Chemical Sciences for the New Decade: Volume 1 Organic and Natural Product Synthesis 9783110752601, 9783110752533

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Ponnadurai Ramasami (Ed.) Chemical Sciences for the New Decade

Also of interest Chemical Sciences for the New Decade Volume : Biochemical and Environmental Applications Ponnadurai Ramasami (Ed.),  ISBN ----, e-ISBN ----

Chemical Sciences for the New Decade Volume : Computational, Education, and Materials Science Aspects Ponnadurai Ramasami (Ed.),  ISBN ----, e-ISBN ----

Chemical Sciences in the Focus Volume : Pharmaceutical Applications Ponnadurai Ramasami (Ed.),  ISBN ----, e-ISBN ----

Chemical Sciences in the Focus Volume : Green and Sustainable Processing Ponnadurai Ramasami (Ed.),  ISBN ----, e-ISBN ----

Chemical Sciences in the Focus Volume : Theoretical and Computational Chemistry Aspects Ponnadurai Ramasami (Ed.),  ISBN ----, e-ISBN ----

Physical Sciences Reviews e-ISSN -X

Chemical Sciences for the New Decade Volume 1: Organic and Natural Product Synthesis Edited by Ponnadurai Ramasami

Editor Prof. Dr. Ponnadurai Ramasami Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit 80837, Mauritius E-mail: [email protected]

ISBN 978-3-11-075253-3 e-ISBN (PDF) 978-3-11-075260-1 e-ISBN (EPUB) 978-3-11-075263-2 Library of Congress Control Number: 2022940996 Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the internet at http://dnb.dnb.de. © 2022 Walter de Gruyter GmbH, Berlin/Boston Cover image: sorbetto/DigitalVision Vectors/Getty Images Typesetting: TNQ Technologies Pvt. Ltd. Printing and binding: CPI books GmbH, Leck www.degruyter.com

A virtual conference on chemistry and its applications (VCCA-2021) was organized online from 9th to 13th August 2021. A virtual conference on chemistry and its applications (VCCA-2021) was organized online from 9th to 13th August 2021. The theme of the virtual conference was “Chemical Sciences for the New Decade”. There were 197 presentations for the virtual conference with 400 participants from 53 countries. A secured platform was used for virtual interactions of the participants. After the virtual conference, there was a call for full papers to be considered for publication in the conference proceedings. Manuscripts were received and they were processed and reviewed as per the policy of De Gruyter. This book, volume 1, is a collection of the thirteen accepted manuscripts within the fields of organic and natural product synthesis. Apollo and Aoyi carried out anaerobic digestion in a fluidised bed reactor and defined its operation using various kinetic models in order to determine the suitable reactor operating conditions. Oyeyiola and Adeosun evaluated the soil sodicity ameliorative effects of biochar types prepared from poultry manure co-pyrolyzed with or without urea on soil organic carbon and selected soil chemical characteristics of a simulated sodic soil. Maundu et al. determined the effects of alum, soda, and dissolved carbon dioxide on 40–50 year old concrete tanks used in a wastewater treatment plant. Apollo reviewed the sludge production in South Africa municipal wastewater treatment plants and analysed the handling cost and the potential minimization methods. Nnodum and co-workers determined the heavy metal concentrations in the sediment of Okeafa canal, Lagos, Nigeria. They found that the average concentration of each metal appears to be within the permissible level by World Health Organisation. Mensah et al. reported on the simultaneous remediation of polyaromatic hydrocarbon and heavy metals by zerovalent iron titanium oxide. Momeni and co-workers investigated on the antioxidant and antibacterial activities of two xanthones derivatives isolated from the leaves extract of Anthocleista schweinfurthii Gilg (Loganiaceae). The research of Chan Sun et al. was focussed to determine the prevalence of Metabolic Syndrome among the employees of a public educational institution in Mauritius. Suhartati et al. carried out cytotoxicity test and antibacterial assay on the compound produced by the isolation and modification of artonin E from Artocarpus kemando Miq. Noviany and co-workers studied the antibacterial, antioxidant and cytotoxic activities of the stem bark of archidendron jiringa (Jack) I.C. Nielsen. Noviany and co-workers reviewed the studied conducted, including the isolation and screening of biological activity of purified compounds from Fabaceae plant. Nedyalkova et al. developed a questionnaire for carrying out a survey on diabetes mellitus type 2 risk effects and precondition factors

https://doi.org/10.1515/9783110752601-201

VI

Preface

and they also carried out a multivariate statistical data analysis. Garcia Rodriguez et al. synthesized the fusion protein SARS-CoV-2 S protein (RBD)-hFc by linking the receptorbinding domain of the SARS-CoV-2 virus and the crystallizable fragment of a human immunoglobulin and characterization was performed using size exclusion liquid chromatography. I hope that these chapters of this volume 1 will add to literature and they will be useful references for researchers. To conclude, VCCA-2021 was a successful event and I would like to thank all those who have contributed. I would also like to thank the Organising and International Advisory committee members, the participants and the reviewers. Prof. Ponnadurai Ramasami Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit 80837, Mauritius E-mail: [email protected]

Contents Preface V List of contributing authors

XIII

Seth Apollo and Ochieng Aoyi 1 Performance and kinetics of a fluidized bed anaerobic reactor treating 1 distillery effluent 1 1.1 Introduction 2 1.2 Methodology 2 1.2.1 Experimental set up 3 1.2.2 Start-up and operation of the bioreactor 3 1.2.3 Experimental analysis 4 1.3 Results and discussion 4 1.3.1 TOC and color removal efficiency 4 1.3.2 Substrate balance model 6 1.3.3 Biorecalcitrant component of distillery effluent 7 1.3.4 Substrate utilization kinetics 8 1.3.5 Michaelis–Menten kinetic model 9 1.3.6 The mean cell residence time 10 1.3.7 MCRT and HRT 11 1.4 Conclusions 12 References Yetunde Bunmi Oyeyiola and Christianah Iyanuoluwa Adeosun 2 Sustainability of ameliorative potentials of urea spiked poultry manure 15 biochar types in simulated sodic soils 15 2.1 Introduction 17 2.2 Materials and methods 17 2.2.1 Soil sampling, preparation and routine analysis 18 2.2.2 Soil sodicity simulation 2.2.3 Preparation of the poultry manure biochar co-pyrolyzed with or without 18 urea 18 2.2.4 Treatments, experimental design and set up 18 2.2.5 Data collection 19 2.3 Results 2.3.1 Effects of poultry manure biochar amendments on pH of a simulated sodic 19 soil 2.3.2 Effects of poultry manure biochar amendments on exchangeable Ca, Mg 20 and K in a simulated sodic soil

VIII

2.3.3 2.3.4 2.3.5 2.3.6 2.3.7

2.4 2.5

Contents

Effects of poultry manure biochar amendments on exchangeable Na and 20 sodium percentage (ESP) in a simulated sodic soil Effects of poultry manure biochar amendments on soil organic carbon in a 21 simulated sodic soil Effects of poultry manure biochar amendments on soil available 21 phosphorus in a simulated sodic soil Effects of poultry manure biochar on dry biomass weight of cowpea 23 seedlings in a simulated sodic soil Regression model for the contributions of reduced soil pH following biochar amendment on selected soil properties in a simulated sodic 23 soil 24 Discussion 25 Conclusions 26 References

Mutua Maundu, Linda Ouma and Francis Maingi 3 Effects of alum, soda ash, and carbon dioxide on 40–50 year old concrete 29 wastewater tanks 29 3.1 Introduction 31 3.2 Experimental 31 3.3 Results and discussions 33 3.3.1 Iron (Fe3+) concentration 33 3.3.2 Aluminium concentration 34 3.3.3 Sulphate ion concentrations in the samples 35 3.3.4 Effect of carbonation on concrete tanks 36 3.4 Conclusions 36 References Seth Apollo 4 A review of sludge production in South Africa municipal wastewater treatment plants, analysis of handling cost and potential minimization 39 methods 39 4.1 Introduction 40 4.1.1 Municipal wastewater generation in South Africa 41 4.1.2 Municipal wastewater treatment 42 4.2 Sludge management 42 4.2.1 Estimated sludge quantity and handling cost for WWTPs 43 4.2.2 Sludge disposal 44 4.2.3 Land application and Environmental impact of sewage sludge 44 4.3 Sludge minimization technologies in WWTPs 4.3.1 Chemical, mechanical, thermal and electrical methods of sludge 45 reduction

Contents

4.3.2 4.4

Integrated biological methods for WAS minimization 47 Conclusions 47 References

IX

46

Chima F. Nnodum, Kafeelah A. Yusuf and Adedoja D. Wusu 5 A comparison of two digestion methods and heavy metals determination in 51 sediments 51 5.1 Introduction 53 5.2 Materials and methods 53 5.2.1 Sampling and pre-treatment 54 5.2.2 Determination of pH, conductivity, and total organic matter 54 5.2.3 Conductivity 54 5.2.4 Organic matter 54 5.2.5 Digestion procedures 55 5.2.6 Digestion method 1 (HCl and Nitric acid) 5.2.7 Method 2 EPA method 3052 (Hydrofluoric acid – Nitric acid, Hydrochloric 55 acid, Hydrogen peroxide) 55 5.2.8 Analysis of metals using Atomic absorption spectrophotometer 55 5.3 Results and discussions 67 5.4 Conclusions 67 References Peter Mensah, Temitope Osobamiro and Ponnadurai Ramasami 6 Simultaneous remediation of polycyclic aromatic hydrocarbon and heavy metals in wastewater with zerovalent iron-titanium oxide nanoparticles 71 (ZVI-TiO2) 72 6.1 Introduction 72 6.2 Materials and methods 72 6.2.1 Study area 73 6.2.2 Collection of samples 73 6.2.3 Production of zerovalent iron (ZVI) 73 6.2.4 Production of titanium oxide nanoparticles (TiO2-NPs) 73 6.2.5 Production of zerovalent iron-titanium oxide nanoparticles (ZVI-TiO2) 73 6.2.6 Adsorption process 74 6.3 Results and discussion 74 6.3.1 Percentage yield 75 6.3.2 Characterization of ZVI-TiO2 NPs 76 6.3.3 Adsorption study 78 6.4 Conclusions 78 References

X

Contents

Francine Tsopjio Nkouam, Jean Momeni, Epse Abdourahman Fadimatou, Gaye Monde, Jean Paul Tsopmejio, Serge Raoul Tchamango and Martin Benoît Ngassoum 7 Antioxidant and antibacterial activities of two xanthones derivatives isolated from the leaves extract of Anthocleista schweinfurthii Gilg 81 (Loganiaceae) 82 7.1 Introduction 83 7.2 Material and methods 83 7.2.1 Chemical reagents and equipment 83 7.2.2 Bacterial strains 83 7.2.3 Plant material 7.2.4 Extraction and isolation of secondary metabolites swertiaperenin (1) and 83 decussatin (2) 84 7.2.5 Evaluation of antioxidant activities 85 7.2.6 Antibacterial activity 85 7.2.7 Data analysis 85 7.3 Results and discussion 85 7.3.1 Identification 88 7.3.2 Antioxidant activity 90 7.3.3 Antimicrobial activity 90 7.4 Conclusions 91 References Marie Chan Sun, Marie A. S. Landinaff and Ruben Thoplan 8 Use of biochemical markers for diabetes prevention in the new decade 94 8.1 Introduction 94 8.2 Methods 95 8.3 Results 96 8.3.1 Logistic regression analysis 98 8.4 Discussion 98 8.4.1 Socio-demographic characteristics 99 8.4.2 Family and personal history 99 8.4.3 Lifestyle pattern 100 8.4.4 Strength and limitation 100 8.4.5 Recommendations 101 8.5 Conclusions 101 References

93

Tati Suhartati, Vicka Andini, Ilham Ramadhan, Yandri Yandri and Sutopo Hadi 9 Cytotoxicity test and antibacterial assay on the compound produced by the isolation and modification of artonin E from Artocarpus kemando 105 Miq. 105 9.1 Introduction 107 9.2 Materials and methods

Contents

9.2.1 9.2.2 9.2.3 9.2.4 9.3 9.3.1 9.3.2 9.3.3 9.3.4 9.3.5 9.3.6 9.3.7 9.4

Instrumentations and tools 107 108 Materials 108 Isolation Modifications of compound (1) using diazomethane 109 Results and discussion 109 UV–Vis spectroscopy analysis 110 IR Spectroscopy analysis Characterization of modified artonin E, compound 2 116 Bioactivity 118 Anticancer Activity Test 119 Data Analysis 119 Antibacterial activity test 120 Conclusions 121 References

XI

108

113

Noviany Noviany, Uswatun Hasanah, Puspa Dewi Lotulung and Sutopo Hadi 10 Antibacterial, antioxidant and cytotoxic activities of the stem bark of 123 Archidendron jiringa ( Jack) I.C. Nielsen 123 10.1 Introduction 124 10.2 Experimental 124 10.2.1 Plant Materials 125 10.2.2 Extraction 125 10.2.3 Antibacterial Assay 125 10.2.4 Antioxidant Assay 125 10.2.5 Cytotoxicity screening 125 10.3 Results and discussion 126 10.3.1 Antibacterial activity 129 10.3.2 Antioxidant activity 129 10.3.3 Toxicity activity 132 10.4 Conclusions 132 References Noviany Noviany, Sutopo Hadi, Risa Nofiani, Puspa Dewi Lotulung, and Hasnah Osman 135 11 Fabaceae: a significant flavonoid source for plant and human health 135 11.1 Introduction 136 11.2 Biosynthesis of Fabaceae flavonoids 140 11.3 Biological activities of Fabaceae compounds 142 11.4 Nutraceutical functions of Fabaceae compounds 143 11.5 Conclusions 144 References

XII

Contents

Miroslava Nedyalkova, Julia Romanova, Ludmila Naneva and Vasil Simeonov 12 Developing a questionnaire for diabetes mellitus type 2 risk effects and 147 precondition factors – multivariate statistical paths 147 12.1 Introduction 149 12.2 Materials and methods 150 12.2.1 Cluster analysis 150 12.2.2 Principal components analysis (PCA) 150 12.2.3 Questionnaire structure 151 12.3 Results and discussion 151 12.3.1 Hierarchical clustering of the variables 152 12.3.2 K-means clustering (nonhierarchical clustering) of patients 154 12.3.3 Principal components analysis 157 12.4 Conclusions 158 References Laura García, Ingrid Ruíz and José A. Gómez 13 Chromatographic characterization of the fusion protein SARS-CoV-2 S 161 protein (RBD)-hFc 161 13.1 Introduction 162 13.2 Material and methods 13.2.1 Sodium dodecyl sulfate polyacrylamide gel electrophoresis 162 (SDS-PAGE) 162 13.2.2 Western Blot 163 13.2.3 Size exclusion chromatography (SEC) 163 13.2.4 Isoelectric focusing (IEF) 163 13.3 Results and discussion 163 13.3.1 Determination of the molecular weight 164 13.3.2 Establishment of the isoelectric point by IEF 165 13.3.3 Evaluation of the molecular integrity 166 13.3.4 Molecular integrity by SDS-PAGE 168 13.3.5 Molecular integrity by SEC-HPLC 170 13.4 Conclusions 171 References Index

173

List of contributing authors Christianah Iyanuoluwa Adeosun Department of Crop Production and Soil Science Ladoke Akintola University of Technology Ogbomoso Nigeria Vicka Andini Department of Chemistry Universitas Lampung Bandar Lampung 35145 Indonesia Ochieng Aoyi Botswana International University of Science and Technology Private Bag 16 Palapye Botswana Seth Apollo Department of Physical Sciences University of Embu P.O. Box 6-60100 Embu Kenya and Department of Chemical Engineering Vaal University of Technology Private Bag X021 Vanderbijlpark South Africa E-mail: [email protected] Epse Abdourahman Fadimatou Department of Chemistry Faculty of Science University of Ngaoundere P.O. Box 454 Ngaoundere Cameroon and Department of Chemistry Higher Teacher Training College University of Maroua P.O 55 Maroua Cameroon

https://doi.org/10.1515/9783110752601-202

Laura García Faculty of Chemistry University of Havana 10400, Havana Cuba E-mail: [email protected] José A. Gómez R&D Quality Control Department Center of Molecular Immunology 11300 Havana Cuba E-mail: [email protected] Sutopo Hadi Department of Chemistry Universitas Lampung Bandar Lampung 35145 Indonesia E-mail: [email protected] Uswatun Hasanah Department of Chemistry Faculty of Mathematics and Natural Sciences University of Lampung Lampung 35145 Indonesia Marie A. S. Landinaff Department of Medicine University of Mauritius Reduit Mauritius E-mail: [email protected] Puspa Dewi Lotulung Research Center for Chemistry – BRIN Indonesian Institute of Sciences South Tangerang 15314 Indonesia

XIV

List of contributing authors

Francis Maingi Department of Science Technology and Engineering Kibabii University P. O. Box 1699 Bungoma 50200 Kenya E-mail: [email protected] Mutua Maundu Department of Science Technology and Engineering Kibabii University P. O. Box 1699 Bungoma 50200 Kenya Peter Mensah Department of Chemical Sciences Faculty of Science Olabisi Onabanjo University Ago Iwoye Ogun State Nigeria E-mail: [email protected] Jean Momeni Department of Chemistry Faculty of Science University of Ngaoundere P.O. Box 454 Ngaoundere Cameroon E-mail: [email protected] Gaye Monde Department of Chemistry Faculty of Science University of Ngaoundere P.O. Box 454 Ngaoundere Cameroon Ludmila Naneva Faculty of Chemistry and Pharmacy University of Sofia “St. Kl. Okhridski” J. Bourchier Blvd. 1 1164, Sofia Bulgaria E-mail: [email protected]

Miroslava Nedyalkova Department of Chemistry University of Fribourg Chemin du Musée 9 1700 Fribourg Switzerland and Faculty of Chemistry and Pharmacy University of Sofia “St. Kl. Okhridski” J. Bourchier Blvd. 1 1164, Sofia Bulgaria E-mail: [email protected] Martin Benoît Ngassoum National Advanced School of Agro-Industrial Sciences University of Ngaoundere P.O. Box 455 Ngaoundere Cameroon Francine Tsopjio Nkouam Department of Chemistry Faculty of Science and National Advanced School of Agro-Industrial Sciences University of Ngaoundere P.O. Box 454/455 Ngaoundere Cameroon Chima F. Nnodum Department of Chemistry Lagos State University Ojo Nigeria E-mail: [email protected] Risa Nofiani Department of Chemistry University of Tanjungpura Pontianak Indonesia

List of contributing authors

Noviany Noviany Department of Chemistry Faculty of Mathematics and Natural Sciences University of Lampung Lampung 35145 Indonesia E-mail: [email protected] Hasnah Osman School of Chemical Sciences Universtiti Sains Malaysia George Town Malaysia Temitope Osobamiro Department of Chemical Sciences Faculty of Science Olabisi Onabanjo University Ago Iwoye Ogun State Nigeria Linda Ouma Department of Science Technology and Engineering Kibabii University P. O. Box 1699 Bungoma 50200 Kenya

Ingrid Ruíz R&D Quality Control Department Center of Molecular Immunology 11300 Havana Cuba E-mail: [email protected] Vasil Simeonov Faculty of Chemistry and Pharmacy University of Sofia “St. Kl. Okhridski” J. Bourchier Blvd. 1 1164, Sofia Bulgaria E-mail: [email protected]fia.bg Tati Suhartati Department of Chemistry Universitas Lampung Bandar Lampung 35145 Indonesia E-mail: [email protected] Marie Chan Sun Department of Medicine University of Mauritius Reduit Mauritius E-mail: [email protected]

Yetunde Bunmi Oyeyiola Department of Crop Production and Soil Science Ladoke Akintola University of Technology Ogbomoso Nigeria E-mail: [email protected]

Serge Raoul Tchamango Department of Chemistry Faculty of Science University of Ngaoundere P.O. Box 454 Ngaoundere Cameroon

Ilham Ramadhan Department of Chemistry Universitas Lampung Bandar Lampung 35145 Indonesia

Ruben Thoplan Department of Economics and Statistics University of Mauritius Reduit Mauritius E-mail: [email protected]

Julia Romanova Faculty of Chemistry and Pharmacy University of Sofia “St. Kl. Okhridski” J. Bourchier Blvd. 1 1164, Sofia Bulgaria E-mail: [email protected]fia.bg

Jean Paul Tsopmejio Department of Organic Chemistry Faculty of Science University of Yaounde 1 P.O. Box 812 Yaounde Cameroon

XV

XVI

List of contributing authors

Adedoja D. Wusu Department of Biochemistry Lagos State University Ojo Nigeria Yandri Yandri Department of Chemistry Universitas Lampung Bandar Lampung 35145 Indonesia

Kafeelah A. Yusuf Department of Chemistry Lagos State University Ojo Nigeria

Seth Apollo* and Ochieng Aoyi

1 Performance and kinetics of a fluidized bed anaerobic reactor treating distillery effluent Abstract: The kinetic analysis of an anaerobic fluidized bed bioreactor treating distillery effluent was carried out. Natural zeolite was used as biomass carrier at various organic loading rates and hydraulic retention times (HRT). The degradation followed first order kinetics and fitted Michaelis–Menten kinetic model for substrate utilization. The kinetic analysis showed that 9% of the TOC was nonbiodegradable which corresponds to about 14% COD. The non-biodegradable component was responsible for the dark-brown color of the distillery effluent and therefore there was a need for employing a post-treatment technology for their removal. Biomass yield was found to be 0.4658 g/g while endogenic microorganisms decay coefficient was 0.0293, which suggested that there was a need to install a sludge handling unit prior to posttreatment. The maximum micro-organisms’ growth rate was found to be 0.136 d−1 while the specific growth rate of the micro-organisms reduced with an increase in HRT at constant feed concentration. The specific substrate utilization rate was found to increase linearly with an increase in the ration of food to micro-organisms and the mean cell residence time was found to be at least 2.5 times the HRT due to application of zeolite as microbial support in the reactor. Keywords: biorecalcitrant; distillery wastewater; fluidisedbed reactor; kinetics.

1.1 Introduction Distillery wastewater is among the most polluting industrial wastewater with COD of between 60,000 mg/l to 120,000 mg/l [1, 2]. Anaerobic digestion is widely applied in the organic load removal and bioenergy recovery from distillery wastewater [3, 4]. Robust anaerobic digesters such as fluidized bed reactors achieve high organic removal efficiency and good energy recovery in terms of biomethane due to efficient mixing in the reactor [5]. Bioconversion of organic matter into biomethane is a complex process

*Corresponding author: Seth Apollo, Department of Physical Sciences, University of Embu, P.O. Box 660100, Embu, Kenya; and Department of Chemical Engineering, Vaal University of Technology, Private Bag X021, Vanderbijlpark, South Africa, E-mail: [email protected]. https://orcid.org/0000-00033296-697X Ochieng Aoyi, Botswana International University of Science and Technology, Private Bag 16, Palapye, Botswana As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: S. Apollo and O. Aoyi “Performance and kinetics of a fluidized bed anaerobic reactor treating distillery effluent” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0142 | https://doi.org/10.1515/9783110752601-001

2

1 Performance of fluidized bed reactor

involving consortia of microorganisms. Due to the complex nature of the process, a poorly operated digester is often prone to inhibition due to accumulation of volatile fatty acids which may lead to total digester failure [6]. During the anaerobic digestion, the operating parameters such as organic loading rate (OLR), hydraulic retention time (HRT), pH and food to microorganisms ratio need to be well regulated to avoid a possible digester failure. This is due to the fact that these parameters directly affect the micro-organisms’ activity in the digester. In this regard, a lot of research work has been done to improve the performance of fluidized bed reactors in the treatment of distillery effluent. One of the improvements which has been made is the application of appropriate biomass support material with a large surface area such as zeolite or activated carbon [7]. These support materials have the advantage in that they have a high capacity to carry micro-organisms, thereby increasing the contact between the pollutants and the microbes leading to an increased reaction rate [8]. Also, the effect of superficial liquid velocity has been studied as this affects both mixing [9] and microbial growth [10]. For instance, operating a fluidized bed reactor at an excessively high superficial liquid velocity results in dislodging of the microbes attached onto the carrier resulting in reduced efficiency, while operating at very low velocities hinders adequate mixing [10, 11] It is therefore important to obtain important information regarding the state of the reactor during anaerobic digestion to avoid impending reactor failure due to poor operation. Kinetic modelling is an acceptable approach in determining the condition in the bioreactor based on substrate utilization and microbial growth [12]. The result of kinetic modelling can be used to determine suitable system parameters which lead to stability and therefore high efficiency of the reactor. Moreover, the results obtained from the kinetic modelling can be used to design an industrial-scale reactor operating under similar conditions. In this study, anaerobic digestion was carried out in a fluidized bed reactor and its operation defined using various kinetic models in order to determine the suitable reactor operating conditions.

1.2 Methodology 1.2.1 Experimental set up The fluidized bed used had an internal diameter of 118 mm and height of 760 mm with a total and working volume of 8.3 L and 6 L respectively. The reactor was packed with 50 g of zeolite (particle size 150–300 μm) and fluidization was attained by the recycle stream using a centrifugal pump (Figure 1.1). The superficial velocity was maintained at about 0.6 cm/s and monitored by a flow meter. The reactor was fed using a peristaltic pump and the biogas produced was collected using the water displacement method.

3

1.2 Methodology

1.2.2 Start-up and operation of the bioreactor For a start up the cow dung was filtered with a sieve then mixed with diluted wastewater [13]. The mixture was fed in the reactor and temperature maintained at 37 °C. Biogas production, COD reduction, and pH were monitored until constant values were obtained indicating stability.

Figure 1.1: Set up of the fluidised bed anaerobic digester. Once the reactor had acclimatized the rate of feeding was varied to obtain different HRT and OLR. The flow rates and OLR of the reactor were varied as shown in Table 1.1.

1.2.3 Experimental analysis Total organic carbon was analyzed using a TOC analyser (TELEDYNE Tekmar). Dissolved organic carbon was analyzed in the similar manner as TOC except that the samples were filtered through a Table .: TOC and color removal efficiencies of the fluidized bed reactor. HRT(d)

    

Influent flow, Q(L/d)

  . . .

Influent

Effluent

Efficiency

tTOC (g/L)

sTOC (g/L)

tTOC (g/L)

sTOC (g/L)

TOC removal%

Color removal%

. . . . .

. . . . .

. . . . .

. . . . .

    

    

4

1 Performance of fluidized bed reactor

0.45 μm filter syringe. Gas was analyzed using a gas chromatograph (Trace 1310 gas chromatograph) fitted with a thermal conductivity detector, while color was analyzed using UV–Vis spectrophotometer (T80 + UV/VIS Spectrophotometer, PG instruments Ltd). Alkalinity was analyzed according to the standard method for wastewater analysis involving titrating samples against 0.02 N H2SO4 solution. Biomass concentration was determined as volatile suspended solids. The volatile suspended solids were determined by evaporating the residue obtained from centrifuged samples at 105 °C for 24 h (until constant mass was obtained) then calcined at 450 °C for an hour. COD was analyzed using the standard method employing chemical oxidation method using acidified potassium dichromate while BOD was analyzed by incubating the samples at 37 °C after inoculation followed by measurement of daily oxygen consumption for five days.

1.3 Results and discussion 1.3.1 TOC and color removal efficiency The TOC and color reduction efficiencies were found to slightly increase with an increase in HRT (Table 1.1). This was due to the fact that at high HRT the substrate had a higher residence time in the reactor than at low HRT. The more time in the reactor means increased contact with micro-organisms leading to higher removal efficiency. The color reduction efficiency was found to be much lower than that of the TOC due to the presence of biorecalcitrant components of distillery effluent which cause color. The biorecalcitrant component is majorly melanoidin [14]. The best HRT can be chosen as 10 days since there is insignificant increase in color and TOC reduction after 10 days.

1.3.2 Substrate balance model Substrate balance around the reactor was formulated based on the following assumption [15, 16]: the assumption was that the anaerobic reactor operated at steadystate conditions as depicted by nearly constant effluent substrate concentration, and biogas production rate. Further assumption was that, even though the feed carried suspended solids (SS) it was too little as it was only 2.3% of the feed total TOC; this SS was assumed to be biodegradable, thus it was considered that the volatile suspended solids (VSS) in the reactor and effluent corresponded to generated biomass. Therefore, TOC balance for the reactor could be expressed as: (tTOC)o = (sTOC)e + (tTOC)biogas + (tTOCvss)e + (tTOC)m

(1.1)

where (tTOC)o is the influent total TOC, (sTOC)e is soluble TOC in the effluent, (tTOC)biogas is the fraction of (tTOC)o converted into biogas, (tTOCvss)e is the fraction of (tTOC)o converted into biomass and (tTOC)m is the fraction of (tTOC)o used for cell maintenance and growth. Considering feed flow rate and methane flow rate, Eq. (1.1) can be expressed as:

1.3 Results and discussion

QSto = QSte + qCH4 Y s/g + q(Ste − Sse ) + K m XV

5

(1.2)

where Q is the feed flow rate (Ld−1), Sto is the feed concentration (g tTOC L−1), Ste is the total effluent concentration (g tTOC L−1), Sse is the soluble effluent concentration (g sTOC L−1), qCH4 is methane production rate (LCH4d−1), Ysubstrate/gas is the coefficient of substrate conversion into methane (g tTOC L−1CH4), Km is cell maintenance coefficient, and X and V are biomass concentration (gVSS/L) and reactor volume (L), respectively. On rearrangement, Eq. (1.2) can be written as: Q(Sto − Ste ) = qCH4 Y s/g + K m XV

(1.3)

Since HRT=V/Q, by dividing both sides by V, Eq. (1.3) becomes: (Sto − Ste )/HRT = qCH4 Y s/g /V + XK m

(1.4)

From Eq. (1.4), a plot of (Sto − Ste)/HRT versus qCH4/V gives a straight line with slope equal to Ys/g and y-axis intercept equals to XKm. In Figure 1.2 the plot supports the validity of this model in describing the anaerobic process in this particular study with a regression coefficient of 0.996. The y-axis intercept was very small indicating that a very small portion of the feed TOC was used for cell maintenance. The Ys/g value was found to be 3.58 g tTOC/LCH4. The inverse of the Ys/g which is Yg/s is the methane yield coefficient which was found to be 0.28 LCH4/g tTOC corresponding to 0.257 L CH4/g COD. This is close to theoretical methane yield of 0.350 LCH4/g tTOC when glucose is used as substrate [7]. The fraction of influent tTOC converted into biogas, biomass and that which is in the effluent can be calculated from Eq. (1.1) by expressing each term in the right hand side as a fraction of (tTOC)o. Figure 1.3 shows the percentages of TOC converted into biogas, biomass and unremoved TOC, it was found that, generally, most of the feed TOC was converted into biogas. The percentage substrate converted into biogas increased

Figure 1.2: Determination of methane yield coefficient.

6

1 Performance of fluidized bed reactor

Figure 1.3: Fraction of feed TOC converted into biogas biomass and that which remained in the effluent.

slightly with an increase in HRT. This suggests that at high HRT, the feed had higher residence time in the reactor thus achieving maximum conversion than at lower HRT where residence time is shorter. Because there was insignificant change in conversion beyond 10 days, HRT of 10 days could be considered as the optimal residence time. The proportion of feed converted into biomass was nearly constant at various HRTs while there was a slight decrease in proportion of feed in the effluent with an increase in HRT.

1.3.3 Biorecalcitrant component of distillery effluent Distillery effluent is considered as fairly biodegradable with traces of biorecalcitrant compounds such as melanoidins [17]. The biodegradability of the distillery effluent was measured by determining the BOD5/COD ratio and it was found to be 0.41 indicating that the distillery effluent is biodegradable. Good biodegradability is achieved when BOD5/COD is greater than 0.25 [18]. However, the recalcitrant parts of distillery effluent which are majorly melanoidins often pass through anaerobic treatment without being degraded and they impart a dark color to biomethanated effluent [1, 19]. The amount of non-biodegradable component can be determined by the relationship between the organics remaining after digestion and HRT. It is proposed that a plot of ln (CODeffluent or TOCeffluent) against 1/HRT gives a straight line, and recalcitrant component can be calculated at infinite HRT. A similar model has been applied in the determination of the nonbiodegradable component of some food waste wastewater [15, 16]. In Figure 1.4, the amount of nonbiodegradable component is calculated as TOC or COD equivalent at y-axis intercept when HRT is infinite. It was found that the nonbiodegradable TOC and

7

1.3 Results and discussion

Figure 1.4: Determination of recalcitrant component of distillery effluent, TOC (●) and COD (:).

COD were 477 mg/L and 756 mg/L, respectively, under prevailing digestion conditions. The amount of nonbiodegradable COD was higher than that of TOC due to the fact that TOC only caters for carbons while COD caters for all oxidizable compounds in wastewater. Apart from organics, distillery effluent has high concentrations of cations and halogen ions [1]. Considering that the influent TOC was 5318 mg/L, the nonbiodegradable TOC only formed ∼9% of the feed TOC indicating that distillery effluent is biodegradable. However, the nonbiodegradable portion is majorly melanoidins which impart a dark brown color to distillery effluent [1, 19]. Thus anaerobic treatment of distillery effluent is not effective for colour removal as shown in Table 1.1.

1.3.4 Substrate utilization kinetics The kinetics of degradation of total and biodegradable constituents of the effluent were compared applying first order rate model: Se ln( ) = kt So

(1.5)

where So and Se are feed and effluent TOC, respectively, k is rate constant (d−1) and t is HRT (days). For the biodegradable component, the So and Se were modified to Sob and Seb for biodegradable feed and effluent, respectively. These values were obtained by subtracting the recalcitrant TOC from So and Se, respectively. Figure 1.5 shows that the rate of uptake of biodegradable constituent (0.185 d−1) was four times faster than that of the total organic compounds (0.048 d−1) in the wastewater sample. The uptake of the

8

1 Performance of fluidized bed reactor

Figure 1.5: First-order reaction kinetic of biodegradable and total organic carbon, biodegradable toc TOC (Δ) and total TOC (○).

biodegradation component fitted first order kinetics better than that of total organic substrate with R2 values of 0.9754 and 0.9096, respectively. The difference can be attributed to a larger proportion of undigested TOC when considering total feed TOC than in the case of biodegradable TOC, due to slow degradation of the recalcitrant components.

1.3.5 Michaelis–Menten kinetic model According to the Michaelis–Menten kinetic model, the specific substrate utilization rate and biodegradable substrate concentration can be related by the following equation: r=

kSb (K s + Sb )

(1.6)

where r is the specific substrate utilization rate, k is the maximum substrate utilization rate (g sTOCg−1VSSd−1), Sb is the concentration of the biodegradable substrate in the reactor and Ks is the Michaelis constant. The nonbiodegradable TOC obtained in Figure 1.4 was subtracted from the experimental total TOC to obtain the biodegradable TOC in this experiment [16]. The specific substrate utilization rate can be expressed as [16]: r=

(So − Sb ) HRT ⋅ X

(1.7)

where So is the biodegradable feed concentration and X is the biomass concentration in the reactor (g VSSL−1). By combining Eqs. (1.6) and (1.7), we obtain Eq. (1.8). The specific substrate utilization rate (r) is plotted against Sb (Figure 1.6(a)).

9

1.3 Results and discussion

Figure 1.6: Michaelis-Menten model. (a) Specific substrate utilization rate against biodegradable TOC in the reactor and (b) determination of k and Ks.

r=

kSb (So − Sb ) = HRT ⋅ X (K s + Sb )

(1.8)

The plot was found to represent a hyperbolic function which is an indication that the substrate utilization followed the Michaelis–Menten model [15]. To determine k and Ks, a linearized plot of 1/r against 1/Sb from Eq. (1.9) was used [15]. Ks was determined from the slope and k from the y intercept (Figure 1.6(b)). Accordingly, the values of k and Ks were found to be 0.292 g sTOCg−1VSSd−1 and 0.166 g sTOC L−1. Senturk et al. (2013) reported a maximum substrate utilization rate (k) of 0.106 g sCOD g−1VSSd−1 and Ks value of 0.535 g sCODL−1 while using anaerobic contact reactor [12]. The fluidized bed reactor achieves adequate mixing [5] hence higher substrate utilization rates are expected than in contact anaerobic reactor. 1 Ks 1 1 = ( )+ r k Sb k

(1.9)

1.3.6 The mean cell residence time The mean cell residence time (MCRT) or sludge retention time (SRT) also known as sludge age is the average amount of time the anaerobic micro-organisms are retained in the reactor. The MCRT directly affects the kinetics of substrate utilization, biogas production, and sludge production. It also affects microorganisms’ growth kinetics since the time spent in the reactor determines feed-microbes contact time which affects growth. It is a function of biosolids in the system and rate of biosolids loss from the system. Mean cell residence time is calculated as [20]: θ=

Br ⋅ V Q ⋅ Beff

(1.10)

10

1 Performance of fluidized bed reactor

where θ is mean cell residence time (days), Br is the concentration of biomass in the reactor (g VSS/L), V is the reactor volume (L), Q is effluent flow rate (L/d), and Beff is the biomass concentration in the effluent (g VSS/L). The mean cell residence time can be related to the specific substrate utilization rate as [21]: 1 = Yr − K d θ

(1.11)

where r is the specific rate of substrate utilization (g COD/g VSS d), Y is the microbial growth yield or biomass yield (g VSS/g COD) and Kd is the endogenous decay coefficient (d−1). This correlation helps to calculate Y and Kd and these two parameters are very significant as biomass yield can be applied to estimate the amount of sludge produced during anaerobic treatment, while Kd is used to calculate the net amount of sludge to be handled. A plot of 1/θ against r gives a straight line with Y as gradient and y-axis intercept as the Kd. In Figure 1.7 the Y value was found to be 0.466 g/g while Kd was 0.029 d−1. Y and Kd values of 0.357 g/g and 0.083 d−1 respectively, have been reported in literature [22]. The higher Kd values in this study could be attributed to application of zeolite which promotes biomass growth due to their porosity [8]. The specific rate of substrate utilization has an inverse relationship with the MCRT due to the fact that low MCRT is achieved at high feed flow rate which translates into higher OLR. Therefore, there is a lot more substrate available as feed at low MCRT than at high MCRT. However, this also depends and interlinks with microorganisms’ growth kinetics and food to microorganism ratio at any time in the reactor.

1.3.7 MCRT and HRT The total duration the biomass resides in the reactor as compared to liquid retention time is an important factor in anaerobic wastewater treatment. In Figure 1.8 the mean cell

Figure 1.7: Correlation between sludge age and specific substrate utilization rate.

1.4 Conclusions

11

Figure 1.8: A comparison of HRT and MCRT at different F:M values, HRT (Δ), MCRT (○) and corresponding OLR(●).

residence time (MCRT) was compared to HRT at various F:M. Generally, the MCRT was always at least 2.5 times higher than the HRT. The higher MCRT as compared to HRT can be attributed to the fact that biomass was attached onto zeolite thus being retained in the reactor instead of being washed out by the effluent. The advantage of attached biomass is that the biomass is able to reside in the reactor for a longer time fostering adaptation to the environment than if old cells are frequently replaced by new ones in a case where the biomass is not attached in the reactor. Attachment also ensures that a sufficient amount of biomass is usually in the reactor thereby ensuring high efficiency.

1.4 Conclusions The kinetics of a fluidized bed anaerobic digester treating distillery effluent was evaluated. Degradation in the reactor followed first order rate kinetics and the recalcitrant component of the effluent was determined to be ∼ 10% TOC of the feed. The reactor operated at best HRT of 10 days. The amount of the biorecalcitrant organic compounds suggested that a post-treatment method is required. The biorecalcitrant compounds were found to be the major color causing compounds in distillery effluent. This was due to the fact that AD was ineffective in color reduction despite a superior TOC reduction. The zeolite applied in the reactor was very effective in biomass retention as the SRT was 2.5 higher than the HRT. The maximum microorganisms’ growth rate was 0.136 d−1 and biomass yield was 0.466 g/g. A microorganisms’ decay coefficient of 0.030 was an indication that the bioreactor effluent needed a settling tank for the removal of suspended biomass if tertiary treatment methods such as advanced

12

1 Performance of fluidized bed reactor

oxidation processes, adsorption, or membrane processes are to be employed for the removal of the bio recalcitrant components.

References 1. Satyawali Y, Balakrishnan M. Wastewater treatment in molasses-based alcohol distilleries for COD and color removal: a review. J Environ Manag 2008;86:481–97. 2. Gebreeyessus GD, Mekonen A, Alemayehu E. A review on progresses and performances in distillery stillage management. J Clean Prod 2019;232:295–307. 3. Fuess LT, Garcia ML. Bioenergy from stillage anaerobic digestion to enhance the energy balance ratio of ethanol production. J Environ Manag 2015;162:102–14. 4. Apollo S, Aoyi O. Combined anaerobic digestion and photocatalytic treatment of distillery effluent in fluidized bed reactors focusing on energy conservation. Environ Technol 2016;37:2243–2251. 5. Andalib M, Hafez H, Elbeshbishy E, Nakhla G, Zhu J. Treatment of thin stillage in a high-rate anaerobic fluidized bed bioreactor (AFBR). Bioresour Technol 2012;121:411–8. 6. Aiyuk S, Forrez I, Lieven DK, van Haandel A, Verstraete W. Anaerobic and complementary treatment of domestic sewage in regions with hot climates–a review. Bioresour Technol 2006;97:2225–41. 7. Fernández N, Montalvo S, Borja R, Guerrero L, Sánchez E, Cortés I, et al. Performance evaluation of an anaerobic fluidized bed reactor with natural zeolite as support material when treating highstrength distillery wastewater. Renew Energy 2008;33:2458–66. 8. Montalvo S, Guerrero L, Borja R, Sánchez E, Milán Z, Cortés I, et al. Application of natural zeolites in anaerobic digestion processes: a review. Appl Clay Sci 2012;58:125–33. 9. Akach J, Ochieng A. Chemical engineering research and design Monte Carlo simulation of the light distribution in an annular slurry bubble column photocatalytic reactor. Chem Eng Res Des 2017; 129:248–58. 10. Jaafari J, Mesdaghinia A, Nabizadeh R, Hoseini M, Kamani H, Mahvi AH. Influence of upflow velocity on performance and biofilm characteristics of anaerobic fluidized bed reactor (AFBR) in treating high-strength wastewater. J Environ Heal Sci Eng 2014;12:139. 11. Rabah FKJ, Dahab MF. Biofilm and biomass characteristics in high-performance fluidized-bed biofilm reactors. Water Res 2004;38:4262–70. 12. Senturk E, Ýnce M, Onkal Engin G. Assesment of kinetic parameters for thermophilic anaerobic contact reactor treating food-processing wastewater. Int J Environ Res 2013;7:293–302. 13. Hampannavar U, Shivayogimath C. Anaerobic treatment of sugar industry wastewater by upflow anaerobic. Int J Environ Sci 2010;1:631–9. 14. Wang H-Y, Qian H, Yao W-R. Melanoidins produced by the Maillard reaction: structure and biological activity. Food Chem 2011;128:573–84. 15. Borja R, González E, Raposo F, Millán F, Martín A. Kinetic analysis of the psychrophilic anaerobic digestion of wastewater derived from the production of proteins from extracted sunflower flour. J Agric Food Chem 2002;50:4628–33. 16. Rincón B, Raposo F, Domínguez JR, Millán F, Jiménez AM, Martín A, et al. Kinetic models of an anaerobic bioreactor for restoring wastewater generated by industrial chickpea protein production. Int Biodeterior Biodegrad 2006;57:114–20. 17. Acharya BK, Mohana S, Madamwar D. Anaerobic treatment of distillery spent wash – a study on upflow anaerobic fixed film bioreactor. Bioresour Technol 2008;99:4621–6. 18. Sankaran K, Premalatha M, Vijayasekaran M, Somasundaram VT. DEPHY project: distillery wastewater treatment through anaerobic digestion and phycoremediation –- a green industrial approach. Renew Sustain Energy Rev 2014;37:634–43.

References

13

19. Kalavathi D, Uma L, Subramanian G. Degradation and metabolization of the pigment—melanoidin in distillery effluent by the marine cyanobacterium Oscillatoria boryana BDU 92181. Enzym Microb Technol 2001;29:246–51. 20. Ng HY, Tan TW, Ong SL. Membrane fouling of submerged membrane bioreactors: impact of mean cell residence time and the contributing factors. Environ Sci Technol 2006;40:2706–13. 21. Nweke C, Igbokwe P, Nwabanne J. Kinetics of batch anaerobic digestion of vegetable oil wastewater. Open J Water Pollut Treat 2014;2014:1–10. 22. Enitan AM, Adeyemo J. Estimation of bio-kinetic coefficients for treatment of brewery wastewater, 6th ed. Int J Environ Chem Ecol Geol Geophys Eng 2014;8:400–4 .

Yetunde Bunmi Oyeyiola* and Christianah Iyanuoluwa Adeosun

2 Sustainability of ameliorative potentials of urea spiked poultry manure biochar types in simulated sodic soils Abstract: Alkaline soil conditions are serious challenges to optimal crop production on irrigated farmlands in arid and semi-arid regions of the world. Unique characteristics of biochar had been utilized in the amelioration of many problematic soils but its use in sodic soil management is not popular in Nigeria. Ameliorative effects of biochar types prepared from poultry manure co-pyrolyzed with or without urea fertilizer were evaluated on soil organic carbon and selected soil chemical characteristics of a simulated sodic soil. The results from the six weeks incubation trial revealed the ability of the biochar types to reduce soil pH from the initial 10.38 to 7.91–10.29 in high sodic (HS) and from initial 9.70 to a range of 7.51–8.39 in low sodic (LS) soil situations compared to 9.88 (HS) and 6.82 (LS) in sole urea treated soil. This accounted for up to 51 and 57% reduction in exchangeable sodium content and percentage (ESP), respectively and 28% increases in exchangeable Ca in the sodic soils. Poultry manure biochar copyrolyzed with urea was most effective in reducing exchangeable sodium and ESP in the soils while poultry manure biochar not co-pyrolyzed with urea was highest in reducing soil pH. Poultry manure biochar not spiked with urea was most superior in increasing soil organic carbon in low sodic situation. Keywords: alkalinesoils; poultry manure biochar; simulated sodic soils; sodic soils; urea fertilizer.

2.1 Introduction Annual increases in arable land lost to problematic soil situations demands attention if future food production will be ascertained. Problematic soils including acidic, expansive, lateritic, collapsible, heavy clayey, hardpan, fluffy paddy, saline and sodic soils are wide spread in the world. Alkaline soils which include saline, sodic and saline –sodic soils covers more than one billion hectare of the world arable land [1]. In Nigeria, nineteen out of its thirty-six states are under semi-arid and arid agro-ecological zones that predispose soils to alkaline condition. Saline-sodic soils are major bottlenecks to profitable crop production in arable lands in arid and semi-arid zones of the

*Corresponding author: Yetunde Bunmi Oyeyiola, Department of Crop Production and Soil Science, Ladoke Akintola University of Technology, Ogbomoso, Nigeria, E-mail: [email protected] Christianah Iyanuoluwa Adeosun, Department of Crop Production and Soil Science, Ladoke Akintola University of Technology, Ogbomoso, Nigeria As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: Y. B. Oyeyiola and C. I. Adeosun “Sustainability of ameliorative potentials of urea spiked poultry manure biochar types in simulated sodic soils” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0137 | https://doi.org/10.1515/ 9783110752601-002

16

2 Poultry manure biochar activated urea as sodic soil amendment

world [2, 3]. Salt affected soils are common in agro-ecological zones characterized by higher solar evaporation intensities with low precipitation leading to accumulation of soluble salts of sodium, calcium and magnesium. Intensively irrigated farmlands are potential sources of alkaline soils in Nigeria [2, 4]. Sodic soils are characterized by pH above 8.5 high concentrations of exchangeable sodium and exchangeable sodium percentage usually above 15% [5]. Sodium toxicity, nutrient antagonism, poor organic matter and clay dispersion arising from degraded soil physical properties are major factors limiting crop productivity in sodic soils [6]. Additionally, sodic soils are generally deficient in organic carbon and total nitrogen due to intense NH3 volatilization [7], organic carbon dispersion and low carbon input by plants and microbes in the degraded soil [5, 6]. Sodic soils have been managed conventionally using chemical amendments such as soluble calcium salts (e.g., gypsum and calcium chloride) and acid forming fertilizers and substances such as urea, sulphuric acid, sulphur, iron sulphate and aluminum sulphate [8]. Unavailability and expensive nature of these conventional amendments had open research areas for alternative options in alkaline soil management of which use of organic based materials especially farm yard manure and recently, biochar had been reported [9–11]. Biochar is a carbon-rich thermally modified product achieved when biomass undergo pyrolysis in the absence or limited supply of oxygen [1, 12, 13]. It is characterized by large surface area, variable charged sites, high carbon, ash and phosphorus contents. Biochar use is advancing in soil and environmental management in many parts of the world for carbon sequestration, improving soil structure, fertility, waste water management, bioremediation, mitigating nutrient leaching and greenhouse gas emissions [14–20]. So much have been reported on effects of sole biochar application for the management of sodium toxicity in soils [9, 21, 22] but reports are scarce on similar effects by biochar co-pyrolyzed with urea as indicated by organic carbon and macronutrient status of amended sodic soils. Soil organic carbon is an important indicator for soil health and sustainability of effects of fertilizers and amendment in soils are best assessed on their contributions to enhancing this vital soil parameter. It is regarded as a fundamental index for evaluating any soil amelioration or fertility management [6, 9, 23]. Sequestering carbon in soil through adoption of sustainable soil fertility management and copping practices is central to achieving reduced greenhouse gas emissions, environmental safety and improved crop production and quality. Soil sodicity is a serious challenge to crop production on irrigated farmlands in arid and semi-arid regions of the world [3, 20, 24]. Efforts to amend these soils for enhanced crop production with locally sourced materials will help achieve food security and zero hunger. The large surface area, variable charged sites, high carbon, calcium and phosphorus contents of biochar had been utilized in the amelioration of many problematic soils but its use in sodic soil management is not popular in Nigeria. Reports on contributions of biochar with or without other inorganic amendments such as urea to soil organic carbon and macronutrients in sodic soil situation are still not clear. This

2.2 Materials and methods

17

work evaluated soil sodicity ameliorative effects of biochar types prepared from poultry manure co-pyrolyzed with or without urea on soil organic carbon and selected soil chemical characteristics of a simulated sodic soil.

2.2 Materials and methods 2.2.1 Soil sampling, preparation and routine analysis Top soil of the Teaching and Research Farm, Ladoke Akintola University of Technology, (T and R Farm, LAUTECH) Ogbomoso (08° 10″N and 04° 10″E) was sampled to 0–10 cm depth. The soil was air dried, crushed and sieved with 2 and 0.5 mm sieves and thereafter subjected to routine analysis following standard procedures described by IITA, 1978. Soil pH was determined on a 1:2 (soil: water) ratio after 15 min equilibration period using a glass electrode calibrated in pH buffers 4, 7 and 9. Organic carbon was determined by the dichromate wet oxidation method. Exchangeable cations (Ca, Mg, K and Na) were extracted with 1 N NH4OAc (pH 7) at a soil: extracting solution ratio of 1:10 for 15 min. The concentrations of Ca and Mg were read on the Atomic Absorption Spectrophotometer, Buck Scientific model 211 while those of K and Na were read on the Flame Photometer. The available phosphorus was extracted by Mehlich reagents and total nitrogen was determined by Macro-Kjeldahl method as described by [25]. The soil is an Alfisol, it developed from basement complex and classified locally as Gambari soil series [26, 27]. The soil is generally sandy, grayish, high in base saturation and severely depleted in total N, available P and organic carbon (Table 2.1).

Table .: Characteristics of the soil studied before and after sodicity simulation. Parameters

Before sodicity simulation

Soil pH (soil: HO, :) EC (dS/m) Available P (mg/kg) Total N (g/kg) Organic Carbon(%) Ex. Cations (cmol/kg) Ca Mg K Na Particle sizes (g/kg) Sand Silt Clay HS, high sodic soil; LS, low sodic soil; ND, not determined.

After sodicity simulation HS

LS

. . . . .

. . . . .

. . . . .

. . . .

ND ND ND .

ND ND ND .

  

ND ND ND

ND ND ND

18

2 Poultry manure biochar activated urea as sodic soil amendment

2.2.2 Soil sodicity simulation Stock solution (1000 ppm Na) of NaOH prepared by dissolving 0.575 g NaOH pellets in 1000 ml volumetric flask made up to the mark with distilled water was diluted to achieve 10 and 5 ppm Na representing High and Low sodic irrigation water respectively. The high and Low sodic irrigation water were prepared by diluting 1.0 and 0.5 ml solutions dispensed respectively from the stock solution in 100 ml volumetric flasks. Single applications of 50 ml of appropriate sodic irrigation water were applied to field capacity in each 230 g soil placed in 1 L capacity incubation cups. Selected characteristics of the simulated sodic soil are given in Table 2.1.

2.2.3 Preparation of the poultry manure biochar co-pyrolyzed with or without urea Fresh poultry manure was sourced from the layer chicken battery cage system, T and R Farm, LAUTECH. After air drying, the poultry manure was pre-treated in the oven at 105 °C for 24 h to reduce the moisture content and to remove non-flammable component like water and CO2. Sole 30 g oven dried poultry manure and 30 g poultry manure spiked with 3 g urea fertilizer were placed in appropriate crucibles and subjected to slow pyrolysis at 350 °C for 20 min in a muffle furnace to achieve poultry manure biochar (PMB-urea) and poultry manure biochar co-pyrolyzed with urea (PMBCPU), respectively. The poultry manure not co-pyrolyzed (PMBNCPU) was achieved by physical mixing of PMB with fresh urea fertilizer at the point of soil application. The resultant biochar types were crushed, sieved (2 mm mesh) and stored in the desiccators prior to use.

2.2.4 Treatments, experimental design and set up The incubation trial was a factorial experiment composing of two soil sodicity levels (High sodicity (HS) and Low sodicity (LS)) and three poultry biochar types (PMB-urea, PMBCPU and PMBNCPU). Two control treatments including sole urea and unamended soil were compared. This gave 10 treatments laid in completely randomized design in three replications. Each incubation cup was filled with 230 g soil, followed by appropriate biochar application at 5 t/ha (equivalent to 0.6 g/230 g soil) and were thoroughly mixed with the soil. The PMBNCPU was achieved by mixing 0.6 g PMB-urea with 0.09 g urea fertilizer. Sole urea treated soil received urea fertilizer at 0.09 g per 230 g soil while unamended soil received neither biochar nor urea. The treated and unamended soils were thereafter moistened to field capacity with 50 ml of either high or low artificial sodic irrigation water prepared earlier to achieve HS and LS soil situations respectively. Each incubation cup was kept covered with foil paper and moist under room temperature that fluctuated between 23 and 25 °C all through the incubation trial that lasted for six weeks. Thereafter, cowpea seeds (Ife bimpe variety) were sown in each treated soil at one plant per cup and the seedlings were nurtured for two weeks.

2.2.5 Data collection The pH in each treated sodic soil was monitored at 24 and 72 h, 7 and 14 days, 4 and 6 weeks of incubation and at harvesting following standard procedure described by [28]. At cowpea seedling harvesting, data were taken on fresh shoot and root weights. Soils sampled at harvesting were prepared for exchangeable bases, available P (extracted by Mehlich reagent) and organic carbon determinations. Exchangeable sodium percentage (ESP) from each treated soil was estimated using:

19

2.3 Results

ESP   ( % )  = (Exchangeable   sodium   concentrations   x   100)   ÷   ∑   Ex.   Ca   +   Mg   +K   +   Na 2.2.5.1 Data analysis: All the data collected were subjected to two-way analysis of variance using Genstat statistical package (8th Edition). Significant means were separated using least significant difference at 5% probability level. Regression analysis was used to establish contributions of soil pH at harvesting in the soils amended with biochar to soil organic carbon and other selected soil chemical characteristics.

2.3 Results 2.3.1 Effects of poultry manure biochar amendments on pH of a simulated sodic soil Soil sodicity levels, poultry manure biochar types and their interactions significantly reduced pH of the sodic soil studied (Table 2.2). At the end of the 6 weeks incubation trial, soil pH had decreased from initial 10.38 to a range of 7.91–10.29 in HS and from initial 9.70 to a range of 7.51–8.39 in LS compared to 9.88 (HS) and 6.82 (LS) in sole urea treated soil. The PMB-urea and PMBCPU were poorest in reducing soil pH at every sampling time in HS and LS soils respectively. The acidifying potentials of urea present in PMBCPU, PMBNCPU and sole urea resulted in 3.6, 23 and 4% reductions in soil pH respectively compared to PMB-urea treated soil at the end of 6 weeks of incubation (WOI). Co-application of poultry manure biochar freshly spiked with urea was most effective in reducing soil pH by 20 and 23% compared to sole urea and PMB-urea respectively. The introduction of plant into the amended soil after the 6 WOI brought Table .: Effects of poultry manure biochar amendments on pH of a simulated sodic soil. Biochar types

PMBCPU PMBNCPU PMB – urea Sole urea Unamended Mean SL (LSD) BT (LSD) SLxBT (LSD)

Soil pH at WOI

Soil pH at Harvesting

Sodicity level

Sodicity level

HS

LS

Mean

HS

LS

Mean

. . . . . . .*** .*** .***

. . . . . .

. . . . .

. . . . . . .*** .*** .***

. . . . . .

. . . . .

PMB, poultry manure biochar; PMBCPU, poultry manure biochar co-pyrolyzed with urea; PMBNCPU, poultry manure biochar not co-pyrolyzed with urea; HS, high sodicity; LS, low sodicity; SL, sodicity levels; BT, biochar types; LSD, least significant difference, *** level of significance at p < ..

20

2 Poultry manure biochar activated urea as sodic soil amendment

about further reductions in the soil pH following similar trend with what were observed at 6 WOI (except PMB-urea been responsible for highest pH especially in HS soils).

2.3.2 Effects of poultry manure biochar amendments on exchangeable Ca, Mg and K in a simulated sodic soil Soil sodicity level, poultry manure biochar types and their interaction significantly affected exchangeable Ca, Mg and K in the soils (Table 2.3). All the biochar types increased the concentrations of these basic cations over the conventional sole urea and unamended soils. The basic cations released into the soil were however soil sodicity level dependent. Biochar amended HS soils had higher exchangeable Mg while amended LS soils were generally higher in exchangeable Ca and K. The unamended soil consistently had least exchangeable Ca, Mg and K.

2.3.3 Effects of poultry manure biochar amendments on exchangeable Na and sodium percentage (ESP) in a simulated sodic soil The poultry manure biochar types, soil sodicity levels and their interactions significantly influenced exchangeable Na and sodium percentage (ESP) in the soil studied (Table 2.4). The Ex. Na and ESP were consistently higher in HS soils regardless the treatments. The PMBCPU was superior to other treatments (except sole urea in LS soil) Table .: Effects of poultry manure biochar amendments on exchangeable Ca, Mg and K in a simulated sodic soil. Biochar types

PMBCPU PMBNCPU PMB – urea Sole urea Unamended Mean SL (LSD) BT (LSD) SLxBT (LSD)

Ex. Ca (cmol/kg)

Ex. Mg (cmol/kg)

Ex. K (cmol/kg)

Sodicity level

Sodicity level

Sodicity level

HS

LS

Mean

HS

LS

Mean

HS

LS

Mean

. . . . . . .*** .*** .***

. . . . . .

. . . . .

. . . . . . .*** .*** .***

. . . . . .

. . . . .

. . . . . . .*** .*** .***

. . . . . .

. . . . .

PMB, poultry manure biochar; PMBCPU, poultry manure biochar co-pyrolyzed with urea; PMBNCPU, poultry manure biochar not co-pyrolyzed with urea; HS, high sodicity; LS, low sodicity; SL, sodicity levels; BT, biochar types; LSD, least significant difference, *** level of significance at p < ..

2.3 Results

21

Table .: Effects of poultry manure biochar amendments on exchangeable Na and sodium percentage (ESP) in a simulated sodic soil. Biochar types

PMBCPU PMBNCPU PMB – urea Sole urea Unamended Mean SL (LSD) BT (LSD) SLxBT (LSD)

Ex. Na (cmol/kg)

ESP(%)

Sodicity level

Sodicity level

HS

LS

Mean

HS

LS

Mean

. . . . . . .*** .*** .***

. . . . . .

. . . . .

. . . . . . .*** .*** .***

. . . . . .

. . . . .

PMB, poultry manure biochar; PMBCPU, poultry manure biochar co-pyrolyzed with urea; PMBNCPU, poultry manure biochar not co-pyrolyzed with urea; HS, high sodicity; LS, low sodicity; SL, sodicity levels; BT, biochar types; LSD, least significant difference, *** level of significance at p < ..

in reducing toxic levels of Na and ESP in the soil been responsible for 19 and 21% reductions in Ex. Na in HS soil compared to sole urea and unamended soils respectively and 17 and 37% reductions in ESP of LS soils respectively.

2.3.4 Effects of poultry manure biochar amendments on soil organic carbon in a simulated sodic soil The soil organic carbon (SOC) contents of the amended soils were significantly affected by the biochar types, sodicity levels and their interactions (Figure 2.1). All the amendments tested showed poor performance in sequestering carbon in the HS soil while sole urea and PMB-urea were highest in improving SOC in LS soil. The SOC sequestering potential of the biochar tested seem to be soil pH sensitive with soil pH conditions not favoring SOC sequestering across all treatments.

2.3.5 Effects of poultry manure biochar amendments on soil available phosphorus in a simulated sodic soil The biochar types, soil sodicity level and their interactions appreciably influenced phosphorus availability in the soil (Figure 2.2). All the biochar types were superior to sole urea in enhancing available P in both sodic soils with highest increases of 193% in

Soil organic carbon (%)

22

2 Poultry manure biochar activated urea as sodic soil amendment

2.5 2 1.5 1 HS 0.5

LS

0

Treatments

Soil available P (mg/kg)

Figure 2.1: Effects of poultry manure biochar on soil organic carbon in a simulated sodic soil PMB is poultry manure biochar; PMBCPU is poultry manure biochar co-pyrolyzed with urea; PMBNCPU is poultry manure biochar not co-pyrolyzed with urea; HS is high sodicity; LS is low sodicity; SL is sodicity levels; BT is biochar types; LSD is least significant difference, *** level of significance at p < 0.001.

45 40 35 30 25 20 15 10 5 0

HS LS

Treatments Figure 2.2: Effects of poultry manure biochar on soil available phosphorus in a simulated sodic soil. PMB is poultry manure biochar. PMBCPU is poultry manure biochar co-pyrolyzed with urea; PMBNCPU is poultry manure biochar not co-pyrolyzed with urea; HS is high sodicity; LS is low sodicity; SL is sodicity levels; BT is biochar types; LSD is least significant difference, *** level of significance at p < 0.001.

HS amended with PMB-urea and 237% in LS amended with PMBNCPU. Presence of urea in biochar reduced P availability in both soils by 9.2% in PMBCPU and 11.5% in PMBNCPU.

2.3 Results

23

2.3.6 Effects of poultry manure biochar on dry biomass weight of cowpea seedlings in a simulated sodic soil The two factors and their interactions did not significantly affect total dry biomass of cowpea seedlings (Figure 2.3). Nevertheless, the PMBCPU of all the biochar types was most supporting in enhancing total dry biomass weight of the cowpea seedlings. Sole urea treated soil however supported higher seedling performance only in HS soil.

2.3.7 Regression model for the contributions of reduced soil pH following biochar amendment on selected soil properties in a simulated sodic soil Contributions of the reduced pH at cowpea seedling harvesting in a simulated sodic soils amended with different poultry manure biochar types to selected soil properties is shown in Table 2.5. The reduced pH from initial 10.38 to a range of 7.91–10.29 in HS soils and from initial 9.7 to a range of 7.51-8.39 in LS soils had positive correlation with ESP (R2 = 0.57*), Ex. Na (R2 = 0.51*), available P (R2 = 0.67*) and Ex. Mg (R2 = 0.30ns). These indicate significant reductions of the ESP and Ex. Na by up to 57 and 51% respectively following biochar application. These reduced sodium toxicities after soil pH reductions accounted for increased Ex. Ca by up to 28%.

Dry biomass weight (g/plant)

0.14 0.12 0.1 0.08 0.06 HS

0.04

LS

0.02 0

Treatments

Figure 2.3: Effects of poultry manure biochar on dry biomass weight of cowpea seedlings in a simulated sodic soil. PMB is poultry manure biochar. PMBCPU is poultry manure biochar co-pyrolyzed with urea; PMBNCPU is poultry manure biochar not co-pyrolyzed with urea; HS is high sodicity; LS is low sodicity; SL is sodicity levels; BT is biochar types; ns is not significant.

24

2 Poultry manure biochar activated urea as sodic soil amendment

Table .: Contributions of final pH of a simulated sodic soil amended with different poultry manure biochar types to selected soil properties. Soil properties

Regression equations

Soil organic carbon Exchangeable sodium percentage Ex. Calcium Ex. Magnesium Ex. Potassium Ex. Sodium Available P

y = −.x + . y = .x − . y = −.x + . y = .x + . y = −.x + . y = .x − . y = .x + .

a

R values .b .a .ns .ns .ns .a .a

and bsignificant at p < . and . respectively; ns is not significant.

2.4 Discussion Mechanisms that involve increases in soil exchangeable Ca, Mg and K and reduce soil pH and exchangeable sodium are generally adopted for the management of sodic soils [3, 29]. In the present study, all the poultry manure biochar amended sodic soils appreciably increased soil exchangeable Ca, Mg and K which drastically brought about soil pH reductions. The redistribution of exchangeable bases in the soil solution pool and on the soil exchangeable sites ultimately accounted for up to 51 and 57% reduction in exchangeable sodium content and percentage respectively as indicated by the regression models. This supported the submissions in the review of [30] where significant increases in exchangeable Ca2+ and reductions of Na+ from sodic soils amended with different organic materials were established. Furthermore, the potentials of biochar to reduce soil sodic conditions had been linked to biochar ability to adsorb Na+ unto the soil exchangeable sites following increases in concentrations of released such as Ca2+ into soil solution [21]. The present results also show possible antagonistic reaction pathway between Ex. Ca and Mg under reduced soil pH conditions. The reduced pH in the sodic soils brought about reduced Ex. Mg for increased Ex.Ca which is the most dominant exchangeable basic cation in the soil. The sodicity amelioration potentials of the poultry manure biochar types tested were more pronounced in the low sodicity soils. Sole urea and poultry manure biochar not co-pyrolyzed with urea were most efficient in reducing soil pH in low and high sodic soils respectively while poultry manure biochar co-pyrolyzed with urea and poultry manure biochar without urea were superior in reducing toxic Na concentrations in the simulated sodic soils. The biochar tested produced generally higher available P in the sodic soils through the reduced soil pH to a range of 7.91–10.29 in high sodic soil and 7.51–8.39 in low sodic soil. These new pH ranges seem to favor moderate calcium dissolution that will not predispose soil available P to fixation by Ca. Solubility and P fixation by Ca were reported to increase as soil pH approaches near neutral [31]. Reduction of soil pH in sole

2.5 Conclusions

25

urea treated soil especially in low sodic soil to 6.82 encouraged sorption of the labile P in the P deficient soil coupled with the fact that urea has no innate phosphorus content that it could release into the soil unlike biochar that are reported to have high fertilizer P value to enhance soil P through creating beneficial soil conditions for P-solubilizing microorganisms such as the Pseudomonas [1, 20]. Similar higher P dissolution and retention is saline-sodic soils amended with different biochar types were documented in [32]. Formation of Hydrogen bond between the phenolic functional group on the active sites of the biochar particles and its mineralized phosphate ions were pinpointed by [33] as dominant mechanism for biochar in ensuring higher labile P and reduced P leaching in saline – sodic soils. In this study, a new reaction pathway was observed with urea in the simulated sodic soil studied. Soil organic carbon depletion following urea application had been reported for near neutral and acidic soils [34, 35]. Urea was found to increase soil organic carbon over biochar treatments in the simulated sodic soils studied. Lower soil organic carbon observed from high sodic soil across all amendments could be linked to intense NH3 volatilization in sodic soils at higher pH range which severely depleted the soil carbon pool where the inorganic N such as NO3− and NH4+ are mineralized. Similar observations were documented in [7, 9, 11, 36]. Additionally, co-application of biochar with other organic materials, inorganic amendments (like gypsum) and fertilizers such as N-fertilizers was found to also enhance biochar potentials to improve soil organic carbon and total nitrogen [1, 37]. Similarly, co-application of biochar with plant growth promoting rhizobacteria was reported by [38] to significantly enhanced physicochemical properties, urease and dehyrogenase activities over their sole application in management of salt stress in sodic soils.

2.5 Conclusions The potentials of poultry manure biochar pyrolyzed with or without urea to ameliorate simulated sodic soil were studied. All the poultry manure biochar types reduced the soil pH and increased calcium content with greater reductions from poultry manure biochar not co-pyrolyzed with urea. Sole urea treatments however had superior soil pH reducing potentials but lower in increasing Ca solubility needed for displacement and reduced concentrations of Na in the soil exchange site. In this study, a new reaction pathway was observed with urea in the simulated sodic soil studied. Urea in the present study enhanced soil organic carbon with higher increases in low sodic soil situation. Poultry manure co-pyrolyzed with urea was most effective in reducing exchangeable sodium and exchangeable sodium percentage in the soils. Mineralization and enhancing calcium content in the soils were the main reaction pathways for the biochar types tested in amending sodic soils. Adapting this work unto farmlands with native sodic conditions is recommended to further evaluate efficiency of these poultry manure biochar types in managing sodic soils for enhanced crop production.

26

2 Poultry manure biochar activated urea as sodic soil amendment

References 1. Alkharabsheh HM, Seleiman MF, Battaglia ML, Shai A, Jalal RS, Alhammad BA, et al. Biochar and its broad impacts in soil quality and fertility, nutrient leaching and crop productivity: a review. Agronomy 2021;11:993. 2. Nzamouhe M, Omar G. Effect of irrigation on some chemical properties of fluvisols in Sudan Savanna Zone of Nigeria. J Res For Wildl Environ 2020;12:105–17. 3. Xiao Q, Zhu LX, Zhang HP, Li XY, Shen YF, Li SQ. Soil amendment with biochar increases maize yield in a semi-arid region by improving soil quality and root growth. Crop Pasture Sci 2016;67:495–507. 4. Tekwa J, Garjila YA, Bashir AA. An assessment of physico-chemical properties and fertility potentials of fallow and cultivated vertisols in Numan Area, Adamawa State, Nigeria. Sch J Agric Sci 2013;3:104–9. 5. Dedeke OA, Akomolafe GF. Influence of salinity on soil chemical properties and surrounding vegetation of Awe salt mining site, Nasarawa State, Nigeria. Afr J Environ Sci Technol 2013;7: 1070–5. 6. Gong H, Li S. Effects of the interaction between biochar and nutrients on soil organic carbon sequestration in soda saline-alkali grassland: a review. Global Ecol Conserv 2021;26. https://doi. org/10.1016/gecco.2020.e01449. 7. Lin XW, Xie ZB, Zhang JY, Liu Q, Bei QC, Zhu JG. Effects of biochar application on greenhouse gas emissions, sequestration and crop growth in coastal saline soil. Eur J Soil Sci 2015;66:329–38. 8. Ezeaku PI, Ene J, Shehu JA. Application of different reclamation methods on salt affected soils for crop production. Am J Exp Agric 2015;9:1–11. 9. Amini S, Ghadiri H, Chen C, Marschner P. Salt-affected soils, reclamation, carbon dynamics and biochar: a review. J Soils Sediments 2016;16:939–53. 10. Najad ZD, Jung MC. The effects of biochar and inorganic amendments on soil remediation in the presence of hyper-accumulator plant. Int J Energy Environ Eng 2017;8:317–29. 11. Sun H, LU H, Chu L, Shao H, Shi W. Biochar applied with appropriate rates can reduce N leaching, keep N retention and not increase NH3 volatilization in a coastal saline soil. Sci Total Environ 2017; 575:820–5. 12. Cantrell KB, Hunt PG, Uchimiya M, Novak JM, Ro KS. Impact of pyrolysis temperature and manure source on physicochemical characteristics of biochar. Bioresour Technol 2012;107:419–28. 13. Tomczyk A, Sokolowska Z, Boguta P. Biochar physicochemical properties: pyrolysis temperature and feedstock kind effects. Rev Environ Sci Biotechnol 2020;19:191–215. 14. Cabeza I, Waterhouse T, Sohi S, Rooke JA. Effect of biochar produced from different biomass sources and at different temperatures on methane production and ammonia concentrations in vitro. Anim Feed Sci Technol 2018;237:1–7. 15. Fungo B, Lehmann J, Kalbitz K, Thiongo M, Okeyo I, Tenywa M, et al. Aggregate size distribution in biochar-amended tropical Ultisol under conventional hand-hoe tillage. Soil Tillage Res 2017;165: 190–7. 16. Hadroug S, Jellali S, Leahy JJ, Kwapinska M, Jaguirim M, Hamdi H, et al. Pyrolysis process as a sustainable management option of poultry manure: characterization of the derived biochars and assessment of their nutrient release capacities. Water 2019;11:2271. 17. Jindo K, Mizumoto H, Sawada Y, Sanchez-Monedero MA, Sonoki T. Physical and chemical characterization of biochars derived from different agricultural residues. Biogeosciences 2014;11: 6613–21. 18. Kimetu JM, Lehmann J. Stability and stabilization od biochar and green manure in soil with different organic carbon contents. Aust J Soil Res 2010;48:577–85.

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19. Li Y, Cheng J, Lee X, Chen Y, Gao W, Pan W, et al. Effects of biochar-based fertilizers on nutrient leaching in a tobacco-planting soil. Acta Geochim 2019;38:1–7. 20. Yao Y, Gao B, Zhang M, Inyang M, Zimmerman AR. Efects of biochar amendment on sorption and leaching of nitrate, ammonium and phosphate in a sandy soil. Chemosphere 2012;89:1467–71. 21. Akhtar SS, Anderson MN, Liu F. Biochar mitigates salinity stress in potato. J Agron Crop Sci 2015; 201:368–78. 22. Usman ARA, Al-Wabel MI, Abdulaziz AH, Mahmoud WA, El-Nagga AH, Ahmad M, et al. Conocarpus biochar induces changes in soil nutrient availability and tomato growth under saline irrigation. Pedosphere 2016;26:27–38. 23. Xu M, Zhang X, Sun N, Zhang W. Advances in research of synergistic effects of soil carbon sequestration on crop yield improvement in cropland. J Plant Nutr Fertil 2017;23:1441–9. 24. Taha RS, Seleimann MF, Alotaibi M, Alhammad BA, Rady MM, Mahdi AHA. Exogenous potassium treatments elevate salt tolerance and performance of Glycine max L. by boosting antioxidant defense system under actual saline field condition. Agronomy 2020;10:1741. 25. Bremner JM. Nitrogen-urea. In: Page AL, Miller RH, editors. Methods of soil analysis, 2nd ed. Madison: American Society of Agronomy, Soil Science Society of America; 1982:699–709 pp. 26. Olatunji OO. Forms and distribution of sesquioxides and effects on phosphate sorption in some soil on basesment complex of south-western Nigeria Ph.D. Thesis. Ogbomoso, Nigeria: LAUTECH; 2011. p. 192. 27. Smyth AJ, Montgomery RF. Soils and land use in central western Nigeria. Ibadan: Government Printer; 1962. p. 214–50. 28. IITA- International Institute of Tropical Agriculture. Selected methods for soil and plant analysis, 2nd ed.; 1978, vol 1. p. 1–24. Manual series. 29. Qadir M, Schubert S, Chafoor A, Murtaza G. Amelioration strategies for sodic soils: a review. Land Degrad Dev 2001;12:357–86. 30. Leogrande R, Vitti C. Use of organic amendments to reclaim saline and sodic soils: a review. Arid Land Res Manag 2019;33. https://doi.org/10.1080/15324982.2018.1498038. 31. Oyeyiola YB, Omueti JAI. Sorption characteristics of phosphorus forms of some alfisols in Osun state. Nigeria. Afr J Phys Sci 2010;3:54–60. 32. Dugdug AAS. Biochar for saline-sodic soil reclamation, phosphorus retention and crop growth improvement PhD Thesis. University of Alberta; 2017. p. 151. 33. Mia S, Dijkstra FA, Singn B. Aging induced changes in biochar’s functionality and adsorption behavior for phosphate and ammonium. Environ Sci Technol 2017;51:8359–67. 34. Lungu OI, Dynoodt RF. Acidification from long term use of urea and its effects on selected soil properties. Afr J Food Nutr Sci 2008;8:63–76. 35. Oyeyiola YB. Phospho-compost amelioration of acid soil for Vigna unguiculata (L.) production. Ph.D. Thesis. University of Ibadan; 2017. p. 182. 36. Esfandbod M, Philip IR, Miller B, Rashti MR, Lan ZM, Srivastava P, et al. Aged acidic biochar increases nitrogen retention and decreases ammonia volatilization in alkaline bauxite residue sand. Ecol Eng 2017;98:157–65. 37. Che Q, Li M, Zhang Z. Effects of biochar application on soil organic carbon in degraded saline-sodic wetlands of Songnen plain, Northeast China. Chin Geogr Sci 2021;31:877–87. 38. Nehela Y, Mazrou VSA, Rady AMS, El-Sherif AMA, Omar AC, El-Monem AM, et al. The integrated amendment of sodic – saline soils using biochar and plant growth –promoting rhizobacteria enhances maize (Zea mays L.) resilience to water salinity. Plants 2021;10:1960.

Mutua Maundu, Linda Ouma and Francis Maingi*

3 Effects of alum, soda ash, and carbon dioxide on 40–50 year old concrete wastewater tanks Abstract: Concrete is among the foremost used construction materials around the world, however, there is limited information to determine how aging concrete is affected by chemicals. Concrete is used in the construction of domestic and industrial infrastructure including walls, beams, roof slabs, pipes and drainage systems. With increasing industrialization, chemicals are continuously released contributing to concrete degradation. Sulfuric acid is one of the most detrimental chemicals to concrete, yet it is commonly used in most industries. The effects of carbon dioxide, alum, and soda ash on 40–50 year old concrete structures were determined. Results showed the presence of Fe3+ ions with a mean concentration of 3.24 ± 0.02 mg/L in the residuum on the alum tank. This was due to the slightly acidic alum solution reacting with calcium hydroxide and iron in the concrete matrix over years thus depriving concrete of its binding power. The high amount of soda ash, a strong base, corrodes the concrete walls and surfaces hence creating cracks on the concrete matrix. Carbonation effects brought about by carbon dioxide were also observed at the time of the study. Keywords: alum; carbonation; concrete; degradation; reinforced concrete.

3.1 Introduction Concrete is among the most widely used construction material around the world [1]. It is prepared by mixing cement, water, and aggregate such as sand and gravel in specified ratios. Since aggregate is mostly considered to be chemically inert in the matrix, the chemistry of concrete mostly lies in the hydration of cement. Portland cement is made up of four main compounds: tricalcium silicate (3CaO·SiO2), dicalcium silicate (2CaO· SiO2), tricalcium aluminate (3CaO·Al2O3), and a tetra-calcium aluminoferrite (4CaO· Al2O3Fe2O3) [2, 3]. The raw materials for manufacturing cement include limestone

*Corresponding author: Francis Maingi, Department of Science, Technology and Engineering, Kibabii University, P. O. Box 1699, Bungoma 50200, Kenya, E-mail: [email protected] Mutua Maundu and Linda Ouma, Department of Science, Technology and Engineering, Kibabii University, P. O. Box 1699, Bungoma 50200, Kenya. https://orcid.org/0000-0002-4975-2495 (L. Ouma) As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: M. Maundu, L. Ouma and F. Maingi “Effects of alum, soda ash, and carbon dioxide on 40–50 year old concrete wastewater tanks” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0227 | https://doi.org/10.1515/9783110752601-003

30

3 Effects of alum, soda ash and carbon dioxide

(CaCO3), silica (SiO2) alumina (Al2O3), and ferrous oxide (Fe2O3). These materials are dried, heated, and fed to a rotating kiln where they react at very high temperatures to form tricalcium silicate (3CaO.SiO2), tricalcium aluminate (3CaO.Al2O3), and tetra calcium aluminoferrate (4CaO.Al4Fe2O3). Calcium oxide is the most abundant oxide in cement with 60–65% abundance, followed by silicate at 17–25%, aluminate at 3.0–8%, and ferrous oxide at 0.5–6% [2–4]. During hydration of cement, water reacts with calcium oxide in cement to form calcium hydroxide (Ca(OH)2), a major constituent of concrete paste, which makes concrete alkaline and highly vulnerable to acid attacks [5–7]. To ensure that the concrete reinforcement is firm, steel rods/bars are incorporated in it to make ferroconcrete [8]. Iron being a constituent of steel is susceptible to acid and alkali attacks [4, 7]. Alum (Al2(SO4)3.nH2O) is employed in wastewater treatment plants as a coagulant to realize coagulation, flocculation, and sedimentation; processes that aid clarification of water [9]. It is prepared by dissolving aluminum sulfate granules typically in concrete holding tanks which provide the requisite capacities for wastewater treatment plants. Alum dissolution produces vitriol which reacts with concrete (Eq. (3.1)). Vitriol is among the foremost deleterious acids to act on concrete; it reacts with lime to supply gypsum (CaSO4) which causes a volume increase [5, 8, 10]. Ordinary hydraulic cement has minimal resistance to acid attacks and is unable to carry up against any solution with a pH value of less than three [7]. Gypsum further reacts with calcium aluminate hydrate to produce ettringite (3CaO.Al2O3.3CaSO4.32H2O) which causes inner pressure within the concrete resulting in the formation of cracks [6, 11, 12]. Ultimately, the corroded concrete loses its mechanical strength that contributes to more cracking, spalling, finally resulting in destruction. Al2 (SO4 )3 + 6H2 O → 2Al(OH)3 + 3H2 SO4

(3.1)

Carbonation is a natural phenomenon that occurs when carbon dioxide from the atmosphere comes into contact with concrete structures, penetrating through them toward the interior [10, 11]. It is a slow process that depends on the concentration of carbon dioxide and natural humidity variation in the target environment and follows Eq. (3.2). Water from the atmosphere dissolves carbon dioxide resulting in the formation of carbonic acid which reacts with concrete as described in Eqs. (3.3) and (3.4). The calcium hydrogen carbonate (Ca(HCO3)2) formed reacts with calcium hydroxide to regenerate calcium carbonate (Eq. (3.5)). Carbonic acid decreases the hydrogen ion potential of the system due to the H+ ions present. As a result, the C-S-H and anhydrous components in the cement paste dissociates in the form of amorphous silica making the concrete highly porous and brittle [11, 13]. Thus, high levels of carbonation can result in loss of structural integrity of the concrete material. CO2 + Ca(OH)2 → CaCO3 + H2 O

(3.2)

H2 CO3 + Ca(OH)2 → Ca(HCO3 )2 + H2 O

(3.3)

3.3 Results and discussions

31

H2 CO3 + CaCO3 → Ca(HCO3 )2

(3.4)

Ca(HCO3 )2 + Ca(OH)2 → CaCO3 + H2 O

(3.5)

Concrete-alkali reaction proceeds as reactive aggregates attack the alkaline components in cement. The reaction causes a volume increase in concrete thus creating tension and swelling in walls. Alkali reactions are responsible for irregular cracks in concrete as well as a reduction in mechanical properties of up to 50% [10]. Sodium carbonate is employed to boost the pH of water during the treatment process. As mentioned earlier within the case of alum, sodium carbonate is additionally prepared by the dissolution of granules in concrete tanks as described by Eqs. (3.6) and (3.7). Sodium bicarbonate reacts with lime to make caustic soda and carbonate as shown in Eq. (3.8) Na2 CO3 + H2 O → NaOH + NaHCO3

(3.6)

Na2 CO3 + Ca(OH)2 → CaCO3 + 2NaOH

(3.7)

2NaHCO3 + Ca(OH)2 → 2NaOH + Ca(HCO3 )2

(3.8)

This study seeks to determine the effects of alum, soda, and dissolved carbon dioxide on 40–50 year old concrete tanks used in a wastewater treatment plant. The concrete tanks were observed for wear as well the determination of ion concentrations in solutions held in the tanks.

3.2 Experimental To determine the effect of the discussed chemicals on aging concrete, water and sludge samples were collected from a 50 year old wastewater treatment plant and analyzed for iron, aluminum sulphate, and calcium carbonate concentrations. The samples collected included rainwater, raw water entering the treatment plant, wastewater after the several treatment stages (Treated water 1, 2, and 3), desludge, stalactite, and stalagmite like protrusions in concrete tanks, and residuum on alum and soda tanks. All samples were analyzed according to procedures reported by Totan et al. [14]. Solid samples were dissolved in nitric acid while water samples were analyzed without further pretreatment [13]. All samples were stored in sealed sample bottles and refrigerated at 4 °C. Solutions of required concentrations were prepared by performing serial dilutions from the relevant stock solutions. Sulphate ion concentration was determined spectrophotometrically on a UV–VIS Spectrometer model DR 5000R while aluminum concentration was determined by complexation with ascorbic acid followed by UV– VIS analysis. Iron concentration was determined using atomic absorption spectrophotometry on an AAS model AA 6300.

3.3 Results and discussions Concrete structures are used for the construction of permanent buildings and structures due to their durability. These structures are however affected by chemical and

32

3 Effects of alum, soda ash and carbon dioxide

environmental factors which adversely affect their structural integrity [10]. Aggressive chemical environments such as those found in chemical dissolution and storage tanks in wastewater treatment plants can cause degradation of concrete structures as the chemicals tend to react with calcium hydroxide in cement a major component of concrete [10, 15]. In addition, aluminum ions may come into contact with iron bars in the concrete and cause galvanic corrosion. The corrosion can cause expansion of the concrete and consequent cracking of the hardened concrete [5]. Effects of degradation on iron concentration and physical observation of 40–50 year old concrete tanks used for handling of liquids (alum and soda) in a wastewater treatment plant indicated wearing of the tanks. The worn out concrete indicated exposure of embedded steel bars and their subsequent corrosion. The tanks used for dilution of alum and soda solution were worst affected as shown in Figure 3.1. Figure 3.1(C) shows a 50 year old tank with degraded concrete exposing the embedded steel bars. As seen, the steel bars are corroded resulting in the dissolution of iron in the solution. The pH of alum was determined to be 2.5 while that of soda ash solution was determined to be 12.5. The low pH of alum solution results from its dissolution producing sulfuric acid as a by-product that reacts with calcium hydroxide in concrete as previously discussed [5]. Soda solutions’ basic nature results from sodium hydroxide and sodium hydrogen carbonate. The highest degradation is therefore attributed to alum and soda ash solutions due to their highly acidic and basic nature, respectively [5, 15].

Figure 3.1: Wastewater tanks. (A) Soda ash, (B) alum solution tanks, and (C) alum tank showing worn concrete worn exposing embedded steel bars.

3.3 Results and discussions

33

3.3.1 Iron (Fe3+) concentration To determine the concentration of iron in the tank, water samples were collected and analyzed for Fe3+ concentrations alongside treated water from the wastewater treatment process. The results obtained for Fe3+ concentrations in Figure 3.2 indicate that the sample obtained from the residuum on the Alum tank had the highest Fe3+ concentration (3.24 ± 0.02 mg/L) followed by the residuum on the soda ash tank (0.66 ± 0.06 mg/L). Comparing these with the Fe3+ ions content in the raw water sample (0.11 ± 0.01 mg/L) shows that iron is introduced into the water within the plant. Since iron is not added during the wastewater treatment process and raw water did not contain significant amounts of iron, the source of iron in the solution is attributed to the degradation of steel bars after concrete degradation (Figure 3.1).

3.3.2 Aluminium concentration The desludge was found to contain 70.00 ± 0.00 mg/L of Al3+. This could be attributed to the fact that alum was used in the wastewater treatment plant as a coagulant (Figure 3.3). The spent alum settles as sludge at the bottom of the clarifiers and is later discharged as desludge. The concentrations of Al3+ in the residuum behind the concrete tank, soda tank, and in raw water were however insignificant. This indicates that aluminum does not seep through the concrete matrix thus does not displace calcium from the concrete matrix. 3.5

Fe3+ Concentration (mg/L)

3.0 2.5 2.0 1.5 1.0 0.5 0.0

er wat Raw

ated Tre

er wat

e ank tank ludg da t um Des n al n so o o m m iduu iduu Res Res

Figure 3.2: Concentration of Fe3+ions (mg/L) in samples from various stages in the wastewater treatment plant.

34

3 Effects of alum, soda ash and carbon dioxide

70

Al3+ Concentration (mg/L)

60 50 40 30 20 10 0

er wat Raw

er wat ated e r T

e ank tank ludg da t um Des n so n al o o m m iduu iduu Res Res

Figure 3.3: Concentration of Al3+ ions in water samples.

3.3.3 Sulphate ion concentrations in the samples Figure 3.4 shows that sulfate ions from calcium sulfate were abundant in the residuum from the alum tank. A mean concentration of 316.67 ± 11.55 mg/L of sulfate ions was obtained in the desludge. The high sulfate ions concentration was an indication that there was a reaction between calcium hydroxide in the concrete with sulfuric acid

SO43- Concentration (mg/L)

300

250

200

150

100

50

0

er wat Raw

er wat ated Tre

e tank tank ludg lum oda Des on s on a m m iduu iduu Res Res

Figure 3.4: Sulfate content in selected samples in the wastewater treatment plant.

3.3 Results and discussions

35

produced by the dissolution of alum. The formed calcium sulfate was later deposited in seepage cracks hence collected as residuum on the tank walls since Portland cement is expected to contain a minimal amount of sulfates present in gypsum (CaSO4·2H2O) [3]. Sulfate ions from alum solution, therefore, react with calcium ions from concrete to form derived gypsum and can react with tricalcium aluminate (in concrete) to form ettringite, 3CaO.Al2O3.3CaSO4.32H2O, aluminum sulfate is able to react with calcium hydroxide to form ettringite without first forming tricalcium aluminate [6]. Continued reaction keeps on disintegrating concrete and as this happens cracks/holes develop on the concrete structures as shown in Figure 3.1(B).

3.3.4 Effect of carbonation on concrete tanks Figure 3.5 showed the formation of stalactite and stalagmite-like formations in soda ash dissolution tanks on its roofs and floors. This could be attributed to the carbonation of concrete. The process of carbonation is continuous with CO2 diffusing through concrete reacting with lime to make carbonate hence wearing the surface [16–18]. The dissolution of calcium hydroxide in the concrete leads to increased capillary porosity and loss of cohesion in the concrete matrix [18]. This weakens the cement paste to aggregate bond leading to the formation of cracks and disintegration or destruction of the concrete structure when subjected to pressure. As this process reaches the depth of concrete, formed calcium carbonate falls from the top resulting in the formation of stalactites and stalagmites. The process utilizes the calcium hydroxide in the concrete matrix therefore degrading it [19]. The mechanism for the carbonation of the concrete wall is similar to that resulting in the formation of stalagmites and stalactites in limestone caves (Figure 3.5). The analysis of their composition revealed that 92.67% of their composition is CaCO3. This indicated that concrete has undergone a roof-carbonation process to form CaCO3. Rainwater from the wastewater treatment plant was determined to be slightly acidic at

Figure 3.5: Formation of stalactites and stalgmatites in concrete tanks. (A) Stalactite and (B) stalagmites formed in concrete tanks.

36

3 Effects of alum, soda ash and carbon dioxide

a pH of 6.75 due to the dissolution of atmospheric CO2. Concrete’s compressive strength and carbonation depth are significantly influenced by its humidity, temperature, and carbon dioxide concentration [15, 17–21]. At humidity of approximately 70%, the carbonation depth is maximized since the chemical reaction and transmission coefficients are proportional to ambient temperatures [15]. The carbonated concrete wall was found to have 99.5% by mass CaCO3. This result indicates that the process of carbonation is well occurring on the walls of concrete structures utilizing calcium hydroxide in the concrete matrix. In pronounced cases, the effects may leave the concrete bond weak and may result in accidents [22].

3.4 Conclusions Alum is a strong acid that highly affects concrete. The acidity is due to its reaction with water to form Sulfuric acid whose pH was found to be less than 3. The Sulfuric acid reacted with calcium hydroxide in the concrete to form calcium sulfate hence wearing the concrete tanks. The wearing process continued and the iron (steel) bar in the concrete matrix was exposed. The high mean concentration levels of Fe3+ (3.24 ± 0.02 mg/L) obtained in the residuum on the alum tank is a clear indication that the exposed iron bars reacted with the acid formed during the dissolution of alum in the alum tank. This study, therefore, indicates that deterioration of concrete by alum is possible. Soda ash solution was found to be highly basic with a pH above 12. This high pH resulted in the corrosion of the concrete tanks’ floors and walls forming holes and cracks hence reducing the binding strength of the aged concrete. The worn concrete exposed the reinforcing steel bars to soda ash chemical attack. Therefore, the soda ash solution in aged concrete tanks was observed to wear the concrete and reduce its efficiency. Acknowledgments: The authors appreciate the Department of Science, Technology and Engineering Kibabii University for the assistance accorded during the study.

References 1. Shaikh FUA. Effects of alkali solutions on corrosion durability of geopolymer concrete. Adv Concr Constr 2014;2:109. 2. Martynov V, Martynova O, Makarova S, Vietokh O. Method for calculating the composition of cellular concrete. Bull Odessa State Acad Civ Eng Archit 2021;4:77. 3. Dunuweera SP, Rajapakse RMG. Cement types, composition, uses and advantages of nanocement, environmental impact on cement production, and possible solutions. Adv Mater Sci Eng 2018; 2018:1. 4. Hay R, Ostertag CP. New insights into the role of fly ash in mitigating alkali-silica reaction (ASR) in concrete. Cement Concr Res 2021;144:106440.

References

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5. Barbhuiya S, Kumala D. Behaviour of a sustainable concrete in acidic environment. Sustainability 2017;9:1556. 6. Krivenko P, Rudenko I, Konstantynovskyi O, Boiko O. Prevention of steel reinforcement corrosion in alkali-activated slag cement concrete mixed with seawater. E3S Web Conf. 2021;280:07004. 7. Shi C, Stegemann JA. Acid corrosion resistance of different cementing materials. Cement Concr Res 2000;30:803. 8. Masood U. Studies on Characteristics of Mixed Fiber Reinforced Concrete For Structural Applications. Hyderabad: Jawaharlal Nehru Technological University; 2013. 9. Al-Jadabi N, Laaouan M, Mabrouki J, Fattah G, El Hajjaji S. Comparative study of the coagulation efficacy of Moringa Oleifera seeds extracts to alum for domestic wastewater treatment of Ain Aouda City, Morocco. E3S Web Conf. 2021;314:08003. 10. Jedidi M, Benjeddou O. Chemical causes of concrete degradation. MOJ Civ Eng 2018;4:40. 11. Sabapathy YK, Sabarish S, Nithish CN, Ramasamy SM, Krishna G. Experimental study on strength properties of aluminium fibre reinforced concrete. J King Saud Univ - Eng Sci. 2021;33:23. 12. Ormellese M, Boizoni F, Perez ER, Goidanich S. Migrating corrosion inhibitors for reinforced concrete structures. NACE -International Corrosion Conference Series 2007;1–16. 073011. https://doi.org/10.1533/9781845692285.211. 13. Millán Ramírez GP, Byliński H, Niedostatkiewicz M. Deterioration and protection of concrete elements embedded in contaminated soil: a review. Materials 2021;14:3253. 14. Totan M, Antonescu E, Gligor FG. Quantitative spectrophotometric determinations of Fe3+ in iron polymaltose solution. Indian J Pharmaceut Sci 2018;80:268. 15. Mitsugi S, Owaki E, Masuda H, Shimamoto R. Accelerated concrete carbonation and resulting rebar corrosion under a high temperature condition in nuclear power plants. J Adv Concr Technol 2021; 19:382. 16. Pravalika A, Venkat N. Effect of carbonation on the properties of concrete. Int. J. Civ. Eng. Technol 2018;9:1605. 17. Liu P, Chen Y, Yu Z, Zhang R. Effect of temperature on concrete carbonation performance. Adv Mater Sci Eng 2019;2019:1. 18. Wang J, Ng P-L, Su H, Chen J, Du J. Effect of concrete stress states on carbonation depth of concrete. J Civ Eng Manag 2019;25:518. 19. Akpinar P, Uwanuakwa ID. Investigation of the parameters influencing progress of concrete carbonation depth by using artificial neural networks. Mater Construcción 2020;70:209. 20. Peng J, Tang H, Zhang J, Cai SCS. Numerical simulation on carbonation depth of concrete structures considering time- and temperature-dependent carbonation process. Adv Mater Sci Eng 2018;2018:1. 21. Liu Z, Van den Heede P, De Belie N. Effect of the mechanical load on the carbonation of concrete: a review of the underlying mechanisms, test methods, and results. Materials 2021;14:4407. 22. Gupta EL, Singh EH. Steel and glass fibre reinforced concrete: a review. Int Res J Eng Technol 2018; 5:291.

Seth Apollo*

4 A review of sludge production in South Africa municipal wastewater treatment plants, analysis of handling cost and potential minimization methods Abstract: The government of South Africa through the department of water and sanitation has installed numerous activated sludge systems in most of the municipal wastewater treatment plants (MWWTPs) to ensure adequate sanitation. However, secondary sludge generation and handling is a major challenge of the AS process. This work reviews the sludge production potential in selected regions in South Africa including Midvaal, Emfuleni and Lesedi municipalities. Further, the sludge handling cost and potential methods of sludge minimization are discussed. This study found that the selected MWWTPs discharge effluent volume of between 3 and 65 ML/day with average COD of about 350 mg/L leading to sludge production of between 5 and 23 tons/ day with an estimated handling cost of €57,000 to €320,000 per year. Some of the technologies reviewed for sludge minimization to cut down plant operation cost include chemical oxidation using ozone and potassium ferrate (K2FeO4), application of oxic-settling-anaerobic (OSA) process, anaerobic/anoxic/oxic (AAO) combined with K2FeO4 oxidation side stream reactor (SSR), SANI® technology and use of anaerobic side stream reactor (ASSR) in the conventional activated sludge (AS) line. Keywords: anaerobic side stream reactor (ASSR); oxic-settling-anaerobic process; SANI®technology; sludge minimization techniques; waste activated sludge.

4.1 Introduction Unreliable rainfall patterns in South Africa have led to water scarcity [1]. In order to make up for the shortage in rainfall, different measures have been put in place to conserve the available water resources. These methods include provision of sanitation services to prevent pollution of the available water resources. Notably is the effort by the government to provide wastewater treatment plants to serve various urban and rural communities, although the number of wastewater treatment facilities is still inadequate [2]. For example, Sedibeng District in Gauteng province which has an

*Corresponding author: Seth Apollo, Department of Chemical Engineering, Vaal University of Technology, Private Bag X21, Vanderbijlpark, South Africa; and Department of Physical Sciences, University of Embu, P.O. Box 6-60100, Embu, Kenya, E-mail: [email protected]. https://orcid.org/ 0000-0003-3296-697X As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: S. Apollo “A review of sludge production in South Africa municipal wastewater treatment plants, analysis of handling cost and potential minimization methods” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0234 | https://doi.org/ 10.1515/9783110752601-004

40

4 Review of sludge production in South Africa MWWTPs

estimated population of 805,000 people has a good provision of water and sanitation services with some 95% and 91% of household served, respectively [3]. South Africa uses biological processes in handling municipal wastewater [4]. The major biological treatment methods used are ponds, biofilters and activated sludge (AS) of which the AS handles approximately 65% of the municipal wastewater [5]. Despite the ability of AS process to handle high organic load in municipal wastewater it leads to generation of waste activated sludge (WAS) which requires additional handling [6, 7]. Major sludge handling cost includes dewatering and disposal which constitutes averagely 40% of the total AS plant running cost [7]. Sludge dewatering in South Africa municipal wastewater treatment plants (MWWTPs) is commonly achieved through dry beds and belt filter press that constitutes 36% and 29% of dewatering methods, respectively [8]. It has been established that more research is necessary to assist MWWTPs in South Africa to overcome challenges of sludge handling [9]. Various methods can be combined with the AS process to ensure reduction in WAS production. Some of these technologies include mechanical processes such as ultrasonic treatment, electrical treatment and chemical oxidation using ozone, free nitrous acid and Fenton reagent [6]. Alternatively, insertion of a settler after the oxic chamber of the AS process with total WAS recycle to an anterior anerobic chamber has been used to achieve adequate sludge reduction [10]. Other promising methods for sludge minimization are Anaerobic/anoxic/oxic (AAO) combined with potassium ferrate (K2FeO4) oxidation side stream reactor (SSR), SANI® technology and use of anaerobic side stream reactor (ASSR) in the AS line. This work reviews the state of sludge generation in South Africa for the past 10 years based on analysis of some selected MWWTPs in Gauteng province and provides possible sludge handling options to reduce the high operation cost of MWWTPs that is associated with sludge handling and disposal. This review therefore provides insight on the need of applying sludge minimization techniques in the MWWTPs in South Africa. The information covered in this work is vital for policy formulation on sludge management in South Africa.

4.1.1 Municipal wastewater generation in South Africa The observed increase in population in South Africa over the past few years has put a lot of pressure on water resources. There has been an increase in the provision of water and sanitation services to various communities in the country. For example, the coverage of sewerage services in the three municipalities in Sedibeng District in Gauteng Province was between 88.7% and 95.3% in 2015 [3]. However, more effort is still required to provide sanitation to families not yet covered as shown in Table 4.1. The water used by the communities in Emfuleni municipality is abstracted from the Vaal River [11]. The domestic wastewater generated is treated by the MWWTPs in the municipality then discharged back to the river. The capacities of some selected WWTPs in Emfuleni Municipality and in other parts of the country are shown in Table 4.2 [3].

41

4.1 Introduction

Table .: Households with sanitation services in Sedibeng District []. Municipality

Sanitation coverage (%)

Families without sanitation services

. . .

 , 

Midvaal Emfuleni Lcsedi

Table .: An estimate of treatment capacity of some IVIWWTPs in South Africa []. MWWTP Capacity (ML/day)

Mcycrton

Lccuwkuil

Rictgat

Sandspruit

Sebokeng

Rictspruit

Darvill

.

.

.

.







4.1.2 Municipal wastewater treatment South Africa uses ponds, biofilters and AS systems for the management of wastewater generated in most of the municipalities. AS plants constitute 33% of the total wastewater treatment plants in the country, the technology handles 65% of the municipal wastewater [5]. AS process, shown in Figure 4.1, consist of anoxic and oxic/aeration chambers where nitrates and organic compounds in wastewater are removed, respectively [12]. At the oxic chamber microorganisms consume the biodegradable organic contaminants in the wastewater generating carbon dioxide and WAS [13]. The WAS is estimated as 1.2 kg TSS/ kg COD [6]. The WAS is made up of dead microorganisms (bacteria), extracellular polymeric substances (EPS) excreted by the bacteria. The sludge is separated using secondary/ final sedimentation tank for further processing and disposal. Detailed characterization of sludge from South Africa MWWTPs is reported in a study by Badza [14]. Some of the sludge characteristics are shown in Table 4.3. The sludge

Figure 4.1: AS process treating municipal wastewater.

42

4 Review of sludge production in South Africa MWWTPs

Table .: Characteristics of WAS [, ]. Parameter pH TS VS VS/TS TCOD SCOD Soluble sugar Soluble protein Bulk density Particle density Ash Higher heating value

Unit % w/w % w/w mg/L mg/L mg/L mg/L kg/L kg/L g/kg MJ/kg

Value .–. .–. .– .–. ,–, –   .–. .–. – .–.

in South Africa is dewatered through dry beds (36%), belt filter press (29%), lagoon (4%) and centrifuge (5%) while 17% of the sludge generated is never dewatered [8]. These posterior sludge handling processes and disposal lead to high operation cost and secondary pollution. Sludge management is a challenge to developing economies owing to the handling cost implication and stringent environmental regulation [15].

4.2 Sludge management 4.2.1 Estimated sludge quantity and handling cost for WWTPs Biological wastewater treatment methods, particularly, anaerobic digestion and AS system have been applied worldwide for the treatment of municipal wastewater. The biological methods are efficient in removing organic pollutants; however, excess production of secondary sludge results from the AS process. For example, USA, Europe and China produces some 240 million tons of WAS annually [17]. Sludge handling requirements is estimated to constitute above 40% of the AS plant running cost [7]. Analysis of the operating cost against running cost of an AS plant is shown in Figure 4.2 adopted from analysis by Dentel and Qi [18]. Some of the major methods used for sludge disposal are landfill, use as fertilzer, energy recovery and incineration [19]. Sludge disposal through any of these methods is reported to cost €30–100 per wet ton, making sludge disposal costly [6]. Table 4.4 shows the estimated WAS production and annual handling cost for some selected MWWTPs in South Africa. The estimation assumed an average influent COD of 350 mg/L [3], COD removal efficiency of 75% and sludge yield of 1.2 kg TSS/kg COD [6]. The WAS disposal

4.2 Sludge management

43

Figure 4.2: Comparative analysis of wastewater treatment cost and sludge handling cost. Table .: An estimate of annual sludge handling cost for some MWWTPs in South Africa. Wastewater treatment plant Mcyerton Lecuwkuil Rictgat Sandspruit Sebokeng Rietspruit Darvill

Capacity (ML/day)

Estimated COD load (ton/day)

Estimated sludge (ton/day)

Estimated sludge handling cost (€/year)

. . . .   

. . . . . . .

. . . . . . .

, , ,  , , ,

cost of €30/ton was adopted as cited previously. The capacities of the identified plants were obtained from literature [3]. The high cost associated with sludge treatment and disposal together with the environmental concerns caused by the methods of sludge disposal has led to the intensification of research targeting methods of sludge minimization or even total elimination in municipal wastewater treatment line [20]. The sludge from MWWTPs can be classified as either primary or secondary sludge, the former is the sludge removed from raw sewage in the primary settler. Secondary sludge or WAS is majorly biomass resulting from the bacterial activity in the biological treatment process [21]. The sludge can be disposed to designated sites or can be used for other activities.

4.2.2 Sludge disposal Approximately 80% of the WAS produced in South Africa is managed using dedicated land disposal (DLD) sites [22], some portion the WAS is used in agriculture [14].

44

4 Review of sludge production in South Africa MWWTPs

Different studies have reported the environmental impact caused by land disposal of sewage sludge. The sludge is supposed to be degraded at the disposal site, the sludge surface should be plowed regularly to facilitate aeration and degradation, also, to control odor and invasion by insects. Dedicated sewage sludge land disposal site are designed for strict control of surface runoff to protect surface water bodies [22]. At the site, the organic pollutants are degraded while some are bound to soil colloids together with metals present in the disposed sludge.

4.2.3 Land application and Environmental impact of sewage sludge The sludge can be beneficiated to be applied in farms as organic fertilizer; it can also be used in making briquette among other uses. Land application in agriculture is the main benefit derived from WAS because of its good nutrients value which helps to improve poor soil conditions and improve crop yield that can be used to generate income. However, environmental concerns are the major drawback of direct land application or disposal of sewage sludge, specifically groundwater pollution through leaching of excess nutrients and heavy metals [23]. If the sludge is to be used for land/firm application then the pathogens in the biosolids should be minimal not to be of any risk to the consumers of farm products as reported by Carolina et al. [24]. Dried sewage sludge requires careful handling since dusts show high risk of selfignition and produces explosive atmosphere [25]. Dried sewage sludges are flammable products that present a self-ignition risk. This calls for caution since the dried sewage sludge is composed of dusts that might not only be at risk of spontaneous combustion but could also produce explosive atmospheres in the form of dust–air mixture (Medic Pejic et al. [26]).

4.3 Sludge minimization technologies in WWTPs Sludge minimization in WWPTs can be achieved through chemical, biological, mechanical, thermal and electrical treatment methods. The methods achieve sludge minimization or elimination by causing lysis of cells in the sludge mass. The cell lysis is accompanied leads to release of cell components which are soluble and readily degradable [6]. These methods are applied after the AS process and the intercellular and extracellular substances from the lysed cells are biodegradable thus are recycled to the main-stream bioreactor (AS unit) for further biodegradation. In many instances, the sewage sludge from the AS process is directed to an anaerobic digestion process for stabilization to achieve sludge reduction [17]. However, the efficiency of the anaerobic digestion process for sludge stabilization is hindered by the low biodegradability of waste AS, this calls for application of some pre-treatment technologies to enhance WAS biodegradability prior to the anaerobic digestion process [27].

4.3 Sludge minimization technologies in WWTPs

45

4.3.1 Chemical, mechanical, thermal and electrical methods of sludge reduction Sludge reduction through chemical treatment includes application of chemical oxidation method and free nitrous acid (FNA) treatment. Chemical oxidation methods include ozonation, use of chlorine and Fenton reagent. Of these methods, ozonation is common as it results in adequate sludge disintegration, cell destruction and solubilization of particulate matter through both direct ozonation and production of hydroxyl radicals [28]. Ozone applied in the range of 0.01–0.74 g O3/g TSS in a full scale WWTP can achieve zero sludge production or at least 10% sludge reduction [6]. Chlorine dose of between 0.07 and 0.20 g Cl2/g TSS achieves efficiency of 45–60%. FNA which is currently at a trial phase in laboratory stage has been found to be effective in biomass degradation achieving sludge reduction of 11–28% at FNA dosage of 1.35–2.0 mg N/L [6]. Mechanical methods of WAS treatment involve the use of ultrasonic treatment and high pressure homogenization. Ultrasonic treatment results in the formation of hydroxyl radicals in water through cavitation. It also lead to generation of high pressure, temperature and shear force through acoustic cavitation that lead to the disintegration of sludge [20]. Ultrasonic applied at full scale resulted in 25–90% sludge reduction when applied at a frequency range of 20–31 kHz [29]. Thermal treatment of WAS at 90 °C enables the release of biodegradable intracellular materials which are recycled to the main bioreactor, this reduces sludge by about 60% [20]. Applying electrical energy of about 1650 kJ/kg TSS achieves sludge reduction of up to 45% by attacking the phospholipids which are the main constituent of cell membrane [6]. The merits and limitations of some methods of WAS reduction is shown in Table 4.5. Table .: Merits and limitations of main technologies applied in WAS reduction []. Approach

Method

Advantages

Disadvantages

Chemical treatment

Use of O

Enhances sludge settling ability Easy to acquire and operate

High ozone generation cost; a spike on outlet COD Production of degradation byproducts; forms fluffy sludge; a spike on outlet COD A spike on outlet COD Under trial

Chlorination

Mechanical treatment Thermal treatment Electrical treatment

Fenton process Easy to acquire and operate Free nitrous Easy to acquire and operate; acid (FNA) no spike on outlet COD, No fluffy sludge Ultrasonic Enhances sludge settling treatment ability Enhances sludge settling ability Enhances sludge settling ability

High initial investment cost, a spike on outlet COD High energy requirement A spike on outlet COD, high energy requirement

46

4 Review of sludge production in South Africa MWWTPs

4.3.2 Integrated biological methods for WAS minimization Various biological and physical methods can be combined with the AS process to ensure WAS minimization. A process that combines physical and biological process patented as Cannibal® process has been applied in WAS reduction. In the cannibal process part of the WAS sequentially passes through physical separation to remove settleable inert components. The WAS then flows into anaerobic/anoxic interchange reactor where lysis of cells occur for final biodegradation in the main-stream bioreactor. Novak et al. [30] reported 60% reduction in WAS production when Cannibal® process was used to treat municipal wastewater. ASSR has also been used to minimize sludge production in the conventional AS line. The arrangement of AS integrated with ASSR is common in new and existing WWTPs. The sludge reduction is achieved in the ASSR where a portion or all the return sludge of the AS process is degraded in an alternating aerobic (anoxic) and anaerobic conditions. Ferrentino et al. [31] reported a WAS reduction of 40–60% when AS process was integrated with the ASSRS process. A SANI® technology employs a process that uses a sequentially integrated three biological reactors that use slow growing bacteria resulting in low sludge yield. The SANI® process is mainly applicable for wastewater containing high sulfate concentration, typical example is wastewater from toilets flushed using sea water [32]. The process consists of three sequentially arranged bioreactors; the first reactor is anaerobic containing sulfate reducing bacteria (SRB) where simultaneous oxidation of organic carbon to CO2 and reduction of sulfate to sulfide takes place. Second reactor is anoxic containing sulfur oxidizing bacteria (SOB) for conversion of sulfide back to sulfate, also reduction of nitrates to nitrogen occurs and oxidation of ammonia to nitrate takes place in the third aerobic reactors that contains autotrophic nitrifiers. A sludge reduction of 60–70% was achieved in a full scale SANI® reactor [33]. An integrated anaerobic digestion followed by autotrophic nitrogen removal stage has been successfully applied to delivery adequately treated municipal wastewater with satisfactory reduction in sludge production. This is because most of the treatment processes employ anaerobic digestion which normally produces less sludge compared to the conventional AS treatment [6]. An integrated system with high-rate AS or anaerobic membrane bioreactor followed by autotrophic nitrogen removal stages has been suggested as a promising wastewater process with low sludge production [17]. The sludge production of anaerobic membrane bioreactor followed by autotrophic nitrogen is significantly reduced due to the low sludge yield of anaerobic microbes which is less than 0.1 g COD/g COD [21]. An arrangement of a modified AS process consisting of a sequentially arranged AAO can be combined with a chemical oxidation side stream to achieve sludge minimization. The SSR used is often K2FeO4 oxidation [34]. The AAO-SSR has been reported to achieve nearly 50% sludge reduction [35].

References

47

Modification of the AS process by incorporating dedicated anaerobic digestion, sludge settling and WAS recycle units improves the quality of treated effluent and significantly reduces amount of WAS. In the oxic-settling-anaerobic (OSA) process the sludge reduction process is obtained by inserting a holding sludge tank for RAS, and it reduces 14.0–63.5% of excess sludge under anaerobic conditions [36]. The holding sludge tank produced more gas and reduced excess sludge through hydrolysis under anaerobic conditions. Sludge reduction is also achieved by incorporating a sludge settler and total WAS recycle and subsequent degradation in a modified AS system incorporating an anaerobic chamber [37]. In this kind of arrangement, the effluent from the oxic chamber of the AS process pass-through classification technology to achieve sludge liquid separation. The settled WAS is recycled to the anterior anaerobic chamber for sludge degradation through hydrolysis and acidification processes [38]. Through sludge hydrolysis the SPRAS system achieves near-zero sludge generation because of high solids retention time (SRT) at minimum hydraulic retention time (HRT) [38].

4.4 Conclusions This review has shown that the investment and operation costs associated with handling the sludge from the AS processes is huge, contributing to nearly 40% of the total MWWTP operational cost. Further, the study showed a need of employing sludge management technologies to minimize MWWTPs operating cost. The estimated sludge production in the seven wastewater treatment plants reviewed in this study were between 5 and 23 tons/day with sludge handling cost of between 57,000 and 320,000 €/year, respectively. This cost is huge and necessitates research on methods for sludge minimization in South Africa. Some of the technologies reviewed for sludge minimization include chemical oxidation using ozone and K2FeO4, application of OSA process, AAO combined with K2FeO4 oxidation SSR, SANI® technology and use of ASSR in the conventional AS line. The mechanism of sludge reduction is largely through lysis and hydrolysis. Some sludge reduction methods such as chemical oxidation and hydrolysis through anaerobic digestion leads to an increase in biodegradable COD in the treated wastewater. The COD is due to the release of biodegradable cell content after the lysis of bacterial cell wall. The biodegradable COD is therefore recycled to the main reactor (AS system) for degradation.

References 1. Alzboon KK, Radaideh J, Hung Y. Municipal wastewater treatment publisher. Singapore: World Scientific Publishing Co; 2012. 2. Herbig FJW. Talking dirty - effluent and sewage irreverence in South Africa: a conservation crime perspective. Cogent Soc Sci 2019;5:1–18.

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3. Teklehaimanot GZ, Kamika I, Coetzee MAA, Momba MNB. Population growth and its impact on the design capacity and performance of the wastewater treatment plants in Sedibeng and Soshanguve, South Africa. Environ Manag 2015;56:984–97. 4. Osuolale O, Okoh A. Human enteric bacteria and viruses in five wastewater treatment plants in the Eastern Cape, South Africa. J Infect Publ Health 2017;10:541–7. 5. Hansen K. Overview of wastewater treatment in South Africa. Award Tech Rep Ser 2015:63. 6. Wang Q, Wei W, Gong Y, Yu Q, Li Q, Sun J, et al. Technologies for reducing sludge production in wastewater treatment plants: state of the art. Sci Total Environ 2017;587–588:510–21. 7. Niu T, Zhou Z, Shen X, Qiao W, Jiang L, Pan W. Effects of dissolved oxygen on performance and microbial community structure in a micro-aerobic hydrolysis sludge in situ reduction process. Water Res 2016;90:369–77. 8. Snyman HG. Management of wastewater and faecal sludge in Southern Africa. Water Pract Technol 2007;2. https://doi.org/10.2166/wpt.2007.089. 9. Friedrich E, Pillay S, Buckley CA. Carbon footprint analysis for increasing water supply and sanitation in South Africa: a case study. J Clean Prod 2009;17:1–12. 10. Zhen Z, Qiao W, Xing C, Shen X, Hu D, Wang L. A micro-aerobic hydrolysis process for sludge in situ reduction: performance and microbial community structure. Bioresour Technol 2014;173:452–6. 11. Iloms E, Ololade OO, Ogola HJO, Selvarajan R. Investigating industrial effluent impact on municipal wastewater treatment plant in vaal, South Africa. Int J Environ Res Publ Health 2020;17:1–18. 12. Zhang S, Huang Z, Lu S, Zheng J, Zhang X. Bioresource Technology Nutrients removal and bacterial community structure for low C/N municipal wastewater using a modified anaerobic/anoxic/oxic (mA2/O) process in North China. Bioresour Technol 2017;243:975–85. 13. Demirbas A, Edris G, Alalayah WM. Sludge production from municipal wastewater treatment in sewage treatment plant. Energy Sources, Part A Recover. Util. Environ. Eff. 2017;39:999–1006. 14. Badza T, Tesfamariam EH, Cogger CG. Agricultural use suitability assessment and characterization of municipal liquid sludge: based on South Africa survey. Sci Total Environ 2020;721:137658. 15. Abdel Wahaab R, Mahmoud M, van Lier JB. Toward achieving sustainable management of municipal wastewater sludge in Egypt: the current status and future prospective. Renew Sustain Energy Rev 2019;127:109880. 16. Eskicioglu C, Ã KJK, Droste RL. Characterization of soluble organic matter of waste activated sludge before and after thermal pretreatment. Water Res 2006;40:3725–36. 17. Zhang Q, Hu J, Lee D, Chang Y, Lee Y. Sludge treatment: current research trends. Bioresour Technol 2017;243:1159–72. 18. Dentel SK, Qi Y. Management of sludges, biosolids, and residuals. Compr Water Qual Purif 2013;3: 223–43. 19. Kacprzak M, Neczaj E, Grobelak A, Rorat A, Brattebo H, Grosser A, et al. Sewage sludge disposal strategies for sustainable development. Environ Res 2017;156:39–46. 20. Trzcinski AP, Tian X, Wang C, Lin LL, Ng WJ. Combined Ultrasonication and thermal pre-treatment of Waste Activated Sludge to increase biogas production. J Environ Sci Health - Part A Toxic/Hazard Subst Environ Eng 2014;50:213–23. 21. Metcalf, Eddy. Wastewater engineering: treatment and reuse. McGraw-Hill; 2003. 22. Herselman JE, Steyn CE, Snyman HG. Dedicated land disposal of wastewater sludge in South Africa: leaching of trace elements and nutrients. Water Sci Technol 2006;54:139–46. 23. Mcgrath SP, Chaudr AM, Giller KE. Long-term effects of metals in sewage sludge on soils, microorganisms and plants. J Ind Microbiol Biotechnol 1994;14:94–104. 24. Carolina M, Cristina M, Braga B. Assessment of the accuracy of a method used for quantification of Ascaris eggs in sewage sludge. Mod Environ Sci Eng 2016;2:31–6.

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25. García-Torrent J, Ramírez-Gómez Á, Querol-Aragón E, Grima-Olmedo C, Medic-Pejic L. Determination of the risk of self-ignition of coals and biomass materials. J Hazard Mater 2012;213–214:230–5. 26. Medic Pejic L, Fernandez Anez N, García Torrent J, Ramírez-Gómez Á. Determination of spontaneous combustion of thermally dried sewage sludge. J Loss Prev Process Ind 2015;36:352–7. 27. Appels L, Dewil R, Baeyens J, Degre J. Principles and potential of the anaerobic digestion of wasteactivated sludge. Prog Energy Combust Sci 2008;34:755–81. 28. Otieno B, Apollo S, Kabuba J, Naidoo B, Simate G, Ochieng A. Ozonolysis pre-treatment of waste activated sludge for solubilization and biodegradability enhancement. J Environ Chem Eng 2019;7: 102945. 29. Zhang G, Zhang P, Yang J, Chen Y. Ultrasonic reduction of excess sludge from the activated sludge system. J Hazard Mater 2007;145:515–9. 30. Novak JT, Chon DH, Curtis B, Doyle M. Biological solids reduction using the cannibal process. Water Environ Res 2007;79:2380–6. 31. Ferrentino R, Langone M, Merzari F, Tramonte L. A review of Anaerobic Side-Stream Reactor for excess sludge reduction: configurations, mechanisms and efficiency. Crit Rev Environ Sci Technol 2015;3389:1–24. 32. Wang J, Lu H, Chen G, Lau GN, Tsang WL, Van Loosdrecht MCM. A novel sulfate reduction, autotrophic denitrification, nitrification integrated (SANI) process for saline wastewater treatment. Water Res 2009;43:2363–72. 33. Wu D, Ekama GA, Chui H-K, Wang B, Cui Y-X, Hao T-W, et al. Large-scale demonstration of the sulfate reduction autotrophic denitrification nitrification integrated (SANI®) process in saline sewage treatment. Water Res 2016;100:496–507. 34. Ye F, Ji H, Ye Y. Effect of potassium ferrate on disintegration of waste activated sludge (WAS). J Hazard Mater 2012;219–220:164–8. 35. An Y, Zhou Z, Yao J, Niu T, Qiu Z, Ruan D, et al. Sludge reduction and microbial community structure in an anaerobic/anoxic/oxic process coupled with potassium ferrate disintegration. Bioresour Technol 2017;245:954–61. 36. Wang Z, Yu H, Ma J, Zheng X, Wu Z. Recent advances in membrane bio-technologies for sludge reduction and treatment. Biotechnol Adv 2013;31:1187–99. 37. Samblante G, Guo W, You S, Price W, Hai F, Nghiem L. Sludge cycling between aerobic, anoxic and anaerobic regimes to reduce sludge production during wastewater treatment: Performance, mechanisms, and implications. Bioresour Technol 2014;155:395–409. 38. Zhou Z, Xing C, Wang Y, Wang C, Wang Y, Qiao W, et al. Sludge reduction and performance analysis of a modified sludge reduction process. Water Sci Technol 2014;69:934–40.

Chima F. Nnodum*, Kafeelah A. Yusuf and Adedoja D. Wusu

5 A comparison of two digestion methods and heavy metals determination in sediments Abstract: This study was conducted to evaluate the levels of heavy metal concentrations in sediments and also involves a comparison of two different digestion protocols. The first digestion procedure was done with a mixture of hydrochloric acid and nitric acid while the second digestion method was done using the United States Environmental Protection Agency method 3052 which comprises nitric acid, hydrofluoric acid, hydrochloric acid, and hydrogen peroxide. The sediment samples were analyzed for cadmium, copper, iron, lead, zinc, chromium, manganese, nickel (Cd, Cu, Fe, Pb, Zn Cr, Mn, and Ni) with the aid of atomic absorption spectrophotometer. Concentrations of metals ranged 0–7.0 mg/kg for Cr, 0.5–20.0 mg/kg for Cd, 10.8–112.0 mg/kg for Fe, 0.10–7.20 mg/kg for Pb, 45.69–184.96 mg/kg for Cu, 1.0–73.75 mg/kg for Zn, 1.5–19.7 mg/kg for Mn and nd −3.0 mg/kg for Ni. The order of concentrations of the metals in the samples are Cu > Fe > Zn > Cd > Mn > Pb > Cr > Ni. The second digestion method yielded higher levels of metal concentration. Comparison with theWorld Health Organization (W.H.O) standards for marine sediments showed that the average concentrations of heavy metals were within the permissible limits. Close monitoring and more publicity are further needed to discourage further pollution of the area. Keywords: Atomic absorption spectrophotometer; digestion; heavymetals; pollution; sediment.

5.1 Introduction Anthropogenic activities such as mining, industrial/agricultural activities, and the production of a variety of chemicals, lead to the making of some unwanted chemicals which are detrimental to human health and the environment. Urban developments as well as other human activities near rivers and estuaries are some of the main contributors of heavy metals in coastal areas [1, 2]. Heavy metals present in industrial effluents also contaminates the river into which they are discharged [3]. Contamination of rivers and lakes and streams lead to loss of biodiversity, reduced ecosystem productivity, and habitat loss in general [4]. It has also been reported that over 80% of pollution load in coastal environments have their origins in agriculture, industries,

*Corresponding author: Chima F. Nnodum, Department of Chemistry, Lagos State University, Ojo, Nigeria, E-mail: [email protected] Kafeelah A. Yusuf, Department of Chemistry, Lagos State University, Ojo, Nigeria Adedoja D. Wusu, Department of Biochemistry, Lagos State University, Ojo, Nigeria As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: C. F. Nnodum, K. A. Yusuf and A. D. Wusu “A comparison of two digestion methods and heavy metals determination in sediments” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0194 | https://doi.org/10.1515/9783110752601-005

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5 A comparative study of two digestion techniques in sediments

urban and rural activities [5]. Heavy metals include metals such as cadmium, chromium, lead, zinc, manganese, copper, and iron. Cadmium is a very toxic metal and a known human carcinogen. Injection of cadmium leads to stomach irritation, vomiting, and diarrhea while long-term exposure to lower levels of cadmium leads to kidney diseases and lung damage [6]. Chromium however can make fish susceptible to infection. A high concentration of chromium can damage or accumulate in various fish tissues and also in invertebrates such as snails and worms. Industrial wastewater discharge into the aquatic environment is a good source of chromium. Chromium vi compound is very toxic and carcinogenic in nature but chromium iii compounds are less toxic and are essential nutrients for humans [7]. Copper is a trace metal necessary for life and may be found in many kinds of foods and drinking water. However, too much copper in the body is not good for human health and can cause some negative adverse effects such as increased blood pressure and respiratory rates, damage to the kidney, liver, vomiting, or even date [7]. When copper enters the soil, it can attach itself strongly to organic matters and other minerals present in the soil thus making it difficult to travel very far after release. In surface water, copper can also travel far distances as free ions or as suspended particles. The periodic increase in the pollution of the aquatic environment is due to urbanization, unwholesome agricultural practices, and industrialization [8]. The origin of metal pollution in Isolo surface – water is from urbanization. There is an increase in vehicular traffic and the emergence of various industries such as petrochemical industries, steel and food processing industries, car battery sales outlets, lots of automobile workshops, and metal smelting companies. Sediments are seen as a mixture of many components of various mineral species and they act as sinks for various pollutants in the aquatic ecosystem. Sediments are also used in the assessment of heavy metal contamination of an area. Heavy metals discharged into the environment directly affect the overlying water body [1, 9]. Contaminated sediments in rivers, lakes, and coastal regions can carry heavy metals into the water bodies and subsequently to aquatic organisms living within depending on the speciation of metals, sediment pH, and other organic matter. Concentrations of some trace elements such as Cd, Cu, Ni, Pb, Zn, and other metals are usually elevated above background levels as a result of some human activities [2, 10]. In the past few decades, many studies have been conducted on the concentrations of heavy metals in fish in various parts of the world [10]. A study performed by [11] on Terkos Lake, which provides a portion of the drinking water to Turkey’s most important metropolitan area, Istanbul in May 2008 revealed the presence of, Al, Cu, Pb, Cd, Fe, Zn, Cr, and Ni were examined. The sediment was discovered to have high enrichment factors (EF) of Zn, Cr, Cd, and Pb metals which come from anthropogenic sources (domestic and industrial input). However, the lake sediment is moderately contaminated by Zn, Cr, and Pb, but heavily contaminated by Cd. The metal concentrations obtained from the sediment samples were compared with the standard quality guidelines for sediments SQGs [12] which showed that cadmium and lead had high values while nickel and zinc

5.2 Materials and methods

53

concentrations exceeded thresh hold effect levels (TEL) and chromium exceeded both TEL and probable effect concentrations (PEC) maximums. Various digestion procedures have been employed by different researchers with different results. In a related work done by Ygor Jacques in 2014, three different digestion procedures were used for the digestion of sediments, they include United States of America Environmental Proyection Agency (USEPA) method 3051A, 3052, and the method stipulated by the ministry of agriculture, livestock and food supply in Brazil (MAPA Brazil, 2006). The first method involved digestion of sediment samples with HNO3 and HCL, the second method was with HNO3 and HF while the third digestion method was with HCl [13]. The author noted that USEPA 3052 promoted more complete digestion as was also observed in this study. In another research work done by Duyusen in 2011, three different digestion methods were employed for metal digestion of sediment samples, the first was with HNO3, the second digestion was done with HNO3, HF, and HCl while the third digestion was done using HCl. The results showed that the soil samples were properly extracted with the second digestion procedure which involved HNO3, HCL, and HF as was also observed in this study. Other procedures however yielded good results in terms of recovery [14]. The author recommended all the procedures for the digestion of soil and sediment samples. This study is aimed at determining the current levels of heavy metal pollution in the study area and also to compare two different digestion protocols for the extraction of heavy metals in sediments.

5.2 Materials and methods Study area. Lagos State is located on the South-Western part of Nigeria, on the narrow plain of the Bight of Benin. Lagos stretches over 180 km along the Guinea Coast of the Bight of Benin on the Atlantic Ocean. Isolo is a City located to the northwest of Lagos, southern Nigeria, on latitude and longitude coordinates of 6.514193 and 3.308678 as shown in Figure 5.1. It comprises lots of residential zones, an international Lagos airport area, some entertainment zones, and other business/official areas. It is estimated that the total population of the district is over 620,000 people. Isolo creek receives wastewater discharges from various industrial companies located within the area. The area is characterized by heavy industrial activities including pharmaceutical industries, beverage industries, lots of car battery and automobile shops, household wastewater discharges, heavy vehicular emissions, and other human activities. Urbanization has led to an increased population of the area over the decades. There are also some health institutions located within the area.

5.2.1 Sampling and pre-treatment Sediment samples were collected in polypropylene containers (1 kg) bi-monthly from 10 locations along the creek for six months by grab method at a depth of 15 cm below the river bed. The samples were collected from January to June 2020. They were then air-dried and sieved through sieves of stainless steel ≤2 mm mesh to ensure homogeneity of the samples in preparation for digestion and heavy metal analysis larger particles were removed from the rest.

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5 A comparative study of two digestion techniques in sediments

5.2.2 Determination of pH, conductivity, and total organic matter The pH of the sediment reflects the acidity or alkalinity of the soil sample. It is vital for the existence of a phase and its speciation. Toxicity is also dependent on pH. The pH of the sediment was determined using USEPA method 9045. 20 g of the sediment sample was weighed in a beaker and 20 ml distilled water was added to form a suspension. The suspension was stirred for 60 mins at room temperature and allowed to stand for 1 h. The pH was measured with a pH meter (Hana portable pH/EC/TDS/temperature meter [15]) Electrical conductivity (EC) is the measure of the ability of a substance to alow the flow of electric current. Total dissolved solids (TDS) in a sample is the measure of the dissolved contents of all the organic and inorganice materials present in a liquid.

5.2.3 Conductivity The conductivity of a sample is a measure of its ability to pass an electrical current. Conductivity in water is affected by the presence of inorganic dissolved solids such as chloride, nitrate, sulfate, and phosphate anions or sodium, magnesium, calcium, iron, and aluminum cations. Organic compounds like oil, phenol, alcohol, and sugar do not conduct electrical current very well and therefore have a low conductivity when in water. Conductivity is also affected by temperature: the warmer the water, the higher the conductivity. The conductivities of the sediment samples were measured with a conductivity meter [16]. The organic matter consists of the carbonyl functional groups such as phenols and amines, metals easily combine with organic materials to form organometal complexes.

5.2.4 Organic matter The organic matter content of the sediment samples were determined by dry combustion according to the ASTM D 2974 [17]. The method is based on converting a known weight of the sediment sample in a crucible into ash at a high temperature between 600 °C and 900 °C in a muffle furnace, the difference in weight is then obtained. Geoaccummulation index (lgeo) is used to evaluate heavy metal pollution in sediment as it can expose the enrichment of exogenous heavy metals. It is calculated as follows: lgeo = log 2 [

Csample ] 1.5C background

Where Csample is the concentration of the heavy metal in the sediment and polluted Cbackground is the geochemical background concentration of the heavy metal. A background matrix correction factor of 1.5 is used as a coefficient to compensate for weathering and lithogenic effects. Heavy metal Pollution is classified into seven classes based on the lgeo value. Class 0 (lgeo ≤ 0), practically unpolluted, class 1 (0 < lgeo ≤ 1), unpolluted to moderately; class 2 (1 < 1 lgeo ≤ 2), moderately polluted; class 3 (2 < lgeo ≤ 3), moderately to heavily polluted; class 4 (3 < lgeo ≤ 4), heavily polluted; class 5 (4 < lgeo ≤ 5), heavily to extremely polluted, class 6 (lgeo > 5), extremely polluted [20].

5.2.5 Digestion procedures Two extraction procedures were employed for this work. The first digestion was done using nitric acid and hydrochloric acid. The second digestion was done with nitric acid, hydrofluoric acid,

5.3 Results and discussions

55

hydrochloric acid, and hydrogen peroxide as described by the United States Environmental Protection Agency 3052 [21].

5.2.6 Digestion method 1 (HCl and Nitric acid) 1.0 g of the sediment sample was treated with 15 ml of Nitric acid and 5 ml of Hydrochloric acid. The mixture was kept at room temperature for 24 h after which it was heated on a hot plate at 50 °C and covered with a watch glass. Filtration of the suspension was done and the filtrate was made up to mark in a 50 ml volumetric flask. Atomic absorption spectrophotometer (AAS 200 Perkin Elmer) was used to measure the metal content of the sample.

5.2.7 Method 2 EPA method 3052 (Hydrofluoric acid – Nitric acid, Hydrochloric acid, Hydrogen peroxide) A total of 0.5 g of sediment sample was treated with 9 ml HNO3 and 3 ml of HF. The mixture was allowed to settle for an hour after which 2 ml of HCL and 1 ml of H2O2 were added. The sample was then kept at room temperature for 24 h and heated on a hot plate in a fume chamber for another 5 h at 50 °C. The sample was washed with doubly distilled water, filtered, made up to mark in a 50 ml volumetric flask.

5.2.8 Analysis of metals using Atomic absorption spectrophotometer The concentrations of the metals were determined using Atomic absorption spectrophotometer 200 Perkin Elmer equipped with a hollow cathode lamp. Quality control was done using standard metal solutions. The blank and standards used were tested periodically. The instrument conditions are presented below. 5.2.8.1 Statistical analysis: Mean and standard deviations were used to describe the sediment physicochemical parameters and also the concentrations of metals in the sediment samples. Two extractions methods were applied to the same sample. Metal analysis was done for several days and each metal analysis was carried out on an average of two measures. The mean and standard deviation of each metal was obtained. Analysis of variance (ANOVA) was however used to test for significant differences in the heavy metal content of the sediment samples and the results were compared with the World Health Organization (WHO) standard 2006 and Standard Organization of Nigeria (SON). Levels of heavy metals in other countries were also compared with the results obtained from this study.

5.3 Results and discussions Heavy metals usually do not attach themselves permanently in sediments. Their movements and rates of attachments are affected by the soil texture, pH, and organic matter present in the soil. The results showed a fluctuating pH from sediment one to 10 as shown in Table 5.1. The more acidic or basic the soil is, the higher the electrical conductivity. A decrease in the concentration of ions in the soil also decreases the

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5 A comparative study of two digestion techniques in sediments

electrical conductivity. Soil electrical conductivity is a measure of the amount of salt in the soil (Salinity of soil). It is a good indicator of soil health. Too much salt in the soil reduces plant growth by altering the soil water balance. Sediments one to six were collected from locations closer to the waste discharge points. Many automobile spare parts workshops discharge their wastes into the Isolo surface water. Heavy metal pollution of the environment is enabled by many factors which include the presence of organic matter, pH, etc. Due to the cationic nature of most metals, they easily cleave with other compounds present in the sediment to form organometallic complexes. The instrument’s conditions are shown in Table 5.2. The results showed the mean concentrations of copper, cadmium, chromium, iron, manganese, zinc, lead, and nickel (Cu, Cd, Cr, Fe, Mn, Zn, Pb, Ni), respectively, in all the sediment samples. Among all the samples, Cu had the highest concentration of 184.96 mg/kg in Table 5.4. Method (2) yielded more metals as shown in Table 5.4. The concentrations of metals ranged from 0 to 7.0 mg/kg for Cr, 0.5–20.0 mg/kg for Cd, 10.8–112.0 mg/kg for Fe, 0.10–7.20 mg/kg for Pb, 45.69–184.96 mg/kg for Cu, 1.0–73.75 mg/kg for Zn, 1.5–19.7 mg/kg for Mn, and −3.0 mg/kg for Ni. The order of concentrations of the metals in all the samples are Cu > Fe > Zn > Cd > Mn > Pb > Cr > Ni. Results in Tables 5.3 and 5.4 show the concentrations of metals in sediment samples using the two different digestion procedures. Digestion with method 2 yielded more concentrations of heavy metals for almost all the metals except zinc. Copper had the highest concentrations of 184 mg/kg in Table .: Physicochemical parameters of the sediment samples and comparison with permissible limits by WHO (World Health Organization) and SON (Standard Organization of Nigeria). Sediment number Sed Sed Sed Sed Sed Sed Sed Sed Sed Sed Sediment average (this study) WHO standard, highest desirable limit SON maximum limit

pH

Conductivity (µs/cm)

Organic matter

% Moisture

% Ash

. ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . .

 ±   ±   ±   ± . . ±  . ±  . ±  . ±  . ±   ±  .

. ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . .

. . . . . . . . . . .

. . . . . . . . . . .

.–.



–

–

– []

.–.



–

–

– []

Sed = sediment Geoaccumulation index.

Ref

Zn

Zn-D-. Zn bulk sci Air/Acet Abs . mA . nm  ppm On  . nm . V . s

Instrumental conditions

Lamp name Lamp Meth Curr/Energy Slit Cal max D Bkg comp Bkg gain WvL Pmt Intgr

Fe-D-. Fe bulk sci Air/Acet Abs . mA . nm . pm On  . nm . V . s

Fe

Table .: Instrument condition and characteristics.

Cd-D-. Cd bulk sci Air/Acet Abs . mA . nm . pm On / . nm . V . s

Cd Pb-D-. Pb bulk sci Air/Acet Abs . mA . nm . pm On  . nm . V . s

Pb Cu-D-. Cu bulk sci Air/Acet Abs . mA . nm . pm On  . nm . V . s

Cu Ni-D-. Ni bulk sci Air/Acet Abs . mA . nm  ppm On  . nm . V . s

Ni

Cr-D-. Cr bulk sci Air/Acet Abs . mA . nm . ppm On  . nm . V . s

Cr

5.3 Results and discussions

57

Cd

. ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . ND ND

Sediment number

Sed Sed Sed Sed Sed Sed Sed Sed Sed Sed

. ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± .

Cu . ± . ND ND ND ND . ± . . ± . . ± . . ± . . ± . . ± . . ± .

Fe . ± . . ± . ND ND . ± . . ± . . ± . . ± . . ± . . ± . . ± .

Pb . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± .

Zn . ± . . ± . ND ND . ± . . ± . . ± . ND ND . ND . ± . ND ND

Cr

Table .: The concentration of metals (mg/kg) determined after digestion with hydrochloric acid and nitric acid (method ).

. ± . . ± . . ± . . ± . . ± . . ± . . ±  . ± . . ± . . ± .

Mn

. ± . . ± . ND ND . ± . . ± . ND ND ND ND . ± . . ND . ± .

Ni

58 5 A comparative study of two digestion techniques in sediments

Cr

ND NILL ND NILL . ± . . ± . ND ND ND ND ND ND . ± . . ± . . ± .

Sediment Number

sed sed sed sed sed sed sed sed sed sed

Fe . ± . . ± . . ±  . ± . . ± . . ± . . ± . . ± . . ± . . ± .

Cd . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± .

. ± . ND ND . ± . . ± . . ± . . ± . . ± . ND ND . ± . ND ND

Pb . ± . . ± . . ± . . ±   ± . . ± . . ± . . ± . . ± . . ± .

Cu . ± . . ± . . ± . . ± . . ± . . ± . ND ND . ± . ND ND . ND

Zn . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± . . ± .

Mn

. ± . . ± . ND ND ND ND . ± . . ± . . ± . ND ND . ± . . ± .

Ni

Table .: The concentration of metals (mg/kg) was determined after digestion with, nitric acid, hydrofluoric, hydrochloric, and hydrogen peroxide (method ).

5.3 Results and discussions

59

60

5 A comparative study of two digestion techniques in sediments

sediment eight as shown in Table 5.4. This may be due to domestic and industrial effluents discharge especially those from various food processing companies in the area, iron smelters, other natural sources. Copper is one of the trace metals necessary for life and human health. It may be found in many kinds of food, drinking water, etc. Too much copper is not good for human health and may cause some negative adverse effects. The presence of copper may be as a result of solid and liquid wastes discharged from various food industries located in the area, fungicide manufacturing companies, automobile brake pads, and automobile spare part workshops which populate most parts of the area. Its concentration ranged from 0.10 mg/kg to 184.96 mg/kg with the highest value in sediment 8. Figure 5.4 shows vividly the levels of copper in the various sediment samples. Ni had the lowest concentration of 0.01 mg/kg in Table 5.3. Nickel is toxic at low concentrations [19]. The highest concentration of nickel was 3.0 mg/kg in sediment nine in Table 5.4. Copper is usually fixed to iron oxides, manganese, organic matter, and clays at high pH [22]. The maximum concentration of chromium detected was 7.0 mg/kg in sediment three as displayed in Figure 5.8, it was below the stipulated thresh hold limit by WHO. Chromium vi is usually converted to chromium under anaerobic conditions and low pH. Chromium is harmful to all living organisms. The hexavalent form of chromium is the most toxic. The minimum concentration of 0.01 mg/kg was found in sediment nine. Its presence signifies danger even at low levels. Lead is a toxic metal usually present in small quantities. The concentrations detected in the samples ranged from 0.10 to 7.20 mg/kg. Although the level was below the thresh-hold limit by the WHO, it is still a threat to living organisms. The source of lead in the samples may be from vehicle exhaust pipes and fumes from steel foundries as the area is characterized by heavy vehicular traffic. Cadmium had a maximum concentration of 20 mg/kg in sediment two; the level was higher than the WHO permissible limit of 5.1 mg/kg for marine sediment. However, the average concentration of cadmium across the 10 sediment samples was 3.10 mg/kg. Because the overall average concentration of cadmium is lower than the thresh hold limit by the WHO, it may not be a source of concern presently but closer monitoring of the area may be needed. The origin may be as a result of some anthropogenic activities going on in the area such as incineration of municipal waste which includes cadmium batteries and depositions of used and damaged cadmium batteries at the dumpsite. Comparing the different digestion procedures, the results showed that method (1), which involves digestion of sediment samples with hydrochloric acid and nitric acid as well as method (2) which involves digestion of sediment samples with hydrochloric acid, hydrofluoric acid, nitric acid, and hydrogen peroxide extracted various amounts of metals. Procedure (2) extracted more Cu, Cd, Fe, Pb, Cr, Mn, and Ni. While procedure (1) extracted more Zn as shown in Figures 5.2 and 5.3. Both procedures are effective for the digestion of heavy metals. In another study by Ygor Jacques in 2014 in which three different sediment digestion methods were compared with one another. They include USEPA 3051A, USEPA 3052, and MAPA (Brazil 2006), the author suggested that the soil

5.3 Results and discussions

61

Figure 5.1: Map of Isolo local government area in Lagos, Nigeria.

Figure 5.2: Mean concentrations of individual metal in mg/kg after digestion with the two different methods.

62

5 A comparative study of two digestion techniques in sediments

Figure 5.3: Mean concentrations of individual metal in mg/kg after digestion with the two different methods.

samples were properly extracted using the second method which comprises HNO3, HF, and HCl [13]. This study is more consistent with the works of Duyusen Eguven et al., WHO, in 2011 compared three different digestion methods of determining heavy metals in soil and sediment samples. The methods include (1). Digestion with HNO3, (2). Digestion with 65% HNO3, 40% HF and 37% HCl, and (3). Digestion of sediment samples with HCl. The author reported that method 2 yielded more complete digestion [14]. Table 5.5 shows the concentrations of various heavy metals reported in other countries. The mean concentrations of each heavy metal using the different methods were also compared as shown in Table 5.6. The Pearson correlation shown in Table 5.7 reveals a positive correlation between Zn and pH of the sediment at p ≤ 0.05 which may have enhanced the accumulation of zinc in the area. However, there is a slightly weak positive correlation between Cu and pH. The deposition of Cu could have been a result Table .: Mean concentrations of metals in sediments from other countries. Nature of sediment Sediment of Seine (France) Sediment of Rhine (Germany) Estuary down Loukkos (Morocco) Unit: mg/kg.

Cd

Cr

Cu

Fe

Mn

Ni

Pb

Zn

Ref

– – –

 – .

  .

– , .

– – –

– – –

  .

  .

[] [] []

a

Mean

b

Mean

b

Mean

Fe a

–

Mean



.

. . . . . . . . . . .

 ND  . .  . ND . ND .

Mean

Pb a

b

Mean





. . . .  . . .  . .

b

 .  . . . ND . ND . .

Mean

Zn a



.

. . ND . . . ND . . ND .

Mean ND ND . . . . . . . . 

Mean

Cr a

b

Mean

–

–

. . . . . . . . . . .

b

. . . .  . . . . . .

Mean

Mn a

–

.

. . ND . . ND ND . . . .

Mean

  ND ND .  . ND .  .

Meanb

Ni a

[]

[]

Refers to the mean concentration of metals in the sediment samples using method (). bRefers to the mean concentration of metals in the sediment samples using method ().



–

. .  . . . . . . . .  . . . . . . .  . . . . . . . . . . . . . . . . . . .  . . . .

.

. . . .  .  .  . .

Mean

Cu a

.

. . . . . . . . . ND .

Sed Sed Sed Sed Sed Sed Sed Sed Sed Sed Average concentrations of metals The WHO guideline for fresh water sediment The WHO guideline for marine sediment

Mean

b

.

Mean

Sample ID

a

Cd

Table .: Comparison of measured concentrations of various metals with the WHO permissible limits (mg/kg).

5.3 Results and discussions

63

a

. −. . −.a −. −. −. . −.

−. . −. . −. . .b −. . −. b

−. −. −. .a .b −. −. −.

Organic matter

−. . −. −. . . −.

Cadmium

−. −. . . . −.

Copper

Correlation is significant at the . level (-tailed), Correlation is significant at the . level (-tailed).

Conductivity Organic Matter Cadmium Copper Iron Lead Zinc Chromium Manganese Nickel

Conductivity

pH

−. −. . −. .

Iron

Lead

.b . −. −.

Table .: Pearson correlation of physicochemical parameters and heavy metals using digestion method .

−. . −.

Zinc

−. .

Chromium

−.

Manganese

64 5 A comparative study of two digestion techniques in sediments

5.3 Results and discussions

65

of some anthropogenic activities going on in the area such as metal disposals from lots of automobile workshops located in the area. The correlation between Pb and organic matter is strongly significant at p ≤ 0.01. Lead is a poisonous metal that even at low concentrations, is dangerous to aquatic organisms. Figures 5.4–5.8 show the pictorial view of concentrations of copper, lead, zinc cadmium and chromium.

Cu 500 400 300 200 100 0 sed 1 sed 2 sed 3 sed 4 sed 5 sed 6 sed 7 sed8 sed9 sed10 HCl/HNO3 HF,HNO3,HCl&H2O2 WHO limit for marine sediment Figure 5.4: Copper concentration in mg/kg. Comparison with the WHO standards.

Pb 500 450 400 350 300 250 200 150 100 50 0 sed 1 sed 2 sed 3 sed 4 sed 5 sed 6 sed 7 sed8 sed9 sed10 HCl/HNO3

HF,HNO3,HCl&H2O2

Figure 5.5: Lead concentration in mg/kg.

WHO

66

5 A comparative study of two digestion techniques in sediments

Zn 500 400 300 200 100 0

HCl/HNO3

HF,HNO3,HCl&H2O2

WHO

Figure 5.6: Zinc concentration in mg/kg.

Cd

25 20 15 10 5 0

sed 1 sed 2 sed 3 sed 4 sed 5 sed 6 sed 7 sed8 sed9 sed10 HCl/HNO3

HF,HNO3,HCl&H2O2

WHO

Figure 5.7: Cadmium concentration in mg/kg.

Cr 300 250 200 150 100 50 0 sed 1 sed 2 sed 3 sed 4 sed 5 sed 6 sed 7 sed8 sed9 sed10 HCl/HNO3

HF,HNO3,HCl&H2O2

Figure 5.8: Chromium concentration in mg/kg.

WHO

References

67

5.4 Conclusions The levels of pollution of some heavy metals in the Isolo canal have been evaluated in this study. Also, the pH, conductivity, and organic matter content of the sediments have been determined. The average concentration of each metal appears to be within the permissible level by the WHO. The two different digestion procedures used in this analysis have shown that they are both effective in extracting heavy metals from sediment samples but with variations. Application of method (2) extracted more metals than method (1). Metals can attach themselves through a cationic exchange in both acidic and alkaline media [28]. The area studied, is characterized by lots of automobile spare parts littering the environment, pharmaceutical industries, steel manufacturing industries, and beverage industries. There is also heavy vehicular traffic within the metropolis. These explain the presence of lead and cadmium as most vehicles use cadmium batteries to operate. Cadmium concentration was found to be high in sediment two probably due to corrosion of damaged cadmium batteries dumped in the area. But the average cadmium concentration across all the sites presently is within the WHO permissible limits. Significant differences were seen between the digestion capacities of the different methods. Digestion of sediment samples using method 2 yielded more metal concentrations. This study has exposed the need to recycle metal wastes rather than outright deposition into the environment as trash. Industries need to effectively treat their effluents to rid them of toxic metals that may be present as this will reduce the quantity of heavy metals entering the aquatic environment. This will further improve the water quality of the area thereby helping government at various levels to meet the sustainable development goals (SDG) [29].

References 1. Yunus K, Yusuf NM, Shazili NAM, Chuan OM, Saad S. Heavy metal concentration in the surface sediment of Tanjung Lumpur. Sains Malays 2011;40:89–92. 2. Tanjung EL. Assessment of heavy metal deposition in surface water and sediment in Balok and Tunggak river. Kuantan: Universiti Malaysia Pahang institutional repository; 2013. 3. Poon WC, Herath G, Sarker A, Masuda T, Kada R. River and fish pollution in Malaysia: a green ergonomics perspective. Appl Ergon 2016;57:80–93. 4. Zeitoun MM, Sayed E, Mehana E. Impact of water pollution with heavy metals on fish health: overview and updates. Global Vet 2014;12:219–31. 5. Tiquio M, Marmier N, Francour P. Management frameworks for coastal and marine pollution in the European and Southeast Asian regions. Ocean Coast Manag 2017;135:65–78. 6. Perera PCT, Sundarabarathy TV, Sivananthawerl T, Kodithuwakku SP, Edirisinghe U. Arsenic and cadmium contamination in water, sediments and fish is a consequence of paddy cultivation: evidence of river pollution in Sri Lanka. Achiev Life Sci 2016;10:144–60. 7. Abbas A, Al-Amer AM, Laoui T, Al-Marri MJ, Nasser MS, Khraisheh M, et al. Heavy metal removal from aqueous solution by advanced carbon nanotubes: critical review of adsorption applications. Separ Purif Technol 2016;157:141–61.

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8. Nadal M, Schuhmacher M, Domingo DL. Metal pollution of soils and vegetation in an area with petrochemical industries. Sci Total Environ 2004;32:59–69. 9. Alkarkhi AFM, Ismail N, Ahmed A, Easa AM. Analysis of heavy metal concentrations in sediments of selected estuaries of Malaysia – a statistical assessment. Environ Monit Assess 2009;153:179–85. 10. Elnabris KJ, Muzyed SK, El-Ashgar NM. Heavy metal concentrations in some commercially important fishes and their contribution to heavy metals exposure in Palestinian people of Gaza Strip (Palestine). J Assoc Arab Univ Basic Appl Sci 2013;13:44–51. 11. Kurun A, Balkıs N, Erkan M, Balkıs H, Aksu A, Erşan MS. Total metal levels in crayfish astacus leptodactylus (eschscholtz, 1823), and surface sediments in lake Terkos, Turkey. Environ Monit Assess 2010;169:385–95. 12. MacDonald DD, Ingersoll CG, Berger T. Development and evaluation of consensus-based sediment quality guidelines for freshwater ecosystems. Arch Environ Contam Toxicol 2000;39:20–31. 13. da Silva YJAB, do Nascimento CWA, Biondi C, Preston W. Comparison of digestion methods to determine heavy metals in fertilizers. Revista Brasileira de Ciencia da Solo 2011;38:650–5. 14. Eguven DE, Akinci G. Comparison of acid digestion techniques to determine heavy metals in sediments and soil samples. Gazi Univ J Sci 2011;24:29–34. 15. United States of America Environmental Proection Agency (USEPA). Method 9045D soil and waste pH. In: Test methods for evaluating solid waste. SW846, Revision Nov 2004;4. 16. United States of America Environmental Protection Agency (USEPA). Method 9040C pH electrometric measurement. In: Test methods for evaluating solid waste, SW846. Revision Nov 2004;3. 17. American Society for Testing and Material (ASTM) Standard Method number 2974-20, for determining the water (moisture) content, ash content and other organic materials of peat and other organic soils. Updated Mar 2020. 18. WHO. Guidelines for drinking water quality, Geneva, Netherland: World Health Organization; 2006:491–3 pp, vol 1. 19. SON. Standards for drinking water quality. Abuja, Nigeria: Standard Organization of Nigeria; 2007. 20. Tekin-Özan S, Aktan N. Relationship of heavy metals in water, sediment and tissues with total length, weight and seasons of Cyprinus carpio L. 1758 from Işikli lake (Turkey). Pakistan J Zool 2012;44:1405–16. 21. Environmental Protection Agency of the United States of America, method number 3052 on the multiwave 3000- Perkin Elmer. 22. Prudent P, Massiani C, Thomas O. Evolution of heavy metal species in leachates and in the solid phase during composting of municipal solid wastes. In: Vernet JP, editor. Environmental contamination. Amsterdam, The Netherlands: Elsevier; 1993:187–2 pp. 23. Eaton AD, Franson MAH. Standard methods for the examination of water and waste and water, 21st ed. APHA-AWWA-WEF: Washington, D.C.; 2005. 24. Meybeck M, Marsily G, FustecE. La seine en son basin,fonctionnement ecologique d’un systems fluvial anthropise. Paris: Elsevier; 1998. 25. Forstiner U, Muller G. Heavy metal accumulation in river sediment, a response to environmental pollution. Geoforum 1973;14:53–62. 26. El Morhit M. Hydrochimic elements traces metalliques et indices ecotoxicologiques sur les differents composantes d un ecosysyteme estharien (bas Loukkos- Marac) [dissertation]. Rabat, Maroe: Universite Mohammed V-NABDAL; 2009. 27. Shallcross AL. Surface water quality and pollutant loading, a technical report for the Raritan Basin water management project. New Jersey Water Supply authority. August 2002. https://rucore. libraries.rutgers.edu.

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28. Kosari M, Vanae M, editors. Survey of the source and amount of pollutants concentration of heavy metal in Tembi river and Bohiol lake. Proceedings of the 1st conference on geological and environmental and medical. Tehran, Iran; 2007. 29. United Nations. The 2030 agenda and the Sustainable Development Goals (SDGs); an opportunity for Latin America and the Caribbean (LC/G. 2681-P / Rev).

Peter Mensah*, Temitope Osobamiro and Ponnadurai Ramasami

6 Simultaneous remediation of polycyclic aromatic hydrocarbon and heavy metals in wastewater with zerovalent iron-titanium oxide nanoparticles (ZVI-TiO2) Abstract: The presence of polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HM) in wastewater is a major challenge to the environment as various approaches have been used to remediate these contaminants from the environment. Zerovalent iron-titanium oxide nanoparticle (ZVI-TiO2 NPs) was synthesized by wet reflux in an inert environment using nitrogen gas and sodium borohydride as reducing agents. Characterization was carried out using a scanning electron microscope (SEM) coupled with electron diffraction X-ray (EDX) and Fourier transform infrared spectrophotometer (FTIR). Assessments of the wastewater were carried out with atomic absorption spectrophotometer (AAS) for HM and a gas chromatography-mass spectrophotometer (GCMS) for PAHs to determine the initial concentration (Ci) compared with permissible limits of surface water and adsorption capacity with ZVI-TiO2 NPs (Cf), respectively. The results obtained indicate a percentage yield of 65.51 ± 0.01 of ZVI-TiO2 NPs, with a particle size of 100 nm, weight composition of iron, titanium, and oxygen at 49.69, 5.24, and 35.41 g, respectively. FTIR shows a vibrational change of 3465, 2929, and 1641 cm−1 of OH, CH, and CO group needed for metal binding and adsorption. Remediation of HM after acid digestion gave effective removal of zinc, copper, cadmium, cobalt, and lead at an adsorption capacity of 64.29, 54.83, 53.13, 48.39, and 42.66% respectively. The adsorptions of benzo[a]pyrene, fluoranthene, pyrene, benzo[b]fluoranthene, and perylene were 77.87, 67.85, 52.17, 29.50, and 25.45%, respectively. These results indicate that metal/metal oxide (ZVI-TiO2) nanoparticles have a high potential in the remediation of heavy metals and PAHs from the water ecosystem. Keywords: heavy metal; nanoparticles; nanotechnology; polycyclic hydrocarbons; remediation.

*Corresponding author: Peter Mensah, Department of Chemical Sciences, Faculty of Science, Olabisi Onabanjo University, Ago Iwoye, Ogun State, Nigeria, E-mail: [email protected] Temitope Osobamiro, Department of Chemical Sciences, Faculty of Science, Olabisi Onabanjo University, Ago Iwoye, Ogun State, Nigeria Ponnadurai Ramasami, Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit 80837, Mauritius; and Department of Chemistry, University of Johannesburg, P. O. Box 524, Auckland Park, Johannesburg, 2006, South Africa As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: P. Mensah, T. Osobamiro and P. Ramasami “Simultaneous remediation of polycyclic aromatic hydrocarbon and heavy metals in wastewater with zerovalent iron-titanium oxide nanoparticles (ZVI-TiO2)” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0213 | https://doi.org/10.1515/9783110752601-006

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6 Removal of polycyclic compounds from wastewater

6.1 Introduction Environmental pollution is one of the major threats facing the ecosystem as a result of the discharge of particulate matter, heavy metals, pesticides, oil spills, toxic gases, industrial effluents, and other organic compounds into the environment [1]. Among these various environmental contaminants, polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HM) have constituted a great threat to the environment as they are found in water, soil, fossils fuel, sewage, and fertilizer due to their persistent nature and low-biodegradability, thereby reducing soil fertility, inhibiting plant growth, and damaging the ecosystem [2–4]. Because of the abundance of water bodies, aquatic ecosystems are the major reservoir of PAHs and HM contamination in the natural environment. The sources of PAHs and HM in the aquatic environment include dissolution from nonaqueous-phase liquids, such as fossil fuels, coal tars, incomplete combustion of fuels, and discharge of effluents wastewater directly or indirectly into the water bodies [5]. In addition, PAHs and HM emitted into the atmosphere are largely adsorbed on particulate matter and the adsorbed pollutants are then deposited into aquatic and soil environments by fallout, subsequently leading to water and soil pollution [6, 7]. In recent times, nanotechnology has gained a lot of attention in the removal of contaminants of PAHs and HM in the aquatic environment due to its high surface area to volume ratio when compared with their bulkier counterparts [8, 9]. Several studies are reported on the high potential of metal or metal oxide nanoparticles (NPs) in the removal of heavy metals and organic pollutants from matrices of aquatic water bodies [10, 11]. However, due to the complexity of these pollutants, high volatility, and nonbiodegradability in the environments, recent studies have shown that to improve performance and remove these sets back, a combination of metal-doped in metal oxide nanoparticles gives better results at lower cost [12–14]. In continuation with our interests in wastewater treatment [15–17] and, in view of the above, this study was aimed at addressing this gap in synthesizing metal/metal oxide nanoparticles using zerovalent iron doped in titanium oxide (ZVI-TiO2) for the simultaneous remediation of polycyclic aromatic hydrocarbon (PAHs) and heavy metal (HM) contaminants in waste oily water in a mechanic market, Lagos, Nigeria.

6.2 Materials and methods 6.2.1 Study area Lagos Ladipo market (Ladipo Auto Spare Parts market), is a market located in Mushin local Government, Lagos State Nigeria, with a geographical coordinate of latitude 6° 33ʹ 6.2018ʺ north, and longitude 3° 20ʹ 41.9769ʺ East. The market is known for its commercial activities in the sales of auto spare parts and

6.2 Materials and methods

73

with neighboring industries around the area with flowing water drainage. This site was selected for the sample of oily wastewater.

6.2.2 Collection of samples All the glassware used was washed with non-ionic liquid detergent and rinsed with potable water and later with purified water. The glassware was soaked in 0.1% nitric acid overnight and rinsed with ultrapurified water before being used. Water was collected from six different locations into airtightened amber bottles placed in an ice chest and then transported to the laboratory for further analysis.

6.2.3 Production of zerovalent iron (ZVI) The production of ZVI involves the reduction of ferrous sulfate hexahydrate (FeSO4·6H2O) with sodium borohydride (NaBH4). A total of 50 mL of 2 M FeSO4·6H2O was placed into a quick fit round bottom flask, 1 M NaBH4 was added in drops and then in excess until a black precipitate complex was formed. It was then placed under reflux and stirred continuously for 4 h for a completely homogenous mixture. The black iron particles were then separated by filtration using Whatman filter paper (110 mm), washed thrice with distilled water, and kept in a desiccator to dry at room temperature [7, 18].

6.2.4 Production of titanium oxide nanoparticles (TiO2-NPs) An amount of 5 g of TiO2 and 50 mL of ethanol were introduced into a 250 mL beaker, the solution was stirred for 30 min with a magnetic stirrer. During this period, it formed a yellow sol phase, 200 mL of distilled water was then added and the solution became clear and colorless. The solution was further stirred for 30 min at room temperature. An amount of 0.5 g of NH4Cl was added to keep the solution in an inert stage with the presence of nitrogen gas from the ammonium chloride. The formed gel was then dried at 50 °C for 24 h at room temperature [7, 18].

6.2.5 Production of zerovalent iron-titanium oxide nanoparticles (ZVI-TiO2) An amount of 2 g of TiO2 NPs and 2 g of ZVI NPs were added to a 100 mL round-bottomed flask. The reaction was stirred in a reflux condenser under nitrogen gas for 4 h in 50 mL of ethanol and 25 mL of water, filtered, and allowed to dry at room temperature for 24 h to yield ZVI-TiO2 NPs (Figure 6.1).

6.2.6 Adsorption process 6.2.6.1 Heavy metal analysis: An amount of 2 g of ZVI-TiO2 nanoparticle was added to 100 mL of the composite oily wastewater. The sample was placed in a water bath shaker for 2 h and allowed to stand for 2 h at room temperature. After 2 h, the sample was filtered out into a 250 mL conical flask and the adsorption capacity of the produced ZVI-TiO2 for the removal of HM was evaluated. The heavy metals analysis was carried out by acid digestion and then analyzed with Buck scientific atomic absorption spectrophotometer (Model 210A). The blank standard was carried out and the statistical analysis of the mean and standard deviation of the metal was calculated using equation (6.1) [16, 17].

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6 Removal of polycyclic compounds from wastewater

FeSO4.6H2O(aq) Addition of NaBH4 (reducing agent) -

Fe2+(aq) + 2BH4 (aq) + 6H2O(l) -

BH4 (aq) reduces Fe2+ to Fe0 Fe0(aq)+ 2B(OH)3(aq) + 6H2(g) Black residue of Fe0 (aq) Fe0(aq) + TiO2(aq) (N2 for inert environment) (Fe0-TiO2)(aq) - Zerovalent iron titanium oxide nanoparticle (ZVI- TiO2)(s)

Figure 6.1: A flow chart showing the production of ZVI-TiO2 NPs.

%HM Adsorption by ZVI − TiO2 NPs =

Ci − Cf × 100 Ci

(6.1)

Ci = initial concentration, Cf = final concentration.

6.2.6.2 Polycyclic aromatic hydrocarbon analysis (PAHs): 50 mL of the composite oil was mixed with 2 g of ZVI-TiO2 NPs with 50 mL of dichloromethane (DCM) into a 250 mL amber bottle. This was kept in the dark for 48 h. Extraction was carried out with a 250 mL separating funnel, and was concentrated by rotary evaporator and then analyzed with gas chromatography-mass spectrometer (GCMS) for PAHs analysis [18–20].

6.3 Results and discussion 6.3.1 Percentage yield The percentage yield of ZVI, TiO2, and ZVI-TiO2 nanoparticles, with ZVI-TiO2 nanoparticles having the highest yield is presented in Table 6.1. It can be noted from Table 6.1 that ZVI NPs have the least percentage yield when compared to other NPs. The difference is due to pre-oxidation of some Fe2+ to Fe3+, before being reduced by the reducing agents (NaBH4) and this is in line with literature [18, 19]. The increase in yield of ZVI-TiO2 NPs could be attributed to the interaction of the iron particles on the titanium oxide surface area due to magnetic force [18–22].

6.3 Results and discussion

75

Table .: Percentage yield of the respective nanoparticles synthesized by wet reflux. Nanoparticles (%) ZVI TiO ZVI-TiO

Yield . ± . . ± . . ± .

6.3.2 Characterization of ZVI-TiO2 NPs 6.3.2.1 SEM-EDX analysis of ZVI-TiO2 NPs The result of the characterization of the produced zerovalent iron-titanium oxide nanoparticles (ZVI-TiO2) using scanning electron microscope (SEM) coupled with electron diffraction X-ray (EDX) is presented in Figure 6.2 and Table 6.2. Figure 6.2 gives the morphological structure, texture, and shape of ZVI-TiO2 NPs. The shape of synthesized ZVI-TiO2 NPs was spherical with a particle size range of 100 nm. The morphology of ZVI-TiO2 NPs also showed chain-like aggregates due to magnetic interaction between small particles of iron with titanium oxide. The interaction corresponds to the report found with the use of ZVI with SiO2 [23–25]. The doping of Fe in TiO2 also enhanced much better dispersion performance than ZVI, suggesting that the coating of TiO2 can prevent agglomeration by reducing the van der Waal’s force and magnetic force between the iron nanoparticles [24, 25]. Table 6.2 shows the elemental composition of the element composed in the ZVI-TiO2 nanoparticles. The percentage composition indicates the three fundamental elements present in synthesized ZVI-TiO2 NPs which indicates the stability of Fe2+ to Fe0 as a characteristic of zeta potential stability [22, 23, 26]. Particles with zeta potential more positive than +30 mV or more negative than −30 mV are more stable. The zerovalent iron synthesized was analyzed at

Figure 6.2: SEM microimage of zerovalent iron titanium oxide nanoparticles (ZVI-TiO2).

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6 Removal of polycyclic compounds from wastewater

Table .: The elemental composition X-ray (EDX) of synthesized ZVI-TiO nanoparticles. Atomic no.

Element

Symbol

         

Iron Oxygen Titanium Sodium Sulfur Nitrogen Zinc Iodine Aluminum Silicon

Fe O Ti Na S N Zn I Al Si

Mass concentration (g) . . . . . . . . . .

15 kV, which is far more than +30 mV, these properties and the electromagnetic surface of iron enhance the adsorption of other positive metals to its surface [23, 25–27]. 6.3.2.2 FTIR-ZVI-TiO2 NPs The vibrational change of the ZVI-TiO2 NPs has a broadband of 3300 cm−1 stretch which is an indication of the hydroxyl functional group (–OH), this species (–OH) aids in the reduction of Fe2+ to Fe0 as they act as nucleophile [27]. The stretchings of carbon hydrogen bond (C–H) at 2939 cm−1 and carbon–oxygen bond (C–O) at 1641 cm−1 correspond to the literature on the adsorption study of organic pollutants in wastewater [27–30].

6.3.3 Adsorption study 6.3.3.1 Adsorption study of heavy metals Table 6.3 presents the adsorption capacity of the synthesized ZVI-TiO2 nanoparticles with sampled waste oily water, with zinc (Zn) having the highest adsorption capacity. The highest percentage of adsorption with ZVI-TiO2 nanoparticles was observed in the adsorption of zinc (Zn) 64.29%, while iron (Fe) had the least adsorption of 7.44%. According to literature [26, 29], the adsorption of metals on ZVI nanoparticles is attributed to its zeta potential and negative surface area (−30 mV), ZVI-TiO2 nanoparticles exhibit these properties, with the adsorption of HM in wastewater. Also, the adsorption of Co2+and Ni2+ was 48.39 and 33.33% respectively which are in accordance to literature [10, 26, 29], using zerovalent iron nanoparticle alone and having a percentage of 51.01 and 38.02% for Co2+ and Ni2+ correspondingly. The relative

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77

Table .: Adsorption concentration of heavy Metals with ZVI-TiO nanoparticles. SN

Metal

       

Pb Cr Co Ni Zn Cu Fe Cd

WHO (mg/L max)

Cf (mg/L)

Cf (mg/L)

Ci − C f

% Of adsorption

. .).

with several double bonds of xanthone chromophore [16, 17]. On its 1H NMR spectrum (Table 7.1), two doublets of a proton at δH 6.41 (1H, d, 3 Hz) and δH 6.35 (1H, d, 3 Hz) were observed, attributed to protons H-5 and H-7, respectively. Two other doublets of a proton were also observed on this spectrum, each at δH 6.88 (1H, d, 9.5 Hz) and δH 7.28 (1H, d, 9.5 Hz) referring to the ortho coupling of protons H-3 and H-4. Two singlets of

7.3 Results and discussion

87

Table .: Result of the antibacterial activity of two xanthones derivatives swertiaperenin () and decussatin ().  (. mM)  (. mM) Gentamicin

. ± .a . ± .a . ± .b

. ± .c . ± .b . ± .d

. ± .b . ± .a . ± .c

: swertiaperenin, : decussatin and Gentamicin. a–d: Means with the same superscript in the same column do not differ significantly (p > .) while those with different letters are significantly different (p > .).

Figure 7.1: Structures, HMBC and COSY correlations of swertiaperenin (1) and decussatin (2).

three protons each at δH 3.92 (3H, s) and δH 3.96 (3H, s) characteristics of two methoxyl groups, respectively, fixed in position C-2 and C-6 and two other singlets of a proton strongly deshielded at δH 12.06 (1H, s) and δH 11.96 (1H, s) characteristics of two chelated hydroxyl groups fixed, respectively, at C-1 and C-8. On the broadband decoupled 13C NMR spectrum, 15 signals corresponding to 15 carbon atoms were observed. The rigorous interpretation of these signals revealed a carbonyl group of ketone at δC 185.0 ppm characteristic of carbonyls of xanthone [15]; four methines at δC 120.3 (C-3); 105.6 (C-4), 92.9 (C-5) and 97.2 (C-7). Four oxygenated carbons, two of which carry the hydroxyl groups at δC 149.6 (C-1); 162.9 (C-8) and the other two carrying the methoxyl group at δC 142.5 (C-2) and 167.4 (C-6). Based on these spectral data and in comparison with those of the literature, the structure (1) has been attributed to this compound which is the structure of 1,8-dihydroxyxanthone (Figure 7.1) which

88

7 Antioxidant and antibacterial activities of two xanthones derivatives

corresponds to the swertiaperenin (1) previously isolated from the aerial parts of the herb, Swertia longifolia (Gentianaceae) by Hadjimehdipour et al. [15]. Compound (2) was obtained in the form of amorphous greenish solids in hexane/ ethyl acetate 9.5/0.5. It is soluble in chloroform and gives a positive reaction with a 5% solution of FeCl3 characteristic of phenolic compounds. Its UV spectrum presents also two absorption bands at λmax (MeOH) 280.5 nm and 340 nm characteristic of a carbonyl function conjugated with several double bonds of xanthone chromophore [16, 17]. Its 1H NMR spectrum (Table 7.1) compared with those of the compound (1, swertiaperenin) has several similarities, but also some differences. As an element of similarity, we observed four doublets of a proton each attributed on the one hand, to the ortho coupling of protons H-5 and H-6 of cycle A to δH 7.17 (1H, d, 9 Hz) and 7.32 (1H, d, 9.5 Hz) and on the other hand to the meta coupling of the H-2 and H-4 protons of the B cycle at δH 6.30 (1H, d, 3 Hz) and 6.33 (1H, d, 3 Hz) of the xanthones. As a difference, there were three singlets of three protons each attributed to the methoxyl groups at δH 4.00 (3H, s); 3.93 (3H, s); 3.86 (3H, s) and a singlet of a strongly deshielded proton at δH 13.50 (1H, s) attributed to the proton of the chelated hydroxyl (C-1). Its fully decoupled 13C NMR spectrum has 16 signals corresponding to 16 carbon atoms. The analysis of these signals by the DEPT-135 and HSQC technique revealed four sp2 hybridized methines, three methyls and nine quaternary carbons, five of which oxygenated, including a ketone carbonyl. The position of the methoxyl group was accomplished based on the spectral data contained in the literature; it was clear that they were positioned respectively at C-3, C-7 and C-8. All these analyses and by comparison with the data of the literature referred compound (2) to as 1-hydroxy-3,7,8-trimethoxyxanthone (Figure 7.1) also known as decussatin (2) compound previously isolated from the root bark of this plant and from the whole plant of S. bimaculata [9, 18]. This is the first time that these two xanthones have been reported and isolated from the same part (leaves) of A. schweinfurthii.

7.3.2 Antioxidant activity Compounds (1) and (2) have, respectively, a scavenging power of 0.910 ± 0.031 and 1.43 ± 0.01 mM and a ferric reducing power of 0.664 ± 0.041 mM and 0.875 ± 0.100 mM showing that swertiaperenin (1) was more antioxidant than decussatin (2). This result also showed that these two compounds have good activity compared to that of the reference compound ascorbic acid (0.865 ± 0.020 mM and 1.25 ± 0.26 mM). The antioxidant activity of these two xanthones derivatives are slightly lower compare to some oxygenated xanthones as 1,2,5-trihydroxyxanthone (3), 1,2-dihydroxy5,6-dimethoxyxanthone (4), and 1,8-dihydroxy-3-methoxyxanthone (5) proven to possess significant activity (MIC = 5–10 μg/mL) in three different assays: antilipid peroxidation (ALP) activity in rat brain homogenates, superoxide anion scavenging activity in the xanthine–xanthine oxidase system (O2.) and free radical scavenging

7.3 Results and discussion

1,2,5-trihydroxyxanthone (3)

1,2,8-trihydroxy-5,6-dimethoxyxanthone (4)

1,8-dihydroxy-3-methoxyxanthone (5)

1,8-trihydroxy-2,6-dimethoxyxanthone or methylswertianin (6)

1,5,8-dihydroxy-3,4-methoxyxanthone (7)

1,3,6,8-tetrahydroxyxanthone or norswertianin (8)

1,2,8-trihydroxy-6-methoxyxanthone or swertianin (9)

1,8-dihydroxy-3,6-dimethoxyxanthone or methylbellidifolin (10)

1,8-dihydroxy-3-methoxyxanthone or bellidifolin (11)

1,2,6,8-tetrahydroxy-3-methoxyxanthone or norswertianin (12)

89

Figure 7.2: Structures of some natural antioxidant hydroxy and oxygenated xanthones [5, 20].

activity of α,α-diphenyl-β-picrylhydrazyl radical (DPPH) in vitro [5]. Structures of compounds (3), (4), and (5) together with some others analogous antioxidant xanthones are given in Figure 7.2. The antioxidant activity of these two compounds was surely due to the presence of phenolic groups in their structures known for their capacity to release easily one or more hydrogen free radicals which converts reactive

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7 Antioxidant and antibacterial activities of two xanthones derivatives

Figure 7.3: Chelation of ferric ion (Fe3+) by isolated xanthones swertiaperenin (1) and decussatin (2)

radicals to less reactive species and their ability to chelate ferric ions as shown in Figure 7.3. The presence of two hydroxyl groups close to carbonyl explains the high scavenging and chelating activity of swertiaperenin (1) compared to decussatin (2) as shown in Figure 7.3. These results are in accordance with previous results who explained that the antioxidant activity of xanthones depends on the existence of hydroxyl groups and substituents on the aromatic ring; and the position of hydroxyls on the xanthones structure gave significant influence on the antioxidant activity [19–21].

7.3.3 Antimicrobial activity To evaluate and compare the antimicrobial activity of swertiaperenin (1) and decussatin (2) against E coli, S aureus and B cereus, the disk method of diffusion was used. The results reveal that swertiaperenin (1) and decussatin (2) have antimicrobial activity against these three strains. At the concentration of 100 μg/mL, S. aureus was extremely sensitive to swertiaperenin (1) and decussatin (2), while E. coli and B. cereus were very sensitive to swertiaperenin (1). The high antimicrobial activity of the swertiaperenin (1) that decussatin (2) is due to the presence of hydroxyl groups attached to the aromatic ring thus allowing the ability of this molecule to destroy the cell membrane of bacteria [22]. Additionally, swertiaperenin (1) has more free hydroxyl than decussatin (2), making it more effective; it is known that the presence of substituted hydroxyl groups of xanthones increases their antimicrobial activity [19–23].

7.4 Conclusions At the end of this work, the phytochemical analyzes enabled the isolation of swertiaperenin (1) and decussatin (2), two xanthones derivatives from the leaves extract of A. schweinfurthii. Xanthones derivatives are taxonomic markers of the family Loganiaceae, thus presence of these two xanthones confirm the belonging of the above plant to this Family. The percentages of inhibitions of free DPPH° and the ferric

References

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reducing power of these two compounds were comparable to those of ascorbic acid taken as a reference antioxidant compound. In addition, E. coli was very sensitive to swertiaperenin (1), whereas Staphylococcus aureus was very sensitive to decussatin (2). These results could in part explain the uses of this plant for the treatment of infectious diseases in by the population of Cameroon. A. schweinfurthii leaves might be considered as a potential source of antioxidant and antimicrobial compounds.

References 1. Prencely S, Basha S, Kirubakaran JJ, Dhanaraju MD. Preliminary phytochemical screening and antimicrobial activity of aerial parts of Stachytarpheta indica L (Vahl.). Med Plants 2013;5:98–101. 2. Puspitasari A, Pramono S, Martono S, Widyarini S. Optimization of extraction process and dechlorophyllation of ethanolic extract of androphis paniculata Ness. Int J Pharm Clin Res 2016;8: 345–51. 3. Ghedadba N, Hambaba L, Ayachi A, Aberkane MC, Bousselsela H, Oueld-Mokhtar SM. Polyphénols totaux, activités antioxydante et antimicrobienne des extraits des feuilles de Marrubium deserti de Noé. Phytothérapie 2015;13:118–29. 4. Momeni J, Tsopmejio JP, Nkouam TF, Ngassoum MB. Antioxidant activity of the natural flavonoid 7Hydroxy-5,6,4′-trimethoxyflavone isolated from the leaves of Lippia rugosa A. Chev. Nat Sci. 2016; 8:70–8. 5. Panda SS, Chand M, Sakhuja R, Jain SC. Xanthones as potential antioxidants. Curr Med Chem 2013; 20:4481–507. 6. Mezui C, Longo F, Nkenfou C, Sando Z, Ndeme E, Vernyuy TP. Evaluations of acute and sub-acute toxicity of stem bark aqueous extract of Anthocleista schweinfurthii (Loganiaceae). World J Pharm Pharmaceut Sci 2015;4:197–208. 7. Sassa K. Pharmacopée traditionnelle Baka et aliments curatifs Bantu. Yaounde: CEPER SA; 2012. 8. Anyanwu GO, Nisar UR, Chukwu EO, Khalid R. Medicinal plants of the genus Anthocleista: a review of their ethnobotany, phytochemistry and pharmacology. J Ethnopharmacol 2015;175:648–67. 9. Mbouangouere NR, Tane P, Ngamga D, Khan SN, Choudhary MI, Ngadjui BT. A new steroid and α-glucosidase inhibitors from Anthocleista schweinfurthii. Res J Med Plant 2007;1:106–11. 10. Koto-te-Nyiwa N, Mubindukila REN, Mpiana PT, Masengo CA, Robijaona B, Fatiany PR, et al. In vitro assessment of antibacterial and antioxidant activities of a Congolese medicinal plant species Anthocleista schweinfurthii Gilg (Gentianaceae). J Mod Drug Discov Drug Deliv Res 2014;V1I3:1–7. 11. Nkouam TF, Tchamango SR, Momeni J, Monde G, Tsopmejio JP, Ngassoum MB, et al. Removal of chlorophyll and tannins from Anthocleista schweinfurthii Gilg leaves by electrocoagulation using iron electrodes: optimization using response surface methodology. J Chem Technol Biotechnol 2020;95:2001–8. 12. Talla E, Nyemb NJ, Tchinda AT, Zambou DSG, Biyanzi P, Sophie L, et al. Antioxidant activity and a new ursane-type triterpene from Vitellaria paradoxa (Sapotaceae) stem barks. Eur J Med Plants 2016;16:1–20. 13. Zekovic Z, Vladic J, Vidovic S, Adamovic D, Pavlic B. Optimisation of microwave-assisted extraction (MAE) of coriander phenolic antioxidants response surface methodology approach. J Sci Food Agric 2016;96:4613–22. 14. Moreira MR, Ponce AG, Valle DCE, Roura SI. Inhibitory parameters of essential oils to reduce a foodborne pathogen. LWT - Food Sci Technol 2005;38:565–70.

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15. Hajimehdipour H, Amanzadeh Y, Ebrahimf SSE, Mozaffariarr V. Three tetraoxygenated xanthones from Swertia longifolia. Pharm Biol 2003;41:497–9. 16. Harborne JB. Phytochemical methods: A guide to modern techniques of plants analysis, 3rd ed. London, UK: Chapmann & Hall; 1998. 17. Vo THT, Nguyen TD, Nguyen QH, Ushakova NA. Extraction of mangiferin from the leaves of the mango tree Mangifera indica and evaluation of its biological activity in terms of blockade of α-glucosidase. Pharm Chem J 2017;51:806–10. 18. Dong M, Liu D, Li H, Yan S, Li R, Chen X. Chemical compounds from Swertia bimaculata. Chem Nat Compd 2018;54:964–9. 19. Tran TH, Nguyen VT, Le HT, Nguyen HM, Tran TH, Do Thi T, et al. Garcinoxanthones S–V, new xanthone derivatives from the pericarps of Garcinia mangostana together with their cytotoxic and antioxidant activities. Fitoterapia 2021;151:104880. 20. Wairata J, Sukandar ER, Fadlan A, Purnomo AS, Taher M, Ersam T. Evaluation of the antioxidant, antidiabetic, and antiplasmodial activities of xanthones isolated from Garcinia forbesii and their in silico studies. Biomedicines 2021;9:1–15. 21. Bouchouka E. Extraction des polyphenols et étude des activités antioxydante et antibactérienne de quelques plantes sahariennes Thèse de Doctorat. Algérie: Université Badji Mokhtar-Annaba; 2016: 126 p. 22. Gondokesumo ME, Pardjianto B, Sumitro SB, Widowati W, Handono K. Xanthones analysis and antioxidant activity analysis (Applying ESR) of six different maturity levels of Mangosteen Rind extract (Garcinia mangostana Linn.). Pharmacog J 2019;11:369–73. 23. Resende DISP, Pereira-Terra P, Moreira J, Freitas-Silva J, Lemos A, Gales L, et al. Synthesis of a small library of nature-inspired xanthones and study of their antimicrobial activity. Molecules 2020;25:1–20.

Marie Chan Sun, Marie A. S. Landinaff* and Ruben Thoplan

8 Use of biochemical markers for diabetes prevention in the new decade Abstract: Use of biochemical markers for diabetes prevention in the new decade. There is established evidence that type 2 diabetes mellitus is preceded by a phase, during which there is a cluster of conditions including raised triglycerides and lowered highdensity lipoprotein cholesterol, raised fasting glucose, high blood pressure and central obesity. This cluster of risk factors for type 2 diabetes mellitus, constitutes the metabolic syndrome (MetS). Therefore, there is need to screen for this syndrome among the population for the primary prevention of type 2 diabetes mellitus which is a global public health problem. Despite the high prevalence of type 2 diabetes in Mauritius, research work on MetS is scarce. This study was thus undertaken with the primary objective to determine the prevalence of MetS among the employees of a public educational institution in Mauritius. A cross-sectional study which involved randomly identified employees was conducted. The participants were requested to fill in a survey questionnaire, undergo biometric measurements (waist circumference and blood pressure) and venous blood sample collection in a fasting condition. The blood tests included the determination of glucose, triglyceride and cholesterol levels. The 2009 International Diabetes Federation criteria were used for the diagnosis of MetS. The presence of any 3 of 5 risk factors, raised triglycerides, raised glucose, lowered highdensity lipoprotein cholesterol, high blood pressure and central obesity constitutes a diagnosis of metabolic syndrome. Ethical clearance was obtained from the Department of Medicine Research Ethics Committee of the University of Mauritius. The prevalence of MetS was found to be 20.1% (40 participants), in the overall population, 31.4% in men (22 out of 70) and 13.95% in women (18 out of 129). The determination of any association by means of the Chi square tests showed there was a significant association between gender and MetS (p < 0.01). Educational level was also associated with the MetS (p < 0.05). Logistic regression analysis confirmed t\he significant association between MetS with gender (p < 0.01) where male gender was more associated with MetS than female. This study with the determination of the prevalence of the MetS among employees constituted the first step in the implementation of a structured workplace health intervention programme in Mauritius. We highlight the importance of workplace interventions with the

*Corresponding author: Marie A. S. Landinaff, Department of Medicine, University of Mauritius, Reduit, Mauritius, E-mail: [email protected] Marie Chan Sun, Department of Medicine, University of Mauritius, Reduit, Mauritius, E-mail: [email protected]. https://orcid.org/0000-0002-7504-8995 Ruben Thoplan, Department of Economics and Statistics, University of Mauritius, Reduit, Mauritius, E-mail: [email protected] As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: M. Chan Sun, M. A. S. Landinaff and R. Thoplan “Use of biochemical markers for diabetes prevention in the new decade ” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0166 | https://doi.org/10.1515/9783110752601-008

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involvement of a multi-disciplinary team of health professionals for the primary prevention of diabetes, through the screening for the MetS among employees. Keywords: biochemical markers; diabetes mellitus; Mauritius; metabolic syndrome; prevalence.

8.1 Introduction The metabolic syndrome (MetS) is a cluster of risk factors for heart disease, stroke and type 2 diabetes mellitus which include elevated blood pressure, central obesity, elevated fasting blood glucose, and abnormal cholesterol or triglyceride levels, as per the most updated definition by the International Diabetes Federation (IDF) [1]. Over the last two decades, the MetS has impacted on the life of a large number of people as the ‘New epidemic’, which constituted, through globalization, the ‘Global epidemic’ [2, 3]. It is to be highlighted that the worldwide prevalence of the MetS ranges from 10 to 50% [4]. The ‘epidemic’ has hit the developing countries with high occurrence of cardiovascular diseases (CVDs) and type 2 diabetes mellitus as development of these countries had led people to adopt lifestyles associated with non-communicable diseases (NCDs) and the MetS [5]. Considering Mauritius, which is a small island developing state situated in the Indian Ocean on the east cost of Madagascar, the World Health Organization (WHO) (2018) reported that 33% of deaths were due to CVD and 24% to type 2 diabetes; the highest rate of mortality due to type 2 diabetes worldwide [6]. The local NCD survey 2015 showed that the prevalence of type 2 diabetes was 20.5% and that of hypertension was 28.4% [7]. It also showed that the prevalence of hypercholesterolemia was 44.1%. On the other hand, there was no mention of the MetS in the NCD report [7]. Despite the high prevalence of type 2 diabetes mellitus in Mauritius, research work on MetS is scarce. The only prevalence study available was carried out by Chan Sun, Abdool Raheem and Ramasawmy (2012) who showed that its prevalence among an employee population of a public educational institution was 32.1% in the year 2012 [8]. In light of the need to screen for this syndrome for the primary prevention of type 2 diabetes mellitus, this study was undertaken with the following objectives: (1) To determine the prevalence of the MetS among the employees of one of the three public higher education institutions in Mauritius, (2) To analyse the associated risk factors and (3) To discuss the strategies which can be put in place for its primary prevention.

8.2 Methods Design: This cross-sectional study was conducted among the employees of one of the three public tertiary educational institutions in Mauritius. Inclusion criteria for participation in the study were the

8.3 Results

95

affiliation to the selected educational institution, regardless of the age, gender and ethnicity while pregnant women were excluded from the study. Sample size: The estimated sample size was 249 participants at 95% confidence interval, with an assumption that the proportion of participants having the MetS was 30% [based on the previous study by Chan Sun, Abdool Raheem and Ramasawmy (2012)] [8] and with the use of the finite employee population size being 1080. The participants were identified from a randomized list of employees. The participants were invited by email with the provision of an information sheet and an informed consent form. Upon expression of interest and prior to participation, the main investigators explained to each participant the procedures of the research work as described below. Data collection: The participants were requested to fill the survey questionnaire which was adapted from the one used by Chan Sun, Abdool Raheem and Ramasawmy (2012) [8] and then underwent the blood tests which included fasting blood glucose, triglyceride levels, HDL Cholesterol levels, and uric acid levels. Blood pressure and anthropometric measurements which included, weight, height, waist circumference of each participant were also measured and recorded. Each participant was assigned a participant identification code which was used on the survey questionnaires, blood test tubes and anthropometry sheets to ensure anonymity of participants. The participant identification codes assigned to each participant were known to the two main investigators only. Data analysis: Using data from the questionnaires, participants were classified according to their level of education, using a classification from Kutlu et al. (2018) [9]. Following the International Diabetes Federation (IDF 2009) diagnostic criteria for the MetS, participants were considered to have the MetS if they had at least 3 of the following criteria: high fasting blood glucose (≥5.6 mmol/L) or the use of drugs for hyperglycemia; high blood pressure (≥130/90 mmHg) or the use of antihypertensive drugs; high triglyceride levels (≥1.7 mmol/L); low HDL Cholesterol (20 mm as very strong [19]. The results of the antibacterial test of compounds (1) and (2) are shown in Table 9.2. Based on the data from Table 9.5, the antibacterial test against B. subtilis compound (1) was categorized as very strong in all of the concentrations, while compound (2) was categorized as very strong in 0.5 mg/disc concentration, and categorized as strong in 0.4 and 0.3 mg/disc concentration. On the other hand, for the antibacterial test against E. coli, compound (1) was categorized as moderate on 0.5 mg/disc and no activity on the lower concentration. Compound (2) did not show any observable activity when tested with all concentrations. The characteristic of antibacterial activity of these two compounds against B. subtilis and E. coli are similar to the synthetic compounds of organotin(IV) benzoate derivatives reported by others [26–28]. The decrease in observable antibacterial activity showed that modifying the hydroxyl group into methoxy on flavonoid (Chalcone, flavone, and flavanone) decreased its antibacterial activity [20]. The antibacterial activity of the artonin E compound and its modification against E. coli bacteria showed that it has little to no activity at all. This is likely to happen as E. coli is a Gram-negative bacteria with an outer

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Table .: Antibacterial test inhibitory zone diameter of compounds () and () against B. subtilis and E. coli. B. subtilis Compound

Inhibition zone diameter (mm) Concentration of compounds . mg/disk

. mg/disk

. mg/disk

 –  

 –  

 –  

(+) control (−) control Compound () Compound ()

E.coil Compound

Inhibition zone diameter (mm) Concentration of compounds . mg/disk

. mg/disk

. mg/disk

 – . –

 – – –

 – – –

(+) control (−) control Compound () Compound ()

membrane, which also explains the main reason for the resistance against β-lactam antibiotic types, quinolones, and other antibiotics [21, 23].

9.4 Conclusions In this study, a pure flavonoid compound known as artonin E from the branch and root bark of the Pudau (Artocarpus kemando Miq.), with physical properties of yellow crystals of melting point 255–258 °C was successfully isolated and identified. The isolated compound showed highly active anticancer activity against P388 murine leukemia cells with an IC50 value of 1.56 μg/mL. The modification of artonin E using diazomethane produced yellow solids of 24 mg (31.3% yield) with 144–144.5 °C melting point. Based on spectroscopy analysis, methylation on the OH group on B ring of the artonin E was discovered. Furthermore, the isolated artonin E compound and the modified artonin E showed antibacterial activity against B. subtilis with a very strong category of activity on 0.5 mg/disc concentration. Against E coli, artonin E showed moderate activity on 0.5 mg/disc concentration. Finally, the modified compound did not show antibacterial activity against E. coli.

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22. Breitmair E. Structure elucidation by NMR in organic chemistry: practical guide. Chichester: John Wiley and Son, LTD.; 2002. 23. Suhartati T, Fatimah N, Yandri Y, Kurniawan R, Bahri S, Hadi S. The anticancer, antimalarial, and antibacterial activities of moracalkon a isolated from Artocarpus kemando Miq. J Adv Pharm Educ Res 2021;11:105–10. 24. Hadi S, Rilyanti M. Synthesis and in vitro anticancer activity of some organotin(IV) benzoate compounds. Orient J Chem 2010;26:775–9. 25. Hadi S, Rilyanti M, Suharso. In vitro activity and comparative studies of some organotin(IV) benzoate derivatives against leukemia cancer cell: L-1210. Indo J Chem 2012;12:172–7. 26. Hadi S, Lestari S, Suhartati S, Qudus HI, Rilyanti M, Herasari D, et al. Synthesis and comparative study on the antibacterial activity organotin (IV) 3-hydroxybenzoate compounds. Pure Appl Chem 2021;93:623–8. 27. Samsuar S, Simanjuntak W, Qudus HI, Yandri Y, Herasari H, Hadi S. In vitro antimicrobial activity study of some organotin(IV) chlorobenzoates against Staphylococcus aureus and Escherichia coli. J Adv Pharm Educ Res 2021;11:17–22. 28. Hadi S, Samsuar S, Qudus HI, Simanjuntak W. In vitro antibacterial activity of some of dibutyltin (IV) chlorobenzoate derivatives against Staphylococcus aureus and Escherichia coli. ARPN J Eng Appl Sci 2021;16:1623–9.

Noviany Noviany*, Uswatun Hasanah, Puspa Dewi Lotulung and Sutopo Hadi

10 Antibacterial, antioxidant and cytotoxic activities of the stem bark of Archidendron jiringa ( Jack) I.C. Nielsen Abstract: Archidendron jiringa ( Jack) I.C. Nielsen plant, locally known as jengkol, is a species belongs to Archidendron genus of the Fabaceae family. This plant is a potential source of biologically active secondary metabolites, which are useful for various purposes, such as to destroy bacteria and fungi, to treat cancer, and as antioxidant agent. In this study, extract of A. jiringa stem bark was fractionated and subsequently tested for antibacterial, cytotoxic and antioxidant activity. Extraction was carried out using maceration and fractionation of the extract was conducted using both vacuum liquid and column chromatography techniques to obtain three fractions. The biological activity of the bulk extract and fractions were then evaluated using disc diffusion method, revealing that the sample with the highest activity against Bacillus subtilis and Escherichia coli is the ethyl acetate extract, while no inhibitory effect on both bacteria was observed for some ethyl acetate fractions tested. The screening tests indicate that the bulk extract and all fractions exhibit promising toxicity, with the LC50 values in the range of 227–837 ppm. In addition, good antioxidant activities, with the IC50 values in the range of 0.7–7.2 ppm, are displayed by bulk extract and the fractions. Keywords: A. jiringa; antibacterial; antioxidant; cytotoxic.

10.1 Introduction Archidendron jiringa is a well-known traditional medicinal plant belonging to Fabaceae family and has been used as antibacterial [1–3], antituberculosis [4–9], antioxidants [9], anticancer [10], and antimalarial [11]. In Indonesian, this plant has been used as traditional medicine to treat various infectious diseases such as eczema, scabies, wounds, and ulcers. A. Jiringa, commonly known as Dogfruit, can be found in the Southeast Asian region and locally called jengkol (Indonesia), jering

*Corresponding author: Noviany Noviany, Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Lampung, Lampung 35145, Indonesia, E-mail: [email protected]. https://orcid.org/0000-0002-4046-6134 Uswatun Hasanah and Sutopo Hadi, Department of Chemistry, Faculty of Mathematics and Natural Sciences, University of Lampung, Lampung 35145, Indonesia Puspa Dewi Lotulung, Research Center for Chemistry – BRIN, Indonesian Institute of Sciences, South Tangerang 15314, Indonesia As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: N. Noviany, U. Hasanah, P. D. Lotulung and S. Hadi “Antibacterial, antioxidant and cytotoxic activities of the stem bark of Archidendron jiringa ( Jack) I.C. Nielsen” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2021-0151 | https:// doi.org/10.1515/9783110752601-010

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(Malaysia), or luk nieng (Thailand) [12]. The seeds of the plant are popular in Malaysia, Thailand, and Indonesia as a food ingredient. A. jiringa has some synonymous names, including Pithecellobium jiringa, Pithecellobium lobatum Benth., and Archindendron pauciflorum [13]. Several studies have been conducted on almost all parts of A. jiringa, such as the leaves, fruit skin, and seeds. It was reported that the seeds, bark, and leaves extract of A. jiringa contain various compounds which possess antibacterial activity, include alkaloids, steroids, triterpenoids, glycosides, saponins, flavonoids, and tannins. Bakar et al. [14] demonstrated the antimicrobial activity of P. jiringa leaves, pods and seeds, and they reported that the leaves extract exhibited the highest activity against Staphylococcus aureus, Staphylococcus epidermidis and Microsporum gypsum. Another researcher has investigated the ethanol extract of Pithecellobium dulce leaves, and reported that the ethanol extract exhibited anti-inflammatory and antibacterial properties against Streptococcus pyrogenes, S. aureus, Escherichia coli and Klebsiella pneumonia [15]. In addition, the methanolic extract of P. dulce seeds was reported to display promising potential against the Gram negative bacteria E. coli and Pseudomonas aeruginosa [16]. Recently, phytochemical and antimicrobial evaluation conducted by Hussin et al. [17], justified a high potential of the stem bark of P. jiringa as a source of active antimicrobial compounds. Furthermore, in our previous research on bioassay-guided separation approach from the stem roots extracts of A. jiringa, it was found that methanol and ethyl acetate extracts of A. jiringa displayed considerably high antibacterial activities against E. coli and Bacillus subtilis [18]. Even though there have been many studies conducted on almost all parts of A. jiringa, but the phytopharmacological study on the stem bark part has not been extensively investigated. Therefore, in current our continuous research, we reported some potential bioactivities of the ethyl acetate extracts of the stem bark of A. jiringa using appropriate methods including antibacterial, antioxidant, as well as the toxicity properties. In this respect, this study is useful to extend utilization and to gain scientific value of the A. jiringa plant.

10.2 Experimental 10.2.1 Plant Materials The stem bark samples of A. jiringa were obtained on May 2019 from the Housing area of Universitas Lampung, at Gedong Meneng District, Bandar Lampung, Lampung Province, Indonesia. Identification of the plant specimens (NV6/NRGD/2018) was conducted at the Herbarium Bogoriense, LIPI Bogor, Indonesia. All chemicals were obtained from Aldrich Chemical and Merck AG. The silica gel 60 GF254 plates (Merck; 0.25 mm) was used for TLC experiment, with Ce(SO4)2 as staining reagent. Silica gel (Kieselgel 60, 70–230 mesh ASTM; Merck) was used for column chromatography and fractionation of the extracts was performed using medium pressure liquid chromatography (MPLC) system (BUCHI, Reverelis Prep Purification System, Switzerland).

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10.2.2 Extraction Maceration technique with gradient polarity of solvent was applied to extract the dried stem bark of A. jiringa (2.7 kg). The extraction method was referred to our previous report [18] producing the extracts of n-hexane (1.6 g), EtOAc (44.2 g) and methanol (131.2 g), respectively. Agar disc diffusion method was applied to evaluate antibacterial, toxicity and antioxidant activities of the extracts.

10.2.3 Antibacterial Assay 10.2.3.1 Preparation of test solution: Test solutions were prepared by weighing 2 mg of the extracts (n-hexane, ethyl acetate, and methanol extract) and then dissolved in 200 L methanol. Two concentrations of 0.5 mg/disc and 0.3 mg/disc were then prepared.

10.2.3.2 Preparation of control solutions: In the antibacterial tests, amoxicillin was utilized as positive control against B. subtilis and chloramphenicol against E. coli. Each of 1.5 mg of positive control was dissolved in 150 µL of methanol, then each control was made in two concentrations of 0.5 mg/disc and 0.3 mg/disc.

10.2.3.3 Antibacterial test: Antibacterial activity tests were conducted using B. subtilis (InaCC-B334) as Gram positive bacteria and E. coli (InaCC-B5) as Gram negative bacteria. Both strains were obtained from Research Center for Chemistry - BRIN, Indonesian Institute of Sciences, Indonesia. The antibacterial activity of the extracts evaluated using disc diffusion method referring to the procedure available in the literature [17, 19–23], and defined in term of the inhibition zone formed around the discs, and the diameter of inhibition zone (mean of three replicates SD) as indicated by clear area on the disc.

10.2.4 Antioxidant Assay Antioxidant test was conducted by mixing 0.5 mL of 400 ppm DPPH (2,2-diphenyl-1-picrylhydrazyl) solution with 2.0 mL of sample solution of several concentrations in the dark. The mixture was allowed to react at room temperature for 30 min, and then the absorption of was measured using a UV–Vis spectrophotometer at 515 nm wavelength [23–27].

10.2.5 Cytotoxicity screening The Brine Shrimp Lethality Test (BSLT) method as described by Meyer et al. [28] was applied for toxicity test. Observation was performed after 24 h.

10.3 Results and discussion Extractions with n-hexane, ethyl acetate and methanol as solvents were carried out and produced obtain 1.59 g, 44.2 g, and 131.2 g of extract of A. jiringa, respectively. All extracts were assayed for their antibacterial, antioxidant, and cytotoxic activities.

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10.3.1 Antibacterial activity Using disc diffusion method, the antibacterial activity of n-hexane, ethyl acetate, and methanol extracts of A. jiringa, was evaluated against B. subtilis and E. coli bacteria. The antibacterial property of A. jiringa extract and fractions against the test bacteria was quantified by the existence or lack of inhibition zones and their diameters. The experimental results are shown in Table 10.1 and Figures 10.1 and 10.2. Based on the bioassay results, E. coli bacteria gave a greater inhibition zone than the inhibition zone of B. subtilis bacteria. The experimental results indicate that no significant different of the inhibitory activities against both bacteria achieved using different concentrations (0.5 mg/disc and 0.3 mg/disc). It was also observed that the ethyl acetate extract exhibits the highest activity against both bacteria, followed by methanol, and n-hexane extracts. These results also imply that ethyl acetate is the most effective solvent to extract secondary metabolites compared to methanol and n-hexane. The methanol extract was found to display higher antibacterial efficacy than that Table .: Inhibition zones (nm) of different A. jiringa extracts against two test bacteria. Concentration (mg/disc)

. .

Inhibitory zone against E. coli

Inhibitory zone against B. subtilis

n-hexane

EtOAc

MeOH

n-hexane

EtOAc

MeOH

 

 

 

 

 

 

Figure 10.1: Antibacterial test of n-hexane (H), ethyl acetate (EA), and methanol extracts (M) against B. subtilis with concentration of (a) 0.3 mg/disc; (b) 0.5 mg/disc.

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Figure 10.2: Antibacterial test of n-hexane (H), ethyl acetate (EA), and methanol extracts (M) on E. coli with concentration (a) 0.3 mg/disc; (b) 0.5 mg/disc.

of n-hexane extract, not likely as a result of higher amount of tannins dissolved in methanol. Hypothetically, methanol extract is reasonable to have the highest antibacterial efficacy due to the presence of both tannins and the most polar secondary metabolites, however the results obtained do not agree with this assumption. This probably is due to dissolution of inhibitory compounds in ethyl acetate solvent. Furthermore, the results of this current research indicate that E. coli was the most susceptible to the ethyl acetate extract. These findings are in agreement with the previous research reports, suggesting implication of antibacterial activity of plants extracts through its different secondary metabolites that potentially hinder the growth of E. coli. The metabolites then could be utilized to inhibit the strains of bacteria that have developed resistant toward synthetic antibiotics and drugs [16]. Antibacterial activity tests were then carried out on the results of ethyl acetate extract fractionation, namely the E11, E114 and E1147 fractions. The method used is the same as the previous antibacterial test, and the results obtained against B. subtilis and E. coli bacteria can be seen in Table 10.2 and Figures 10.3 and 10.4. Table .: Inhibitory zone (nm) of some fractions of ethyl acetate extract against E. coli and B. subtilis. Concentration (mg/disc) . .

Against E. coli

Against B. subtilis

E fr.

E. fr.

E.. fr.

E fr.

E. fr.

E.. fr.

 

 

 

 

 

 

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Figure 10.3: Antibacterial test of some fractions of ethyl acetate extract (EA) against B. subtilis with concentration of (a) 0.3 mg/disc; (b) 0.5 mg/disc.

Figure 10.4: Antibacterial test of some fractions of ethyl acetate extract (EA) against E. coli with concentration of (a) 0.3 mg/disc; (b) 0.5 mg/disc.

The results demonstrated that all ethyl acetate fractions tested exhibit no antibacterial activity against both test bacteria. Although the ethyl acetate extracts display good potential as antibacterial, in contrast to our expectation, a limited antibacterial potential of its fractions suggests that the antimicrobial activities have a direct relation with increased concentration (%) of the extracts. Additionally, the difference in inhibition of plant extracts might be the consequence of varied chemical constituents and volatility of the components [23].

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10.3.2 Antioxidant activity Antioxidant activity of the extract and the fractions obtained were evaluated using the DPPH method as described by others [23–27] with minor modification. Quercetin was used as a positive control with concentrations of 50, 10, 5, and 1 ppm which prepared from a stock solution of 1000 ppm, and methanol as the negative control. The DPPH immersion activity of antioxidant substances is based on the ability of antioxidants to neutralize DPPH radicals by donating their protons to form more stable radicals. The addition of substances that are antioxidants will reduce the purple color of the DPPH solution and the more active the solution is added (the more DPPH radicals are neutralized), the DPPH solution will turn yellow. The samples and quercetin that had been soaked for 30 min showed a color change at concentrations of 1 and 4 ppm the solution was still slightly purple, while at concentrations of 7 and 10 ppm the solution was getting yellow. This shows that the higher the concentration, the greater the activity of the sample in reducing DPPH radicals so that more DPPH is neutralized and the solution becomes yellow. After all the solutions were ready, quantitative measurements were carried out using UV–Vis spectrophotometry at 515 nm which is the maximum wavelength for DPPH. The negative control has an absorbance value of 1.5524. The % inhibition obtained will be used to determine the IC50 value through a linear regression equation. The percentage of inhibition of the extract and fraction of A. jiringa stem bark is presented in Table 10.3. The data in Table 10.3 indicate that % inhibition increased with increased sample concentration. The value of % inhibition was used to determine the IC50 of the tested extracts and fractions using linear regression equations. IC50 is a necessary concentration of the sample to inhibit 50% of free radicals. The IC50 result of the extract and fraction of A. jiringa stem bark was shown in Table 10.4. Based on the IC50 data in Table 10.4, it was observed that both the extract and the fraction of A. jiringa stem bark showed an IC50 value below 50 ppm, indicated that the extract and fraction of A. jiringa stem bark has strong antioxidant activity [20]. Previous studies have been conducted by others to evaluate antioxidant of all parts of P. dulce (Roxb.) Benth. Form the results of DPPH scavenging activity indicates that the plant was potentially active, and it was suggested that the radical scavenging activity of extracts is most likely related to the properties of the phenolics [18, 25, 26].

10.3.3 Toxicity activity Toxicity screening of extract and fractions of A. jiringa stem bark was done using BSLT method described in Meyer et al. [28]. The value of % mortality of the extract and fraction of A. jiringa stem bark can be seen in Table 10.5. The experimental results demonstrated that concentration of the sample loaded in the media could kill A. salina Leach larvae which could be seen from the % mortality,

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Table .: The results of the antioxidant assay of extracts and fractions of A. jiringa stem bark. Sample tested

Quarcetin

n-hexane extract

EtOAc extract

MeOH extract

E fraction

E. fraction

E.. fraction

Concentration (ppm)

Absorbance

% of Inhibition

                           

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

Table .: IC values of tested samples. Tested samples Quarcetin n-hexana extract EtOAc extract MeOH extract E fraction E fraction E fraction

IC (ppm) . . . . . . .

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131

Table .: Toxicity of tested sample samples. Sample tested n-hexane extract

EtOAc extract

MeOH extract

E fraction

E. fraction

E.. fraction

Concentration (ppm)

Accumulated life

Dead accumulation

% Mortality

                       

                       

   `            `        

. . . . . . . . . . . . . . . . . . . . . . . .

respectively, with concentrations of 2000, 1000, 200, and 20 ppm. The number of deaths of A. salina Leach larvae in each hole in various concentrations of the sample treatment of jengkol bark extract is shown in Table 10.5. From these tables it can be seen that variations in the concentrations of jengkol bark extract in this experiment showed different effects on the mortality of A. Salina Leach. The % mortality obtained will be used to determine the LC50 value, which is the concentration that causes the death of 50% of the test animals. The LC50 values of tested samples are presented in Table 10.6. Table .: LC value of tested samples. Tested samples n-hexane extract EtOAc extract MeOH extract E fraction E fraction E fraction

LC (ppm) . . . . . .

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10 Antibacterial, antioxidant and cytotoxic activities of the stem bark

According to Meyer et al. [28] an extract is considered to exhibit toxic activity in a toxicity test if it causes the death of 50% of test animals at concentrations