Contents 1 Mercury Removal onto Smart Materials... 1 1.1 Smart Materials General Characterisation... 1 1.2 Mercury Methods for its Removal and Determination... 2 1.3 Smart Materials used for Mercury Removal... 9 1.3.1 Nanometals and Nanooxides... 9 1.3.2 Carbon-Based Smart Materials... 11 1.3.3 Aluminosilicate-Based Smart Materials... 15 1.3.4 Smart Materials with a Magnetic Core... 16 1.4 Conclusions... 19 2 Nanometal Oxide Adsorbents for the Remediation of Heavy Metals in Water... 25 2.1 Introduction... 25 2.2 Adsorption onto Nanometal Oxides... 28 2.3 Synthesis, Preparation and Characterisation of Nanometal Oxides... 28 2.3.1 Nanoaluminium Oxide... 29 2.3.2 Nanocopper(II) Oxide... 29 2.3.3 Nanoiron Oxide... 30 2.3.4 Nanomanganese Oxide... 31 2.3.5 Nanonickel Oxide... 32 2.3.6 Nanotitanium Dioxide... 32 2.3.7 Nanozinc Oxide... 32 2.3.8 Nanoiron(III) Aluminium(III) Mixed Oxide... 33 2.3.9 Nanostrontium Hydroxyapatite/Magnetite... 33 ix
Nanomaterials for Water Remediation: Inorganic Oxide Materials, Volume 2 2.3.10 Guar Gum Nanozinc Oxide Biocomposite... 34 2.4 Use of Nanooxides as Adsorbents for Heavy Metals... 34 2.4.1 Removal of Arsenic(III and V)... 34 2.4.2 Cadmium... 36 2.4.3 Chromium... 37 2.4.4 Lead... 38 2.5 Future Perspectives and Conclusion... 39 3 Nanoadsorbents for the Removal of Harmful Fluoride from Drinking Water... 47 3.1 Introduction... 47 3.2 Occurrence and Sources... 47 3.3 Effects on Human Health... 48 3.4 Methods of Defluoridation... 49 3.4.1 Membrane Techniques... 49 3.4.1.1 Reverse Osmosis and Nanofiltration... 49 3.4.1.2 Dialysis and Electrodialysis... 50 3.4.1.3 Adsorption Technique... 50 3.5 Nanoadsorbents for Fluoride Removal... 51 3.6 Conclusions... 65 4 Characterisation of Natural Bentonite Materials and their Applications... 73 4.1 Introduction... 73 4.2 Chemical Composition of Materials... 75 4.2.1 Bentonite... 75 4.2.2 Smectite Group... 75 4.2.3 Clay... 76 4.2.4 Montmorillonite... 76 4.3 Material Structure... 77 4.3.1 Structure of Bentonite... 77 4.3.1.1 Octahedral Layer... 77 x
Contents 4.3.1.2 Tetrahedral Layer... 78 4.3.2 Structure of Clay... 78 4.3.3 Structure of Montmorillonite... 79 4.4 Behaviour and Characterisation... 81 4.4.1 Models... 82 4.4.2 Physical and Chemical Properties... 82 4.4.2.1 Grain Size... 83 4.4.2.2 Grain Density... 83 4.4.2.3 Specific Surface Area and Charges... 83 4.4.2.4 Swelling... 84 4.4.2.5 Thermal and Hydraulic Conductivity... 86 4.5 Purification of Bentonite Materials... 86 4.6 Applications... 87 4.6.1 Applications in Industry... 88 4.6.2 Applications in Construction and Civil Engineering... 88 4.6.3 Adsorbents used for Impurity Removal... 88 4.6.3.1 Heavy Metal Impurities... 89 4.6.3.2 Inorganic Impurities... 90 4.6.3.3 Organic Impurities... 92 4.6.4 Pathogens... 94 4.6.4.1 Bentonite Materials as Catalysts... 95 4.6.4.2 Nanocomposite Materials... 96 4.6.4.3 Application of Bentonite Materials for the Removal of Pathogens, Nanocomposite Materials and Medical Implementations... 96 4.7 Summary and Future Direction... 97 5 Removal of Ammonium from the Aquatic Environment using Bentonite and its Modified Forms... 107 5.1 Introduction... 107 xi
Nanomaterials for Water Remediation: Inorganic Oxide Materials, Volume 2 5.2 Adsorption of Ammonia and Ammonium from Water using Zeolites... 108 5.3 Bentonite as a Promising Adsorbent for Ammonia Adsorption... 113 5.4 Adsorption of Ammonia from Aqueous Solutions using Bentonite... 115 5.5 Adsorption of Ammonia from Aqueous Solutions using Modified Bentonite... 127 5.6 Adsorption of Total Ammonia Nitrogen from Aquaculture: A Case Study... 134 5.7 Future Direction for the Application of Bentonite in the Aquaculture Industry... 137 5.8 Conclusions... 138 6 Ion-Imprinted Thermosensitive Macroporous Cryogels for Heavy Metal Removal... 145 6.1 Introduction... 145 6.2 Materials and Methods... 146 6.2.1 Materials... 146 6.2.2 Preparation of Polymeric Hydrogels... 146 6.2.2.1 Prepolymer Complex of N-Methacryloyl-L- Cysteine with Cd(II) Ions... 146 6.2.2.2 Preparation of Poly(N-Isopropylacrylamide-N- Methacryloyl-L-Cysteine)-Cd(II) Hydrogels... 147 6.2.3 Characterisation of the Hydrogels... 147 6.2.3.1 Temperature Dependence of Swelling Ratios... 147 6.2.3.2 Swelling Rate... 148 6.2.3.3 Fourier-Transform Infrared Characterisation... 148 6.2.3.4 Hydrogel Morphology... 149 6.2.3.5 Energy Dispersive X-Ray Analysis... 149 6.2.4 Adsorption and Desorption Studies... 149 6.2.4.1 Temperature-Dependent Adsorption Studies... 149 6.2.4.2 Desorption and Reusability Studies... 150 xii
Contents 6.2.5 Selectivity Experiments... 150 6.3 Results and Discussion... 150 6.3.1 Preparation of Hydrogels... 150 6.3.1.1 Temperature Dependence of the Hydrogel Swelling Ratios... 150 6.3.1.2 Swelling Rates... 154 6.3.1.3 Fourier-Transform Infrared Characterisation... 155 6.3.1.4 Scanning Electron Microscopy Observation of Hydrogels... 156 6.3.1.5 Energy Dispersive X-Ray Analysis... 158 6.3.2 Adsorption Studies... 158 6.3.2.1 Adsorption Rate... 158 6.3.2.2 Effect of ph... 161 6.3.2.3 Adsorption Capacity... 161 6.3.2.4 Temperature-Dependent Adsorption... 162 6.3.3 Selectivity Experiments... 164 6.3.4 Desorption and Reusability... 165 6.3.5 Determination of Cd(II) Ions in a Certified Sample... 167 6.4 Conclusion... 168 7 Silver and Gold Nanoparticles for the Detection of Heavy Metals in Water... 171 7.1 Introduction... 171 7.2 Electrochemical Detection... 172 7.3 Colorimetric Detection... 173 7.4 Gold Nanoparticles for the Detection of Hg 2+, Pb 2+ and As 3+ in Water... 173 7.4.1 Electrochemical Detection... 173 7.4.1.1 Detection of Hg 2+... 173 7.4.1.2 Detection of Pb 2+... 174 7.4.1.3 Detection of As 3+... 176 xiii
Nanomaterials for Water Remediation: Inorganic Oxide Materials, Volume 2 7.4.2 Colorimetric Detection... 177 7.4.2.1 Detection of Hg 2+... 177 7.4.2.2 Detection of Pb 2+... 179 7.4.2.3 Detection of As 3+... 180 7.5 Silver Nanoparticles for the Detection of Hg 2+, Pb 2+ and As 3+ in Water... 182 7.5.1 Electrochemical Detection... 182 7.5.1.1 Detection of Pb 2+... 182 7.5.1.2 Detection of As 3+... 182 7.5.2 Colorimetric Detection... 183 7.5.2.1 Detection of Hg 2+... 183 7.5.2.2 Detection of Pb 2+... 185 7.5.2.3 Detection of As 3+... 185 8 Nanomaterials: Versatile Tools for Water Remediation... 189 8.1 Introduction... 189 8.2 Nanoremediation Process... 190 8.3 Classification of Nanomaterials as Nanoadsorbents... 190 8.4 Nanomaterials as Remediation Agents... 191 8.4.1 Metallic Nanoparticles... 192 8.4.1.1 Silver Nanomaterials... 192 8.4.1.2 Nanoscale Iron Nanoparticles... 192 8.4.2 Metallic Oxide Nanoparticles... 193 8.4.2.1 Titanium Dioxide-Based Nanoparticles... 193 8.4.2.2 Zinc Oxide-Based Nanoparticles... 194 8.4.3 Magnetic Nanoparticles... 195 8.4.4 Carbonaceous Nanomaterials... 196 8.4.4.1 Carbon Nanotubes... 196 8.4.4.2 Graphene-Based Nanoparticles... 197 8.4.5 Silicon Nanomaterials... 197 xiv
Contents 8.4.6 Nanoclays... 198 8.4.7 Dendrimers... 198 8.4.8 Polymer-Supported Nanosorbents... 199 8.4.9 Nanofibres... 199 8.4.10 Other Nanomaterials... 200 8.5 Environmental Risk... 200 8.6 Conclusion... 201 8.7 Future Aspects... 201 Abbreviations... 211 Index... 217 xv
Nanomaterials for Water Remediation: Inorganic Oxide Materials, Volume 2 xvi