Electrochemistry for the Environment (eBook)

This 350 pages volume contains the contributions from 18 international experts on the key topics concerning environmental chemistry. It is co-edited by Dr. Chen and Prof. Comninellis. Dr. Chen has been working actively in this field for nearly 10 years and is currently an Editor of Separation and Purification Technology. Professor Comninellis is an international authority on environmental electrochemistry with over 30 years of experiences. He is the Chairman of the Electrochemical Process Division of  the International Society of Electrochemistry.

Preface 5
Contents 7
Contributors 9
1 Basic Principles of the Electrochemical Mineralization of Organic Pollutants for Wastewater Treatment 12
1.1 Introduction 12
1.2 Thermodynamics of the Electrochemical Mineralization 13
1.3 Mechanism of the Electrochemical Mineralization 16
1.3.1 Activation of Water by Dissociative Adsorption 17
1.3.2 Activation of Water by Electrolytic Discharge 17
1.4 Influence of Anode Material on the Reactivity of Electrolytic Hydroxyl Radicals 18
1.5 Determination of the Current Efficiency of the Electrochemical Mineralization 20
1.5.1 Determination of ICE by the Chemical Oxygen Demand Technique 21
1.5.2 Determination of ICE by the Oxygen Flow Rate Technique 22
1.6 Kinetic Model of Organics Mineralization on BDD Anode 22
1.6.1 Influence of the Nature of Organic Pollutants 26
1.6.2 Influence of Organic Concentration 27
1.6.3 Influence of Applied Current Density 27
1.7 Intermediates Formed During the Electrochemical Mineralization Process Using BDD 28
1.8 Electrical Energy Consumption in the Electrochemical Mineralization Process 30
1.9 Optimization of the Electrochemical Mineralization Using BDD Anodes 30
1.10 Fouling and Corrosion of BDD Anodes 32
References 32
2 Importance of Electrode Material in the Electrochemical Treatment of Wastewater Containing Organic Pollutants 35
2.1 Introduction 35
2.2 Electrochemical Parameters 36
2.3 Oxidation Mechanisms 37
2.4 Electrode Materials 40
2.4.1 Carbon and Graphite 40
2.4.2 Platinum 43
2.4.3 Dimensionally Stable Anodes 45
2.4.4 Tin Dioxide 49
2.4.5 Lead Dioxide 51
2.4.6 Boron-Doped Diamond 52
2.5 Conclusions 57
References 58
3 Techniques of Electrode Fabrication 65
3.1 Thermal Decomposition Method 65
3.1.1 Ruthenium-Oxide-Based Electrode (RuOx) 68
3.1.2 Iridium-Oxide-Based Electrode (IrO2) 68
3.1.3 Tin-Dioxide-Based Electrode (SnO2) 69
3.1.4 Tantalum-Oxide-Based Electrode (Ta2 O5) 71
3.1.5 Rhodium-Oxide-Based Electrode (RhOx) 72
3.2 Chemical Vapor Deposition (CVD) 72
3.3 Surface Modifications 83
3.3.1 Metal Film Deposition 83
3.3.2 Metal Ion Implantation 84
3.3.3 Electrochemical Activation 84
3.3.4 Organic Surface Coating 84
3.3.5 Nanoparticle Deposition 85
3.3.6 GOx Enzyme-Modified Electrode 87
3.3.6.1 Chemical Deposition 87
3.3.6.2 Sol--Gel Method 89
3.3.6.3 Electrochemical Deposition 89
3.3.7 DNA-Modified Electrode 89
3.4 Ultramicro- or Nanoscale Electrode 90
3.5 Concluding Remarks 95
References 96
4 Modeling of Electrochemical Process for the Treatment of Wastewater Containing Organic Pollutants 109
4.1 Why Is It Important to Use Mathematical Modeling in Electrochemical Wastewater Treatment? 109
4.2 Mathematical Modeling in Chemical Engineering 110
4.3 Selection of the Description Level in Electrochemical Coagulation and Oxidation Processes 112
4.4 Constitutive Equations for Electrochemical Oxidation and Coagulation Processes 117
4.4.1 Mass-Transfer Processes 117
4.4.2 Electrochemical Processes 118
4.4.3 Chemical Processes 120
4.5 Electrochemical Oxidation Models 121
4.5.1 A Single-Variable Model to Describe the Time-Course of the COD During Electrochemical Oxidation Processes 122
4.5.2 A Multivariable Model to Describe the Time Course of Pollutant, Intermediates, and Final Products During Electrochemical Oxidation Processes 123
4.6 Electrochemical Coagulation Models 128
4.6.1 A Single-Variable Model to Describe Electrochemical Coagulation Controlled by Hydrodynamic Conditions 128
4.6.2 A Multivariable Model to Describe Electrochemical Coagulation Based on Pseudoequilibrium Approaches 129
4.6.3 A Multivariable Model to Describe Electrochemical Dissolution Processes 130
4.7 Conclusions 133
References 133
5 Green Electroorganic Synthesis Using BDD Electrodes 135
5.1 Introduction 135
5.2 Experimental Equipment and Practical Aspects 137
5.3 Anodic Transformations 138
5.3.1 Alkoxylation Reactions 139
5.3.2 Cleavage of C, C-Bonds 141
5.3.3 Phenolic Coupling Reactions 142
5.4 Cathodic Transformations 146
5.4.1 Reduction of Oximes 146
5.4.2 Reductive Carboxylation of Aldehydes to -Hydroxycarboxylic acids 147
5.5 Stability of BDD in Electrolytes 148
5.6 Future Perspectives 149
References 149
6 Domestic and Industrial Water DisinfectionUsing Boron-Doped Diamond Electrodes 152
6.1 Introduction 152
6.2 Diamond Electrodes 153
6.2.1 Manufacturing 153
6.2.2 Features and Properties 155
6.3 Electrolytic Disinfection with Boron-Doped Diamond Electrodes 156
6.3.1 Actives Species, Advantages, and Implementation 157
6.3.2 Data on Several Microorganism Inactivations 159
6.4 Examples of Disinfection Applications: Dedicated Systems and Field/Evaluation Results 163
6.4.1 Swimming Pools (Private and Public) 164
6.4.2 Spas 165
6.4.3 Rainwater 165
6.4.4 Sewage Water 166
6.4.5 Process Water 168
6.5 Conclusion 169
References 169
7 Drinking Water Disinfection by In-line Electrolysis: Product and Inorganic By-Product Formation 171
7.1 Introduction 171
7.2 Experimental Conditions 173
7.2.1 Apparatuses 173
7.2.2 Chemicals 174
7.2.3 Analytical Methods 174
7.2.4 Bacterial and Yeast Cultures 175
7.2.5 Transmission Electron Microscopy 176
7.3 Electrochemical In-line Disinfection 176
7.3.1 Killing of Microorganisms 176
7.3.2 The Production of Disinfection Products 178
7.3.3 The Production of Inorganic Disinfection By-Products 183
7.3.3.1 Formation of Chlorate 183
7.3.3.2 Formation of Chlorine Dioxide 186
7.3.3.3 Formation of Perchlorate 190
7.3.3.4 Formation of Nitrogen Containing By-Products 192
7.3.3.5 Formation of Reactive Oxygen Species 195
7.3.3.6 The Role of Technology, Operation Mode and Geometric Factors 198
7.3.3.7 Analytical Problems 202
7.4 Conclusions 204
References 205
8 Case Studies in the Electrochemical Treatment of Wastewater Containing Organic Pollutants Using BDD 213
8.1 Introduction 213
8.2 Oxidation of Model Substances 216
8.3 Oxidation of Phenolic Compounds 219
8.4 Oxidation of Dyes 222
8.5 Oxidation of Pesticides and Drugs 224
8.6 Oxidation of Surfactants 225
8.7 Economic Considerations 227
8.8 Conclusions 231
References 231
9 The Persulfate Process for the Mediated Oxidation of Organic Pollutants 236
9.1 Introduction 236
9.2 Kinetic and Mass-Transfer Barriersand Mediated Oxidation 238
9.3 The Mediated Oxidation with Persulfate 240
9.3.1 Production of Persulfate 240
9.3.2 Activation of Persulfate 241
9.4 Alternative Methods of Mediated Oxidation 242
9.4.1 Single-Step Mediated Oxidation Method 242
9.4.2 Two-Step Mediated Oxidation Method 245
9.4.2.1 Yield of Organic Pollutants' Oxidation 246
9.4.2.2 Chemical Oxidation of Salicylic Acid 247
9.5 Conclusions 249
References 250
10 Electrocoagulation in Water Treatment 252
10.1 Theoretical Aspect 252
10.1.1 Principle of Electrocoagulation 252
10.1.2 Reactions at the Electrodes and Electrodes Assignment 253
10.1.3 Electrode Passivation and Activation 255
10.1.4 Comparison Between Electrocoagulation and Chemical Coagulation 256
10.2 Typical Designs of the EC Reactors 257
10.2.1 Liquid Flow Assignment 257
10.3 Factors Affecting Electrocoagulation 258
10.3.1 Effect of Current Density or Charge Loading 258
10.3.2 Effect of Conductivity 260
10.3.3 Effect of Temperature 261
10.3.4 Effect of pH 261
10.4 Application of Electrocoagulation in Water Treatment 262
10.4.1 Arsenic Removal from Water by EC 263
10.4.2 Other Heavy Metal Removal from Water by EC 263
10.4.3 Dye Removal from Water by EC 264
10.5 A New Bipolar EC--EF Process for Wastewater Treatment 266
References 268
11 Electroflotation 270
11.1 Theoretical 270
11.1.1 Electrochemical Reactions and Gas Generating Rate 270
11.1.2 Electrolysis Voltage and Specific Energy Consumption 271
11.2 Features of EF 272
11.2.1 Bubbles' Size 272
11.2.2 Operation 273
11.2.3 Simultaneous Separation and Disinfection 273
11.3 Electrodes System 274
11.3.1 Cathodes 274
11.3.2 Anodes 274
11.3.3 Electrodes Arrangement 276
11.4 Typical Designs 278
11.4.1 Single-Stage EF 278
11.4.2 Two-Stage EF 280
11.4.3 Combination of EF with EC 280
11.5 Water and Wastewaters Treated by EF 282
References 282
12 Electroreduction of Halogenated Organic Compounds 285
12.1 Introduction 285
12.2 The Reaction Pathways 286
12.3 The Combined Role of Electrode Material and Reaction Medium 290
12.4 Cell Design and Operations 294
12.5 Electroreductive Treatments of Halogenated Organic Pollutants 296
12.5.1 Organic Volatile Halides 297
12.5.2 Chlorofluorocarbons 298
12.5.3 Polyhaloacetic Acids 299
12.5.4 Polyhalophenols 299
12.5.5 Polychlorohydrocarbons 300
12.5.6 Other Compounds 301
12.5.7 Sensors 301
12.6 Conclusions 302
References 303
13 Principles and Applications of Solid Polymer Electrolyte Reactors for Electrochemical Hydrodehalogenation of Organic Pollutants 313
13.1 Introduction 313
13.2 Background 314
13.3 The Solid Polymer Electrolyte Hydrodehalogenation Reactor 315
13.3.1 Principle of Solid Polymer Electrolyte Reactors 315
13.3.2 SPE HDH Reactor Equipment 319
13.3.3 Principle of the SPE HDH Reactor 319
13.3.4 Parameters Used for Performance Evaluation 320
13.3.5 Voltammetry 321
13.3.6 Percentage of Halogenated Organics Removal and Space--Time Yield 322
13.3.7 Selectivity 325
13.3.8 Current Efficiency and Energy Consumption 325
13.3.9 Stability of the HDH Reactor 326
13.4 Conclusion 327
References 328
14 Preparation, Analysis and Behaviors of Ti-Based SnO2 Electrode and the Function of Rare-Earth Doping in Aqueous Wastes Treatment 330
14.1 Introduction: Background and Significance 330
14.2 Electrode Fabrication Methods 332
14.2.1 Pretreatment of the Ti-Base Metal 332
14.2.2 Dip-Pyrolysis Method 332
14.2.3 Electrodeposition 334
14.2.4 Technologies for Nanometer Coating Fabrication 334
14.2.5 Technologies of Increasing the Life Service of the Electrodes 335
14.3 Analysis Method 337
14.3.1 Analysis of the Degradation Solution 337
14.3.2 Structure of the Electrodes 342
14.3.2.1 Crystal Structure of Electrodes 342
14.3.2.2 Micrograph of the Electrodes 343
14.3.2.3 Chemical Environmental Analysis with XPS 343
14.3.3 Electrochemical Analysis 345
14.3.3.1 Cyclic Voltammograms Analysis 345
14.3.3.2 Tafel Curve 348
14.3.3.3 Electrochemical Impedance Spectroscopy Tests 349
14.3.4 Summary 351
14.4 Characteristics of Rare-earth Doped Ti-Base SnO2 Electrode 351
14.4.1 Sb Doping SnO2 Electrode 351
14.4.2 Effects of Rare-Earth Doping on Structure and Performance of Ti/Sb--SnO2 Electrode 352
14.4.3 Reaction Pathway of Electrochemical Degradation of Phenol on Ti/SnO2--Sb Electrodes 353
14.4.4 Summary 355
References 355
15 Wet Electrolytic Oxidation of Organics and Application for Sludge Treatment 358
15.1 Introduction 358
15.2 Peculiar Electrolysis of Aqueous Solution at Higher Temperatures 361
15.3 Wet Electrolytic Oxidation of Organics 363
15.4 Behavior of Organic Sludge Under Hydrothermal Conditions 367
15.5 Wet Electrolytic Oxidation of Organic Sludge 369
15.6 Materials for WEO 371
15.7 Conclusions 374
References 374
16 Environmental Photo(electro)catalysis: Fundamental Principles and Applied Catalysts 376
16.1 Introduction 376
16.2 Description of Photocatalytic Systems 377
16.2.1 The Semiconductor--Electrolyte Interface in the Absence of Redox Systems 377
16.2.2 The Semiconductor--Electrolyte Interface in the Presence of Redox Systems 379
16.2.3 The Semiconductor--Liquid Interface Under Illumination 383
16.2.4 Photocatalytic Reactions at Semiconductor Particles 388
16.2.4.1 Charge Transfer at Semiconductor Particles 388
16.2.4.2 Quantum Size Effect 389
16.2.4.3 Photonic Efficiency and Quantum Yield in Photocatalytic Systems 391
16.3 Materials for Photocatalysis 392
16.3.1 Single Semiconductors 392
16.3.1.1 TiO2 392
16.3.1.2 ZnO 397
16.3.1.3 SnO2 398
16.3.1.4 WO3, Fe2 O3 and CdS 399
16.3.2 Coupled Semiconductors 401
16.3.2.1 TiO2/WO3 402
16.3.2.2 TiO2/SnO2 403
16.3.2.3 TiO2/CdS 405
16.3.3 Noble Metal/Semiconductor Composites 409
16.3.3.1 Ag/TiO2 410
16.3.3.2 Au/TiO2 413
16.3.3.3 Pt/TiO2 415
16.3.4 Doped Semiconductors 418
16.3.4.1 Nonmetal-Ion Doped Photocatalysts 419
16.3.4.2 Metal-Ion-Doped Photocatalysts 426
16.4 Concluding Remarks 431
References 431
17 Solar Disinfection of Water by TiO2 Photoassisted Processes: Physicochemical, Biological, and Engineering Aspects 448
17.1 Introduction 448
17.2 Experimental Part 450
17.2.1 Photoreactors and Light Sources 450
17.2.1.1 Pyrex Glass Bottle Illuminated by Solar Lamp 450
17.2.1.2 Coaxial Photocatalytic Reactor 450
17.2.1.3 Compound Parabolic Reactor CPC 451
17.2.2 Materials 451
17.2.3 Bacterial Strain and Growth Media 451
17.3 Physicochemical Aspects 452
17.3.1 TiO2 Concentration 452
17.3.2 Presence of Natural Anions 453
17.3.3 Presence of Iron 456
17.3.4 pH Influence 458
17.3.5 Physicochemical Characteristics of Suspended TiO2 459
17.3.6 Supported TiO2 459
17.3.6.1 TiO2 Fixed in Nafion Membranes 460
17.3.6.2 TiO2 Fixed on Glass 460
17.3.6.3 TiO2 Coated on Fibrous Web 462
17.3.7 Oxygen Concentration 463
17.4 Biological Aspects 464
17.4.1 Initial Bacterial Concentration 464
17.4.2 Physiological State of Bacteria 464
17.5 Technological Aspects 466
17.5.1 Durability of Disinfection and Postirradiation Events 466
17.5.2 Water Disinfection by Sunlight Using a CPC Photoreactor 467
17.5.3 Water Disinfection by Sunlight and TiO2 Using a CPC Photoreactor 467
17.5.4 Postirradiation Events at Field-Scale Experiments 468
17.5.5 Dose in Water Disinfection 470
17.5.6 Flow Rate and TiO2 Concentration 471
17.6 Outgoing Work in Photocatalytic Disinfection 473
References 473
18 Fabrication of Photoelectrode Materials 478
18.1 Sol--Gel Methods 478
18.2 Film Assembly Using Particles 479
18.2.1 Simple Sintering of Particles 479
18.2.2 Layer-by-Layer Self-Assembly 480
18.2.3 Electrophoretic Deposition 481
18.3 Aqueous Phase Deposition 482
18.3.1 Electrodeposition 482
18.3.2 Hydrothermal Methods 485
18.3.3 Electrochemical Anodization 486
18.3.4 Template Methods 488
18.3.4.1 ``Hard'' Template Methods 489
18.3.4.2 ``Soft'' Template Methods 491
18.3.5 Methods for Synthesis of Composite Photoelectrodes 492
18.3.5.1 Wet Impregnation Method 492
18.3.5.2 Photodeposition 494
18.3.5.3 Deposition--Precipitation 495
18.4 Gas-Phase Deposition 496
18.4.1 CVD Methods 496
18.4.2 Spray Pyrolysis 498
18.4.3 Magnetron Sputtering 499
18.4.4 Ion-Implantation 503
18.5 Concluding Remarks 507
References 508
19 Use of Both Anode and Cathode Reactions in Wastewater Treatment 519
19.1 Introduction 519
19.2 Fundamentals of Indirect Electro-oxidation Methods Based on H2O2 Electrogeneration 520
19.2.1 Cathodic Electrogeneration of Hydrogen Peroxide 520
19.2.2 Anodic Oxidation with Electrogenerated H2O2 525
19.2.3 Electro-Fenton Method 526
19.2.4 Photoelectro-Fenton Method 528
19.2.5 Peroxi-coagulation Method 529
19.3 Electro-Fenton Degradation of Organics Using a Divided Cell 529
19.4 Treatment of Wastewaters Using an Undivided CellUnder Potentiostatic Control 533
19.5 Degradation of Organic Pollutants Using an Undivided Cell Under Galvanostatic Control 535
19.5.1 Pt/Carbon-Felt Cell 536
19.5.2 Pt/O2 Cell 537
19.5.3 BDD/O2 Cell 544
19.5.4 Fe/O2 Cell 548
19.6 Conclusions 551
References 552
Index 557