SUSTAINABLE INORGANICCHEMISTRY

EIBC BooksEncyclopedia ofInorganic andBioinorganicChemistry

Application of Physical Methods to Inorganic and Bioinorganic ChemistryEdited by Robert A. Scott and Charles M. LukehartISBN 978-0-470-03217-6Nanomaterials: Inorganic and Bioinorganic PerspectivesEdited by Charles M. Lukehart and Robert A. ScottISBN 978-0-470-51644-7Computational Inorganic and Bioinorganic ChemistryEdited by Edward I. Solomon, R. Bruce King and Robert A. ScottISBN 978-0-470-69997-3Radionuclides in the EnvironmentEdited by David A. AtwoodISBN 978-0-470-71434-8Energy Production and Storage: Inorganic Chemical Strategies for a Warming WorldEdited by Robert H. CrabtreeISBN 978-0-470-74986-9The Rare Earth Elements: Fundamentals and ApplicationsEdited by David A. AtwoodISBN 978-1-119-95097-4Metals in CellsEdited by Valeria Culotta and Robert A. ScottISBN 978-1-119-95323-4Metal-Organic Framework MaterialsEdited by Leonard R. MacGillivray and Charles M. LukehartISBN 978-1-119-95289-3The Lightest Metals: Science and Technology from Lithium to CalciumEdited by Timothy P. HanusaISBN 978-1-118-70328-1Sustainable Inorganic ChemistryEdited by David A. AtwoodISBN 978-1-118-70342-7

ForthcomingMetalloprotein Active Site AssemblyEdited by Michael K. Johnson and Robert A. ScottISBN 978-1-11915983-4The Heaviest Metals: Science and Technology of the Actinides and BeyondEdited by William J. Evans and Timothy P. HanusaISBN 978-1-11930409-8

Encyclopedia of Inorganic and Bioinorganic ChemistryThe Encyclopedia of Inorganic and Bioinorganic Chemistry (EIBC) was created as an online reference in 2012 by mergingthe Encyclopedia of Inorganic Chemistry and the Handbook of Metalloproteins. The resulting combination proves to bethe defining reference work in the field of inorganic and bioinorganic chemistry. The online edition is regularly updatedand expanded. For information see:

www.wileyonlinelibrary.com/ref/eibc

SUSTAINABLE INORGANICCHEMISTRY

Editor

David A. AtwoodUniversity of Kentucky, Lexington, KY, USA

This edition first published 2016© 2016 John Wiley & Sons Ltd

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Library of Congress Cataloging-in-Publication Data

Names: Atwood, David A., 1965- editor.Title: Sustainable inorganic chemistry / David A. Atwood, editor.Description: Chichester, West Sussex : John Wiley & Sons Ltd, 2016. |

Includes bibliographical references and index.Identifiers: LCCN 2016018241 (print) | LCCN 2016019886 (ebook) | ISBN 9781118703427(cloth) | ISBN 9781118751466 (pdf) | ISBN 9781118751473 (epub)Subjects: LCSH: Green chemistry. | Chemistry, Inorganic. | Conservation of natural resources. |Environmental protection.Classification: LCC TP155.2.E58 S88 2016 (print) | LCC TP155.2.E58 (ebook) | DDC660–dc23LC record available at https://lccn.loc.gov/2016018241

A catalogue record for this book is available from the British Library.

Front cover image used with permission from Tessa L. Adkins

ISBN: 9781118703427

Set in 10/12pt TimesNewRomanMTStd by SPi-Global, Chennai, IndiaPrinted and bound in Singapore by Markono Print Media Pte Ltd.

1 2016

Encyclopedia of Inorganic and Bioinorganic Chemistry

Editorial Board

Editor-in-Chief

Robert A. ScottUniversity of Georgia, Athens, GA, USA

Section Editors

David A. AtwoodUniversity of Kentucky, Lexington, KY, USA

Timothy P. HanusaVanderbilt University, Nashville, TN, USA

Charles M. LukehartVanderbilt University, Nashville, TN, USA

Albrecht MesserschmidtMax-Planck-Institute für Biochemie, Martinsried, Germany

Robert A. ScottUniversity of Georgia, Athens, GA, USA

Associate Editors

Boniface FokwaUniversity of California, Riverside, CA, USA

Rebecca L. MelenCardiff University, Cardiff, UK

Yvain NicoletInstitut de Biologie Structurale, Grenoble, France

Tim StorrSimon Fraser University, Burnaby, BC, Canada

Editors-in-Chief Emeritus & Senior Advisors

Robert H. CrabtreeYale University, New Haven, CT, USA

R. Bruce KingUniversity of Georgia, Athens, GA, USA

International Advisory Board

Michael BruceAdelaide, Australia

Tristram ChiversCalgary, Canada

Valeria CulottaMD, USA

Mirek CyglerSaskatchewan, Canada

Marcetta DarensbourgTX, USA

Michel EphritikhineGif-sur-Yvette, France

Robert HuberMartinsried, Germany

Susumu KitagawaKyoto, Japan

Leonard R. MacGillivrayIA, USA

Thomas PoulosCA, USA

David SchubertCO, USA

Edward I. SolomonCA, USA

Katherine ThompsonVancouver, Canada

T. Don TilleyCA, USA

Karl E. WieghardtMülheim an der Ruhr, Germany

Vivian YamHong Kong

Contents

Contributors XI

Series Preface XVII

Volume Preface XIX

Recovery of Gold from Incinerated Sewage Sludge 1Katsuyasu Sugawara

Rare Earth Recycling from NdFeB 9Zhongsheng Hua

Life Cycle Sustainability Assessments 25Anthony Halog and Yosef Manik

Trends in Food and Agricultural Waste Valorization 43Anand Burange, James H. Clark and Rafael Luque

Toxicity Assessment of Molecular Rhenium(VII) Epoxidation Catalysts 53Mirza Cokoja, Fritz E. Kühn, Marta Markiewicz and Stefan Stolte

Challenges in Green Analytical Chemistry 67Salvador Garrigues, Sergio Armenta and Miguel de la Guardia

Mobile Apps for Green Chemistry 77Alex M. Clark, Antony J. Williams and Sean Ekins

Renewable Plant-Based Raw Materials for Industry 87Divya Bajpai Tripathy and Anuradha Mishra

Sustainable Synthesis of Fine Chemicals from Aliphatic Nitro Compounds 105Roberto Ballini and Alessandro Palmieri

Sustainable Production of Glycerol 119Rosaria Ciriminna and Mario Pagliaro

Production of Biopropylene Using Biomass-Derived Sources 129Efterpi S. Vasiliadou and Angeliki A. Lemonidou

VIII CONTENTS

Methylethers from Alcohols and Dimethyl Carbonate 143Fabio Aricò and Pietro Tundo

Sustainable Surfactants Based on Amino Acids 159Lourdes Pérez, M. Rosa Infante and Aurora Pinazo

Sustainable Biosurfactants 175Divya Bajpai Tripathy and Anuradha Mishra

Solvent Systems for Sustainable Chemistry 193Francesca M. Kerton

Fluorous Hydrocarbon Oxidation 211Gianluca Pozzi and Silvio Quici

Ionic Liquids: Industrial Applications 221Geeta Durga and Anuradha Mishra

Ionic Liquids: Enzymatic Hydrolysis of Lignocellulose 235Ronny M. Wahlström and Anna K. Suurnäkki

Ionic Liquids: Applications by Computational Design 249Arunprakash T. Karunanithi, Reza Farahipour and Kamila Dilmurat

Ionic Liquids: Recycling 263Evangelos Sklavounos, Jussi K.J. Helminen, Ilkka Kilpeläinen, Alistair W.T. King and Lasse Kyllönen

Ionic Liquids: Bacterial Degradation in Wastewater Treatment Plants 279Elena Diaz, Victor Monsalvo, Jose Palomar and Angel F. Mohedano

Water Treatment by Electrocoagulation 293Ville V. Kuokkanen

Sustainable Water Remediation 305Anjali Gupta and Anuradha Mishra

Dimethylcarbonate for the Catalytic Upgrading of Amines and Bio-Based Derivatives 321Maurizio Selva, Alvise Perosa, Sandro Guidi and Lisa Cattelan

Sustainable Syntheses with Microwave Irradiation 333Tanvi Vats and Anuradha Mishra

Radical Reactions, 𝛃-Cyclodextrin and Chitosan and Aqueous Media: From Fundamental Reactions to PotentialApplications 351Victoria T. Perchyonok

CONTENTS IX

Catalytic Epoxidation of Organics from Vegetable Sources 373Matteo Guidotti and Chiara Palumbo

Catalytic Cyclic Carbonate Synthesis with Sustainable Metals 385James W. Comerford, Ian D.V. Ingram, Michael North and Xiao Wu

Solid Catalysts for Epoxidation with Dilute Hydrogen Peroxide 399José M. Fraile

TiO𝟐-Based Heterogeneous Catalysis for Photocatalytic Hydrogen Generation and Photodegradation 409Jing Wang, Wei Li Ong, Minmin Gao, Liangliang Zhu and Ghim Wei Ho

Photocatalytic Production of Hydrogen with Earth-Abundant Metal Catalysts 439Shunichi Fukuzumi and Yusuke Yamada

Multifunctional MOF-Based Photocatalysis 451Dengrong Sun and Zhaohui Li

Sustainable Nanomaterials 467Shahzad Ahmad, Divya Bajpai Tripathy and Anuradha Mishra

Sustainable Synthesis of Metal Oxide Nanostructures 483Nasir Baig R.B., Mallikarjuna N. Nadagouda and Vivek Polshettiwar

Micellar Nanoreactors 495Alessandro Scarso

Index 513

Contributors

Shahzad Ahmad Gautam Buddha University, Greater Noida, India• Sustainable Nanomaterials

Fabio Aricò Ca’ Foscari University, Venezia Mestre, Italy• Methylethers from Alcohols and Dimethyl Carbonate

Sergio Armenta University of Valencia, Valencia, Spain• Challenges in Green Analytical Chemistry

Nasir Baig R.B. WQMB, US Environmental Protection Agency, Cincinnati, OH, USA• Sustainable Synthesis of Metal Oxide Nanostructures

Roberto Ballini University of Camerino, Camerino, Italy• Sustainable Synthesis of Fine Chemicals from Aliphatic Nitro Compounds

Anand Burange Wilson College, Mumbai, India• Trends in Food and Agricultural Waste Valorization

Lisa Cattelan Ca’ Foscari University Venezia, Venezia Mestre, Italy• Dimethylcarbonate for the Catalytic Upgrading of Amines and Bio-Based

Derivatives

Rosaria Ciriminna Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Palermo, Italy• Sustainable Production of Glycerol

Alex M. Clark Molecular Materials Informatics, Montreal, QC, Canada• Mobile Apps for Green Chemistry

James H. Clark University of York, York, UK• Trends in Food and Agricultural Waste Valorization

Mirza Cokoja Technical University of Munich, Munich, Germany• Toxicity Assessment of Molecular Rhenium(VII) Epoxidation Catalysts

James W. Comerford University of York, York, UK• Catalytic Cyclic Carbonate Synthesis with Sustainable Metals

Elena Diaz Universidad Autonoma de Madrid, Madrid, Spain• Ionic Liquids: Bacterial Degradation in Wastewater Treatment Plants

Kamila Dilmurat University of Colorado Denver, Denver, CO, USA• Ionic Liquids: Applications by Computational Design

Geeta Durga Sharda University, Greater Noida, India• Ionic Liquids: Industrial Applications

XII CONTRIBUTORS

Sean Ekins Collaborations in Chemistry, Fuquay-Varina, NC, USA; Collaborations Pharmaceuti-cals Inc., Fuquay-Varina, NC, USA• Mobile Apps for Green Chemistry

Reza Farahipour University of Colorado Denver, Denver, CO, USA• Ionic Liquids: Applications by Computational Design

José M. Fraile CSIC-Universidad de Zaragoza, Zaragoza, Spain• Solid Catalysts for Epoxidation with Dilute Hydrogen Peroxide

Shunichi Fukuzumi Ewha Womans University, Seoul, Korea; Meijo University, ALCA and SENTAN, JapanScience and Technology Agency (JST), Nagoya, Japan• Photocatalytic Production of Hydrogen with Earth-Abundant Metal Catalysts

Minmin Gao National University of Singapore, Singapore• TiO2-Based Heterogeneous Catalysis for Photocatalytic Hydrogen Generation and

Photodegradation

Salvador Garrigues University of Valencia, Valencia, Spain• Challenges in Green Analytical Chemistry

Miguel de la Guardia University of Valencia, Valencia, Spain• Challenges in Green Analytical Chemistry

Sandro Guidi Ca’ Foscari University Venezia, Venezia Mestre, Italy• Dimethylcarbonate for the Catalytic Upgrading of Amines and Bio-Based Deriva-

tives

Matteo Guidotti Institute of Molecular Sciences and Technologies, CNR, Milano, Italy• Catalytic Epoxidation of Organics from Vegetable Sources

Anjali Gupta Galgotias University, Greater Noida, India• Sustainable Water Remediation

Anthony Halog The University of Queensland, Brisbane, QLD, Australia• Life Cycle Sustainability Assessments

Jussi K.J. Helminen University of Helsinki, Helsinki, Finland• Ionic Liquids: Recycling

Ghim Wei Ho National University of Singapore, Singapore• TiO2-Based Heterogeneous Catalysis for Photocatalytic Hydrogen Generation and

Photodegradation

Zhongsheng Hua Anhui University of Technology, Maanshan, China• Rare Earth Recycling from NdFeB

M. Rosa Infante IQAC-CSIC, Barcelona, Spain• Sustainable Surfactants Based on Amino Acids

Ian D.V. Ingram University of York, York, UK• Catalytic Cyclic Carbonate Synthesis with Sustainable Metals

Arunprakash T. Karunanithi University of Colorado Denver, Denver, CO, USA• Ionic Liquids: Applications by Computational Design

CONTRIBUTORS XIII

Francesca M. Kerton Memorial University of Newfoundland, St. John’s, NL, Canada• Solvent Systems for Sustainable Chemistry

Fritz E. Kühn Technical University of Munich, Munich, Germany• Toxicity Assessment of Molecular Rhenium(VII) Epoxidation Catalysts

Ilkka Kilpeläinen University of Helsinki, Helsinki, Finland• Ionic Liquids: Recycling

Alistair W.T. King University of Helsinki, Helsinki, Finland• Ionic Liquids: Recycling

Ville V. Kuokkanen University of Oulu, Oulu, Finland• Water Treatment by Electrocoagulation

Lasse Kyllönen Kemira Oyj, Espoo, Finland• Ionic Liquids: Recycling

Angeliki A. Lemonidou Laboratory of Petrochemical Technology, Aristotle University of Thessaloniki,Thessaloniki, Greece• Production of Biopropylene Using Biomass-Derived Sources

Zhaohui Li Fuzhou University, Fuzhou, P R China• Multifunctional MOF-Based Photocatalysis

Rafael Luque Universidad de Cordoba, Cordoba, Spain• Trends in Food and Agricultural Waste Valorization

Yosef Manik Del Institute of Technology, North Sumatra, Indonesia• Life Cycle Sustainability Assessments

Marta Markiewicz University Bremen, Bremen, Germany• Toxicity Assessment of Molecular Rhenium(VII) Epoxidation Catalysts

Anuradha Mishra Gautam Buddha University, Greater Noida, India• Ionic Liquids: Industrial Applications• Renewable Plant-Based Raw Materials for Industry• Sustainable Syntheses with Microwave Irradiation• Sustainable Nanomaterials• Sustainable Water Remediation• Sustainable Biosurfactants

Angel F. Mohedano Universidad Autonoma de Madrid, Madrid, Spain• Ionic Liquids: Bacterial Degradation in Wastewater Treatment Plants

Victor Monsalvo Universidad Autonoma de Madrid, Madrid, Spain• Ionic Liquids: Bacterial Degradation in Wastewater Treatment Plants

Mallikarjuna N. Nadagouda WQMB, US Environmental Protection Agency, Cincinnati, OH, USA• Sustainable Synthesis of Metal Oxide Nanostructures

Michael North University of York, York, UK• Catalytic Cyclic Carbonate Synthesis with Sustainable Metals

XIV CONTRIBUTORS

Wei Li Ong National University of Singapore, Singapore• TiO2-Based Heterogeneous Catalysis for Photocatalytic Hydrogen Genera-

tion and Photodegradation

Mario Pagliaro Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Palermo, Italy• Sustainable Production of Glycerol

Alessandro Palmieri University of Camerino, Camerino, Italy• Sustainable Synthesis of Fine Chemicals from Aliphatic Nitro Compounds

Jose Palomar Universidad Autonoma de Madrid, Madrid, Spain• Ionic Liquids: Bacterial Degradation in Wastewater Treatment Plants

Chiara Palumbo Institute of Molecular Sciences and Technologies, CNR, Milano, Italy• Catalytic Epoxidation of Organics from Vegetable Sources

Victoria T. Perchyonok VTPChem Pty Ltd, Melbourne, VIC, Australia• Radical Reactions, β-Cyclodextrin and Chitosan and Aqueous Media: From

Fundamental Reactions to Potential Applications

Lourdes Pérez IQAC-CSIC, Barcelona, Spain• Sustainable Surfactants Based on Amino Acids

Alvise Perosa Ca’ Foscari University Venezia, Venezia Mestre, Italy• Dimethylcarbonate for the Catalytic Upgrading of Amines and Bio-Based

Derivatives

Aurora Pinazo IQAC-CSIC, Barcelona, Spain• Sustainable Surfactants Based on Amino Acids

Vivek Polshettiwar Tata Institute of Fundamental Research (TIFR), Mumbai, India• Sustainable Synthesis of Metal Oxide Nanostructures

Gianluca Pozzi CNR, Milano, Italy• Fluorous Hydrocarbon Oxidation

Silvio Quici CNR, Milano, Italy• Fluorous Hydrocarbon Oxidation

Alessandro Scarso Università Ca’ Foscari di Venezia, Venezia, Italy• Micellar Nanoreactors

Maurizio Selva Ca’ Foscari University Venezia, Venezia Mestre, Italy• Dimethylcarbonate for the Catalytic Upgrading of Amines and Bio-Based

Derivatives

Evangelos Sklavounos University of Helsinki, Helsinki, Finland• Ionic Liquids: Recycling

Stefan Stolte University Bremen, Bremen, Germany• Toxicity Assessment of Molecular Rhenium(VII) Epoxidation Catalysts

Katsuyasu Sugawara Graduate School of Engineering Science, Akita University, Japan• Recovery of Gold from Incinerated Sewage Sludge

CONTRIBUTORS XV

Dengrong Sun Fuzhou University, Fuzhou, P R China• Multifunctional MOF-Based Photocatalysis

Anna K. Suurnäkki VTT – Technical Research Centre of Finland Ltd, Espoo, Finland• Ionic Liquids: Enzymatic Hydrolysis of Lignocellulose

Divya Bajpai Tripathy Gautam Buddha University, Greater Noida, India• Renewable Plant-Based Raw Materials for Industry• Sustainable Biosurfactants• Sustainable Nanomaterials

Pietro Tundo Ca’ Foscari University, Venezia Mestre, Italy• Methylethers from Alcohols and Dimethyl Carbonate

Efterpi S. Vasiliadou Catalysis Center for Energy Innovation, University of Delaware, Newark, DE,USA• Production of Biopropylene Using Biomass-Derived Sources

Tanvi Vats Gautam Buddha University, Greater Noida, India• Sustainable Syntheses with Microwave Irradiation

Ronny M. Wahlström VTT – Technical Research Centre of Finland Ltd, Espoo, Finland• Ionic Liquids: Enzymatic Hydrolysis of Lignocellulose

Jing Wang National University of Singapore, Singapore• TiO2-Based Heterogeneous Catalysis for Photocatalytic Hydrogen Genera-

tion and Photodegradation

Antony J. Williams ChemConnector, Wake Forest, NC, USA• Mobile Apps for Green Chemistry

Xiao Wu University of York, York, UK• Catalytic Cyclic Carbonate Synthesis with Sustainable Metals

Yusuke Yamada Osaka City University, Osaka, Japan• Photocatalytic Production of Hydrogen with Earth-Abundant Metal

Catalysts

Liangliang Zhu National University of Singapore, Singapore• TiO2-Based Heterogeneous Catalysis for Photocatalytic Hydrogen Genera-

tion and Photodegradation

Series Preface

The success of the Encyclopedia of InorganicChemistry (EIC), pioneered by Bruce King, the foundingEditor in Chief, led to the 2012 integration of articlesfrom the Handbook of Metalloproteins to create the newlylaunched Encyclopedia of Inorganic and BioinorganicChemistry (EIBC). This has been accompanied by asignificant expansion of our Editorial Advisory Boardwith international representation in all areas of inorganicchemistry. It was under Bruce’s successor, Bob Crabtree,that it was recognized that not everyone would necessarilyneed access to the full extent of EIBC. All EIBC articlesare online and are searchable, but we still recognized valuein more concise thematic volumes targeted to a specificarea of interest. This idea encouraged us to produce aseries of EIC (now EIBC) Books, focusing on topics ofcurrent interest. These will continue to appear on anapproximately annual basis and will feature the leadingscholars in their fields, often being guest coedited byone of these leaders. Like the Encyclopedia, we hopethat EIBC Books continue to provide both the startingresearch student and the confirmed research worker acritical distillation of the leading concepts and provide astructured entry into the fields covered.

The EIBC Books are referred to as spin-on books,recognizing that all the articles in these thematic volumesare destined to become part of the online content of EIBC,usually forming a new category of articles in the EIBCtopical structure. We find that this provides multiple routesto find the latest summaries of current research.

I fully recognize that this latest transformation ofEIBC is built on the efforts of my predecessors, Bruce Kingand Bob Crabtree, my fellow editors, as well as the Wileypersonnel, and, most particularly, the numerous authorsof EIBC articles. It is the dedication and commitment ofall these people that are responsible for the creation andproduction of this series and the “parent” EIBC.

Robert A. ScottUniversity of Georgia

Department of Chemistry

September 2016

Volume Preface

Inorganic chemistry seeks to elucidate the funda-mental properties of the elements and has been instru-mental in the integration of the earth’s inorganic resourcesinto every aspect of modern society. Inorganic chemistrymust now provide the foundation for the sustainable useof the elements. This is an immediate and unavoidablenecessity if protection of what now remains of the natu-ral world is to remain a priority alongside human welfare.Over the past several decades, many new fields of scientificendeavor, beginning with green chemistry and green engi-neering, have encouraged and fostered the development ofproducts and processes that are environmentally benignwhile remaining economically viable. Sustainable InorganicChemistry was prepared in recognition that sustainabilitymust now be the goal of all chemical endeavors.

This volume seeks to demonstrate the importantrange of subjects found at the intersection of inor-ganic chemistry and sustainability. The articles utilizefundamental concepts to explain many recent discoveries,

developments, and applications that could be categorizedas “sustainable inorganic chemistry.” The range of subjectsis broad and includes: inorganic resources, sustain-able synthetic methods, alternative reaction conditions,heterogeneous catalysis, photocatalysis, sustainable nano-materials, renewable and clean fuels, water treatment andremediation, waste valorization and life cycle assessment.Ultimately, the field of sustainable inorganic chemistrymust continue to expand until sustainability is a routinecomponent of all chemical research and development.

*The term “inorganic chemistry” should be under-stood in the broadest sense to mean “the chemistry of theelements” or “the nonliving chemistry of the elements.”

David A. AtwoodUniversity of Kentucky

Lexington, KY, USA

September 2016

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Recovery of Gold from Incinerated Sewage SludgeKatsuyasu Sugawara

Graduate School of Engineering Science, Akita University, Japan

1 Overview 12 Introduction 13 Experimental Procedure 24 Results and Discussion 35 Conclusions 66 Acknowledgments 67 Abbreviations and Acronyms 68 References 6

1 OVERVIEW

Although processes using mercury amalgam,cyanide, and electrolysis are used for gold recovery world-wide, these conventional processes cause serious harm tohuman health and the environment, increase the need forwastewater and residue treatments, and consume a lot ofenergy. While gold distribution is unevenly spread whereonly 20 countries account for 90% of the world’s knowngold reserves, the increasing e-waste and incinerated ashare attractive as secondary resources of gold. The objec-tive of this study is to develop a dry process of selectiveseparation of gold with short reaction time and less energyconsumption. As an example of secondary resource, asewage sludge ash that contained gold coexisting withcarbon particles was heated in a chlorine gas stream. Theoptimum reaction condition was determined for releasingthe gold from the incinerated ash as well as for recoveringall the gold by carbon. The carbon particles play a role inlowering the release temperature of gold and in capturingthe volatile gold efficiently. Figure 1 shows a proposed pro-cess of selective recovery of gold from ore and secondaryresources by chlorination with carbon.

2 INTRODUCTION

The outstanding ductility, thermal/electrical con-ductivity, and chemical stability of gold have enabled itsuse widely in a variety of products, most notably in jew-elry and electronics. Its distribution, however, is unevenlyspread in the sense that just 20 countries account for 90%

Sustainable Inorganic Chemistry. Edited by David A. Atwood.© 2016 John Wiley & Sons, Ltd. ISBN 978-1-118-70342-7

of the world’s known gold reserves. At present, the annualproduction for gold is around 4000 t y−1, 2500 t of whichis produced by refining of ores and 155 t by the recyclingof spent industrial products.1 Typically, these secondaryresources such as electronic circuit boards and incineratedash contain a higher content of gold than primary ores.For example, economic ore grades are typically within arange of 0.3–17 g t−1, whereas the circuit board of a cellularphone contains 300–350 g t−1.2,3

In Southeast Asian, African, and South Americancountries, the use of mercury in the recovery of gold hascaused serious problems to human health and the environ-ment. Indeed, about 40% of all mercury that is releasedto the atmosphere and aquatic environments comes fromgold refineries.4 The use of sodium cyanide has renderedthe use of mercury largely obsolete and has been widelyused for dissolving precious metals in ores due to the highyields that can be achieved. However, cyanidation processesdo have their own disadvantages, such as the long treat-ment time required of multistep extraction and the dis-charge of harmful residue and effluents.5 Because of this,a number of alternative leachants have been consideredover recent years, including thiourea, thiosulfate, bromide,iodide, and sodium hypochlorite. Of these, thiourea is car-cinogenic and requires high cost to recover the metals, thio-sulfate exhibits low solubility, and both iodide and bromideare highly volatile. The search for a leachant that can bemore effective than sodium cyanide is, therefore, still verymuch ongoing.6–8

The commercial recovery of gold is normallydependent on aqueous solutions; however, a suitable dry

2 SUSTAINABLE INORGANIC CHEMISTRY

Ash

Electric circuit board

Cl2C Au

Au

Au

AuAu

Au

Au

CarbonC C

ChlorinationChlorination GravityGravityseparationseparation CombustionCombustion

Figure 1 A proposed dry recovery process of gold from secondary resources

process would be expected to greatly simplify the process ofseparation and reduce the need for wastewater treatment.But the reducing atmosphere process using CO gas or solidcarbon is not economically viable for elements with a highboiling point. On the other hand, chlorination providesa means to volatilize target elements as chlorides, withlow melting and boiling points, by heating with a suitablechlorine source such as Cl2 gas or vinyl chloride. Moreover,the volatilization temperature of the target elements can belowered by incorporating both chlorinating and reducingreagents. In this way, the authors have previously reportedon the release behavior of Pb and Zn from fly ash, Ta andNb from sintered hard alloys, and rare metals such as La,Gd, Nb, and Ta from optical lenses using chlorination inconjunction with added carbon.9–12

In the present study, an incinerated sewage sludgeash from the Lake Suwa area in Nagano Prefecture, Japan,containing 0.83 wt% of gold was used as the test subject forchlorination. In order to develop a selective dry separationprocess, the release behavior of gold from the incineratedash was investigated under a chlorine gas stream at temper-atures from 100 to 1000 ∘C, both with and without the addi-tion of solid carbon. By optimizing the reaction conditions,it is intended to propose a new method for the recovery ofgold by chlorination with solid carbon.

3 EXPERIMENTAL PROCEDURE

3.1 Samples

A gold-bearing incinerated ash derived fromsewage sludge was used as the basis of this study; itselemental analysis is provided in Table 1. The averageparticle size of the sample is 24.2 μm, with a gold andsulfur content of 0.83 and 2.70 wt%, respectively. Thesolid carbon used as the reducing agent was prepared bythe pyrolysis of phenolphthalein at 500 ∘C for 10 min ina nitrogen stream. Phenolphthalein was chosen here toobtain the solid carbon without impurities. The particlesize of the resulting solid carbon was 73 μm.

3.2 Chlorination

The solid carbon was added to the incinerated ashwith a mixing ratio of 1:1 by weight. The sample was thenplaced in the center of a fixed bed reactor with a fused silicatube (26 mm i.d.) and heated at 10 ∘C min−1 to a terminaltemperature of between 100 and 1000 ∘C. The exhaust gaswas trapped by sodium hydroxide solution.

In all, three types of experiments were carried out.In the Type I experiment, a 100 mL NTP/min flow of chlo-rine gas was supplied to the reactor during heating tothe desired final temperature, after which the sample wascooled by a nitrogen gas flow. In the Type II experiment,nitrogen gas was supplied to the reactor during heating.Upon reaching the final temperature, chlorine gas was sup-plied, and the temperature was maintained for 1 h, and thesamples were then cooled by nitrogen gas. Finally, in theType III experiment, the samples were heated and cooledin a nitrogen atmosphere, without being held at their finaltemperatures.

3.3 Analysis of Gold

The sequential leaching scheme proposed byTerashima et al.13 and depicted in Figure 2 was applied forthe quantitative determination of gold. In this method, thesample was first dissolved by a combination of aqua regiaand hydrofluoric acid at 115 ∘C. The resulting solutionwas then evaporated at 150 ∘C to remove the hydrofluoricacid, with the obtained solid dissolved again in aquaregia and hydrochloric acid at 115 ∘C. After cooling, theobtained solution was separated into a filtrate and solidresidue, the former containing any gold that remained inthe incinerated ash sample. The solid residue that consistedof the added solid carbon, was then combusted at 500 ∘Cfor 2 h in air. The residue obtained was then dissolved byaqua regia and hydrochloric acid. This dissolved solutioncontained gold that was released from the incinerated ashand subsequently captured by the added carbon.

The concentrations of gold and other elementsin the dissolved solutions were determined by inductively

RECOVERY OF GOLD FROM INCINERATED SEWAGE SLUDGE 3

Table 1 Elemental analysis of incinerated ash (wt%)

P K Zn Fe S Ca Al Au Cu Ag Si Ni Ti Pd

15.33 9.41 3.50 2.17 2.70 2.17 1.38 0.83 0.49 0.40 0.26 0.05 0.03 0.02

Reprinted with permission from Kakumazaki, J.; Kato, T.; Sugawara, K. Recovery of Gold from Incinerated Sewage Sludge Ashby Chlorination. ACS Sustainable Chem. Eng., 2014, 2, 2297–2300 © (2014) American Chemical Society.

Sample

Dissolution byaqua regia and HF

Evaporation

Dissolution byaqua regia

Filtration

Filtrate

Residue

Ashing

Dissolution byaqua regia

Filtration

Filtrate

Atomic absorption spectroscopyICP emission spectroscopy

Figure 2 Procedure of quantitative analyses of gold and coexist-ing elements. (Reprinted with permission from Kakumazaki, J.;Kato, T.; Sugawara, K. Recovery of Gold from Incinerated SewageSludge Ash by Chlorination. ACS Sustainable Chem. Eng., 2014,2, 2297–2300 © (2014) American Chemical Society)

coupled plasma emission spectroscopy (Shimadzu ICPE-9000) and atomic absorption spectroscopy (ShimadzuAA-6800). X-ray diffractometry (Rigaku, Ultima IV),scanning electro-microscopy SEM (Hitachi, S-2000), andwavelength dispersed X-ray fluorescence spectrometer(Shimadzu, XRF-1700) were also used to confirm the formand distribution of gold in the carbon.

4 RESULTS AND DISCUSSION

4.1 Calculation of Thermodynamic Equilibrium

In order to determine the chemical species of goldpresent in the chlorination gas atmosphere, a thermody-namic equilibrium calculation was carried out using a HSCsoftware (Outokumpu, ver. 5.0), where Cl2 was assumed tobe excess of the gold content. The results shown in Figure 3

0

0.5

1.0

00 200 400 600 800 1000

Temperature (°C)

AuCl3

(a) Au–Cl2 system

(b) Au–C–Cl2 system

AuCl3

AuCl(g)

AuCl(g)

AuCl

AuCl

Au

Au

0.5

1.0

Equ

ilibr

ium

com

posi

tion

(km

ol)

Figure 3 Thermodynamic equilibrium calculation for (a)Au–Cl2 and (b) Au–C–Cl2 systems

indicate that gold is released to the gas phase above 500 ∘Cin the form of AuCl, with all gold being volatilized by750 ∘C. The addition of carbon does not show any appre-ciable influence on the form taken by the released gold.

4.2 Release of Gold from Incinerated Ash

Figure 4 shows the behavior of the gold releasedduring heating of the incinerated ash in a Cl2 gas stream(Type I experiment). The extent of this release is defined bythe following equation

Aurel[%] = {(Au0 − AuC1)∕Au0} × 100

where Aurel is the extent of gold released, Au0 is the initialamount of gold, and AuCl is the amount of gold afterchlorination.

When the incinerated ash sample is heated in aCl2 gas stream without the addition of carbon, gold beginsto release starting from a temperature of 600 ∘C. A moredrastic release of gold is observed above 800 ∘C, with 90%of the gold volatilized by 1000 ∘C. On the other hand,an appreciable release of gold is observed at temperaturesfrom 400 to 700 ∘C when carbon is added to the incin-erated ash. Indeed, all of gold in the incinerated ash is

4 SUSTAINABLE INORGANIC CHEMISTRY

0Before

treatment 200 400 600 800 1000

Temperature (°C)

20

40

60

80

100

Rel

ease

ext

ent o

f Au

(%) With carbon

Withoutcarbon

Figure 4 Release behavior of gold from ash during heating in achlorine gas stream (Type I experiment). (Reprinted with permis-sion from Kakumazaki, J.; Kato, T.; Sugawara, K. Recovery ofGold from Incinerated Sewage Sludge Ash by Chlorination. ACSSustainable Chem. Eng., 2014, 2, 2297–2300 © (2014) AmericanChemical Society)

0400

Sample Carbon Gas

500 600 700

Temperature (°C)

20

40

60

80

100

Dis

trib

utio

n of

Au

(%)

0Time (min)

N2

Terminaltemperature

Tem

pera

ture

(°C

) ClCl2Cl2 N2N2

Figure 5 Distribution of gold during heating in a chlorine gasstream (Type I experiment). (Reprinted with permission fromKakumazaki, J.; Kato, T.; Sugawara, K. Recovery of Gold fromIncinerated Sewage Sludge Ash by Chlorination. ACS SustainableChem. Eng., 2014, 2, 2297–2300 © (2014) American ChemicalSociety)

Sample Carbon Gas

600 800 1000Temperature (°C)

0

20

40

60

80

100

Dis

trib

utio

n of

Au

(%)

Time (min)

Terminaltemperature Holding time

60 min

0

Tem

pera

ture

(°C

) ClCl2Cl2N2N2 N2N2

Figure 6 Distribution of gold during heating in nitrogen andchlorine gases stream (Type II experiment). (Reprinted with per-mission from Kakumazaki, J.; Kato, T.; Sugawara, K. Recovery ofGold from Incinerated Sewage Sludge Ash by Chlorination. ACSSustainable Chem. Eng., 2014, 2, 2297–2300 © (2014) AmericanChemical Society)

released to the gas phase by 700 ∘C. Furthermore, theaddition of solid carbon lowers the volatilization temper-ature from 700 to 400 ∘C, thus accelerating the rate ofgold volatilization. This is in contradiction to the calcu-lated thermodynamic equilibrium, which suggested thatthe presence of carbon should not have any influence onthe change in gold form. However, the presence of com-plexes between gold and other elements within the ashcould explain this observed behavior, with the release ofgold potentially being accompanied by the volatilization ofchlorides of other elements.14–17

X-ray fluorescence analysis of the volatiles pro-duced during low temperature chlorination indicates thatthey contain Au, Fe, and Cl; thus, the release of Au atlow temperatures seems likely to occur in the chemicalform of AuCl3⋅FeCl3.15 It has been previously reportedthat chlorination of metal oxides in the presence of carbonis accelerated via complexes of four elements: carbon,oxygen, chlorine, and various metals.18 Future theoreticalconsiderations on the data are now ongoing.

4.3 Distribution of Gold

Figure 5 shows the distribution of gold followingthe Type I experiment, in which “Sample” indicates the

RECOVERY OF GOLD FROM INCINERATED SEWAGE SLUDGE 5

N2N2

Time (min)

Terminaltemperature

0

Tem

pera

ture

(°C

)

0

20

40

60

80

100

Dis

trib

utio

n of

Au

(%)

Sample Carbon Gas

600 800 1000Temperature (°C)

Figure 7 Distribution of gold during heating in a nitrogen gasstream (Type III experiment). (Reprinted with permission fromKakumazaki, J.; Kato, T.; Sugawara, K. Recovery of Gold fromIncinerated Sewage Sludge Ash by Chlorination. ACS SustainableChem. Eng., 2014, 2, 2297–2300 © (2014) American ChemicalSociety)

unreactive and residual gold, and “Carbon” representsthe gold captured by the carbon particles. “Gas” denotesthe gold that transitioned to the gas phase and subse-quently flowed out of the reactor; this being obtained bythe difference between the initial gold content and thecombined gold content of the Sample and Carbon. Theseresults demonstrate that the released gold is distributed toboth the gas and carbon phases, with the gold in Gas firstobserved above 500 ∘C and increasing to 40% at 700 ∘C.Similarly, the gold distributed to Carbon also increaseswith temperature from 10% at 400 ∘C to 60% at 700 ∘C.

00 200 400 600 800 1000

Temperature (°C)

0.2

0.4

0.6

0.8

1.0

Equ

ilibr

ium

com

posi

tion

(km

ol)

Au

AuS (g)

Figure 8 Thermodynamic equilibrium calculation for Au–Ssystem

10

Au

Inte

nsity

(au

)

20 30 40 50 60 70 80

2θ (°)

Figure 9 XRD pattern of solid carbon . (Reprinted with permis-sion from Kakumazaki, J.; Kato, T.; Sugawara, K. Recovery ofGold from Incinerated Sewage Sludge Ash by Chlorination. ACSSustainable Chem. Eng., 2014, 2, 2297–2300 © (2014) AmericanChemical Society)

According to the results of Figures 4 and 5,although gold chloride is released rapidly above 400 ∘C,its deposition on the carbon is reliant on its capture, withthe remaining gold lost to the gas phase. Because thesecompeting reactions of carbon capture and volatilizationexhibit different tendencies in relation to temperature, a60:40 split is obtained at 700 ∘C.

4.4 Optimum Conditions for Gold Recovery

The Type II experiment was usedto optimize thecarbon capture of gold in relation to the volatilization ratesof the various metal chlorides, with the use of a nitrogenatmosphere intended to inhibit the volatilization of thegold. From the distribution of gold obtained in this way(Figure 6), we can see that 80% of the gold is transferredto the carbon when the ash is heated ton 600 ∘C, with norelease of gold to gas phase being observed. In contrast,7% and 20% of the gold was released to the gas phase at500 and 600 ∘C, respectively, by the Type I experiment asshown in Figure 5. Furthermore, by heating the incineratedash and carbon to 800 ∘C in a Type II experiment, all of thegold can be captured by solid carbon. Further heating to1000 ∘C, however, results in 80% of the gold being lost tothe gas phase.

The distribution of gold resulting from the Type IIIexperiment, in which the samples were not held at tempera-ture, is shown in Figure 7. From this, it is clear that there isno release of gold at 600 ∘C, with 10% and 70% of the goldreleased to the gas phase at 800 and 1000 ∘C, respectively.No transfer of gold to carbon was observed, and becausethe incinerated ash and carbon were rapidly cooled when

6 SUSTAINABLE INORGANIC CHEMISTRY

× 700 × 700

Au 0 170

50 μm 50 μm

Figure 10 SEM-EDX image of solid carbon

the sample reached its terminal temperatures, the goldreleased at 1000 ∘C is believed to be that released during theheating period in the nitrogen gas atmosphere. Specifically,the release behavior of gold upon heating to 1000 ∘C maybe related to the sulfur in the slag. Figure 8 shows a ther-modynamic equilibrium calculation of the Au–S system,in which gold forms AuS (g) above 800 ∘C that is likely toreport to the gas phase. Thus, in order to separate and cap-ture all of the gold from incinerated ash, it should be mixedwith carbon and heated to 800 ∘C in a nitrogen atmosphereand then held for 1 h in a chlorine gas stream.

The form of gold produced on the carbon at800 ∘C during the Type II experiment was analyzed byXRD, and the results are shown in Figure 9. The smallpeaks observed at 38∘, 45∘, and 76∘ are all attributed tometallic gold. The SEM-EDX images shown in Figure 10confirm that very fine gold particles are distributed inthe carbon. Consequently, although gold in the ash isvolatilized as gold chlorides during chlorination, it is thefine particles of metallic gold that are precipitated on thecarbon surface by reduction. Sutter et al. have previouslyinvestigated the interaction between carbon and goldnanoparticles, identifying that gold is incorporated intocarbon with a high degree of solubility above 500 ∘C.Further, nanoparticles of gold in carbon exhibit graingrowth by coalescence,19,20 which is likely to have hadsome influence over the selective capture and precipitationof gold by solid carbon observed in this study.

5 CONCLUSIONS

In order to develop a process of selective sepa-ration of gold by a dry process, release behavior of Aufrom the incinerated ash was investigated. Through thisstudy, it has been demonstrated that the addition of car-bon to an incinerated sewage sludge ash reduces the tem-perature at which gold is volatilized by chlorine from 700to 300 ∘C; however, such behavior contradicts predictions

based on thermodynamic equilibrium calculations of theAu–Cl2 system. The released gold was effectively capturedby the solid carbon, with the proportion recovered in thisway increasing with temperature. In this way, it is possiblefor all of the gold contained in the incinerated ash to berecovered by solid carbon by heating to 800 ∘C in a nitro-gen gas stream and then holding at that temperature for1 h in a chlorine gas stream. The gold captured by the car-bon is reduced to form fine metallic particles that are evenlydistributed over the carbon surface.

6 ACKNOWLEDGMENTS

The authors are grateful to Dr. Masao Shimada ofthe Japan Sewage Works Agency for the financial supportand supply of samples. This work was partly supported bya Grant-in-Aid for Scientific Research (15K00598).

7 ABBREVIATIONS AND ACRONYMS

Au0 = initial amount of gold in ash; AuCl =amount of gold in ash after chlorination; Aurel = extent ofgold released from ash.

8 REFERENCES

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4. Global Mercury Assessment 2013. Sources, Emissions,Release and Environmental Transport, UNEP ChemicalBranch, Geneva, Switzerland, 2013, 9.

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15. J. A. Eisele, D. D. Fischer, H. J. Hinen and D. G. KesterkeGold Transport by Complex Metal Chloride Vapors,Report of Investigations No. 7489; U.S. Bureau of Mines,Washington, DC, March 1971.

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