P.N., Cheng S.L., Water Res. 31 (1997) 249-261. Beolchini F., Pagnanelli R., Toro L., Vegliò F., Water Res. 40(2006) 144-152. Bingol A., Ucun H., Bayhan Y. K., Karagunduz A., Cakici A. e Keskinler B. Bioresour. Technol. 94(2004) 245-249. Borrok D. M., Fein J. B., J. Colloid Interface Sci. 286(2005) 110-126. Brady J. M., Tobin J. M., Enzyme Microb. Technol. 17(1995) 791-796. Brinza L., Dring M. J., Gavrilescu M., Environ. Eng. Manage. J. 6(2007) 237-251. Chen J. P., Tendeyong F., Yiacoumi S., Environ. Sci. Technol. 31(1997) 1433-1439. Chojnacka K., Chojnacki A., Gorecka H., Inz. Chemiczna Proces. 25(2004) 789-794. Das S. K., Kedari C. S., Shinde S. S., Ghosh S., Jambunathan U., J. Radioanal. Nucl. Chem. 253(2002) 235-240. Daughney C. J., Fein J. B., J. Colloid Interface Sci. 198(1998) 53-77. Dostalek P., Patzak M., Matejka P., Int. Biodeterior. Biodegrad. 54(2004) 203-207.

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

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Can Chen and Jianlong Wang

Engl A., Kunz B., J. Chem. Technol. Biotechnol. 63(1995) 257-261. Esposito A., Pagnanelli F., Veglio F., Chem. Eng. Sci. 57(2002) 307-313. Ferraz A. I., Tavares T., Teixeira J. A., Chem. Eng. J. 105(2004) 11-20. Ferraz A. I., Teixeira J. A., Bioprocess Eng. 21(1999) 431-437. Garnham G. W., In: Biosorbents for Metal Ions. Edited by Wase J., Forster C. London, UK: CRC Press; 1997. Goksungur Y., Uren S., Guvenc U., Bioresour. Technol. 96(2005) 103-109. Gomes N. C. M., Rosa C. A., Pimentel P. F., Mendonça-Hagler, L.C.S., Braz. J. Microbiol. 33(2002) 62-66. Goyal N., Jain S. C., Banerjee U. C., Adv. Environ. Res. 7(2003) 311-319. Ho Y. S., Ofomaja A. E., Biochem. Eng. J. 30(2006) 117-123. Jones R. P., Gadd G. M., Enzyme Microb. Technol. 12(1990) 402-418. Kapoor A., Viraraghavan T., In: Biosorbents for Metal Ions. Edited by Wase J, Forster C. London, UK: CRC Press; 1997. Ledin M., Earth-Sci. Rev. 51(2000) 1-31. Liu N., Luo S. H., Yang Y. Y., Zhang T., Jin J.N.,Liao J.L., J. Radioanal. Nucl. Chem. 252(2002) 187-191. Liu Y., Xu H., Yang S.F., Tay J.H., J. Biotechnol. 102 (2003a), 233-239. Liu Y., Yang S.F., Xu H., Woon K.H., Lin Y.M., Tay J.H., Process Biochem. 38 (2003b), 997-1001. Lopez Errasquin E., Vazquez C., Chemosphere. 50(2003) 137-143. Loukidou M.X., Zouboulis A.I., Karapantsios T.D., Matis K.A., Colloids Surf., A 242 (2004), 93-104. Malekzadeh F., Farazmand A., Ghafourian H., Shahamat M., Levin M., Colwell R. R., World J. Microbiol. Biotechnol. 18(2002) 295-300. Malik A., Environ. Int. 30(2004) 261-278. Mapolelo M., Torto N., Talanta. 64(2004) 39-47. Mark S. S., Crusberg T. C., DaCunha C. M., Di Iorio A. A., Biotechnol. Progr. 22(2006) 523531. Marques P., Rosa M. F., Pinheiro H M., Bioprocess Eng. 23(2000) 135-141. Metcalf & Eddy, Wastewater engineering : treatment and reuse, 4th ed. McGraw-Hill, Boston, 2003. Mehta S. K., Gaur J. P., Crit. Rev. Biotechnol. 25(2005) 113-152. Mehta S. K., Singh A., Gaur J. P., J. Environ. Sci. Health Part A-Toxic/Hazard. Subst. Environ. Eng. 37(2002) 399-414. Morel F., Hering J.G., Morel F. Principles and applications of aquatic chemistry, 1st ed. Wiley, New York, 1993. Naeem A., Woertz J. R., Fein J. B., Environ. Sci. Technol. 40(2006) 5724-5729. Nieboer E., Richardson D. H. S., Environ. Pollut. Ser. B 1 (1980) 3-26. Ozer A., Ozer D., J. Hazard. Mater. 100(2003) 219-229. Pearson R. G., J. Am. Chem. Soc. 85 (1963) 3533-3539. Pulsawat W., Leksawasdi N, Rogers P L, Foster, L.J.R., Biotechnol. Lett. 25(2003) 12671270. Puranik P.R., Modak J.M., Paknikar K.M., Hydrometallurgy 52 (1999) 189-197. Reddad Z., Gerente C., Andres Y., Cloirec P., Environ. Sci. Technol. 36(2002) 2067-2073.

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Romera E., Gonzalez F., Ballester A., Blazquez M. L., Munoz J. A., Crit. Rev. Biotechnol. 26(2006) 223-235. Rudzinski W., Plazinski W., J. Phys. Chem. B 110 (2006) 16514-16525. Sag Y., Sep. Purif. Methods. 30(2001) 1-48. Santana-Casiano J. M., Gonzalez-Davila M., Perez-Pena J., Millero, F.J., Mar. Chem. 48(1995) 115-129. Schiewer S., Volesky B., Biotechnol. Tech. 9(1995) 843-848. Schiewer S., Volesky B., Environ. Sci. Technol. 31(1997a) 2478-2485. Schiewer S., Volesky B., Environ. Sci. Technol. 31(1997b) 1863-1871. Schiewer S., Wong M. H., Chemosphere. 41(2000) 271-282. Simmons P., Singleton I., Appl. Microbiol. Biotechnol.. 45(1996) 278-285. Stoll A., Duncan J. R., Biotechnol. Lett. 18(1996) 1209-1212. Suh J. H., Kim D. S., Bioprocess Eng. 23(2000) 327-329. Texier A. C., Andres Y., Le Cloirec P., Environ. Sci. Technol. 33(1999) 489-495. Tobin J. M., Cooper D. G., Tatara C. P., Appl. Environ. Microbiol. 7(1984) 821-824. Uslu G., Tanyol M., J. Hazard. Mater. 135(2006) 87-93. Valdman E., Leite S.G.F., Bioprocess Eng. 22 (2000) 171-173. Vasudevan P., Padmavathy V., Dhingra S. C., Bioresour. Technol. 89(2003) 281-287. Vianna L. N. L., Andrade M. C., Nicoli J. R., World J. Microbiol. Biotechnol. 16(2000) 437440. Vijayaraghavan K., Yun Y. S., Biotechnol. Adv. 26(2008) 266-291. Volesky B., Holan Z. R., Biotechnol. Progr. 11(1995) 235-250. Wang J. L., Beijing: Science Press; 2002. Wang J. L., Chen C., Biotechnol. Adv. 24(2006) 427-451. Xu H. Kinetics, equilibrium isotherm and mechanisms of heavy metal biosorption by aerobic granules. PhD thesis, Nanyang Technological University, Singapore, 2007. Zhao M., Duncan J. R., Biotechnol. Lett. 20(1998) 603-606. Zhou D., Zhang L. N., Zhou J. P., Guo S. L., Water Res. 38(2004) 2643-2650.

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In: Fundamentals and Applications of Biosorption… ISBN: 978-1-60741-169-7 Ed: Yu Liu and Jianlong Wang © 2009 Nova Science Publishers, Inc.

Chapter 7

CORRELATING METAL IONIC CHARACTERISTICS WITH BIOSORPTION CAPACITY Can Chen and Jianlong Wang

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7.1. EFFECTS OF ION CHARACTERISTICS ON METAL BIOSORPTION In order to obtain deep insight in metal properties which may be relevant in the context of metal uptake capacity by a biomass, utilizing similar methods and ideas of QSAR (or QCAR or QICAR or SAR) in assessment of biological toxicology, we tried to find out in the field of biosorption of metal ions how metal ion characteristics influence metal uptake capacity by a certain biomass such as Saccharomyces cerevisiae. Thus, we could possibly realize two goals: (1) to explore the interaction of metal ion and the biomass and the mechanisms of biosorption of metal ions; (2) to predict biosorption capacity of metal ions under similar conditions. Biosorptive capacity is roughly influenced by three kinds of influential factors: metal ion characteristics (e.g. atomic weight, ion radius, valence, etc.), the nature of the biosorbents (e.g. cell age), and biosorption conditions (e.g. pH, temperature, contact time, etc.). Obviously metal ion properties in aqueous solution are an important inherent factor to interference ion uptake (Tobin et al., 1984; Remacle, 1990; Brady and Tobin, 1995; Tsezos et al., 1996). The environmental conditions (such as pH value) have been discussed widely in most references on biosorption. The mechanisms of metal biosorption were also explored through instrumental analysis technologies of FTIR, SEM, TEM etc. to a some extent although a limited extent (Wang and Chen, 2006). However, ion characteristics have never been fully investigated in the field of metal biosorption. As noted by Avery and Tobin (1993), “despite the quite extensive literature available on metal-microbe interactions, few authors have attempted to relate differing mechanism and/or relative levels of metal uptake or toxicity to the chemical characteristics of the metals under investigation”. In some relevant references, only about one to three metal ion characteristics were discussed accounting for metal uptake, e.g. ionic radius (r), covalent index (Xm2r, where Xm is

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electronegativity) and the first hydrolysis constant (log KOH). Biosorption of metal cations such as Sr2+, Mn2+, Zn2+,Cu2+, Cd2+ and Pb2+ by freeze-dried Rhizopus arrhizus was observed to be related to covalent index (Xm2r) (Brady and Tobin, 1995). The greater the covalent index value of metal ion is, the greater is potential to form covalent bonds with biological ligands, and the larger is the metal ion uptake. Tobin et al. (1984) reported the amount of uptake of the cations by dry cells of Rhizopus arrhizus was directly related to ionic radius of La3+, Mn2+, Cu2+, Zn2+, Cd2+, Ba2+, Hg2+, Pb2+, UO22+ and Ag+, which could be explained by a complexation mechanism involving sites in the biomass containing carboxylate, phosphate, and other functional groups. However, the ionic radius did not appear to reflect the adsorption capacities when Pb2+, Cu2+, Zn2+, Cd2+ and Ni2+ were adsorbed onto sugar beet pulp (Reddad et al., 2002). In this case, the log of first hydrolysis constant showed a linear relationship with the initial sorption rate and the maximum adsorption capacities, respectively. However, many other parameters of metal ion characteristics (such as electronic configuration, ionization potential, etc.) nearly have not been mentioned as far as we know in the field of biosorption of metal ions. Walker et al. (2003) discussed about 20 physical and chemical properties of cations, and examined the relationships between those properties and their toxic effects. Now significant progress has been made in solving the technical problems with quantum chemical computations of transition metals. Thus the tools are available for computing more properties of aqueous ions for use in QSARs (Capitani and Di Toro, 2004).

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7.2. THEORETIC BASIS FOR APPLICATION OF QICARS IN METAL BIOSORPTION QSARs, abbreviated for Quantitative Structure Activity Relationships, have been applied widely to predict bioactivity (toxicity or bioavailability) of organic compounds in pharmacology and toxicology. Toxicity predictions by the QSARs (or SARs or QCARs or QICARs) methods were actually based on metal-ligand binding tendencies. In QCARs approach to predict the toxicity of metals, a number of simplifying assumptions were supposed: The ionic form was the most active form of a metal; the bioactivity of a dissolved metal was correlated with its free ion concentration or activity; most metals exist in biological systems as cations, and differences in metal toxicity result from differences in metal ion binding to biological molecules (ligand-binding) (Walker et al. 2003). According to the various studies for the mechanisms of metal biosorption, metal sequestration by different parts of the cell could occur by complexation, coordination, chelation, ion exchange, adsorption, inorganic microprecipitation. A number of anionic ligands participate in binding the metal: phosphoryl, carboxyl, sulfhydryl, and hydroxyl groups appearing on the cell, especially on the cell wall (Remacle, 1990; Volesky, 1990). Reasonably, the QICARs approach could be used to account for the metal-ligand interactions. Thus the QSARs (or SARs or QCARs or QICARs) methods offered a new way to explore the interaction between the absorbed metal ions and the functional groups on the biomass. Classification of metal cations according to some certain criteria was a basis for understanding metal-ligand interaction. Wolterbeek and Verburg (2001) summarized six classifications of metal ions supposed by some authors, such as Ahrland et al.(1958);

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Schwarzenbach (1961); Pearson (1963); Nieboer and Richardson (1980); Turner et al. (1981); Kaiser (1980, 1985). Pearson’s classification based on the Hard Soft Acid Base Principle (HASB) proposed by Pearson in 1963, was regarded as a useful tool to explain the phenomena of metal uptake. Pearson classified metal cations (acids) as hard, borderline and soft, according to whether they preferentially formed complexes with nonpolarizable (hard) or polarizable (soft) ligands based on thermodynamic considerations. According to HSAB principle, Hard (Lewis) acids prefer to bind to Hard (Lewis) bases and Soft (Lewis) acids prefer to bind to Soft (Lewis) bases. Soft lewis acids and soft bases tend to form covalent bonds whereas hard acids and hard bases prefer to form ionic bonds. Hard metals, such as Na+, K+, Ca2+, Mg2+ , are usually nontoxic and often essential macronutrients for microbial growth, they bind preferentially to oxygen-containing (hard) ligands, such as OH-, HPO42-, CO32-, R-COO-, and =C=O, whereas soft metals, such as Hg2+, Cd2+ and Pb2+, which often display greater toxicity, form stable bonds with nitrogen- or sulfur-containing (soft) ligands, such as CN-, R-S-, -SH-, NH2-, and imidazol. Borderline or intermediate metals are less toxic and can even be detected in certain bimolecular where they assist in mediating specific biochemical reactions, e.g., Zn2+, Cu2+ and Co2+ (Pearson, 1963; Remacle, 1990). Nieboer and Richardson (1980) proposed a refinement of this classification for biological systems, considering the atomic properties and the solution chemistry of the metal ions, e.g. electronegativity, charge and ionic radius of metal ions. They discriminated metal ions into there classes: Class A (hard, relatively nontoxic, O-seeking), preferentially to oxygen-containing (hard) ligands; Class B (soft, relatively toxic, N,S-seeking), preferentially to nitrogen or sulfur-containing (soft) ligands; Borderline, or intermediate class. According to Nieboer and Richardson (1980), there was a sharp separation between class A and borderline metal ions, but the distinction between class B and borderline metal ions was less clear. It should be noted that Cd2+ fell among the borderline metals rather than in the class B group where previously placed by Pearson. According to the chemistry and chemical reactivity calculations, H+ also should be regarded as a borderline ion, rather than a pure class A cation in traditional view. Although Pb2+ was classified as a borderline metal, Pb2+ exhibited the highest degree of class B character among the borderline metal ions: Pb2+ > Cu2+ > Cd2+ > Co2+≈ Fe2+ > Ni2+ > Zn2+ > Mn2+ (Nieboer and Richardson, 1980). In our study Pb2+ was regarded as soft ion. Avery and Tobin (1993) investigated the metal adsorption characteristics for metabolismindependent uptake of the metal ions of Sr2+, Mn2+, Zn2+,Cu2+, Cd2+, Tl+ by S. cerevisiae. The results proved that the hard-and-soft principle could well account for the nature of bonding and preferred ligand binding of the metals examined. Tsezos et al. (1996) also demonstrated that Pearson classification was a useful tool for the proper understanding of the ionic competition in the biosorpiton of metal ions: palladium, gold, uranium, yttrium, silver and nickel. Therefore, we intended to probe into metal-microbe interactions in the field of metal biosorption on the basis of the achievements on QICAR in toxicology. We applied the QICARs approach to explore the interaction between uptake capacity of the yeast and properties of the metal ions based on the data of ion characteristics and methods from Newman group and other authors to explore the effects of ion characteristics on metal uptake capacities of a biomass.

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7.3. APPLICATION OF QSARS METHOD IN BIOSORPTION OF METAL IONS Although QSARs approach is not a novel idea, predictive models of metal uptake have never been fully developed or applied to the extent that QSARs have for organic chemicals. In contrast, models relating metal ion characteristics to their bioactivity remain poorly explored and underutilized (Ownby, 2002). Walker et al. (2003) thought that, developing and validating Quantitative Cationic–Activity Relationships or QCARs, “to predict the toxicity metals is challenging because of issues associated with metal speciation, complexation and interactions within biological systems and the media used to study these interactions”. During past one and a half century (1839-2003), many researchers had endeavored to probe into correlations between physical and chemical properties of cation metals and metal toxicity (Newman and McCloskey, 1996; Newman et al., 1998; Wolterbeek and Verburg, 2001; Kaiser, 2003; Ownby and Newman, 2003; Walker et al., 2003). Indeed “it appears that certain useful correlations can be made between several physical and chemical properties of ions (mostly cations) and toxicity of metals” (Walker et al., 2003). Newman and co-workers (McCloskey et al., 1996; Newman and McCloskey, 1996; Newman et al., 1998; Tatara et al., 1998; Ownby, 2002) developed a novel Quantitative Ion Character-Activity Relationships (QICARs) as a useful tool to predict the relative toxicity of metal ions based on metal-ligand binding tendencies. They summarized many parameters to describe metal ion characteristics, and found that a softness index and |log KOH| (absolute MOHn-1 + H+) were value of the log of the first hydrolysis constant (KOH for Mn++H2O among the ion qualities with the highest predictive value for toxicity in single metal studies. Tatara et al. (1997) argued that the first hydrolysis constant reflects a metal ion's tendency to bind to intermediate ligands such as biochemical functional groups with O donor atoms. Intermediate ligands includes carboxyls, hydroxyls, aldehydes, ketones and amino compounds The softness parameter σρ was a measure of the ability of a metal ion to give up its valence electrons, also was a measure of metal ion affinity to soft donor atoms, like S containing ligands. McKinney et al. (2000) also discussed Structure Activity Relationship or SAR (qualitative and quantitative modeling methods relating to chemical structure to biological activity) to analyze biological activity of metal ions. The QICARs approach, based on metal-ligand binding tendencies, has been applied successfully to a wide range of effects, species, and media on a single metal basis. Ownby and Newman further demonstrated that the QICARs approach also were suitable for prediction of toxicity in binary metal mixtures (Ownby, 2002; Ownby and Newman, 2003).

7.4. METAL ION CHARACTERISTICS PARAMETERS AND CORRELATION APPROACH 7.4.1. Biomass and Metal Ions The waste biomass of Saccharomyces cerevisiae was collected from a local brewery in China and used as the biosorbents to adsorb 10 metal ions. Ten metal ions tested were nitrate

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salts: hard metal ions Sr2+ and Cs+, the borderline ions Zn2+, Ni2+, Cu2+, Co2+, Cr3+ and soft ion Pb2+and Ag+. Initial concentration of each metal ion ranged from 0.16 mmol l-1 to 8.0 mmol l-1. The biosorption of metal ion by the yeast basically met with the Langmuir isotherm model. The maximum uptake capacity of each metal ion was determined by the Langmuir absorption model. In the precedent chapter, 22 parameters reflecting various properties of metal ions and their effects on metal uptake capacities have been discussed. To determine the maximum metal sorption (qmax) to the yeast cells, the equilibrium isotherms of metal sorption was fitted with the Langmuir model: qe = qmax b Ce/(1+bCe)

(7.1)

For the fitting of the experimental data, we used the following equation of linear form of the Langmuir model: 1/qe=1/qmax+1/(qmaxb)Ce

(7.2)

where, qe is equilibrium metal uptake (mmol g-1), Ce is the equilibrium concentration in solution (mmol l-1), qmax represents the maximum uptake of metal and b is a constant, ratio of the adsorption/desorption rates, i.e., related to the energy of adsorption through the Arrhenius equation, (l mmol-1).

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7.4.2. Selection of Characteristic Parameters Based on the information available in the literature (McCloskey et al., 1996; Lewis et al., 1999; Wolterbreek and Verburg, 2001; Walker, 2003; Zhang and Xiao, 2004; Jiang et al., 2006), 22 variables (physiochemical properties) of metal ions were selected and summarized in table 7.1 (x1 to x22), i.e. OX, AN, r (Å), ∆IP (eV), ∆E0 (V), Xm, |log KOH|, Xm2r , Z2/r, AN/∆IP, σρ, AR, AW, IP, AR/AW, Z/r2, Z/AR2, Z/r, Z/AR, Z*2/r. N. These abbreviations represent the ion properties, and specified as follows: AN = atomic number; r = Pauling ionic radius (Å); ∆IP = the difference of the ionization potential between the element’s oxidation number and the next lower one (eV); ∆E0 = electrochemical potential of the ion and its first stable reduced state (V); Xm = electronegativity; |log KOH| = log of the first hydrolysis constant; Xm2r = covalent index; Z2/r = the cation polarizing power, where Z = ion charge; AN/∆IP = atomic number/ change in ionization potential; σρ = softness index; defined as: （ (Coordinate bond energy of the metal fluoride)-(Coordinate bond energy of the metal iodide) ）/(Coordinate bond energy of the metal fluoride). OX = oxidation number; AR = atomic radius; AW = atomic weight; IP = ionization potential; AR/AW = the ratio between atomic radius and atomic weight; Similar to Z2/r, Z/r2, Z/r or Z*2/r was another form of polarizing power (Z* = effective ion charge), Z/r also as ionic potential (Walker et al., 2003). Here, we produced the new parameters Z/AR2 and Z/AR by replacing r as AR in the polarizing power Z/r2 and Z/r, in order that using more easily available data AR than r to express polarizing power express according to the suggestion of Wolterbeek and Verburg (Wolterbeek and Verburg, 2001); N = the number of valence shell electrons. The values of AN, r (Å), ∆IP (eV), ∆E0 (V), Xm, |log KOH|, Xm2r , Z2/r, AN/∆IP, σρ came from (McCloskey et al., 1996).

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The data of OX, AR, AW, IP, AR/AW came from the reference of (Wolterbeek and Verburg, 2001). The values of Z*2/r and N was obtained from Zhang and Xiao (2004). All listed in the table 7.1. According to McCloskey et al. (1996) and Wolterbeek and Verburg (2001), AN reflects the size of the ion or inertia of ion. ∆E0 reflected the ion’s ability to change its electronic state, and was seen as related to the ion’s desolvation energy and regarded as including other solvent and ligand controlled effects on the ions. Xm, was correlated with the energy of an empty valence orbital reflects the ability of the metal to accept electrons (electron attraction capabilities), the power (relative strength) of an atom in a molecule to attract electrons to itself from a ligand. Electronegativity decreases with increasing atomic size (best reflected by the normal covalent radius) and with decreasing number of valence electrons. (Walker et al., 2003). |log KOH|, the absolute value of the log of the first hydrolysis constant (KOH for Mn++H2O MOHn-1 + H+), reflects a metal ion’s affinity to intermediate ligands (e.g. those ligands with O donor atoms). Xm2r, the covalent index, electron-attracting capability of an atom in a molecule, and quantifies the importance of covalent interactions relative to ionic interactions. The polarizing power, expressed as various parameters Z2/r, Z/r2, Z/r, or Z*2/r, was a measure of the electrostatic interaction strength between a metal ion and ligand, and indicated ionic bond stability. Z2/r was regarded as ionic index by Nieboer and Richardson (1980) or indicated degree of hydrolysis in aqueous solution (Wolterbeek and Verburg, 2001). Z/r, also as ionic potential, the charge/radius ratio of a metal ion indicates the distance between an ion and another charge and the size of the electrostatic force created and, therefore, is an index of the tendency to form ionic bonds (Walker et al., 2003). AN/∆IP and ∆E0 reflect qualities affecting interactions with ligands. ∆IP and ∆E0 reflect the effects of atomic ionization potential and the ability of the ion to change electronic state, respectively. The softness parameter σρ reflected ion binding to soft ligands (e.g. those ligands with S donor atoms), also a measure of. AR/AW, was a measure of the ion’s electron density (as a reciprocal reflection of the ion’s charge to size ratio), IP as an expression of the involved orbital energies. Oxidation state reflects a particular electronic configuration. Wolterbeek and Verburg (2001) suggested to use fixed (general) metal properties in QSAR for predicting toxicity, such as AR, IP, AR/AW, Xm, electrochemical potential ∆E0 because data of ion characteristics are easily available and general. Ionic radius r was not a definite physical or geometrical quantity but rather depends on an arbitrary definition which may be modified for different purposes (Walker et al., 2003). ∆IP was taken as, ∆IP = IP (X) but because corrections for OX-1 form could not be found in the respective Kaiser (1980) IP values (Wolterbeek and Verburg, 2001). Using these general variables (properties) (using AR rather than ionic radius r, and used IP rather than ∆IP, etc.), they successfully predict metal toxicity for various organisms without any division of metals into classes, or grouping of toxicity tests. Therefore, replacing r as AR in the formula of polarizing power Z2/r, Z/r or Z/r2, we created two new parameters, i.e. pseudo polarizing power: Z/AR and Z/AR2 (Wolterbeek and Verburg, 2001).

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest Ebook

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Table 7.1. Values of metal ion characteristics used in correlations

x1 x2 x3 x4 x5 x6 x7 x8 x9

Properties OX AN r (Å) ∆IP (eV) ∆E0 (V) Xm |log KOH|

Pb2+ 2 82 1.18 7.61 0.13 2.33 7.7

Ag+ 1 47 1.15 7.57 0.8 1.93 12.0

Cr3+ 3 24 0.62 14.46 0.41 1.66 4.0

Cu2+ 2 29 0.73 12.57 0.16 1.9 8.0

Zn2+ 2 30 0.75 8.57 0.76 1.65 9.0

Cd2+ 2 48 0.95 7.91 0.4 1.69 10.1

Co2+ 2 27 0.75 9.19 0.28 1.88 9.7

Sr2+ 2 38 1.13 5.34 2.89 0.95 13.2

Ni2+ 2 28 0.69 10.52 0.23 1.91 9.9

Cs+ 1 55 1.7 3.89 2.92 0.79 14.9

Xm2r

6.41

4.28

1.71

2.64

2.04

2.71

2.65

1.02

2.52

1.06

2

x10 x11 x12 x13 x14 x15

Z /r AN/∆IP σρ AR AW IP AR/AW

3.39 10.78 0.131 1.54 207.19 15.032 0.0074

0.87 6.21 0.074 1.52 107.87 7.576 0.0141

14.52 1.66 0.107 1.25 51.996 30.960 0.0240

5.48 2.31 0.104 1.35 63.54 20.292 0.0213

5.33 3.5 0.115 1.31 65.37 17.964 0.0200

4.21 6.07 0.081 1.48 112.4 16.908 0.0132

5.33 2.94 0.13 1.25 58.93 17.083 0.0212

3.54 7.12 0.174 2.07 87.62 11.030 0.0236

5.8 2.66 0.126 1.25 58.71 18.169 0.0213

0.59 14.14 0.218 2.62 132.91 3.894 0.0197

x16

Z/r2

1.44

0.76

7.8

3.75

3.56

2.22

3.56

1.57

4.2

0.35

0.84

0.43

1.92

1.10

1.17

0.91

1.28

0.47

1.28

0.15

1.69

0.87

4.84

2.74

2.67

2.11

2.67

1.77

2.9

0.59

x17

Z/AR

x18

Z/r

x19

Z/AR

1.29

0.66

2.4

1.48

1.53

1.35

1.6

0.97

1.6

0.38

x20

Z*2/r

2.97

2.1

1.98

2.82

2.67

2.74

2.05

0.83

2.37

0.46

x21

Z*

19.8

15.4

11.35

14.25

14.9

16.4

12.95

9.9

13.6

8.9

x22

N

20

18

11

17

18

18

15

8

16

8

2

238

Can Chen and Jianlong Wang

The linear models between ion characteristics and qmax were determined with regression analysis using the software EViews 4.0. The level of significance was set as α = 0.05. The contribution of a variable (ion property) to each model was firstly tested for statistical significance (F statistic) and t test (t statistic). Then based on one variable regression analyses, some of models with two variables were generated. In multi linear regression of statistics, adjusted R (R = correlation coefficient), AIC (Akaike Information Criterion), SC (Schwarz Criterion) could be used for evaluate the predictive models. Newman group specially supposed the AIC as a more rigorous criterion in order that models that differ in complexity (one or two explanatory variable) can be compared. Newman group supposed that the model with the smallest AIC was judged to have the most information (Newman and McCloskey, 1996). Therefore, the models were evaluated regardless of the number of variables also according to the Minimum Akaike Information Criterion Principle (MAICP) in our study. The following statistic parameters were computed by the software of EViews: n = number of metals considered; R = correlation coefficient; R2 = coefficient of determination; R2 adj. = adjusted R square; SE = standard error of regression; F ratio (F test); P = level of significance; P = probability of significance; AIC = Akaike Information Criterion; MAPE = mean absolute percent error between observed and predicted values in prediction. All listed model were statistical significance (F statistic and t statistic) at α = 0.05. Some models were not significant but also listed for convenience of comparing the fitting effect for different class of metals.

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7.4.3. Maximum Biosorption Capacity qmax The maximum metal uptake qmax was determined by fitting the data to the Langmuir absorption model (Equation 7.2). The resulting values of qmax were listed in table 7.2. qmax decreased in the order on mole basis: Pb2+> Ag+> Cr3+> Cu2+> Zn2+> Cd2+> Co2+> Sr2+> Ni2+>Cs+. The highest uptake of 0.413 mmol/g was observed for Pb2+. Whereas, the lowest uptake was of 0.092 mmol g-1 for Cs+, a kind of alkali metal ion. The parameter qmax reflects the metal affinity for the yeast sites. The yeast cells really showed a preferential binding capacity for Pb2+ from the values of q max.. This result was also in agreement with the previous study (Wang and Chen, 2006). Table 7.2. Maximum biosorption capacity (qmax)

Metal ion Pb2+ Ag+ Cr3+ Cu2+ Zn2+ Cd2+ Co2+ Sr2+ Ni2+ Cs+

q max (mmol g-1) 0.413 0.385 0.247 0.161 0.148 0.137 0.128 0.114 0.108 0.092

R2

Class

0.917 0.991 0.935 0.976 0.956 0.954 0.967 0.973 0.977 0.982

Class B (soft) Class A (soft) Borderline Borderline Borderline Borderline Borderline Class A (hard) Borderline Class A (hard)

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Correlating Metal Ionic Characteristics with Biosorption Capacity

239

On molar basis, this affinity order was basically similar to the absorption by freeze dried Rhizopus arrhizu Pb2+> Cu2+> Cd2+> Zn2+> Mn2+>Sr2+ (Brady and Tobin, 1995) except for the order of Cd2+and Zn2+. Reddad also reported the same order (maximum uptake by Langmuir model): Pb2+> Cu2+> Zn2+> Cd2+> Ni2+ when using sugar beet pulp as biosorbent (Reddad et al., 2002). Tobin reported the similar order for the metal uptake affinity of Rhizopus arrhizu: UO22+> Cr3+> Pb2+> Ag+>Ba2+>La3+>Zn2+> Hg2+>Cd2+>Cu2+>Mn2+>Na+, K+, Rb+, Cs+ (=0), except Cr3+ and Cu2+. The difference in biosorption capacities among Ag+, Cs+, Zn2+, Pb2+, Ni2+, Cu2+, Co2+, 2+ Sr , Cr3+ and Cd2+ for a given strain (S.. cerevisiae) under the similar environmental conditions could be attributed to different characteristics of these meal ions.

For all metals tested (n=10), only one property of covalent index Xm2r showed very statistical significant (at the level of significance 0.002) on the maximum uptake capacities qmax: qmax =0.0287 +0.061 (Xm2r ). Xm2r alone accounted for 67% of the variation in qmax values for all metals ions. AR/AW and Z* also showed moderate significant (α=0.05), but had less influence than Xm2r on metal uptake (see model 2 and 3), see table 7.3. The model 1 (table 7.3) gave the mean absolute percent error (MAPE) between observed and predicted values was 27%, Theil Inequality Coefficient was 0.14 and the covariance proportion was near to 1 (0.91). Figure 7.1 shows that the greater the covalent index value of a metal ion, the greater its uptake capacity by the biomass. It was found that modeling mono-, di-, and trivalent metal ions separately for toxicity improved the models (McCloskey et al., 1996; Tatara et al., 1998). Therefore, we generated models using the data of divalent metal ions. Here we did not make models for mono- and trivalent metal ions because the number of them was small. The modeling results showed that, not only the model with the one variable Xm2r, AR/AW, or Z* did improve the fit, but also more variables became statistically significant, i.e., AN, AN/∆IP, AW. 0.5 Ag

(mmol/g)

0.3

max

0.4

0.2

Pb

+

2+

3+

Cr

Zn

2+

Sr

q

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7.4.4. Characteristic and Qmax: Correlation of Relationships

0.1

Cs

0 0

+

2+

2+

Cu 2+ Cd 2+ 2+ Co Ni 2

4

6

8

2

Xm r

Figure 7.1. Maximum biosorption capacity plotted against corresponding covalent index values.

The statistic parameters, for example, R2adj changed from 0.67 to 0.87, F value from 19.04 to 39.77 when fitting data from all metals to only divalent metals for the model with one variable Xm2r, (comparing table 7.3, model 1 and table 7.4, model 9.5). The MAPE decreased from 27% for all metals (model 1) to 22% for divalent metal ions (model 5) with one variable model 5 (table 9.4).

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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Table 7.3. The linear regression analysis of qmax and metal ion characteristics for all metal ions tested (n = 10) Model (qmax =) 1 2 3

(Xm2r

0.029 +0.061 ) 0.47 - 14.9 (AR/AW) - 0.127 + 0.023 (Z*)

R

R2

R2 adj.

SE

F

P

AIC

MAPE

0.84 0.68 0.64

0.70 0.46 0.41

0.67 0.39 0.34

0.067 0.091 0.095

19.04 6.84 5.61

0.002 0.030 0.045

-2.38 -1.78 -1.70

27.36 37.82 39.97

Correlating Metal Ionic Characteristics with Biosorption Capacity

241

The regression results of table 7.4 showed that metal uptake capacities of divalent cations increased with increase of atomic number (AN), covalent index (Xm2r ), (AN/∆IP), atomic weight (AW), or effective ionic charge (Z*), but decreased with increase of AR/AW. It appears from table 7.4 that the highest fitting value for one variable model was also with Xm2r for divalent cations (R2adj. = 0.87, AIC = -3.39, MAPE = 22.30). However, using MAICE, the two-independent variable model 10 gave the best fitting (R2adj. = 0.91, AIC = -3.74, MAPE = 15.70): qmax = -0.018+ 0.05 (Xm2r) +0.01 (AN/∆IP), which offered better fitting than one variable model with Xm2r. It is obvious that Xm2r alone explained 87% indicating that AN/∆IP contributed little to the model fit for divalent metal ions. Pb2+ was classified as soft ion (Class B) in our study for its high uptake performance and high toxicity similar to soft ion in many reports (McCloskey et al., 1996; Wang and Chen, 2006) although it had been regarded as borderline ions by Pearson (1963) or by Niebore and Richardson (1980). Thus when soft ions (Class B) Ag+ and Pb2+ were removed from 10 metal ions tested, different metal ions characteristics were found to correlate well with qmax, i.e., OX, ∆IP, |log KOH|, Z2/r, IP, Z/r2, Z/AR2, Z/r and Z/AR rather than Xm2r for borderline and hard ions, The fitting results were shown in the table 7.5.Among the significant variables, only the parameter of |log KOH| exerted negative effect on metal uptake, and other parameters including OX, ∆IP, Z2/r, IP, Z/r2, Z/AR2, Z/r and Z/AR had the positive on qmax. Representative linear relationship between four ion characteristics, Z2/r, |log KOH|, ∆IP and IP separately with qmax were displayed clearly in the serious of figures 7.2-7.5. Table 7.4. The linear regression analysis of qmax and metal ion characteristics for divalent cations (n = 8)

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Model (q max =) 4 5 6 7 8 9

10

-0.026 + 0.005 (AN) 0.060 (Xm2r ) 0.039+0.02 6 (AN/∆IP) 0.002+0.00 2 (AW) 0.457 15.56 (AR/AW) -0.24 + 0.028 (Z*) -0.018+ 0.05 (Xm2r ) +0.01 (AN/∆IP)#

R

R2

R2 adj.

SE

F

P

AIC

MAPE

0.91

0.83

0.79

0.049

24.01

0.004

-2.96

24.20

0.94

0.89

0.87

0.039

39.77

0.001

-3.39

22.30

0.77

0.59

0.50

0.076

7.07

0.045

-2.08

32.30

0.92

0.84

0.81

0.047

25.94

0.004

-3.03

23.14

0.84

0.70

0.64

0.064

11.87

0.018

-2.42

23.42

0.81

0.65

0.58

0.069

9.35

0.028

-2.26

30.38

0.97

0.94

0.91

0.032

31.66

0.004

-3.74

15.70

#

: variable was not significant on qmax (α = 0.05).

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Can Chen and Jianlong Wang

0.5

Pb

Ag q max (mmol/g)

0.4 0.3

Cr Cu

0.2 0.1 Cs

Zn Cd Co Sr Ni

0 0

5

10

15

20

2

Z /r Figure 7.2. The model for qmax and Z2/r for borderline and hard ions (n=8).

0.5

Pb

Ag

q max (mmol/l)

0.4 0.3

Cr Cu

0.2 0.1

Sr

Ni

Cs

0 0

5

10

15

20

|log KOH| Figure 7.3. The model for qmax and |log KOH| for borderline and hard ions (n=8).

0.5

Pb Ag

0.4 q max (mmol/g)

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Zn Cd

Co

0.3

Cr

0.2 Sr 0.1 Cs

Zn Cu Cd Co Ni

0 0

10

20

30

40

IP Figure 7.4. The model for qmax and ionization potential IP for borderline and hard ions (n=8). Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

Correlating Metal Ionic Characteristics with Biosorption Capacity

0.5

Pb

0.4 q max (mmol/l)

243

Ag

0.3

Cr

0.2 Sr

0.1

Cd

Zn Co

Cu Ni

Cs 0 0

5

10

15

20

∆IP

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Figure 7.5. The model for qmax and ∆IP for borderline and hard ions (n=8).

It should be pointed out that the best fitting variable was the polarizing power Z2/r. However, other forms of polarizing power Z/r2, Z/r (also as ionic potential), Z/AR2, Z/AR also gave the considerable fitting results although the pseudo polarizing power Z/AR2, Z/AR were not so good after using more general property AR replacing ionic radius r. It was worthy noted that another parameter of polarizing power Z*2/r was not able to correlate well with qmax although Z*2/r considered the influence of not only ionic charge and ionic radius but also electron configuration of metal ion. This was true for other class of metal ions, such as borderline ions (or plus hard ions), see table 7.7 and table 7.8. It was interesting that the above trends (linear correlations between qmax and Z2/r, or IP, or |log KOH|) were also observed for only soft ions Pb2+ and Ag+ from the Figure 7.2-7.4 although the number of soft ions tested was small. It was also exciting that the general parameter IP offered better fitting than ∆IP for qmax. Ni2+, as a borderline ion, showed an unexpected low uptake, and as an outlier was removed from the borderline and hard ions. The models improved drastically as compared to tables 7.5 and 7.6. Moreover, the two-variable model 35 showed the highest prediction value in all models for borderline and hard ions: qmax = -0.03 +0.008 (IP) + 0.006 (AN/∆IP). Obviously, suitable two-variable model generally fitted better than one variable model according to the values of R2, AIC and MAPE. For soft and borderline ions (n=8), i.e. hard ions Sr2+ and Cs+ did not participate in modeling, We found that AN, r, Xm2r, AN/∆IP, AR and AR/AW showed linear relationship with qmax, similar to that of ion properties for divalent metal ions except r. However, fittings for borderline and soft ions were much worse than for divalent ion except ionic radius r as compared to tables 7.3 and 7.5). There is no very significant variable on qmax.(α= 0.01). Nevertheless, Xm2r still gave the best prediction than other ion characteristics as for all metal ions or divalent ions. It can be seen in table 7.7 that a bigger ionic radius was obviously helpful for metal uptake without hard ions, which is consistent with the positive effect of Xm2r on metal uptake.

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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Table 7.5. The linear regression analysis of qmax and metal ion characteristics for borderline and hard ions (n = 8)

#

11 12 13

Model (q max =) -0.013 + 0.077 (OX) 0.042 +0.011 (∆IP) 0.273 - 0.013 (|log KOH| )

R 0.87 0.81 0.91

R2 0.75 0.65 0.83

R2 adj. 0.71 0.59 0.80

SE 0.026 0.031 0.021

F 17.76 11.19 29.21

P 0.005 0.015 0.002

AIC -4.25 -3.92 -4.64

MAPE 15.94 15.24 12.01

14 15 16

0.079 + 0.011 (Z2/r ) 0.047 + 0.006 (IP) 0.077 + 0.019 (Z/r2)

0.93 0.89 0.88

0.87 0.80 0.77

0.85 0.77 0.73

0.019 0.023 0.025

39.21 24.42 19.74

0.001 0.003 0.004

-4.89 -4.49 -4.33

10.20 11.80 12.97

17 18 19 20

0.069 + 0.07 (Z/AR2) 0.053 + 0.035 (Z/r) 0.044 + 0.069 (Z/AR) 0.102 + 0.02 (Z*2/r)#

0.79 0.88 0.83 0.37

0.63 0.77 0.69 0.14

0.57 0.73 0.64 0.00

0.031 0.025 0.029 0.048

10.20 20.09 13.47 0.945

0.019 0.004 0.010 0.369

-3.86 -4.34 -4.05 -3.02

15.92 13.01 14.52 17.46

: variable was not significant on qmax (α = 0.05).

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Table 7.6. The linear regression analysis of qmax and metal ion characteristics for borderline and hard ions (n = 7) (excluding Ni2+)

#

21 22 23

Model (q max =) - 0.008 + 0.077 (OX) 0.04 + 0.012 (∆IP) 0.277 - 0.013 (|log KOH| )

R 0.90 0.91 0.95

R2 0.81 0.82 0.90

R2 adj. 0.78 0.78 0.88

SE 0.023 0.023 0.017

F 21.95 22.90 45.27

P 0.005 0.005 0.001

AIC -4.44 -4.47 -5.06

MAPE 13.42 9.70 9.57

24 25 26 27

0.084 + 0.011 (Z2/r) 0.190 - 0.008 (AN/∆IP) 0.050 + 0.006 (IP) 0.080+ 0.02 (Z/r2)

0.98 0.71 0.95 0.97

0.96 0.51 0.91 0.95

0.95 0.41 0.89 0.93

0.011 0.038 0.016 0.013

112.23 5.11 51.55 80.53

0.000 0.070 0.001 0.000

-5.91 -3.46 -5.18 -5.59

5.56 15.95 8.42 6.17

28 29 30 31 32 33 34 35 36

0.069 + 0.078 (Z/AR2) 0.055 + 0.037 (Z/r) 0.045 + 0.073 (Z/AR) 0.102 + 0.023 (Z*2/r)# 0.069+ 0.003 (∆IP) + 0.009 (Z2/r )# 0.145 - 0.004 (|log KOH| ) + 0.008 (Z2/r )# 0.086 + 0.011 (Z2/r) - 0.0003 (AN/∆IP)# -0.03 +0.008 (IP) + 0.006 (AN/∆IP) 0.03 - 0.018 (|log KOH| ) + 0.005 (AN/∆IP)#

0.90 0.96 0.92 0.45 0.98 0.98 0.98 0.99 0.97

0.81 0.92 0.84 0.20 0.97 0.97 0.96 0.98 0.95

0.77 0.91 0.81 0.04 0.96 0.96 0.94 0.97 0.92

0.024 0.015 0.022 0.049 0.010 0.010 0.012 0.009 0.014

20.94 58.71 25.77 1.22 70.17 69.17 45.17 90.18 36.22

0.006 0.001 0.004 0.319 0.001 0.001 0.002 0.000 0.003

-4.40 -5.30 -4.57 -2.97 -6.05 -6.04 -5.63 -6.30 -5.42

11.02 8.14 10.84 17.24 4.59 4.31 5.66 4.13 6.71

: variable was not significant on qmax (α = 0.05).

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Table 7.7. The linear regression analysis of correlation relationship between qmax and metal ion characteristics for soft and borderline ions (n = 8)

37 38 39 40 41 42 #

Model (q max =) 0.037 + 0.004 (AN) - 0.156 + 0.436 r 0.017 + 0.064 (Xm2r) 0.087 + 0.028 (AN/∆IP ) - 0.714 + 0.679 (AR) 0.467 - 14.082 (AR/AW)#

: variable was not significant on qmax (α = 0.05).

R 0.73 0.77 0.81 0.72 0.71 0.66

R2 0.54 0.60 0.65 0.52 0.50 0.43

R2 adj. 0.46 0.53 0.59 0.43 0.42 0.34

SE 0.089 0.082 0.077 0.091 0.092 0.098

F 6.94 9.04 11.21 6.38 6.04 4.58

P 0.039 0.024 0.015 0.045 0.049 0.076

AIC -1.79 -1.94 -2.08 -1.75 -1.72 -1.59

MAPE 32.83 31.36 30.15 35.98 33.92 38.93

Can Chen and Jianlong Wang

247

Tobin et al. (1984) found that Chromium(Ⅲ) was absorbed at anomalously high levels and alkali metal ions appeared no absorption when dry R. arrhizus absorb a variety of different metal cations. In order to generate figure 7.6, the outlier Cr3+ was thus excluded. The data show a linear correlation between the maximum metal uptake and ionic radius.

0.5 q max = - 0.29 + 0.57 r q max (mmol/l)

0.4

2

R = 0.84

0.3 Cr

0.2

Sr

0.1

Cs

0 0

0.5

1

1.5

2

r

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Figure 7.6. The model for qmax and ionic radius except Cr3+, Sr2+ and Cs+ (n=7).

For the borderline ions (n=6), the most valuable predicting ion characteristics for qmax were |log KOH|, IP, polarizing power Z2/r, similar to borderline ions and hard ions (comparing tables 7.5 and 7.8). Generally the fitting was better for borderline ions than for borderline plus hard ions, e.g., the MAPE of the one variable model 45 with |log KOH| was only 5.6% for borderline ions (table 7.8).

7.5. CLASSIFICATION OF METAL IONS AND THEIR SORPTION CAPACITY The modeling results improved when the metal ions were classified according to the valence of metal ions (divalent ions) or hard/soft ions. We also found that different metal ions characteristics played an important role in metal uptake for different class of metal ions, which implied different mechanisms played role in metal uptake. All metal ions tested in our study was basically classified as Class A (hard), borderline and Class B (soft) according to Nieboer and Richardson classification (Nieboer and Richardson, 1980), but with a little variation. Pb2+ was classified as Class B(soft) in our study rather than in borderline group where it has been previously placed by Pearson (1963) and by Nieboer and Richadson (1980). Cd2+ was classified as borderline ion rather than as soft ion previously supposed by Pearson. Now our study showed that Pb2+ as soft ion and Cd2+ as borderline ion were more applicable in biosorption.

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Table 7.8. The linear regression analysis of correlation relationship between qmax and metal ion characteristics for borderline ions (n=6)

#

SE

F

P

AIC

MAPE

0.59 0.95

R2 adj. 0.48 0.94

0.035 0.012

5.66 77.40

0.076 0.001

-3.61 -5.74

17.90 5.60

0.78

0.61

0.51

0.034

6.24

0.067

-3.67

16.51

Model (q max =)

R

R2

43 44

0.01 (∆IP )# 0.328 - 0.02 (|log KOH| )

0.77 0.97

45

0.376 - 0.093 (Xm2r)# 2

46 47 48

0.076 + 0.011 (Z /r) - 0.018 + 0.008 (IP) 0.065 + 0.022 (Z/r2)

0.91 0.95 0.84

0.82 0.90 0.70

0.78 0.88 0.63

0.023 0.017 0.029

18.85 36.66 9.50

0.012 0.004 0.037

-4.47 -5.04 -3.94

11.75 7.89 15.34

49 50 51 52

0.014 + 0.11 (Z/AR2)# 0.021 + 0.045 (Z/r) - 0.03 + 0.11 (Z/AR) 0.278 - 0.05 (Z*2/r)#

0.78 0.87 0.85 0.37

0.61 0.75 0.73 0.14

0.51 0.69 0.67 -0.07

0.034 0.027 0.028 0.050

6.24 12.26 11.02 0.67

0.067 0.025 0.029 0.460

-3.66 -4.13 -4.05 -2.88

18.24 14.15 15.11 22.03

: variable was not significant on qmax (α = 0.05).

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249

Nieboer and Richardson (1980) pointed out that Pb2+ owned the highest character of Class B (soft). In fact, many references reported Pb2+ exhibited the similar toxicity to soft ions, just like McCloskey et al. (1996) reported. Moreover, the absence clear distinction between the three metal classes supposed by Woltebreek and Verburg (2001). In many multi metal biosorption studies, Pb2+ generally showed high uptake by various biomass (Wang and Chen, 2006). So did in our study. Cd2+ was classified as soft ion by Pearson. However, Niebore and Richardson (1980) especially pointed out that Cd2+ falls among the borderline metals. Avery and Tobin (1993) demonstrated that Cd2+ classified as borderline ion intended to be more applicable to biological systems, correlates more closely with the results when the metal ion Sr2+, Mn2+, Zn2+, Cu2+, Cd2+, Tl+ was absorbed by metabolism-independent S. cerevisiae. Therefore, Cd2+ was regarded as borderline ion in our study. Therefore it sounded reasonable for such classification of Pb and Cd ions. Metal uptake capacity by the dry yeast cells qmax decreased in the order on mole basis: Pb2+> Ag+> Cr3+> Cu2+> Zn2+> Cd2+> Co2+> Sr2+> Ni2+>Cs+. This tendency showed that the biomass preferentially absorb soft ions (Pb2+ and Ag+), then borderline ions (Cr3+, Cu2+, Zn2+, Cd2+, Co2+), and last hard ions (Sr2+ and Cs+). Ni2+ was unexpected lower. Kogej and Pavko (2001) also showed the similar results in metal biosorption by R. nigricans. Tobin et al. (1984) reported that the R. arrhizus did not absorb alkaline metal ions such as K+, Na+ and Cs+, which were usually hard ions. More reports basically demonstrated this tendency in metal biosorption by various biaomss, including various S. cerevisiae, R. arrhizu, R. nigrican, sugar beet pulp waste etc (table 7.9). Usually, the soft ions interacted with the biomass ligands mainly by covalent bonding and hard ions such as Ca2+ harder than Sr2+ exclusively by electrostatics attraction. Ni2+, as a borderline ion, showed unexpected low uptake, even lower than that of hard ion Sr2+. Reddad et al. (2002) also reported that lowest uptake for Ni2+ when the waste sugar beet pulp absorb several cations (Cd2+, Cu2+, Pb2+, Zn2+, Ni2+) separately. Ni2+ seemed to be exclusively adsorbed by an ion exchange mechanism. Sr2+, a hard ion, showed a degree of covalency although the ionic bonding was much important than that of covalent bonding to the overall adsorption of the biomass (Avery and Tobin, 1993). Here the hard soft acid base principle was also successfully used in predicting metal adsorption characteristics in a biological context. Table 7.9. Affinity order of metal uptake in some biosorption systems Biomass Freeze dried Rhizopus arrhizus Rhizopus nigricans

Sugar beet pulp waste Rhizopus arrhizus

Affinity order In mol/g: Pb2+> Cu2+> Cd2+> Zn2+> Mn2+>Sr2+ In mmol/g: Fe2+> Ag+> Fe3+ >Pb2+ >Cu2+> Cd2+> Sr2+ >Zn2+ > Ni2+ >Li+> Al3+ In mmol/g: Pb2+> Cu2+> Zn2+> Cd2+> Ni2+ In mmol/g: UO22+> Cr3+> Pb2+> Ag+> Ba2+> La3+> Zn2+> Hg2+> Cd2+> Cu2+> Mn2+>Na+, K+, Rb+, Cs+ (=0)

Refence (Brady and Tobin, 1995) (Kogej and Pavko, 2001) (Reddad et al., 2002) (Tobin et al., 1984)

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Can Chen and Jianlong Wang Table 7.9 (Continued).

Waste brewery yeast Immobilized S. cerevisiae in solgel matrix Free cell of S. cerevisiae living and nonliving brewer's yeast non-living baker's yeast living baker's yeast

In mmol/g: Cu > Pb > Cd In mg/g: Pb> Cu > Cd In mg/g: Hg(II)> Zn(II) > Pb(II) > Cd(II) > Co(II) = Ni(II) > Cu(II) In mg/g: Hg(II)> Pb(II)> Zn(II) > Cd(II) > Co(II) = Ni(II) > Cu(II) : U > Zn > Cd > Cu;

(Al-Saraj et al., 1999)

Zn > (Cd) > U > Cu;

Isolated cell wall

In mmol/g: Cu2+ > Cd2+ > Co2+

(Volesky and Mayphillips, 1995) (Volesky and Mayphillips, 1995) (Brady and Duncan, 1994)

Zn > Cu approximate to (Cd)> U

(Kim et al., 2005) (Al-Saraj et al., 1999)

(Volesky and Mayphillips, 1995)

7.6. EFFECT OF ION CHARACTERISTICS ON METAL-BIOMASS INTERACTION For all metals tested (n=10), or for divalent metals, or for soft ions plus borderline ions, among 22 parameters showed the best fitting. The maximum uptake increased with increase of the covalent index values (figure 7.1). Equilibrium metal uptake values were also positively correlated with the covalent index of the metal ions when the freeze-dried R. arrhizus absorbed Sr2+, Mn2+, Zn2+, Cd2+,Cu2+ and Pb2+. Kogej and Pavko (2001) reported that the maximum biosorption capacities and the binding constant of R.nigricans were positively correlated with the covalent index of metal ions (Fe2+, Ag+, Fe3+, Pb2+, Cu2+, Cd2+, Sr2+, Zn2+, Ni2+, Li+, Al3+). The Xm2r was a measure for a metal ion of the importance of covalent interactions relative to ionic interactions. It also approximates to the ratio of orbital energy (energy released when negative charge is transferred form the ligand to the valence orbital of the metal ion) divide by the desolvation energy (the hydration energy lost by the metal ions due to the concomitant reduction in its positive charge) (Nieboer and Richardson, 1980). Therefore, the values of Xm2r was greater, the stronger of covalent bonding between metal and biomass, the less contribution of ionic bonding in metal uptake, then the qmax was larger. According to Nieboer and Richardson (1980), the larger of Xm2r the more characteristics of Class B, then the metal ions preferentially interacted with the functional group in the following order: S->N->O- containing group. Class B preferred to form the most stable complexes with the groups such as CO, S2-, RS-, R2S, CN-, H-, R-, then R2NH, R3N, =N-, CO-N-R, RNH2, and the least stable complexes with ROH, RCOO-, C=O, ROR, HPO42-, OH-, O2-, H2O, NO3-, ROSO3-, CO32-, etc. In contrast, Class A ion with small value of Xm2r, preferred to form stable complex with O-containing ligands, in the order: O>N>S. Borderline

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Xm2r

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ions were able to form stable complexes with all categories of ligands. Preferences did exist which reflect the degree of class A or B character of the particular borderline metal and the relative availability of the different ligands in a system. Cysteine is a sulfur-containing amino acids (sulfhyddryl group –SH). Simmons and Singleton (1990) found that incorporation of L-cysteine into the growth medium resulted in biomass with increased silver biosorption capacities, protein and sulphydryl group content. This result proved that interaction of S and soft ion Ag+. The carboxylate groups were proved as the major ligands responsible for the binding of lead by beer yeast because the esterification of carboxylate groups of native yeast made the maximum adsorbed quantities of Pb2+ decreased from 11.5 mg g-1 to 4.1 mg g-1, decreasing about 75% (Han et al., 2004).. Other researches also proved that amino, carboxyl, or hydroxyl group in the yeast cells played important role in Cu2+ removal by S. cerevisiae (Brady and Duncan, 1994; Wang, 2002). It seemed that these hard or borderline ligands (carboxyl, hdryoxyl, amino groups) played more important role than soft ligands (such as S containing ligands) for Pb2+ (Class B) or Cu2+ (borderline). It appeared that the content of the O or N containing groups especially carboxyl group was much richer than that of S containing group. Then why was the higher uptake for soft ions than for borderline or hard ions if according to the theory of hard soft acid base principle? Nieboer and Richardson (1980) pointed out, “Class B ions, in spite of their own preference for ligands in column Ⅲ of table 7.1 (mainly S- or N- containing ligands), when reacting with the ligands in column Ⅰ (mainly O-containing ligands), form complexes that are more stable than those with Class A ions of comparable Z2/r values. The same observation holds for borderline ions relative to Class A ions”. Ten ions tested in our study had the similar Z2/r less than 8. Thus, presumably, Class B or borderline ions would bind the various ligands including hard ligands such as carboxyl groups especially when carboxyl group was main functional groups on the cell. It also signified that borderline and Class B ions of comparable size and charge makes significant covalent contributions to the overall interaction energy in addition to the largely ionic interaction observed for Class A ions. Xm2r did not displayed significant linear correlation with qmax for borderline or plus hard ions, but could account for metal ions containing soft ions Pb2+ and Ag+. This fact inferred that Xm2r was suitable for explaining biosorption phenomena of metal ions containing soft ions, in which covalent bonding contributed much in metal-biomass interaction. For metal ions (borderline or plus hard ions) without soft ions, in contrast, the polarizing power (especially Z2/r), ionization potential IP and |log KOH| became very significant in qmax (α = 0.005). The polarizing power, such as Z2/r as ionic index or Z/r also as ionic potential, was a measure of the electrostatic interaction strength between a metal ion and ligand. As if, ionic bonding became important to account for metal uptake behavior when no important covalent bonding existed because of soft ions. The polarizing power, in fact, owned rich information of metal ion, which could explain many other parameters, such as color or solubility of ion compound or the hydrolysis ability of metal ions. It was reported that the value of |log KOH| was basically negative linear relationship with the polarizing power (Z2/r) (Jiang et al., 2006). In our study |log KOH| and Z2/r did exerted the contrary effect on qmax, which had been clearly in the figure 7.2. The hydrolysis ability was bigger when the value of |log KOH| was smaller, the greater the qmax. This tendency seemed also existed for soft ions Ag+ and Pb2+ from the figure 7.2.

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It was found that the values of |log KOH| correlate well with metal toxicity which reflected the metal ion’s tendency binding the intermediate ligands such as O-containing ligands (however, most O-containing ligands was regarded as hard ligands. In our views, the negative linear correlation between |log KOH| and qmax implied that possible mircropreciptiation caused by strong hydration and hydrolysis for some metal ions in biosorption probably played important role in metal uptake. Especially metal ions with large ionic charge and small ionic radius (i.e. large polarizing power, large ionic potential, low |log KOH|) tend to form insoluble (micro) precipitates like ion Pb2+ (Volesky and Holan, 1995). That Cr3+ had high ionic charge and strong hydrolysis ability (chromium in aqueous solution forms various complex oxyaninons (Tobin et al., 1984)) could also partly explain its relative high metal uptake. Marques et al. (2000) studied the pH effects on the removal of Cu2+, Cd2+ and Pb2+ from unbuffered aqueous solution by non-vialble S.cerevisiae. A shift in the medium pH from 4.5-5.0 (optimum pH range) to a final value in the 7.0-8.0 range was observed. They suggested different removal mechanisms for each cation: Cu2+ was removed by both the metal sorption and precipitation due to the pH shift that occured during the process, while Cd2+ removal showed to be completely dependent on this pH shift. Pb2+ was totally and quickly removed by precipitation in the presence of the yeast suspension and at pH4.5. Nieboer and Richardson (1980) pointed out that metal ions with values of Z2/r greater than 8 tend to hydrolyze forming metal hydroxides and oxo anions in mildly acidic and some even in quit acidic solutions. Some other Class B ions are exceptions presumably because of large covalent contributions to the metal-oxygen bond. This tendency to react with water increased with Class B character. Consequently Pb(Ⅳ) had no simple cation chemistry, even in acid solution. Therefore, metal hydrolysis to form microprecipitate could be one mechanism for metal uptake, to some extent to explain the high uptake of Pb2+ and Cr3+. In our study ionization potential IP also fitted very well for qmax of borderline or plus hard ions, whereas ∆IP only offer moderate or even not significant on qmax. IP, as a general parameter of metal ion, thus was suggested to be used rather than ∆IP in fitting qmax. The ion with larger OX had a greater uptake for borderline ion plus hard ions. Among various polarizing power, Z2/r fitted data best. Z/r2 and Z/r also gave good fitting. Z2/r was regarded as ionic index by Nieboer and Richardson (1980) or indicated degree of hydrolysis in aqueous solution (Wolterbeek and Verburg, 2001).Replacing r as more general property AR in the presentation polarizing power, Z/AR and Z/AR2 also gave moderate significance in qmax. However, Z*2/r, considering the effective ion charge and electron configuration (N, electron shell number), basically did not produce linear correlation to qmax. According to the suggestion of using fixed or more general properties of metal ions by Woltbeek and Verburg (2001), the two pseudo polarizing power Z/AR and Z/AR2 were applicable in metal uptake prediction for borderline or plus hard ion, although moderate significant at level of 005. However, ion properties including ∆E0 (V), Xm, σρ, N, Z*2/r seemed to have no direct effect and clear relationship on qmax. Ion properties including ∆IP, AN, AN/∆IP, AR, AW, AR/AW seemed to model qmax at moderate significance level, and exert less important influence on qmax. It was found the softness parameter σρ, had the highest values of toxicity prediction besides of |log KOH|. ∆E0 also offer adequate fitting for metal toxicity (Newman et al., 1998). The σρ reflected the binding tendency to S containing ligands, but clear relationship with qmax was not found. It seemed that a certain relationship existed between

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Xm2r and AN, AN/∆IP, AR, AW, AR/AW for metal ions containing soft ions, whereas OX, ∆IP, IP, polarizing power and |log KOH| own some commonness in predicting metal uptake. Different parameters correlate well with qmax made it difficult to identify their potential significance. Sometimes there was no reasonable explanation for why some parameter could fit well and some not. Many parameters often reflect the same nature of metal ions and the values were influenced by some same other parameters. For example, electronegativity and ioization potential both reflected the relative ease for a metal ion lose electrons. Ion charge, atomic radius, and electron configuration influence ionic index or covalent index. Some two-variable models, such as the model -0.018+ 0.049 (Xm2r) +0.01(AN/∆IP)# for divalent cations, 0.0085 (IP) + 0.006 (AN/∆IP) -0.03 for borderline plus hard ions (without Ni2+) gave the best prediction for one variable model. Obviously the parameter of AN/∆IP was more valuable in two-variable model than in one variable model for qmax prediction.

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7.7. REMARKS The maximum biosorption capacity qmax by S. cerevisiae determined by the Langmuir model decreased in order on mol basis: Pb2+> Ag+> Cr3+> Cu2+> Zn2+> Cd2+> Co2+> Sr2+> Ni2+>Cs+. The biomass prefer to bind Class B ions (Pb2+ and Ag+), then borderline ions (Cr3+, Zn2+, Cd2+, Co2+), and last hard ions (Sr2+ and Cs+) based on the HASB principle. The qmax were modeled with 22 ion properties. Models improved based on metal classification such as divalent cations according to valence or soft/hard ions according to Niebero and Richardson classification. The covalent index Xm2r among 22 parameters offered best fitting for metal ions containing soft ions. The Xm2r indicated the importance of covalent interactions relative to ionic interactions. The greater the covalent index value of a metal ion, the greater its potentical to form covalent bonds with biological ligands, generally in order: S>N>O. However, the absolute first hydrolysis constant |log KOH|, or polarizing power Z2/r or ionization IP, were especially useful in model construction for metal ions without soft ions. IP, ionization potential was a measure of the electron affinity or electronegativity of a metal ion. Z2/r showed electrostatic interaction strength between a metal ion and ligand, also indicated degree of hydrolysis in aqueous solution. |log KOH| was a measure of the ability of a metal ion to form a metal hydroxide. The bigger value of Z2/r, the smaller value of |log KOH|, the greater hydrolysis ability of a metal ion, the greater the metal uptake capacity. Precipitate caused by metal hydrolysis contributing to bisorption uptake could not be neglected for some metal ions with large Z2/r, such as Pb2+ and Cr3+. |log KOH| also reflected the ability of metal binding atom O. Using more general parameters of metal ions in predicting qmax was applicable, such as pseudo polarizing power Z/AR, Z/AR2, IP, AR/AW. Few two-variable models usually including one parameter (AN/∆IP) could fit better than one-variable model. Better correlation models with three or more-variable could be expected. However, more numbers of metal ions tested was necessary to support such meaningful fitting in statistics. In short, utilizing methods and achievements of QSARs (qualitative structure activity relationships) in metal toxicity assessment to investigate effect of metal ion characteristics on metal uptake capacity were applicable, regardless of limitations of these data and their interpretations. Our research offered a new way and idea to explore the metal biomass interaction by application QSAR in metal biosorption. Obviously further studies will

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be required to elucidate more fully the rationale underlying the mechanism by which metals ion characteristics to elicit uptake capacities in metals and biomass.

ACKNOWLEDGMENTS The authors would like to acknowledge the financial support from the National Natural Science Foundation of China (Grant Nos. 50830302; 50808111; 50278045), China Postdoctoral Science Foundation funded project (Grant No. 20080430350), special fund of State Key Joint Laboratory of Environment Simulation and Pollution Control (Grant No. 08K05ESPCT) and the Basic Research Fund of Tsinghua University (Grant No. JC2002054), to carry out the relevant research works.

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REFERENCES Al-Saraj M., Abdel-Latif M. S., El-Nahal I., Baraka R., J. Non-Cryst. Solids 248 (1999)13740. Avery S. V., Tobin J. M., Appl. Microbiol. Biotechnol. 59 (1993) 2851-2856. Brady D., Duncan J. R., Enzyme Microb. Technol. 16 (1994) 633-638. Brady J. M., Tobin J. M., Enzyme Microb. Technol. 17 (1995) 791-796. Capitani J. F., Di Toro D. M., In: Center for the Study of the Bioavailability of Metals in the Environment-Annual Report, Submitted to U.S. Environmental Protection Agency, Submitted by University of Delaware: Project Officer:Iris Goodman; 2004. Han R. P., Zhang J. H., Shi J., Liu H. M., J. ZhengZhou Univ. (Natural science) 36 (2004) 8691. Jiang Y. X., Jin M. M., Wu F. Q., J. Liaoning Teachers College. 8 (2006) 16-17. Kaiser K. L. E., QSAR Comb. Sci. 22 (2003) 185-190. Kim T. Y., Park S. K., Cho S. Y., Kim H. B., Kang Y., Kim S. D., Kim, S.J., Korean J. Chem. Eng. 22 (2005) 91-98. Kogej A., Pavko A., World J. Microbiol. Biotechnol. 17 (2001) 677-685. Lewis D. F. V., Dobrota M., Taylor M. G., Parke D. V., Environ. Toxicol. Chem. 18 (1999) 2199-2204. Marques P., Rosa M. F., Pinheiro H. M., Bioprocess. Eng. 23 (2000) 135-141. McCloskey J. T., Newman M. C., Clark S. B., Environ. Toxicol. Chem. 15 (1996) 1730-1737. McKinney J. D., Richard A., Waller C., Newman M. C., Gerberick F., Toxicol. Sci. 56 (2000) 8-17. Newman M. C., McCloskey J. T., Environ. Toxicol. Chem. 15 (1996) 275-281. Newman M. C., McCloskey J. T., Tatara C. P., Environ. Health Perspect. 106 (1998) 14191425. Nieboer E., Richardson D. H. S., Environ. Pollut. B 1 (1980) 3-26. Ownby D. R., Predicting metal interactions with a novel quantitative ion character-activity relationship (QICAR) approach, Ph.D. thesis, The College of William and Mary ,Virginia, USA; 2002. Ownby D. R., Newman M. C., QSAR Comb. Sci. 22 (2003) 241-246.

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Pearson R. G., J. Am. Chem. Soc. 85 (1963) 3533-3539. Reddad Z., Gerente C., Andres Y., Le Cloirec P., Environ. Sci. Technol. 36 (2002) 20672073. Remacle J., In: Biosorption of heavy metals. Edited by Volesky B. Boca Raton: CRC Press; 1990. Tatara C. P., Newman M. C., McCloskey J.T., Williams P.L., Aquat. Toxicol. 39 (1997) 279290. Tatara C. P., Newman M. C., McCloskey J.T, Williams P.L., Aquat. Toxicol. 42 (1998) 255269. Tobin J. M., Cooper D. G., Neufeld RJ., Appl. Microbiol. Biotechnol. 47 (1984) 821-824. Tsezos M., Remoudaki E., Angelatou V., Int. Biodeterior. Biodegrad. 38 (1996) 19-29. Volesky B., In: Biosorption of Heavy Metals. Edited by Volesky B. Boca Raton: CRC press; 1990. Volesky B., Holan Z. R., Biotechnol. Progr. 11 (1995) 235-50. Volesky B., Mayphillips H. A., Appl. Microbiol. Biotechnol. 42 (1995) 797-806. Walker J. D., Enache M., Dearden J. C., Environ. Toxicol. Chem. 22 (2003) 1916-1935. Wang J. L., Process Biochem. 37 (2002) 847-850. Wang J. L., Chen C., Biotechnol. Adv. 24 (2006) 427-451. Wolterbeek H. T., Verburg T. G., Sci. Total Environ. 279 (2001) 87-115. Zhang Y. T., Xiao S. L., Comput. Appl. Chem. 21 (2004) 690-694.

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In: Fundamentals and Applications of Biosorption… ISBN: 978-1-60741-169-7 Ed: Yu Liu and Jianlong Wang © 2009 Nova Science Publishers, Inc.

Chapter 8

BIOSORPTION OF HEAVY METALS BY AEROBIC GRANULES: AN INNOVATIVE APPROACH Hui Xu and Yu Liu

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8.1. INTRODUCTION As presented in the precedent chapter, a very wide spectrum of biomaterials have been tested and used as biosorbents, ranging from living to dead biomass (Chapter 2). Due to the extremely complex physical, chemical and biological natures of biosorbents studied so far, biosorption indeed involves highly complicated mechanisms that are often unknown in the most cases. In order to develop the kinetic and isotherm equations for biosorption, the complex mechanisms have been simplified according to various assumptions. This chapter attempted to offer the in-depth insights into three major biosorption mechanisms, namely chemical precipitation-associated biosorption, ECP-associated biosorption and ion exchangeassociated biosorption. To be more focus, biosorption of cadmium, copper and nickel by aerobic granules was used as a model for elaboration of the above mentioned three biosorption mechanisms. This chapter is mainly based on the works by Xu and Liu (2008) and Liu and Xu (2007).

8.2. WHAT ARE AEROBIC GRANULES? Activated sludge with a loose structure is the microbial biomass that utilizes nutrient substrates present in wastewater, while aerobic granules can be regarded as compact and dense microbial aggregates with a spherical outer shape (figure 8.1). Aerobic granule can be regarded as a special form of biofilm. It has been evidenced that aerobic granulation is quite fundamental in biology and can be defined as the gathering together of cells to form a fairly stable, contiguous, multicellular association without assistance of biocarriers. Each aerobic granule is an enormous metropolis of microbes containing millions of individual bacteria. Aerobic granulation may be initiated by microbial self adhesion under certain selection

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pressures. Nowadays, aerobic granules are known to have regular round shape, compact and dense structure leading to enhanced settleability, higher biomass density, multi-microbial functions, higher tolerance to toxicity, robustness to shock loading, and relatively low excess sludge production.

Figure 8.1. Close-up view of aerobic granules.

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8.3. PROBLEM ASSOCIATED WITH APPLICATION OF BIOSORPTION TECHNOLOGY Biosorption has been regarded as an effective technology for the removal of soluble heavy metals from aqueous solution. Most biosorbents currently used are in the form of suspended biomass, which are not effective and durable in repeated long-term application, and also make the post-separation of suspended biomass from the treated effluent extremely difficult (Vieira and Volesky, 2007). These would cause problems associated with maintenance of biosorbent stability and regeneration of used biosorbents, and also limit application of conventional biosorbents in the form of suspended biomass in the removal of soluble metals from industrial wastewater. As Eccles (1999) noted, a small number of pilotplant studies have been carried out to investigate the potential of microorganisms to remove metals from liquid wastes but only one system in the past 15 years has been commercialized. Unfortunately, compared to basic research of biosorption, today application of biosorption technology falls far behind and there is along journey ahead. In order to overcome the drawbacks associated with biosorbents in the forms of dispersed microorganisms, some attention has been turned to developing immobilized-type biosorbents, e.g. immobilized blue green microalgae and fungal biomass were used to remove cadmium and chromium (Bai and Abraham, 2003; Saeed and Iqbal, 2006), while entrapped fungal hyphae in structural fibrous network of papaya wood was also explored for the removal of heavy metals (Iqbal and Saeed, 2006). In addition, Zhang et al. (2005) studied the biosorption of Cu2+ ions onto biofilm under various experimental conditions. When selecting appropriate biosorbents for the removal of heavy metals from industrial wastewater, three criteria need to taken into account, i.e., effectiveness in terms of effective

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separation of biosorbent from the treated water, adsorption capacity and rate, robustness to harsh operating conditions and reliability without release of harmful materials from adsorbent. Previous research showed that aerobic granules have the advantages of compact microbial structure, and excellent settling ability. The settling velocity of aerobic granules is as high as 71 m h-1, which is 5 to 8 times higher than that of microbial flocs, and aerobic granules can be completely separated out of the treated effluent by gravity in one minute (Liu and Tay, 2004; Liu, 2007). It is apparent that the characteristics of aerobic granules could satisfy the basic requirements for biosorbents. Recent study showed that aerobic granulebased biosorption process is an efficient and cost-effective technology for the removal of heavy metals from industrial wastewater streams (Liu et al., 2002; Xu et al., 2004, 2005; Liu and Xu, 2007).

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8.4. ELEMENTAL COMPOSITION OF FRESH AEROBIC GRANULES Xu and Liu (2008) determined the elemental composition of fresh aerobic granules. Results indicated that fresh aerobic granules mainly comprised seven major elements, i.e. C, H, O, N, S, P and Ca. As for heavy metals, element Cd was not detected in the fresh aerobic granules. However, very small amounts of Cu, Ni and Zn at the respective levels of 0.25, 0.027 and 0.239 mg g-1 were found in the fresh aerobic granules due to the fact that Cu, Ni and Zn were all present in the synthetic wastewater as the trace elements required for microbial growth. The Ca content in aerobic granule was as high as 150.36 mg g-1, while 1.37 and 3.47 mg g-1 for Mg and K respectively, indicating that aerobic granules would contain a significant amount of light metal ions. In fact, Qin et al. (2004) also reported a high Ca content of 180 mg g-1 in aerobic granules. XRD was used to analyze the compounds phase presented in the fresh aerobic granules. The main crystal compounds detected in the fresh aerobic granules were ragonite (CaCO3) and magnesium calcite synthesis ((Mg0.03Ca0.97) (CO3)). Both would contribute to the ash content of the fresh aerobic granules as CaCO3 and (Mg0.03Ca0.97) (CO3) would not be decomposed at 550°C. According to Xu and Liu (2008), the amount of Ca2+ in fresh aerobic granules was 150.36 mg g-1. If all the Ca2+ was in the form of CaCO3 and (Mg0.03Ca0.97) (CO3), the amount of CaCO3 and (Mg0.03Ca0.97) (CO3) could be around 375.6 mg g-1, i.e. the calculated amount of CaCO3 and (Mg0.03Ca0.97) (CO3) would be much larger than the ash content in fresh aerobic granules. Obviously, such estimate is not reasonable because CaCO3 and (Mg0.03Ca0.97) (CO3) may only represent part of the total granule ash. This in turn implies that Ca2+ could also bind to negatively charged functional groups present on bacterial surfaces and extracellular polymeric substances, and act as a bridge to interconnect these components (Jiang et al., 2003). Davis et al. (2003) reported that untreated biomass generally contained the light metal ions, such as K+, Na+, Ca2+ and Mg2+, which were originally bound to the acid functional group of biomass.

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8.5. ELEMENTAL COMPOSITION OF AEROBIC GRANULES AFTER BIOSORPTION The XPS survey scanning spectra of aerobic granules before and after Cd2+, Cu2+ and Ni2+ biosorption were analyzed by Xu and Liu (2008). It was found that the main elemental peaks detected in the spectrum of fresh aerobic granules are O 1s, Ca 2s, Ca 2p, N 1s and C 1s, while the peaks of Cd, Cu and Ni were not presented in the XPS survey scanning spectrum of fresh aerobic granules. However, the peaks of Cd 3p and Cd 3d3/2 and Cd 3d5/2 appeared in the wide scanning spectrum of aerobic granules after Cd2+ biosorption, which demonstrated that Cd was really biosorbed on the aerobic granular sludge. It is also clear that Cu and Ni peaks were detected in the XPS survey scanning spectra of aerobic granules after Cu and Ni biosorption, respectively. The presence of these peaks provided the evidence that Cd, Cu and Ni were adsorbed on the aerobic granules. Comparison of the XPS survey scanning spectra of aerobic granules before and after heavy metal biosorption confirmed the presence of Cd, Cu and Ni on the Cd2+, Cu2+ and Ni2+-contaminated aerobic granules, respectively (Xu and Liu, 2008). For instance, the Cd2+ removed by aerobic granules was 1.607 meq g-1, while 1.504 meq g-1 Cd2+ was recovered from the Cd2+-contaminated aerobic granules after the biosorption experiment, giving a Cd2+ recovery efficiency of 93.57

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8.6. CHEMICAL PRECIPITATION OF HEAVY METALS DURING BIOSORPTION Xu and Liu (2008) examined the possible formation of the metal crystal in aerobic granules after the Cd2+, Cu2+ and Ni2+ biosorption by X-ray powder diffraction. The sample crystallinity was evidenced by the clear peaks appearing in the patterns of all samples. In the case of nickel biosorption by aerobic granules, it was found that the peaks position and ratio of aerobic granules before after the Ni2+ biosorption were nearly the same, indicating that there would be no new crystal formation in the Ni2+-contaminated aerobic granules or the amount of new crystal precipitation was negligible. For the Cd2+ and Cu2+-contaminated aerobic granules, their peaks positions and ratios are different with those of fresh aerobic granules. The appearances of some new peaks imply that there were different crystals precipitated in the Cd2+ and Cu2+-contaminated aerobic granules and more complicated mechanisms would be involved in the Cd2+ and Cu2+ biosorption. The further XRD phase matches reveal that otavite (CdCO3), aragonite (CaCO3) and magnesium calcite synthesis ((Mg0.03Ca0.97) (CO3)) would be the main compounds in the Cd2+ contaminated aerobic granules. The appearance of otavite (CdCO3) seems to indicate that precipitation would contribute to the removal of Cd2+ by aerobic granules. From the XRD analysis of the Cu2+-contaminated aerobic granules, it was found that aragonite (CaCO3) could not be detected in the other samples. However, magnesium calcite synthesis ((Mg0.03Ca0.97) (CO3)) can be detected in the Cu2+-contaminated aerobic granules. The new compound formed in the Cu2+ -contaminated aerobic granules was found to be copper metallic synthesis clinoatacamite (Cu2(OH)3Cl), i.e. the removal of Cu2+ by aerobic granules could be partly attributed to the microprecipation of copper in the form of

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Cu2(OH)3Cl. For Ni2+ contaminated aerobic granules, no new crystal compounds were detected indicated that chemical precipitation did not occur during the Ni2+ biosorption or its quantity was lower than the detection limit. Xu and Liu (2008) found that the intensity of precipitations otavite CdCO3 and clinoatacamite (Cu2(OH)3Cl) was very low (the intensity major reflection line less than 300 counts). Scheckel et al. (2005) reported that chloropyromorphite standard was diluted to 10 mg/g soil, the intensity of XRD major reflection line identifying chloropyromorphite was around 700 counts. Since intensity is proportional to concentration in the mixture (Ouhadi and Yong, 2004), the amount of otavite CdCO3 and clinoatacamite (Cu2(OH)3Cl) in the Cd2+ and Cu2+ contaminated aerobic granules would be very small, i.e. the contribution of precipitation to Cd2+ and Cu2+ removal by aerobic granules would be minor. It was also shown that otavite (CdCO3) was found in the Cd2+-contaminated aerobic granules, i.e. Cd2+ existed in the form of CdCO3 precipitate (Xu and Liu, 2008). After the Cu2+ biosorption, clinoatacamite (Cu2(OH)3Cl) was precipitated out on the Cu2+-contaminated aerobic granules, which also contributed to the Cu2+ removal by aerobic granules. The presence of clinoatacamite (Cu2(OH)3Cl) could satisfactorily explain the phenomena that the color of aerobic granules was changed from yellow brown (before) to green (after). In fact, previous studies also reported that the mechanisms involved in heavy metals removal by biomaterial might also include chemical precipitation and sorption onto minerals such as calcium carbonate (Garcia-Sanchez and Alvarea-Ayuso, 2002; Prieto et al. 2003; Hullebusch et al., 2004). Precipitation could occur in both cellular metabolism dependent and independent processes (Veglio and Beochini, 1997). Micro-precipitation is the deposition of electrically neutral material at the surface of the biomass and does not necessarily involve a bond between the biomass and the deposited layer. Micro-precipitation may, however, be facilitated by initial binding of metal ions to reactive sites of the biomass, which serve as nucleation sites for further precipitation (Mayers and Beveridge, 1989). This process is not limited to a mono-layer (or saturation of sites). Schneider et al. (2001) reported that heavy metals could be adsorbed onto the dead biomass of many macrophytes through two mechanisms: specific ion exchange and simple surface precipitation, although it is not possible to differentiate between them based solely on sorption data. For cellular metabolism independent precipitation, it might be a consequence of the chemical interaction between the metal and the cell surface. For the cellular metabolism dependent precipitation, the active defense system microorganism would react in the presence of a toxic metal, producing compounds which favor the precipitation (Veglio and Beochini, 1997).

8.7. CONTRIBUTION OF ECP TO BIOSORPTION Xu and Liu (2008) investigated the possible involvement of ECP in biosorption of Cd2+, Cu and Ni2+ by aerobic grnauels, and found that the specific Cd2+, Cu2+and Ni2+ biosorption capacities of fresh aerobic granules were 1.607, 1.403 and 0.764 meq metal g-1 dried aerobic granules, respectively, while after the ECP extraction, the corresponding specific biosorption capacities for Cd2+, Cu2+and Ni2+ were found to decrease to 1.296, 1.176 and 0.656 meq g-1. 2+

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These may imply that the granule ECP would contribute to 19.36, 16.19 and 12.20% of the total Cd2+, Cu2+and Ni2+ removed by aerobic granules. The metal removal from solution may also take palace through complex formation on the cell surface after interaction between the metal and active groups. Yee and Fein (2001) reported the Cd2+ adsorption onto bacterial surface would be attributed to Cd-phosphato surface complexes along with Cd-carboxyl complexation, while metal carboxyl groups complexation plays a more important role in the sorption of zinc than in the sorption copper and nickel (Chubar et al., 2004).

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8.8. CONTRIBUTION OF ION EXCHANGE TO BIOSORPTION Xu and Liu (2008) determined the amounts (meq/g) of biosorbed heavy metals on aerobic granules and light metal ions (Ca2+, Mg2+ and K+) released into the solution during the biosorption experiment. It was found that light metal ions Ca2+, Mg2+ and K+ released into aqueous solution accompanied with the uptake of heavy metal ions. For instance, the amount of released Ca2+ is far larger than the other two light metal ions Mg2+ and K+. Accompanied with 1.607, 1.403 and 0.764 meq g-1 of Cd2+, Cu2+ and Ni2+ uptake on the aerobic granules, the respective released Ca2+ amounts are 1.117, 0.835 and 0.524 meq/g. It seems that a larger heavy metal uptake would associate with a larger Ca2+ release. It was further shown that the ratio of total released Ca2+, Mg2+ and K+ to the biosorbed heavy metal was 75.51, 71.31 and 82.43% for Cd2+, Cu2+and Ni2+, respectively (Xu and Liu, 2008). The simultaneous release of light metals with the uptake of heavy metals by aerobic granules may indicate that an ion exchange mechanism would be involved, but the observed non-stoichoimetric exchange of ion also shows that the ion exchange mechanism was not the sole mechanism involved in the Cd2+, Cu2+and Ni2+ biosorption by aerobic granules. Release of light metals, such as Ca2+, Mg2+ and K+ from aerobic granules during the biosorption of Cd2+, Cu2+ and Ni2+ by aerobic granules was confirmed, e.g. 71.31 to 82.43% of heavy metal uptake would be associated with the release of light metals (Xu and Liu, 2008). It thus appears that ion exchange could be one of the main mechanisms involved in metal removal by aerobic granules. In study of metal biosorption by anaerobic granules, Hawari and Mulligan (2006) reported that 77%, 82% and 50% of adsorbed copper, cadmium and lead would be attributed to an ion exchange mechanism. Furthermore, Schnierder et al. (2001) demonstrated that the surface group responsible for metal exchange was primarily the carboxylate group, while Tsezos and Volesky (1981) reported the bivalent metal ions exchange with counter ions of polysaccharides. As shown above, ion exchange would be one of the mechanisms involved in the removal of heavy metal by biomass because it can explain many the observations made during heavy metal uptake experiments. The multi-elemental analysis of solution after biosorption revealed the release of some light metal ions (Na+, Mg2+, Ca2+, K+), which were not present in the solution before the process (Chojnacka et al., 2005). This may confirm that ion exchange occurred during the biosorption process. The simultaneous release of Ca ions with the uptake of lanthanides indicated an ion exchange mechanism was involved in biosorption of La by Sargassum biomass (Diniz and Volesky, 2005). Biosorption of lead and cadmium on raw biomass accompanied with Ca2+, Mg2+ and K+ release into the reaction solution, suggesting

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that biosorption was similar to metal removal by ion-exchange resins (Kapoor and Viraraghavan, 1995). The release of light metals (K+, Na+, Ca2+ and Mg2+) is available during the biosorption because untreated biomass generally contains these metals (Davis et al., 2003).

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8.9. ROLE OF GRANULE FUNCTIONAL GROUPS TO METAL BIOSORPTION In general, the mechanism of algae biosorption is based on a number of metal-binding processes taking place with components of the algal cell wall (Volesky, 1990; Wase and Forster, 1997). Algal cell walls can be made up with polysaccharides: mannan, xylan, alginic acid, chitin, etc. These components, along with the proteins present, can provide acid binding sites, such as amino, amine, hydroxyl, phosphate and sulphate groups (Crist et al., 1981). Greene and Darnall (1990) reported that ionic charge and bonding were involved in the metal biosorption process and van der Walls’ forces at the cellulose network of the cell wall was not involved in the biosorption mechanism. It is thought that the proteins and polysaccharides are the major components responsible for the biosorption. Covalent bonding could be expected with amino and carboxyl groups and ionic charge bonding with carboxyl and sulphate groups associated with these components. The role of carboxylic groups in the adsorption process has been clearly demonstrated by a reduction in cadmium and lead uptake by dried Sargassum biomass following partial or complete esterification of the carboxylic sites (Fourest and Volesky, 1996). Raize et al. (2004) reported that the main chemical groups involved in the metallic cation like Cd2+, Ni2+ and Pb2+ biosorption were apparently carboxyl, amino, sulfhydyl and sulphonate, and these groups were part of the algal cell wall structural polymers, namely, polysaccharide, protein and peptidoglycans. The FTIR spectra of aerobic granules before and after the Cd2+, Cu2+ and Ni2+ biosorption are shown in figures 8.2 to 8.4. These spectra were obtained from scanning in the range of 400-4000 cm-1. The main functional groups found in fresh aerobic granules include O-H stretching of polymeric compounds, an asymmetric/symmetric vibrations of CH2, stretching vibration and deformation vibration of C=O of carboxylic acids, the stretching vibration of C=O and C-N (amide I) peptidic bond of protein, stretching vibration of C-N and deformation vibration of N-H (amide II) peptidic bond of protein. stretching of C-O-C and OH of polysaccharides were also detected (Xu and Liu, 2008). Some bands observed in the “fingerprint” zone could be attributed to the phosphate or sulphur groups. Consequently, different functional groups would be responsible for the biosorption of Cd2+, Cu2+ and Ni2+. Compared to the spectra of fresh and Cd2+-contaminated aerobic granules (figure 8.2), the broad stretching absorption band at 3407 cm-1 shifted to 3414 cm-1 after the Cd2+ biosorption. The band intensity at 1725 cm-1 clearly decreased after the Cd2+ biosorption, i.e. there would be an interaction of Cd2+ with carboxylate groups. The shoulder band at 1520 cm-1 became sharper in the spectra of the Cd2+-contaminated aerobic granule, and the band at 1384 cm-1 only appeared in the spectra of Cd2+-contaminated aerobic granules and could be assigned to bending vibration of –CH3. Low intensities of the bands in the range of 1200-1320 cm-1 in the spectra of fresh aerobic granules became smoother and a band at 1245 cm-1appeared in the

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spectra of Cd2+-contaminated aerobic granules. The enhancement of the band intensities at 1520 and 1245 cm-1 would result from the complexation of Cd2+ with the functional groups from protein. Comparison of the IR spectra between fresh and Cu2+-contaminated aerobic granules is shown in figure 8.3. After the Cu2+ biosorption, the peaks on the spectra of Cu2+contaminated aerobic granules show a series of changes as compared to those of fresh aerobic granules. The broad and strong bands ranging from 3200 to 3600 cm-1 split into two sharper bands at 3446 and 3335 cm-1, which could be assigned to NH stretching of amine and OH stretching of polymeric compounds. The band at 1082 cm-1 could be assigned to C-O from polysaccharide, while the band at 1787 cm-1 disappeared. On the other hand, the band at 1488 cm-1 would be attributed to the C-H bending shifted to 1468 cm-1. The new bands at 1535 and 1240 cm-1 could be assigned to –NH and C=O, respectively. Figure 8.3 further shows the IR spectra of fresh and Ni2+-contaminated aerobic granules. The bands ranging from 3200 to 3600 cm-1 were shifted by 4 cm-1. The peaks at 1725 cm-1 turned to a shoulder after the Ni2+ biosorption, and this may indicate a possible Ni2+ interaction with C=O (figure 8.4). A band new band at 1385 cm-1 appeared after the Ni2+ biosorption, which could be attributed to the bending mode of C-O-H that would occur in an alcoholic group or a protonated alcoholic group or a protonated ether group (Chen et al., 2002). The respective intensity of band at 1725 and 982 cm-1 was found to decrease after the 2+ Cd and Ni2+ adsorption (figures 8.2 and 8.4), which indicated that C=O stretching band and O-H out-of –plane band of the carboxyl group would be attributed to the biosorption of the Cd2+ and Ni2+ ions. Lin et al. (2005) also reported similar phenomenon in the Ag+ biosorption by Lactobacillus sp. strain A09, and they thought that both the carboxylate anion and the hydroxyl group from the peptidoglycan layer of the cell wall would play the key roles in binding of Ag+ to the biomass. In fact, the decrease of intensity of these bands may represent a typical complexation of the carboxylate anion functional group by coordination with metal cation (Lin et al., 2005).The shift of absorbance peak of -OH after Cd2+, Cu2+ and Ni2+ biosorption provided the evidence that alcoholic groups would be one of the biosorption sites for removing these three metal ions. In addition, Zhou et al. (2005) also found that the wave number of hydroxyl group shifted from 3415 cm-1 before lead biosorption to 3427 cm-1 after lead sorption. For the Cu2+ biosorption by aerobic granules, the main changes of spectra are different with Cd2+ and Ni2+. In the protein zone, the band at 1787 cm-1 vanished, thus this band was assigned to theν C =O of the carboxylic acid anhydride formed by dehydration of both carboxyl groups (Lin et al., 2005). A clear shift of ν O − H + ν C −O from 1082 to 1056 cm-1 was found after Cu2+ biosorption by aerobic granules (figure 8.15) due to the interaction of Cu2+ with alcoholic group. The new band at 1385 cm-1 appeared after Cd2+, Cu2+ and Ni2+ biosorption by aerobic granules. According to Chen et al. (2002), this would indicate the interaction between the metals and the bending mode of C-O-H from alcoholic groups. The X-ray photoelectron spectroscopy can also provide the elemental information of aerobic granules as well as to illustrate the interaction between the organic functional groups in aerobic granules and the metals adsorbed. The functional groups were characterized by the binding energy of C 1s, while the metal ions adsorbed on these functional groups were also analyzed.

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Figure 8.2. FTIR spectra of aerobic granules before and after Cd2+ biosorption. Top: before biosorption; Bottom: after Cd2+ biosorption (Xu and Liu, 2008).

Figure 8.3. FTIR analysis of aerobic granules before and after Cu2+ biosorption. Top: before biosorption; Bottom: after Cu2+ biosorption (Xu and Liu, 2008).

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Figure 8.4. FTIR spectra of aerobic granules before and after Ni2+ biosorption. Top: before biosorption; Bottom: after Ni2+ biosorption (Xu and Liu, 2008).

Xu and Liu (2008) determined the changes of binding energy (BE) of the coordination carbon atom (C ls) in aerobic granules before and after the metal biosorption (figure 8.5). It was found that the C 1s spectra of these samples comprised four peaks with corresponding BE of 285.60, 287.07, 288.82 and 290.23 eV that were identified via the deconvolution. According to the guidelines for XPS analysis, these peaks could be assigned to ether, alcoholic, carboxylate and carbonate groups (Biniak et al., 1997; Chen et al., 2002; Sheng et al., 2004; Chada et al., 2005). It was found that ether and alcoholic would be the dominant carbon forms in aerobic granules (Xu and Liu, 2008), and the ether carbon ratio was found to decrease after the metal biosorption, which indicates that ether-metal species might be formed in aerobic granules. Consequently, the area ratios of alcoholic and carboxylate group carbon were also changed. The alcoholic group area ratio increased more after the Cd2+ biosorption. On the other hand, the carboxylate group area ratio increased after the Cu2+ biosorption. The carbonate carbon BE peak was not detected after the Cu2+ biosorption and there was no significant difference between the area ratios before and after the Cd2+ biosorption. These seem to indicate that the interaction and the coordination affinity between the functional groups and metals would be more complicated than expected. High-resolution of O 1s and N 1s spectra show no significant shifts before and after the Cd2+, Cu2+ and Ni2+ biosorption.

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Binding Energy (eV) Figure 8.5. XPS spectra (C 1s) of four kinds of aerobic granules. (a) Fresh; (b) Cd2+-contaminated; (c) Cu2+-contaminated; (d) Ni2+-contaminated granules (Xu and Liu, 2008).

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Figures 8.6a-c further show the XPS spectra of elements Cd 3d, Cu 2p and Ni 2p for aerobic granules after Cd2+, Cu2+ and Ni2+ biosorption. As far as the adsorption of Cd2+ on the aerobic granules, the peak of Cd 3d5/2 at BE of 406.18 eV could be assigned to (-COO)2Cd sorption species. Similar spectra of cadmium were observed in the biosorption of cadmium by marine algal biomass Padina and Sargassum (Sheng et al., 2004). As to the adsorption of Cd2+ by aerobic granules, the observed peak of Cd 3d5/2 at BE of 406.18 eV could be assigned to (-COO)2Cd species. Similar spectra of cadmium were also reported in the biosorption of cadmium by marine algal biomass Padina and Sargassum (Sheng et al., 2004). Two sets of Cu core-level XPS spectra (Cu 2p3/2 and Cu 2p5/2) were found on the Cu2+-contaminated aerobic granules. The peak of Cu 2p3/2 could be differentiated into three subpeaks at BE of 933.3, 935.6 and 943.40 eV, while the peak of Cu 2p5/2 could be composed of three subpeaks at BE of 952.90, 955.27 and 962.97 eV. The component at BE binding energy of 943.40 and 962.97 eV would be the cupric complexation with functional group on aerobic granules, and the signals at BE of 933.3 and 955.27 eV might be due to the cuprous complexation with functional groups on aerobic granules. These observations are consistent with the alginate-bound Cu2+ peak characterized at BE of 932.8 eV (Chen et al., 2002), cupric xanthate at BE of 944 and 963 eV, cuprous xanthate at BE of 934 and 952.90 eV. The other two peaks at 935.6 and 952.90 eV could be attributed to the Cu2+ and Cu+ ions with lower electron density in its valence shell, respectively. XPS spectra Ni 2p3/2 comprised two deconvoluted peaks at 856.75 and 862.38 eV, while Ni 2p1/2 comprised two deconvoluted peaks at 874.27 and 880.32 eV (Xu and Liu, 2008). 1000

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8.10. SPATIAL DISTRIBUTION OF ADSORBED HEAVY METAL IN AEROBIC GRANULE

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Using nickel as a model heavy metal, Liu and Xu (2007) investigated the distribution of the adsorbed nickel in aerobic granules. The fresh (before biosorption) and Ni2+-contaminated (after biosorption) aerobic granules were analyzed by SEM coupled with EDX, and results are shown in figures 8.7 and 8.8. It can be seen that C, O and Ca would be three major elements detected in the fresh as well as in the Ni2+-contaminated aerobic granules. It is logic that no Ni signal was detected in the EDX spectrum of the fresh aerobic granule (figure 8.7), i.e. there was no Ni present on the fresh aerobic granule or the amount of Ni was not detectable. After the Ni2+ biosorption, Ni signal clearly appeared in figure 8.8. This indicates a certain amount of Ni was biosorbed on aerobic granules during the biosorption experiment.

Figure 8.7. SEM image (left) and EDX spectrum (right) of fresh aerobic granule (Liu and Xu, 2007).

In order to look into the distribution of the adsorbed N2+ in aerobic granule, the Ni2+contaminated granule was sectioned from the surface to the centre of granule by a thickness of 50 µm, and the sectioned granule samples were further analyzed by EDX. In this study, depth-0 µm (at surface), depth-150, depth-300 and depth-450 µm from surface of granule, namely No.1 to No. 4, were defined to represent four slices of one aerobic granule at depth of 0, 150, 300 and 450 µm from the surface, respectively (Liu and Xu, 2007). The mean size of aerobic granules used was about 1mm. The atomic mass percentages of C, O, Ca and Ni were also obtained from the EDX analysis (Liu and Xu, 2007). The results showed that the biosorbed Ni percentage fell into the range of 3 to 3.75 percent, i.e. 30 to 37.5 mg Ni was biosorbed by per gram aerobic granules. This finding is in accordance with the maximum biosorption capacity for Ni experimentally determined (32.35 mg Ni/g dried granules) at initial pH of 6. It was also observed that there was no significant difference between the Ni percentages in the four granule slices, i.e. the biosorbed Ni2+ ions would be uniformly distributed along the radium of aerobic granules.

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Figure 8.8. SEM image (left) and EDX spectrum (right) of Ni-contaminated aerobic granule (Liu and Xu, 2007).

Figure 8.9. SEM image, EDX spectrum and element mapping of depth-0 of aerobic granule (Liu and Xu, 2007). Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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Figures 8.9 to 8.12 show the SEM image, EDX spectra and elemental mapping of the granule slices No. 1 to 4, respectively. It can be seen that an EDX characteristic peak corresponding to nickel was detected in all four samples, i.e. Ni2+ could penetrate into aerobic granule through the channel or pore of aerobic granules and biosorbed on interior sites. In comparison with the images of depth-0, depth-150 and depth-300, the Ni element mappings indicated that biosorbed Ni2+ almost uniformly distributed over these three slices. For slice of depth-450, the Ni2+ distribution was similar to what were observed in other three slices except that more Ni ions were concentrated on a small part where the density of Ni pixel was much higher that on the rest parts. These seem to show a nearly uniform distribution of Ni2+ across aerobic granule.

Figure 8.10. SEM image, EDX spectrum and element mapping of depth-150 of aerobic granule (Liu and Xu, 2007). Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

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Figure 8.11. SEM image, EDX spectrum and element mapping of depth-300 of aerobic granule (Liu and Xu, 2007).

The complexity of the microorganism structure implies that there are many ways for the metal to be captured by the cell. Biosorption mechanisms are therefore various and in some cases they are not very well understood. It appears from the above discussion that biosorption mechanism basically can be classified according to metabolism dependent and no-metabolism dependent, while biosorption may also be classified as extracellular accumulation/ precipitation, cell surface sorption/precipitation and intracellular accumulation according to the location where the removed metal is found. The intracellular accumulation or metabolic processes may result in the accumulation of relatively large amounts of metals, but these processes are slow and mostly dependent on nutrient and environmental conditions (Brierley et al., 1985). Surface and wall binding is a passive process and takes place with both living and dead biomass. This non-metabolic surface binding is very rapid, and this kind of metal uptake occurs by ion exchange process involving specific chemical sites on the cell wall.

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Figure 8.12. SEM image, EDX spectrum and element mapping of depth-450 of aerobic granule (Liu and Xu, 2007).

Physical adsorption is not sufficiently discussed in this chapter, and it often occurs as a result of van der Waals forces, and the adsorbed molecule is not affixed to specific site (Arican et al., 2002). Kuyucak and Volesky (1988) hypothesized that uranium, cadmium, zinc, copper and cobalt biosorption by dead biomass of algae, fungi and yeasts, would take place through electrostatic interactions between ion in solution and cell walls. The heats of Cr(VI) and Pb(II) adsorption by Z. ramigera were found to be of the same order of magnitude as the heat of physical adsorption, and equilibrium between the cell surface and the metal ions was usually rapidly attained and easily reversible (Sag and Kutsal, 2000).

8.11. EFFECT OF PH ON BIOSORPTION OF HEAVY METAL BY AEROBIC GRANULES Xu et al. (2006) investigated the effect of initial pH on biosorption of a model heavy metal, nickel by aerobic granules, and found that in the pH range studied (e.g. pH3 to pH7),

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the Ni2+ biosorption was pH-dependent, and a high initial pH would favor the Ni2+ biosorption by aerobic granules. For instance, figure 8.13 shows the effect of initial pH on the e

e

biosorption capacity ( q th ) of Ni2+ by aerobic granules at equilibrium. The q th values e

reported in figure 8.13 were calculated from Equation 3.43. It was found that the q th was

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pH-dependent, i.e. the amount of nickel adsorbed by granules tends to increase with the increase of pH until a platform was reached at a pH value above 6. These seem to indicate that the optimum initial pH value for the Ni2+ biosorption by aerobic granules would be around 6.

Figure 8.13. Effect of initial pH on the biosorption capacity of Ni2+ at equilibrium. Data from Xu et al. (2006).

Xu et al. (2006) also determined the zeta potentials of aerobic granules at different pH values (figure 8.14). At pH 2, the aerobic granules had a positive zeta potential of 11.5 mV, while the zeta potential decreased steeply in the pH range of 2 to 5 and they carried a negative zeta potential of 31.50 mV at pH 5. Beyond pH value of 5, the negative increase of zeta potential became slowly. It appears from figure 8.14 that at a pH value above 3, aerobic granules would be negatively charged. Both the cell surface binding sites and the availability of metal ions in solution are pH-related. At low pH, the cell surface binding sites should be protonized, thereby making them unavailable for the other cations. However, with an increase in pH, there is an increase in ligands with negative charges which in turn would result in increased binding of cations. Obviously, negatively charged aerobic granules would be more attractive to positively charged Ni2+ ion. These results would be helpful for better understanding the observed pH-dependent biosorption of Ni2+ by aerobic granules. at various pH values.

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Figure 8.14. Zeta potential of aerobic granules at various initial pH. Data from Xu et al. (2006).

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REFERENCES Arican B., Celal F.G., Yetis U., Process Biochem. 37 (2002) 1307-1315. Bai R.S., Abraham T.E., Bioresour. Technol. 87 (2003) 17-26. Biniak S., Szymanski G., Siedlewski J., Swiatkowski A., Carbon. 35 (1997) 1799-1810. Brierley J.A., Brierley C.L., Goyak G.M., A new wastewater treatment and metal recovery technology, Elsevier, Amsterdam, 1985. Chada V.G.R., Hausner D.B., Strongin D.R., Rouff A.A., Reeder R.J., J. Collide Interface Sci. 288 (2005) 350-360. Chen J.P., Hong L., Wu S.N., Wan L., Langmuir 18 (2002) 9413-9421. Chojnacka K., A Chojnacki A., Gorecka H., Chemosphere 59 (2005) 75-84. Chubar N., Carvalho J.R., Correia M.J.N., Eng. Aspects. 230 (2004) 57-65. Crist R.H., Oberholser K., Nguyen M., Environ. Sci. Technol. 15 (1981) 1212-1217. Davis T.A., Volesky B., Mucci A., Water Res. 37 (2003) 4311-4330. Diniz V., Volesky B., Water Res. 39 (2005) 239-247. Eccles H., Trend Biotechnol. 17 (1999) 462-465. Fourest E., Volesky B., Environmen. Sci. Technol. 30 (1996) 261-267. Garcia-Sanchez A., Alvarez-Ayuso E., Mineral Eng. 15 (2002) 539-547. Greene B., Darnell D.W., Microbial oxygenic photoautotrophes (Cyanobateria and algae) for metal-ion binding, Mc Graw-Hill, 1990. Hawari A. H., Mulligan C. N., Bioresource Technol. 97 (2006) 692-700. Hullebusch E.D., Zandvoort M.H., Lens P.N.L., J. Chem. Technol. Biotechnol. 79 (2004) 1219-1227. Iqbal M., Saeed A., Enzyme Microb. Technol. 39 (2006) 996-1001.

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Jiang H.L., Tay J.H., Liu Y., Tay S.T.L., Biotechnol. Lett. 25 (2003) 95-99. Kapoor A., Viraraghavan T., Bioresource Technol. 53 (1995) 195-206. Kuyucak N., Volesky B., Biotechnol. Lett. 10 (1988) 137-142. Lin Z.Y., Zhou C.H., Wu J.M., Zhou J.Z., Wang L., Spectrochim. Acta, Part A 61 (2005) 1195-1200. Liu Y., Yang S.F., Tan S.F., Lin Y.M., Tay J.H., Lett. Appl. Microbiol. 35 (2002) 548-551. Liu Y., Tay J.H., Biotechnol. Adv. 22 (2004) 533-563. Liu Y., Wastewater Purification: Aerobic Granulation in Sequencing Batch Reactors. CRC Press, 2007. Liu Y., Xu H., Biochem. Eng. J. 35 (2007) 174-182. Mayers I.T., Beveridge T.J., Can. J. Microbiol. 35 (1989) 764-770. Ouhadi V.R., Yong R.N., Appl. Clay Sci. 23 (2003) 141-148. Prieto M., Cubillas P., Andez-Gonzalez A.F., Geochimica et Cosmochimica Acta. 67 (2003) 3859–3869. Qin L., Tay J.H., Liu Y., Process Biochem. 39 (2004) 579–584. Raize O., Argaman Y., Yannai S., Biotechnol. Bioeng. 87(2004) 451-458. Saeed A., Iqbal M., World J. Microbiol. Biotechnol. 22 (2006) 775-782. Sag Y., Kutsal T., Biochem. Eng. J. 6 (2000) 145-151. Scheckel K.G., Ryan J.A., Allen D., Lescano N., Sci. Total Environ. 350 (2005) 261-272. Schneider I.A.H., Rubio J., Smith R.W., Internatl. J. Mineral Proc. 62 (2001) 111–120. Sheng P.X., Ting Y.P., Chen J.P., Hong L., J. Colloid Interf. Sci. 275 (2004) 131-141. Tsezos M., Volesky B., Biotechnol. Bioeng. 23 (1981) 583-604. Veglio F., Beochini F., Hydrometallurgy 44 (1997) 301-316. Vieira R., Volesky B., Internatl. Microbiol. 3 (2000) 17-24. Volesky B., Biosorption of Heavy Metals, CRC Press Inc, 1990. Wase J., Forster C., Biosorbents for Metal Ions, Taylor and Francis Publishers, 1997. Xu H., Tay J.H., Foo S.K., Yang S.F., Liu Y., Water Sci. Technol. 50 (2004) 155-160. Xu H., Liu Y., Tay J.H., Bioresource Technol. 97 (2006) 359-363. Xu H., Liu Y., Sep. Purif. Technol. 58(2008) 400-411. Yee N., Fein J., Geochimica et Cosmochimica Acta. 65 (2001) 2307-2042. Zhang J., Jiang B., Li X.G., Liu R.X., Sun Y.L., Chinese J. Chem. Eng. 13(2005) 135-139. Zhou D., Zhang L., Guo S.L., Water Res. 39 (2005) 3755-3762.

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INDEX

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A Aβ, 128 AAS, 182 absorption, 54, 175, 179, 182, 184, 186, 207, 208, 209, 241, 244, 245, 253, 269 absorption spectroscopy, 179, 182, 207, 209 accessibility, 176, 184 accounting, 95, 102, 237 acetate, 199 acetic acid, 223 acetone, 198 acid, 3, 8, 10, 11, 12, 14, 23, 36, 45, 49, 56, 61, 63, 64, 66, 70, 73, 74, 162, 165, 166, 168, 175, 181, 183, 185, 188, 190, 198, 220, 223, 228, 231, 255, 257, 258, 265, 269, 270 acidic, 14, 48, 54, 166, 168, 170, 183, 189, 190, 227, 258 acidity, 188 Acinetobacter, 164 acrylic acid, 70 activated carbon, 54, 65, 73, 75, 76, 101, 104 active site, 68, 108, 175, 189, 222, 225, 226 adducts, 211 adhesion, 205, 263 adjustment, 75, 222 adsorption, vii, 29, 40, 45, 49, 52, 53, 58, 61, 62, 65, 67, 68, 71, 73, 87, 88, 89, 91, 93, 94, 96, 97, 100, 101, 102, 103, 104, 105, 106, 108, 110, 111, 112, 120, 121, 125, 126, 127, 128, 129, 130, 131, 133, 134, 135, 136, 137, 138, 139, 140, 146, 148, 149, 150, 151, 161, 162, 163, 164, 166, 168, 169, 172, 175, 176, 184, 190, 191, 197, 198, 199, 200, 220, 222, 228, 229, 231, 232, 238, 239, 241, 255, 265, 268, 269, 270, 275, 281 adsorption isotherms, 172, 176

aerobic, vii, viii, 42, 106, 108, 109, 110, 111, 113, 235, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 274, 275, 276, 277, 278, 279, 280, 281, 282, 283 aerobic granulation, 263 aerobic granules, vii, viii, 106, 108, 109, 110, 111, 113, 235, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 274, 275, 276, 277, 279, 281, 282, 283 AFM, 182, 183, 202, 204, 205, 206 Ag, 26, 37, 39, 40, 42, 43, 44, 51, 52, 55, 72, 104, 169, 170, 171, 172, 173, 175, 177, 178, 181, 187, 191, 196, 199, 200, 201, 202, 203, 206, 221, 222, 223, 224, 229, 230, 232, 233, 238, 241, 243, 244, 245, 247, 249, 255, 256, 257, 259, 270 agar, 23, 57, 210 age, 210, 219, 237 agent, 162, 199 agents, 12, 66, 72, 76 aggregates, 56, 263 aggregation, 71, 164, 182, 197 agricultural, 30, 76 agriculture, 204 aid, 66 air, 45, 207 alanine, 10, 12 Alaska, 74 alcohol, 185 aldehydes, 240 algae, vii, 2, 3, 17, 20, 21, 22, 23, 24, 25, 26, 29, 30, 31, 53, 55, 56, 57, 58, 59, 61, 62, 63, 66, 70, 72, 74, 76, 80, 111, 118, 119, 161, 164, 169, 174, 175, 207, 212, 220, 222, 223, 225, 227, 228, 230, 269, 281, 283 Algal, 20, 25, 56, 269 Alginate, 24, 25 algorithm, 188 alkali, 39, 52, 63, 64, 179, 229, 244, 253 alkaline, 64, 66, 72, 73, 74, 76, 229, 255

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280 alkaline earth metals, 72, 74, 229 alpha, 168 alternative, 71, 74, 188, 189, 200, 232 aluminum,39, 54, 199 aluminum oxide, 54 ambiguity, 38 amide, 165, 185, 186, 269 amine, 164, 167, 169, 174, 187, 189, 269, 270 amino, 8, 14, 71, 108, 162, 168, 174, 183, 184, 185, 186, 207, 221, 223, 231, 240, 257, 269 amino acid, 8, 14, 71, 175, 183, 185, 207, 222, 223, 231, 257 amino acids, 8, 14, 71, 185, 207, 222, 223, 231, 257 amino groups, 185, 186, 222, 257 ammonium, 64, 132, 232 ammonium chloride, 64, 232 ammonium sulphate, 64, 232 amorphous, 8, 23, 24, 167, 181, 207 amplitude, 207, 209 Amsterdam, 81, 82, 83, 283 AMT, 72, 76 anaerobic, 165, 268 analytical techniques, 182 anhydrase, 180 animals, 1, 36 Anions, 167, 222, 228 antagonistic, 229 anthrax, 14 antibiotic, 138 antibiotics, 8, 36 antimony, 39 application, vii, viii, 29, 31, 38, 54, 65, 66, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 81, 95, 98, 141, 145, 146, 164, 181, 182, 205, 219, 231, 259, 264 aquatic habitats, 20 aqueous solution, vii, 3, 37, 39, 44, 45, 49, 58, 61, 63, 64, 65, 95, 126, 161, 162, 166, 169, 170, 191, 204, 221, 222, 229, 237, 242, 258, 259, 264, 268 aqueous solutions, 3, 37, 39, 44, 45, 49, 64, 166, 222, 229 aqueous suspension, 201 aragonite, 266 Archaea, 1, 5, 164 aromatics, 101 Arrhenius equation, 241 Arthrobacter nicotianae, 35 ash, 265 Asian, 44 Aspergillus niger, 48, 49, 50, 51, 64, 178, 179, 190, 193 Aspergillus terreus, 51 assessment, viii, 67, 74, 76, 220, 237, 259 assumptions, 87, 149, 238, 263

Index asymmetry, 12, 44 atomic absorption spectrometry, 182 atoms, 24, 26, 183, 207, 209, 211, 240, 242 attachment, 15, 224 Au nanoparticles, 201 autolysis, 179, 232 availability, 37, 57, 75, 134, 162, 163, 219, 220, 223, 257, 282 averaging, 19

B B. subtilis, 190 Bacillus, 2, 5, 10, 11, 14, 29, 31, 32, 34, 35, 53, 54, 72, 76, 79, 164, 189, 190, 206, 221, 222, 228 Bacillus subtilis, 32, 35, 72, 76, 189, 190, 228 Bacillus thuringiensis, 34 backscattered, 191 bacteria, 1, 2, 3, 5, 6, 8, 10, 11, 12, 16, 20, 26, 29, 30, 31, 36, 44, 53, 55, 56, 57, 63, 70, 72, 161, 164, 166, 167, 168, 169, 175, 176, 178, 183, 184, 185, 188, 189, 190, 199, 201, 207, 220, 228, 229, 263 bacterial, 2, 6, 7, 8, 12, 14, 20, 31, 36, 54, 164, 166, 167, 168, 169, 175, 183, 185, 186, 188, 189, 190, 222, 228, 232, 265, 268 bacterial cells, 14, 36, 164, 168, 169, 183, 232 bacterium, 7, 166, 168, 175, 197, 226, 232 baking, 17 barrier, 2, 164, 200 barriers, 19, 176 basic research, vii, 264 beer, 17, 171, 191, 257 beet molasses, 49 behavior, 19, 29, 36, 104, 105, 121, 134, 158, 179, 211, 228, 257 Beijing, 84, 235 bending, 185, 187, 269, 270 binding, 14, 23, 26, 30, 49, 54, 59, 63, 64, 67, 69, 70, 71, 73, 78, 87, 95, 107, 108, 111, 112, 162, 163, 164, 165, 166, 167, 168, 169, 170, 172, 174, 175, 176, 177, 181, 182, 183, 184, 186, 187, 188, 189, 190, 192, 198, 200, 210, 211, 212, 219, 220, 221, 222, 223, 224, 226, 227, 228, 229, 230, 232, 233, 238, 239, 240, 242, 244, 256, 257, 258, 259, 267, 269, 270, 275, 280, 282, 283 binding energy, 211, 270, 275 bioaccumulation, 38, 53, 166 bioavailability, 238 biochemistry, 23, 57 bioconversion, 49 biodegradation, 49 biofilms, 66, 164 biological activity, 240

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Index biological systems, 26, 219, 238, 239, 240, 255 biomass materials, 161, 169, 184, 187 biomaterial, 40, 54, 72, 74, 169, 267 biomaterials, vii, 30, 53, 68, 72, 77, 161, 169, 263 Biometals, 80, 83, 214 bioreactors, 41 bioremediation, 39, 71, 175, 182, 231 biosynthesis, 8 biotechnological, 48, 76 biotechnologies, 38 biotechnology, 65, 77, 160 biotransformations, 49 boiling, 63 bonding, 15, 174, 239, 255, 256, 257, 269 bonds, 12, 26, 184, 185, 186, 187, 219, 239, 242 borderline, 174, 227, 239, 241, 247, 248, 249, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259 Boston, 234 Bradyrhizobium, 175 Brazilian, 79 breeding, 71 budding, 15, 16, 17, 180 buffer, 191, 198, 199, 204 building blocks, 4, 25 by-products, 54

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C Ca2+, 26, 64, 73, 169, 170, 171, 172, 173, 174, 212, 219, 225, 228, 229, 239, 255, 265, 268 cadmium, 36, 38, 39, 49, 53, 58, 59, 61, 62, 64, 70, 72, 73, 76, 120, 142, 162, 163, 165, 175, 181, 182, 183, 211, 224, 232, 233, 263, 264, 268, 269, 275, 281 calcium, 23, 49, 56, 65, 72, 166, 169, 181, 225, 267 calcium carbonate, 23, 56, 267 Canada, 72, 74, 76 Candida, 15, 37, 53, 54 capacitance, 225 capsule, 14, 175 carbohydrate, 4, 12, 14, 23, 24, 167, 168, 174, 211, 232 carbon, 3, 8, 20, 24, 54, 56, 73, 75, 76, 101, 104, 166, 191, 201, 219, 231, 232, 272 Carbon, 21, 22, 197, 283 carbon atoms, 24 carbon dioxide, 20 carbonates, 66, 229 carboxyl, 10, 12, 26, 70, 108, 162, 164, 165, 167, 169, 174, 176, 182, 183, 184, 185, 186, 187, 189, 205, 210, 221, 222, 238, 257, 268, 269, 270 carboxyl groups, 10, 12, 70, 176, 182, 185, 186, 187, 210, 222, 257, 268, 269, 270 carboxylates, 212

281

carboxylic, 70, 166, 185, 189, 269, 270 carboxylic acids, 269 carboxylic groups, 185, 269 carboxymethylcellulose, 65 carotenoids, 23, 56 carrier, 73, 166 cashmere, 44 catalyst, 94 cation, 12, 167, 169, 170, 172, 173, 174, 175, 221, 239, 240, 241, 258, 269, 270 CBS, 232 C-C, 187 cell, vii, viii, 1, 2, 3, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 23, 24, 25, 26, 29, 36, 38, 40, 41, 42, 56, 62, 63, 64, 65, 70, 71, 161, 162, 167, 168, 169, 170, 174, 175, 176, 177, 178, 179, 180, 181, 182, 183, 184, 186, 187, 189, 191, 193, 194, 196, 198, 199, 200, 201, 202, 204, 205, 206, 207, 210, 219, 220, 221, 222, 224, 227, 228, 229, 230, 231, 232, 237, 238, 256, 257, 267, 268, 269, 270, 280, 281, 282 cell division, 8 cell membranes, 19, 64 cell surface, vii, viii, 3, 11, 12, 15, 26, 62, 63, 64, 71, 161, 162, 175, 176, 177, 178, 182, 183, 184, 189, 191, 192, 193, 200, 204, 205, 206, 220, 222, 224, 227, 230, 231, 232, 267, 268, 280, 281, 282 cellulose, 16, 18, 23, 21, 22, 24, 25, 26, 56, 200, 227, 269 cellulosic, 30, 74 ceramics, 23 channels, 163, 180 charcoal, 54, 63 chemical engineering, 72 chemical interaction, 267 chemical kinetics, 130, 145 chemical properties, 168, 238, 240 chemical reactivity, 239 chemicals, 3, 29, 49, 52, 64, 73, 80, 240 chemisorption, 106, 152 China, viii, 27, 78, 187, 213, 220, 233, 240, 260 chirality, 24 chitin, 16, 18, 23, 26, 56, 174, 205, 227, 269 Chitin, 17 chloride, 64, 66, 73, 167, 230, 232 chlorophyll, 3, 19, 20, 55, 56 chloroplasts, 2, 3, 4, 20, 56 cholesterol, 3 chromatin, 20 chromatography, 168 chromium, 39, 40, 49, 61, 76, 222, 229, 253, 258, 264 chromosome, 3, 4

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282 classes, 26, 27, 239, 242, 255 classical, 68 classification, 26, 56, 75, 219, 239, 253, 255, 259 clay, 66 cleanup, 71 clients, 74 CLSM, 182, 213 clusters, 6 CMC, 65 C-N, 187, 269 Co, 26, 37, 38, 39, 43, 53, 55, 57, 70, 73, 84, 108, 109, 110, 111, 112, 113, 115, 116, 118, 120, 181, 256 cobalt, 39, 73, 175, 281 coccus, 5 cocoa, 169 coconut, 224 Colorado, 72, 74 commercialization, 74, 76, 77 community, 57 compatibility, 77 competition, 77, 170, 225, 226, 228, 229, 230, 239 competitive conditions, 45, 52, 229 competitor, 74 complex systems, 151 complexity, 15, 149, 187, 244, 280 components, 2, 12, 21, 26, 56, 64, 75, 164, 166, 168, 174, 175, 186, 189, 228, 265, 269 composites, 186 composition, 2, 3, 8, 17, 29, 54, 64, 73, 168, 169, 174, 175, 205, 210, 219, 222, 231, 265 compounds, 3, 64, 68, 212, 240, 265, 266, 267, 269, 270 computing, 238 concentration, 31, 38, 40, 45, 49, 53, 54, 58, 59, 68, 69, 72, 73, 74, 75, 76, 77, 87, 88, 90, 91, 95, 96, 97, 104, 108, 110, 111, 112, 113, 114, 115, 116, 118, 119, 121, 127, 128, 129, 130, 133, 134, 146, 149, 151, 161, 162, 163, 170, 171, 172, 174, 176, 179, 181, 187, 188, 191, 200, 206, 212, 219, 220, 223, 227, 228, 229, 230, 232, 233, 238, 241, 267 condensation, 106 confidence, 158 configuration, 176, 191, 238, 242, 249, 258, 259 construction, 71, 230, 259 consulting, 74 contact time, 110, 164, 171, 191, 206, 219, 231, 237 contaminant, vii, 75 contaminants, 76 continuity, 73 control, 37, 66, 168, 172, 173, 186, 200, 206, 211, 221, 233

Index copper, 39, 40, 43, 49, 53, 59, 61, 62, 64, 70, 71, 120, 142, 144, 145, 165, 167, 168, 175, 181, 182, 199, 201, 207, 208, 209, 210, 221, 224, 231, 232, 233, 263, 266, 268, 281 coral, 23 corn, 30 correlation, 100, 110, 111, 121, 125, 140, 141, 147, 153, 157, 159, 163, 244, 252, 253, 254, 257, 258, 259 correlations, 240, 243, 249 Corynebacterium, 31, 35, 190 cost-effective, viii, 63, 74, 77, 108, 265 costs, 37, 66, 74, 75, 76, 78 covalency, 255 covalent, 10, 15, 26, 170, 172, 174, 175, 220, 227, 237, 239, 241, 242, 245, 247, 255, 256, 257, 258, 259 covalent bond, 10, 174, 175, 220, 238, 239, 255, 256, 257, 259 covalent bonding, 174, 255, 256, 257 covering, 196 CRC, 28, 79, 80, 81, 84, 217, 234, 261, 284 critical value, 158 cross-linking, 63 crystal structure, 199, 201, 202, 208 crystalline, 15, 183, 201, 202, 207 crystallinity, 266 crystals, 178, 199, 266 cultivation, 167 culture, 10, 16, 23, 38, 41, 42, 64, 164, 181 curing, 52 cuticle, 17 cyanide, 44, 72 cyanobacteria, 20, 55, 62, 166 cyanobacterium, 6, 167 cycles, 65, 66, 72, 73, 167 cycling, 36 cysteine, 64, 70, 73, 181, 232, 257 Cysteine, 232, 257 cytoplasm, 2, 3, 6, 16, 17, 19, 162, 167, 175 cytoplasmic membrane, 2, 10, 17, 56 cytoskeleton, 4, 17 cytosolic, 199 cytotoxic, 10

D damping, 209 data analysis, 208, 209 data collection, 207 decay, 56 decision making, 74 deconvolution, 272 defense, 267

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Index definition, 95, 103, 146, 174, 242 deformation, 269 degrading, 168 dehydration, 167, 197, 198, 202, 270 density, 65, 72, 91, 227, 242, 264, 275, 279 deoxyribonucleic acid, 3 deposition, 56, 161, 167, 169, 175, 183, 199, 267 deposits, 178, 180, 181, 196 derivatives, 8 desorption, 53, 65, 66, 72, 88, 89, 112, 127, 128, 129, 130, 137, 162, 167, 175, 225, 231, 241 destruction, 64 detection, 191, 198, 208, 267 detergents, 63 detoxification, 38, 70, 181, 183, 231, 232 dextrose, 232 diamond, 199 diatoms, 20, 21, 56 diffraction, 182, 199, 202, 266 diffuse reflectance, 184 diffusion, 152, 161, 163, 179 digestion, 1 digestive enzymes, 200 direct measure, 204 dispersion, 112 displacement, 166, 170, 174, 208 dissociation, 220, 221, 226 distilled water, 199 distribution, 56, 76, 93, 94, 180, 197, 201, 209, 211, 213, 277, 279 diversity, 56 division, 6, 8, 15, 16, 17, 23, 56, 242 DNA, 3, 4, 180 donor, 24, 177, 240, 242 dosage, 35 drainage, 74, 165 drinking, 74 drinking water, 74 drying, 40, 63, 64, 76, 197 dyes, 29, 104 dynamic systems, 163

E E. coli, 12, 71 earth, 73 ECM, 163 ecology, 5, 166, 204 economic performance, 78 economics, 75 effluent, viii, 75, 77, 228, 231, 232, 264, 265 effluents, 66, 75, 76, 77, 78, 229 elaboration, 263 electrolytes, 228

283

electron, 2, 91, 174, 177, 178, 183, 190, 191, 192, 197, 198, 199, 200, 201, 202, 204, 207, 208, 242, 249, 258, 259, 275 electron density, 91, 242, 275 electron diffraction, 178, 202 electron microscopy, 182, 183, 190, 191, 227 electron pairs, 174 electron spin resonance, 183 electronegativity, 238, 239, 241, 259 electrons, 211, 240, 241, 242, 259 electroplating, vii, 73, 74, 76, 231, 232 electrostatic force, 242 electrostatic interactions, 281 emission, 182, 183, 197 encoding, 71 endoplasmic reticulum, 17, 19 endothermic, 106, 108, 223, 225 energy, 68, 91, 93, 97, 102, 103, 104, 118, 161, 178, 179, 182, 190, 193, 198, 201, 207, 208, 209, 223, 224, 227, 231, 241, 242, 256, 257, 272 entrapment, 65, 161 entropy, 105, 106, 223 environment, 2, 179, 191, 207 environmental conditions, 68, 161, 163, 219, 237, 245, 280 environmental factors, 68, 219, 220 Environmental Protection Agency, 260 enzymatic, 174 enzymes, 3, 8, 12, 36, 48, 71, 180, 181, 200 epoxy, 199 equilibrium, viii, 35, 38, 40, 63, 64, 67, 68, 69, 87, 88, 89, 90, 94, 95, 96, 97, 98, 103, 104, 105, 108, 110, 111, 112, 115, 118, 119, 121, 125, 126, 127, 131, 137, 138, 145, 146, 149, 162, 163, 170, 172, 173, 183, 186, 187, 188, 209, 222, 223, 224, 227, 230, 231, 235, 241, 281, 282 equilibrium sorption, 63, 69, 104 equilibrium state, 40, 69, 97, 108, 110, 115, 149, 162, 172 Escherichia coli, 6, 7, 8, 13, 17, 71, 168, 189, 190 ESR, 183 ester, 11, 12, 25, 185, 186 esterase, 48 esterification, 186, 257, 269 estimator, 153, 158, 159 ethanol, 36, 38, 64, 197, 198, 199, 229 Ethanol, 41 ethanolamine, 12 ethylenediamine, 230 eucaryotic cells, 1, 19 eukaryote, 17 eukaryotic cell, 1, 2, 3, 6, 17, 36 evaporation, vii, 75

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284

Index

EXAFS, 176, 183, 207, 208, 209, 210 examinations, 190 excretion, 181 experimental condition, 43, 55, 119, 145, 211, 264 explosives, 23 exposure, 69, 168, 167, 172, 186, 202, 206, 232 external environment, 3 extraction, 73, 74, 108, 168, 267 extraction process, 74

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F failure, 76, 77 family, 30, 74, 78 fascia, 57, 227 fatty acids, 3 fermentation, 17, 29, 30, 36, 37, 38, 41, 42, 53, 70, 232 fern, 166, 169 ferritin, 180 fibers, 4, 18, 24 fibrillar, 24, 25, 161, 167 fibrils, 56, 198 field emission scanning electron microscopy, 197 field trials, 73 filament, 15 films, 17, 201, 213 financial support, 27, 78, 213, 233, 260 fish, 207 fission, 4, 180 fitness, vii, 158, 159 fixation, 20, 167, 190, 197, 198, 199, 201 flexibility, 24, 74, 189 flocculation, 169 flora, 72 flow, 53, 65, 67, 69, 70, 73, 76, 163 fluid, 3 fluidized bed, 72 fluorescence, 183, 208, 211 fluoride, 241 foams, 66 focusing, 77, 161 food, 20, 23, 29, 36, 37, 49 Food and Drug Administration, 49 food industry, 30 formaldehyde, 41, 42, 64, 168, 174, 225 Fourier, 182, 184, 208, 209 free energy, 96, 97, 104, 105, 118, 119, 223 freeze-dried, 42, 62, 174, 220, 238, 256 freezing, 63 frequency distribution, 93 freshwater, 20, 72 Freundlich isotherm, vii, 90, 91, 92, 93, 94, 100, 101, 166, 168

fruit juice, 36 fruit juices, 36 fruits, 17, 36 FTIR, 162, 165, 168, 177, 182, 184, 185, 186, 187, 237, 269, 271, 272 FT-IR, 165 FTIR spectroscopy, 184 fungal, 17, 18, 23, 30, 36, 43, 44, 49, 52, 53, 64, 178, 193, 199, 201, 207, 210, 228, 229, 230, 232, 264 fungi, vii, 1, 2, 3, 15, 16, 17, 19, 26, 29, 30, 31, 36, 37, 44, 52, 53, 56, 57, 70, 74, 76, 161, 164, 168, 169, 170, 174, 178, 184, 185, 186, 210, 220, 228, 281 fungus, 15, 16, 19, 52, 63, 65, 168, 200, 201, 205, 210 fungus spores, 65 Fusarium, 44 fusion, 4, 71

G gametes, 4 gas, 93, 97, 105, 118, 151, 168, 196 gas chromatograph, 168 gases, 23, 56, 87, 150 gel, 23, 2, 65, 72, 175 gene, 71 generation, 66 genes, 70, 71, 179, 180, 182, 205 genetic information, 5 genetics, 5 genome, 17 germanium, 184 germination, 19 Gibbs, 104, 105, 223 Gibbs free energy, 104, 105, 223 glass, 66 glucose, 10, 12, 13, 14, 23, 36, 45, 56, 64, 166, 168, 231, 232 glucose oxidase, 45 glucose tolerance, 231 glutamate, 230 glutamic acid, 14, 232 glutaraldehyde, 72, 197, 198, 199 glutathione, 70, 181 glycans, 18 glycerol, 9, 11, 12, 22 glycine, 231 glycogen, 19 glycoproteins, 15, 24, 57 glycosyl, 11 goals, 237 gold, 36, 44, 65, 72, 178, 196, 197, 200, 201, 239 gold nanoparticles, 201

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Index grafting, 70 Gram-negative, 12, 190 gram-negative bacteria, 8, 10, 11, 168, 178, 189 Gram-positive, 11, 190 gram-positive bacteria, 8, 228 granules, vii, viii, 72, 106, 108, 109, 110, 111, 113, 180, 181, 235, 263, 264, 265, 266, 267, 268, 269, 270, 271, 272, 274, 275, 276, 277, 279, 281, 282, 283 grapes, 17 gravity, viii, 265 Greece, 42 grids, 199, 201 grouping, 242 groups, vii, 1, 3, 6, 8, 10, 11, 12, 15, 20, 21, 24, 26, 27, 30, 36, 56, 57, 63, 70, 73, 108, 161, 162, 164, 165, 166, 167, 169, 170, 174, 175, 176, 182, 183, 184, 185, 186, 187, 188, 189, 190, 205, 209, 210, 211, 221, 222, 225, 227, 228, 229, 232, 238, 240, 256, 257, 265, 268, 269, 270, 272, 275 growth, 23, 37, 57, 62, 64, 65, 150, 168, 219, 231, 232, 239, 257, 265 growth rate, 231 guidelines, 272

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H H2, 72 habitat, 20 handling, 73 hardness, 219 harmful effects, 164 hazards, 3 heat, 63, 64, 66, 105, 106, 181, 281 heating, 63 heavy metal, vii, viii, 23, 26, 28, 30, 36, 37, 38, 39, 44, 45, 49, 52, 53, 57, 59, 61, 66, 70, 71, 72, 74, 77, 78, 84, 108, 118, 119, 132, 164, 165, 168, 169, 170, 174, 176, 181, 182, 198, 211, 220, 222, 225, 227, 229, 230, 232, 235, 261, 264, 265, 266, 267, 268, 277, 281 heavy metals, vii, viii, 28, 30, 36, 37, 44, 45, 49, 59, 71, 72, 74, 78, 84, 164, 165, 168, 176, 198, 211, 225, 227, 261, 264, 265, 267, 268 hemoglobin, 180 heterogeneous, 93, 101, 105, 176, 188 heterogeneous systems, 176, 188 heterotrophic, 19 high pressure, 65 high resolution, 198, 199, 204 high temperature, 106, 107, 108, 223 histidine, 71, 182 Holland, 79 host, 49

285

humic acid, 207 humic substances, 188 humidity, 42, 196 hybrid, 76, 134, 138 hydration, 256, 258 hydro, 2, 12 hydrocarbon, 73, 168 hydrodynamic, 69, 70 hydrogen, 15, 24, 167, 189 hydrogen bonds, 24 hydrolysates, 182 hydrolysis, 186, 220, 238, 240, 241, 242, 257, 258, 259 Hydrometallurgy, 83, 84, 122, 217, 234, 284 hydrophilic, 2, 12 hydrophilicity, 24, 213 hydrophobic, 2, 12 hydrophobic interactions, 12 hydrophobicity, 175, 213 hydrostatic pressure, 65 hydroxides, 64, 179, 207, 229, 258, 259 hydroxyl, 10, 24, 108, 162, 164, 167, 174, 177, 184, 185, 186, 189, 238, 257, 269, 270 hydroxyl groups, 24, 164, 174, 185, 186, 238 hyperbolic, 87, 149, 150 hypothesis, 158, 180

I ice, 71 id, 172, 267 identification, 184, 199 identity, 184, 207 illumination, 231 images, 191, 197, 198, 199, 201, 203, 204, 206, 212, 279 imaging, 204, 211, 213 immobilization, 65, 66, 72, 75, 77, 211 immunity, 75 impurities, 229, 230 in situ, 212 inactive, 19, 29, 161, 162, 224 incineration, 75 inclusion, 6, 181 inclusion bodies, 6, 181 income, 76 increased competition, 229 incubation, 62, 65 independent variable, 247 Indian, 79 indication, 223 industrial, vii, viii, 29, 36, 37, 38, 65, 66, 70, 73, 75, 76, 77, 78, 132, 135, 228, 229, 264 industrial application, 38, 65, 66, 73, 75, 76

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286

Index

industrial wastes, 29 industrialization, 37 industry, viii, 30, 37, 41, 42, 75, 76, 171, 204 inefficiency, 159 inert, 66, 77, 181, 192 inertia, 242 infinite, 115, 152 infrared, 182, 184 infrared spectroscopy, 184 inhibitory, 229, 230 inhibitory effect, 229, 230 initial state, 108 initiation, 104 inorganic, 17, 23, 64, 162, 169, 220, 223, 238 insertion, 12, 71 insight, 237 integration, 93, 126, 133 integrity, 3 interaction, viii, 12, 29, 37, 77, 88, 103, 104, 169, 171, 172, 175, 182, 186, 207, 211, 220, 222, 226, 237, 238, 239, 242, 257, 259, 268, 269, 270, 272 interactions, 12, 15, 38, 162, 167, 174, 176, 186, 188, 205, 207, 229, 237, 238, 239, 240, 242, 256, 259, 260, 281 intercalation, 183 interface, 3, 106, 112, 137, 207, 223 interference, 75, 95, 207, 209, 237 intermolecular, 24 intrinsic, 76, 172 investment, 75 ion channels, 180 ion exchangers, 73 ion transport, 179, 223 Ion-exchange, 169 ionic, viii, 12, 26, 68, 69, 71, 171, 172, 174, 180, 188, 219, 220, 222, 225, 226, 227, 228, 229, 237, 238, 239, 241, 242, 247, 249, 253, 255, 256, 257, 258, 259, 269 ionization, 183, 209, 238, 241, 242, 248, 257, 258, 259 ionization energy, 209 IP, 241, 242, 243, 245, 247, 248, 249, 250, 251, 252, 253, 254, 257, 258, 259 IR, 166, 167, 182, 184, 186, 187, 270 IR spectra, 165, 166, 167, 186, 270 Ireland, 74 iron, 39, 49, 73, 176, 181, 188, 199, 210, 211 isolation, 167 isotherms, vii, 49, 68, 69, 87, 99, 100, 105, 106, 172, 176, 210, 241

J

Jung, 82, 199

K K+, 169, 170, 171, 172, 173, 192, 219, 229, 230, 233, 239, 245, 255, 265, 268 KBr, 184 ketones, 240 kinetic equations, 115, 125, 140, 141, 145, 149, 151, 152, 153, 155, 156, 157, 158 kinetic model, vii, 121, 125, 131, 134, 140, 148, 153, 159 kinetic studies, 145, 171, 172 kinetics, vii, 69, 70, 75, 76, 108, 109, 110, 111, 114, 122, 125, 127, 130, 131, 132, 136, 137, 138, 139, 140, 145, 148, 149, 150, 151, 156, 157, 158, 159, 160, 163, 171 KOH, 238, 240, 241, 242, 243, 247, 248, 249, 250, 251, 253, 254, 257, 258, 259 Korea, 61, 62 Korean, 81, 260

L L1, 188 L2, 188 laboratory method, 211 lactic acid, 8 Lactobacillus, 270 lamellar, 20, 23 land, 23, 75 Langmuir, vii, 35, 49, 54, 58, 59, 62, 64, 67, 68, 79, 87, 88, 89, 90, 91, 93, 94, 100, 101, 103, 104, 105, 120, 122, 137, 138, 139, 140, 149, 150, 159, 163, 165, 166, 172, 176, 213, 241, 244, 245, 259, 283 lanthanide, 167, 183 lanthanum, 186 large-scale, 30, 36, 70, 73, 74, 77 laser, 183, 213 lattice, 104 law, vii, 95, 105, 130, 140, 145, 146, 148, 151, 152, 156, 158 leather, 36 lectin, 169 lichen, 179 ligand, 174, 176, 183, 188, 189, 223, 229, 238, 239, 240, 242, 256, 257, 259 ligands, 26, 175, 187, 210, 219, 220, 221, 223, 232, 238, 239, 240, 242, 255, 256, 257, 258, 259, 282 limitation, 95, 96 limitations, 38, 66, 76, 95, 164, 259

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Index linear, 4, 8, 10, 24, 91, 112, 113, 115, 125, 126, 132, 136, 167, 176, 188, 189, 226, 238, 241, 244, 246, 247, 249, 250, 251, 252, 253, 254, 257, 258 linear model, 244 linear programming, 167, 188, 189 linear regression, 244, 246, 247, 250, 251, 252, 254 linkage, 8 lipase, 48 lipases, 36 lipids, 2, 10, 17, 19, 54, 165 lipoid, 166 lipophilic, 10 lipopolysaccharide, 12, 13, 164, 175, 183 lipoproteins, 12, 71 liquid phase, 112 liquor, 73 localization, 183 location, 161, 198, 199, 200, 280 London, 28, 80, 84, 122, 174, 214, 217, 234 long period, 56 low molecular weight, 70, 180, 181 LPS, 12, 13, 175, 183 LTD, 214 lying, 9, 14, 20 lysis, 2, 8

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M macroalgae, 61, 186 macromolecules, 56 macronutrients, 219, 239 magnesium, 56, 72, 169, 170, 265, 266 magnetic, 211 magnetic field, 211 Maine, 74 maintenance, 264 maltose, 71, 232 mammals, 37, 183 manganese, 61, 167, 230 manipulation, 36, 37 mannitol, 21 mapping, 197, 278, 279, 280, 281 market, 74 marketplace, 74 markets, 74, 77 mask, 56 masking, 63 mass transfer, 66, 69, 95, 110, 163, 164 material sciences, 207 material surface, 207 matrix, 3, 6, 17, 20, 23, 24, 41, 57, 65, 213, 256 maximum sorption, 59, 61, 64, 68, 222 MBP, 71 meanings, 100, 149

287

measurement, 39, 40, 78, 153, 201, 205, 211, 212 mechanical properties, 205 media, 37, 62, 74, 219, 232, 240 medicine, 204 meiosis, 1, 4 membranes, 2, 3, 19, 161 mercury, 39, 40, 43, 71, 73, 163, 183, 186, 197, 199, 200 metabolic, 3, 6, 29, 36, 166, 280 metabolism, 23, 29, 36, 161, 162, 174, 178, 179, 198, 220, 231, 232, 239, 255, 267, 280 metabolizing, 170, 174 metal chelators, 71 metal hydroxides, 258 metal ions, viii, 26, 29, 31, 38, 39, 40, 43, 45, 49, 53, 55, 57, 62, 63, 66, 70, 71, 72, 110, 127, 132, 162, 163, 164, 166, 168, 169, 170, 172, 174, 175, 177, 179, 180, 181, 182, 183, 184, 187, 188, 191, 199, 201, 207, 219, 220, 221, 222, 223, 224, 225, 226, 228, 229, 230, 231, 232, 237, 238, 239, 240, 241, 245, 246, 247, 249, 253, 255, 256, 257, 258, 259, 265, 267, 268, 270, 281, 282 metal oxides, 188 metal recovery, 62, 76, 283 metal salts, 211 metalloids, 161 metallothioneins, 70, 71, 181 metals, viii, 12, 23, 26, 29, 30, 31, 36, 37, 38, 39, 40, 44, 45, 49, 52, 54, 58, 59, 62, 70, 72, 74, 75, 76, 79, 161, 164, 165, 166, 167, 168, 169, 175, 176, 180, 181, 183, 184, 210, 211, 220, 226, 228, 229, 231, 232, 237, 238, 239, 240, 242, 244, 245, 255, 256, 260, 264, 265, 268, 269, 270, 272, 280 methane, 5 methanol, 64, 174 methanotrophs, 5 methyl group, 187 methylation, 181 methylene, 94 Mexico, 72 Mg2+, 26, 73, 169, 170, 171, 172, 173, 174, 192, 219, 225, 229, 230, 233, 239, 265, 268 microalgae, 61, 62, 232, 264 microbes, 29, 30, 38, 76, 179, 263 Microbes, 37 microbial, vii, viii, 1, 3, 29, 37, 38, 63, 65, 67, 71, 72, 76, 108, 150, 176, 182, 183, 204, 219, 220, 239, 263, 265 Microbial, 1, 28, 214, 216, 283 microbial cells, 29, 63, 65 microorganism, 17, 31, 36, 48, 64, 167, 267, 280 microorganisms, 2, 3, 10, 28, 29, 31, 36, 55, 70, 81, 162, 164, 179, 181, 205, 264

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288

Index

micro-organisms, 30, 63 microscope, 2, 199, 201 microscopy, 178, 183, 190, 204, 213 microtubules, 4 migration, 16, 179 milligrams, 40, 49 minerals, 175, 176, 207, 267 mining, 49, 73, 74, 165 misleading, 68 mitochondria, 4, 17, 19, 23, 180 mitosis, 1 model system, 37 modeling, 69, 176, 188, 189, 190, 208, 240, 245, 249, 253 models, vii, 17, 36, 67, 68, 69, 100, 125, 140, 159, 163, 172, 176, 188, 189, 210, 240, 244, 245, 249, 259 moieties, 212 mold, 15, 17 mole, 95, 244, 255 molecular biology, 37, 161 molecular forces, 204 molecular structure, 24, 184, 205 molecular weight, 56, 70, 166, 180, 181, 231 molecules, 3, 10, 19, 24, 25, 56, 88, 91, 104, 152, 174, 175, 211, 219, 238 molybdenum, 39 monolayer, 68, 93, 102, 103, 104 monomers, 25, 56, 70 monosaccharide, 12 monosaccharides, 166, 168 morphological, 199, 202, 206 morphology, 5, 16, 17, 20, 191, 200 mosaic, 3, 19 movement, 1, 186 MRA, 72, 73 MRI, 211, 212 MTs, 70, 71 multilayered structure, 12 mushrooms, 36 mutant, 167, 175, 181, 205 mutants, 38, 181 mycelium, 15, 16, 19, 210

N NA, 31, 32, 33, 34, 35 Na+, 26, 169, 170, 171, 172, 173, 219, 226, 227, 229, 230, 239, 245, 255, 265, 268 N-acety, 8, 10, 11, 12, 13, 17, 56, 168 NaCl, 227, 229 NAM, 8 nanocrystalline, 202 nanoparticles, 200, 201, 204

nanostructures, 197 Nanyang Technological University, viii, 123, 160, 235 natural, 30, 36, 74, 77, 78, 102, 132, 170, 179, 188, 204, 207 natural environment, 36 Nd, 48 negativity, 219, 220 network, 23, 56, 161, 264, 269 New Mexico, 72 New York, 28, 122, 123, 214, 216, 217, 234 Ni, 26, 34, 37, 38, 39, 42, 43, 45, 46, 49, 50, 51, 52, 53, 57, 58, 59, 60, 61, 62, 63, 74, 81, 100, 163, 166, 178, 183, 215, 221, 223, 224, 256, 265, 266, 275, 277, 278, 279 nickel, 39, 40, 43, 49, 53, 58, 59, 64, 76, 163, 165, 166, 178, 210, 239, 263, 266, 268, 277, 279, 281 nicotinic acid, 231 nitrate, 167, 210, 230, 240 nitrates, 211 nitric acid, 66 nitrogen, 3, 17, 26, 70, 181, 183, 197, 210, 212, 219, 239 NMR, 182, 183, 211, 212, 213 non-destructive, 66, 184, 207, 211, 213 nonequilibrium, 125, 152 non-invasive, 207, 211 nontoxic, 219, 239 normal, 8, 188, 242 normalization, 93, 209 normalization constant, 93 North America, 72 nuclear, 2, 4, 20, 199, 211 nuclear magnetic resonance, 211 nuclear material, 199 nucleation, 71, 175, 267 nuclei, 3, 16 nucleic acid, 213 nucleoli, 4 nucleolus, 20 nucleus, 1, 3, 4, 16, 17, 20, 36 nuclides, 37, 44 null hypothesis, 158 numerical tool, 115 nutrient, 23, 36, 219, 231, 263, 280 nutrient cycling, 36 nutrients, 3, 56, 191, 219, 232 nutrition, 16

O observations, 110, 157, 167, 169, 174, 179, 199, 201, 268, 275 oceans, 30, 57

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Index Ohio, 28 oil, 175 olive, 23, 49, 70 on-line, 38, 66, 184 optical, 211, 213 optimization, 77 ores, 49 organelles, 1, 3, 17, 19, 20, 180 organic, vii, 26, 27, 36, 38, 45, 48, 56, 63, 64, 66, 73, 126, 166, 176, 178, 179, 180, 188, 190, 210, 211, 212, 220, 223, 228, 238, 240, 270 organic chemicals, 240 organic compounds, 26, 27, 238 organic matter, 38, 45, 66, 176, 188, 210, 211 organic solvent, 63 organic solvents, 63 organism, 3, 6, 14, 37, 164, 168, 169, 179, 180 orientation, 69, 175, 199 oscillations, 207, 209 osmosis, 74, 75 osmotic, 2, 8 oxalate, 178 oxalic, 223 oxalic acid, 223 oxidation, 169, 179, 181, 207, 211, 241 oxide, 54, 188 oxides, 188 oxygen, 26, 183, 197, 209, 210, 219, 239, 258 oxyhydroxides, 176 ozone, 70 Copyright © 2009. Nova Science Publishers, Incorporated. All rights reserved.

P palladium, 197, 239 paramagnetic, 212 parameter, 225, 240, 242, 244, 247, 249, 258, 259 particles, 3, 56, 65, 69, 104, 178, 191, 196, 198, 199, 201, 207 partnership, 74, 76 passive, 161, 162, 230, 231, 280 patents, 72 pathogenesis, 175 pathogens, 36 pathways, 56 Pb, 26, 31, 32, 37, 39, 40, 41, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 55, 57, 58, 59, 60, 61, 62, 63, 72, 74, 100, 166, 170, 172, 173, 176, 193, 210, 221, 222, 224, 229, 255, 256, 258, 281 PCA, 210 PCR, 53 PCs, 70, 71 peat, 72, 73, 74, 212 pectin, 23, 56 penicillin, 44

289

peptide, 9, 10, 12, 71, 164, 182 peptide chain, 10 peptides, 70, 180 perchlorate, 225 permeability, 2, 213 permeation, 175, 200 peroxisomes, 5 pH, viii, 31, 32, 33, 34, 35, 38, 49, 54, 68, 69, 71, 72, 75, 120, 161, 166, 169, 170, 171, 172, 178, 188, 191, 199, 205, 206, 219, 220, 221, 222, 223, 224, 225, 226, 227, 228, 229, 237, 258, 277, 281, 282, 283 pH values, 72, 220, 222, 282 phagocytic, 56 phagocytosis, 1, 56 pharmaceutical, 37 pharmacology, 238 phenol, 64 phenolic, 167, 189 phosphate, 10, 12, 13, 64, 108, 162, 166, 167, 169, 176, 183, 185, 186, 187, 189, 198, 199, 205, 209, 210, 221, 230, 232, 238, 269 phosphates, 181, 190, 232 phospholipids, 2, 12, 19 phosphorous, 212 phosphorus, 3, 183, 209 phosphorylation, 59 photoelectron spectroscopy, 270 photosynthesis, 3, 20, 55, 56 photosynthetic, 21, 56 phycocyanin, 22 phycoerythrin, 22 physical force, 161 physical properties, 204 physical treatments, 63 physicochemical, 29, 169, 213 physiological, 205, 210 physiology, 28 pigments, 20, 56 planar, 3 plants, 1, 3, 23, 36, 37, 38, 56, 66, 70, 181, 212 plasma, 1, 2, 7, 9, 10, 12, 17, 19, 54, 182, 201 plasma membrane, 1, 2, 7, 9, 10, 12, 17, 19, 201 Plasmids, 5 plastics, 66 platelets, 196 play, 23, 26, 164, 166, 172, 174, 179, 188, 270 plums, 17 plutonium, 179 polarization, 208 pollutant, 75 pollutants, 29 pollution, 37, 71, 182

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290 polyacrylamide, 65, 72 polyethyleneimine, 72 polymer, 8, 11, 24, 25, 56, 70 polymerization, 70, 199 polymers, 9, 10, 12, 14, 23, 56, 164, 168, 175, 269 polypeptide, 14 polypeptides, 14 polyphosphates, 17 polysaccharide, 9, 12, 13, 14, 17, 23, 25, 30, 56, 161, 164, 166, 168, 175, 185, 187, 269, 270 polysaccharides, 14, 18, 23, 26, 36, 56, 57, 164, 165, 166, 167, 175, 182, 184, 185, 211, 213, 268, 269 polyurethane, 51, 65 polyurethane foam, 51 polyvinyl chloride, 66 poor, 59, 65, 73, 157 pores, 16, 20, 23, 56, 279 porosity, 65 porous, 8, 66, 72, 102 porous materials, 66 positive correlation, 110 potassium, 56, 169 powder, 63, 176, 182, 210, 266 power, 134, 152, 241, 242, 249, 253, 257, 258, 259 precipitation, vii, viii, 74, 75, 76, 108, 161, 164, 169, 176, 179, 191, 201, 220, 221, 227, 229, 258, 263, 266, 267, 280 prediction, 99, 106, 113, 114, 115, 116, 117, 121, 136, 147, 153, 155, 156, 157, 158, 159, 240, 244, 249, 258, 259 predictive model, 240, 244 preference, 52, 223, 230, 257 pressure, 65, 197 principal component analysis, 176, 210 pristine, 186, 187, 197, 200 probability, 158, 160, 244 probe, 183, 188, 202, 205, 207, 239, 240 producers, 36 production, 19, 36, 37, 38, 45, 72, 76, 166, 167, 264 progesterone, 49 program, 199, 209 prokaryotes, 1, 2, 6, 15, 70, 181 prokaryotic, 2, 3, 8, 164 propagation, 74, 219 property, 23, 39, 71, 182, 244, 245, 249, 258 proportionality, 163 protection, 2 protein, 2, 3, 4, 11, 14, 15, 19, 56, 70, 71, 168, 169, 174, 181, 186, 192, 207, 221, 232, 257, 269, 270 proteins, 3, 12, 17, 18, 19, 26, 57, 71, 164, 165, 166, 169, 180, 181, 183, 213, 269 protons, 188, 220, 222, 228 protoplasm, 19

Index protoplasts, 16 protozoa, 1, 56 pseudo, vii, 114, 115, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 140, 145, 148, 149, 153, 157, 162, 163, 164, 171, 242, 249, 258, 259 Pseudomonas, 31, 32, 33, 34, 35, 63, 164, 166, 167, 168, 176, 183, 184, 185, 186, 189, 190, 197, 199, 200, 224, 229 Pseudomonas aeruginosa, 31, 33, 63, 164, 166, 167, 183, 190, 229 public, 37 pulse, 183 P-value, 154, 155, 156, 158, 159 pyrophosphate, 230

Q QSAR, viii, 220, 237, 242, 259, 260 quantum, 238

R R&D, 75, 77 radial distribution, 209 radiation, 184, 208 radio, 37, 44 radionuclides, 39, 57, 161, 166, 229 radium, 39, 277 radius, 219, 220, 237, 239, 241, 242, 249, 253, 258, 259 random, 140 randomness, 106, 223 range, 1, 6, 31, 36, 37, 39, 49, 53, 54, 58, 63, 65, 68, 72, 73, 74, 75, 94, 101, 106, 130, 145, 151, 156, 157, 158, 159, 170, 172, 174, 184, 221, 223, 224, 228, 231, 240, 258, 269, 277, 281, 282 rare earth, 211 rationality, 151 raw material, 24, 30, 37, 38, 76 reactants, 114 reaction mechanism, 130, 140, 145, 149 reaction order, 128, 130, 138, 140, 141, 145, 146, 148, 151, 153, 156, 158, 159 reaction rate, 114, 126, 137, 146, 149 reaction time, 192 reactive sites, 176, 267 reactivity, 24, 188, 239 reading, 40 reagents, 64 real time, 204 reality, 191 receptors, 4 recombinant DNA, 36

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Index recovery, 36, 39, 59, 65, 66, 72, 73, 75, 76, 84, 231, 232, 266 recycling, 76 red light, 187 redox, 177, 178, 179, 220 Redox, 177 reducing sugars, 177, 182 reefs, 23 refining, 209 reflection, 184, 242, 267 regenerate, 65, 66 regeneration, 38, 66, 73, 74, 75, 76, 77, 225, 231, 264 regression, 112, 151, 188, 244, 246, 247, 250, 251, 252, 254 regular, 168, 264 regulation, 75, 179 rejection, 158 relationship, 2, 6, 105, 107, 112, 113, 136, 172, 212, 228, 238, 247, 249, 252, 254, 257, 258, 260 relationships, viii, 220, 238, 259 relative toxicity, 240 relaxation, 149, 212 reliability, 265 remediation, 181 reproduction, 16 residues, 17, 23, 70, 175, 183 resilience, 31 resin, 63, 72, 74, 75, 76, 199 resins, 65, 73, 76, 269 resistance, 53, 62, 65, 95, 97 resolution, 183, 184, 187, 197, 198, 199, 201, 204, 211, 272 retention, 164, 168, 175 reticulum, 17, 19 revenue, 37 reverse reactions, 128, 130 RF, 211 Rhizobium, 164, 167, 230 Rhodophyta, 22, 23, 56, 57 ribonucleic acid, 3 ribose, 166, 168 ribosomes, 3, 6, 19 rigidity, 56, 65 RNA, 3 robustness, 74, 264, 265 rods, 6, 23, 196 room temperature, 199, 225

S Saccharomyces cerevisiae, 17, 36, 37, 54, 170, 179, 190, 191, 221, 237, 240 salinity, 225

291

Salmonella, 13 salt, 15, 23, 227 salts, 56, 229, 241 sample, 40, 184, 186, 197, 199, 201, 204, 208, 210, 211, 212, 266 sand, 66 SAR, 237, 240 saturation, 102, 103, 104, 163, 176, 267 sawdust, 52 Scanning electron, 190, 197 scanning electron microscopy, 182, 191, 197, 227 scatter, 207 scattering, 199, 211 scientific community, 57 SCMs, 188 search, 30, 57, 77 searching, 30 seawater, 73, 225 seaweed, 30, 76, 185, 186, 196, 199, 211 secret, 37 sediment, 207 sedimentation, 53 seed, 188 selecting, 264 selectivity, 30, 59, 61, 62, 70, 71, 73, 74, 75, 78, 229, 230 selenium, 39, 183 SEM, 162, 179, 182, 190, 191, 192, 193, 194, 196, 197, 205, 227, 237, 277, 278, 279, 280, 281 semi-permeable membrane, 19 sensitivity, 38, 70, 167, 180, 181, 184, 199, 211 separation, 38, 65, 239, 264, 265 septum, 16 sequestration proteins, 180 series, 53, 72, 168, 177, 198, 211, 230, 270 sewage, 70, 232 sexual reproduction, 16 SH, 26, 70, 174, 181, 219, 239, 257 shape, 5, 6, 8, 17, 24, 176, 191, 263 shock, 264 short supply, 179 shoulder, 269, 270 signals, 211, 275 significance level, 258 silica, 21, 56, 65, 72 silver, 36, 39, 182, 200, 201, 202, 204, 232, 239, 257 simulation, 90, 109, 115, 153, 157, 158, 159 simulations, 114 sine, 209 sine wave, 209 Singapore, viii, 123, 160, 235 sites, 10, 12, 19, 63, 64, 68, 70, 87, 88, 89, 94, 95, 107, 108, 111, 112, 127, 130, 131, 133, 134, 146,

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292 149, 150, 151, 163, 166, 167, 170, 175, 176, 177, 183, 184, 188, 189, 196, 211, 220, 222, 224, 225, 226, 228, 229, 230, 232, 238, 244, 267, 269, 270, 279, 280, 282 skeleton, 24 sludge, vii, 49, 53, 54, 70, 75, 142, 143, 147, 164, 166, 167, 189, 232, 263, 266 SO2, 167 sodium, 56, 64, 65, 73, 163, 166, 169, 225, 227 sodium hydroxide, 64 software, 132, 135, 201, 226, 227, 244 soil, 20, 21, 45, 166, 176, 207, 267 sol-gel, 41, 256 solid phase, 164 solid surfaces, 87 solubility, 179, 220, 222, 257 solvent, 93, 108, 242 sorbents, 63, 68, 71, 188 sorption, viii, 31, 40, 43, 45, 53, 54, 55, 57, 59, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 74, 77, 87, 94, 104, 118, 119, 126, 130, 134, 161, 163, 164, 165, 167, 168, 171, 172, 175, 176, 183, 184, 186, 188, 220, 221, 222, 223, 225, 227, 229, 230, 231, 238, 241, 258, 267, 268, 270, 275, 280 sorption kinetics, 69, 163 sorption process, 74, 130, 134, 163, 220 spatial, 26, 211 speciation, 220, 223, 240 species, 11, 16, 17, 19, 31, 32, 33, 34, 35, 36, 39, 44, 45, 52, 58, 59, 61, 63, 69, 78, 103, 120, 163, 172, 179, 180, 190, 191, 199, 210, 219, 222, 223, 228, 229, 230, 240, 272, 275 specific adsorption, 167, 230 specific surface, 38 specificity, 12, 75 spectra analysis, 182 spectrophotometry, 175 spectroscopy, 168, 176, 182, 183, 184, 205, 207, 210, 211 spectrum, 115, 182, 184, 186, 189, 197, 200, 202, 207, 208, 209, 263, 266, 277, 278, 279, 280, 281 spin, 183 spirillum, 5 sponges, 66 spontaneity, 105, 223 spore, 15, 16, 19, 49 SPSS, 201 stability, 75, 228, 230, 242, 264 stabilization, 164 stabilize, 3 stages, 53, 162, 163 standard error, 244 standards, 74

Index Staphylococcus, 33, 34 starch, 20, 22, 23, 56 starvation, 232 statistical analysis, 59 statistical mechanics, 93 statistics, 160, 244, 259 steric, 176 sterilization, 64 sterols, 3, 4, 5, 19 stoichiometry, 40, 71, 130 storage, 3, 19, 20, 23, 70, 168, 181 strain, 38, 42, 164, 167, 169, 175, 178, 181, 205, 232, 245, 270 strains, 30, 36, 38, 44, 58, 62, 71, 167, 178, 212, 228, 232 strategies, 180, 181 streams, viii, 73, 76, 265 strength, viii, 8, 24, 65, 68, 69, 206, 219, 225, 226, 227, 228, 229, 242, 257, 259 streptococci, 11 Streptomyces, 31, 32, 33, 34, 54 stretching, 184, 185, 186, 212, 269, 270 stroma, 20 strong interaction, 24, 186, 223 structural changes, 224 sub-cellular, 180 substances, vii, 8, 23, 36, 56, 70, 164, 166, 167, 168, 179, 181, 191, 207, 216, 265 substitution, 98, 135 substrates, 263 sugar, 8, 17, 170, 230, 238, 245, 255 sugar beet, 230, 238, 245, 255 sugars, 10, 166, 168, 177, 182 sulfate, 25, 73, 165, 167, 175, 189, 211, 221, 232 sulfur, 3, 26, 212, 219, 239, 257 sulphate, 164, 166, 167, 230, 269 sulphur, 70, 162, 181, 233, 269 Sun, 160, 284 supernatant, 192 superoxide, 180 superoxide dismutase, 180 supply, 1, 10, 37, 76, 219 surface area, 64, 232 surface component, 191 surface layer, 15, 193 surface structure, 3, 26 surfactant, 222 surviving, 232 swelling, 65 symmetry, 15 synchronous, 211 synchrotron, 176, 211 synergistic, 229

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

Index synthesis, 3, 20, 73, 167, 168, 232, 265, 266 systems, 1, 43, 53, 55, 57, 59, 62, 65, 67, 68, 69, 73, 75, 76, 151, 163, 164, 170, 172, 179, 180, 213, 229, 230, 255

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

T taxonomic, 57 technetium, 222 technology, vii, viii, 36, 66, 70, 71, 72, 74, 75, 77, 108, 162, 177, 182, 264, 265, 283 TEM, 162, 167, 182, 183, 193, 198, 199, 201, 203, 205, 233, 237 temperature, viii, 40, 68, 75, 93, 105, 106, 107, 108, 114, 118, 199, 219, 223, 224, 225, 237 temporal, 211 Texas, 28 thawing, 63 thermodynamic, 87, 96, 98, 100, 105, 106, 219, 223, 239 thermodynamic equilibrium, 98, 105 thermodynamic parameters, 100, 223 thermodynamics, vii, 87, 105, 118 thorium, 178 three-dimensional, 10, 204, 207, 213 threshold, 158, 208 time, 35, 36, 37, 40, 69, 89, 94, 96, 108, 126, 127, 131, 133, 134, 135, 137, 146, 149, 150, 151, 162, 168, 183, 186, 191, 211, 212, 231 TIR, 184 tissue, 207 titration, 167, 182, 183, 188, 189 tolerance, 70, 73, 181, 182, 231, 264 topsoil, 176 toxic, 8, 26, 36, 38, 39, 49, 53, 57, 70, 72, 75, 161, 168, 180, 181, 188, 200, 210, 219, 222, 238, 239, 267 toxic effect, 238 toxic metals, 36, 38, 39, 70, 161, 181, 210 toxic substances, 8 toxicity, viii, 39, 180, 219, 220, 237, 238, 239, 240, 242, 245, 247, 255, 258, 259, 264 toxicological, 29 toxicology, 237, 238, 239 trace elements, 231, 265 traits, 169 transcriptional, 179 transfer, 4, 70, 112, 161, 163, 180, 191 transformation, 49, 135, 137, 138, 207 transition metal, 238 translation, 3 transmembrane, 71 transmission, 183, 184, 199, 201, 208 transmission electron microscopy, 183

293

Transmission Electron Microscopy (TEM), 167, 182, 183 transnational, 74 transparency, 211 transport, 19, 110, 131, 161, 163, 179, 180, 223 transportation, 179 trial, 70 tubular, 20, 23 turgor, 175 two-dimensional, 15, 104

U uncertainty, vii, 141, 145 uniform, 16, 65, 197, 208, 279 United States, 49 universal gas constant, 93 uranium, 39, 43, 45, 53, 73, 179, 221, 229, 231, 232, 239, 281

V vacuole, 38, 180, 181, 231 vacuum, 63 valence, 211, 219, 237, 240, 241, 242, 253, 256, 259, 275 validity, 158 values, 58, 59, 62, 64, 66, 68, 72, 108, 109, 111, 131, 145, 150, 151, 153, 156, 157, 158, 159, 163, 171, 188, 189, 190, 220, 222, 223, 225, 226, 227, 228, 232, 241, 242, 244, 245, 249, 256, 257, 258, 259, 282 van der Waals forces, 174, 281 vapor, 197 variability, 188, 222, 226, 227 variables, 241, 242, 244, 245, 247 variance, 153, 156, 157 variation, 23, 73, 169, 223, 245, 253 vector, 208, 209 velocity, viii, 265 versatility, 73, 74 vibration, 187, 269 Visa, 72 visible, 198 vitamins, 36

W waste treatment, 49 waste water, 76, 77 wastes, 29, 74, 76, 187, 264 wastewater, viii, 36, 49, 72, 73, 165, 168, 225, 229, 263, 264, 265, 283 water, 14, 23, 56, 72, 74, 164, 166, 191, 196, 199, 201, 258, 265

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest

294

Index

water vapor, 196 wave number, 270 waxes, 17 welding, 23 wheat, 49, 51 wild type, 38, 181, 205 wood, 36, 66, 264 workers, 188, 240

168, 170, 174, 177, 178, 179, 180, 181, 182, 186, 188, 191, 192, 205, 211, 220, 221, 222, 223, 224, 225, 226, 227, 229, 230, 231, 232, 233, 239, 241, 244, 255, 256, 257, 258 Yeasts, 15, 16, 37 yield, 188, 208 yttrium, 239

Z X

XANES, 207 XPS, 177, 178, 182, 211, 266, 272, 274, 275, 276 X-ray absorption, 176, 183, 207, 209, 210 X-ray analysis, 227 X-ray diffraction (XRD), 183, 167, 176, X-ray photoelectron spectroscopy (XPS), 211 XRD, 177, 182, 183, 186, 265, 266, 267

Y

zeolites, 126, 132 zeta potential, 282 zinc, 39, 40, 49, 53, 58, 59, 62, 72, 76, 110, 120, 165, 167, 170, 171, 172, 180, 186, 187, 191, 192, 231, 232, 268, 281 Zinc, 171, 186, 192 Zn, 26, 32, 37, 38, 39, 40, 41, 43, 44, 45, 46, 47, 48, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 62, 70, 72, 73, 167, 170, 172, 173, 176, 177, 181, 183, 186, 192, 221, 229, 256, 265

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yeast, vii, 1, 3, 16, 17, 19, 29, 30, 36, 37, 38, 39, 40, 41, 42, 43, 44, 53, 55, 63, 64, 70, 71, 72, 163,

Fundamentals and Applications of Biosorption Isotherms, Kinetics and Thermodynamics, Nova Science Publishers, Incorporated, 2009. ProQuest