Ion Exchange in Environmental Processes
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Preface xiii
Acknowledgment xvii
1 Ion Exchange and Ion Exchangers: An Introduction 1
1.1 Historical Perspective 1
1.2 Water and Ion Exchange: An Eternal Kinship 6
1.3 Constituents of an Ion Exchanger 9
1.4 What is Ion Exchange and What it is Not? 10
1.5 Genesis of Ion Exchange Capacity 12
1.5.1 Inorganic 12
1.5.2 Organic/Polymeric Ion Exchanger 13
1.5.3 Strong-Base Type I and Type II Anion Exchanger 20
1.6 Biosorbent, Liquid Ion Exchanger, and Solvent Impregnated Resin 23
1.6.1 Biosorbent 23
1.6.2 Liquid Ion Exchange 25
1.6.3 Solvent-Impregnated Resins 27
1.7 Amphoteric Inorganic Ion Exchangers 28
1.8 Ion Exchanger versus Activated Carbon: Commonalities and Contrasts 33
1.9 Ion Exchanger Morphologies 34
1.10 Widely Used Ion Exchange Processes 34
1.10.1 Softening 35
1.10.2 Deionization or Demineralization 40
Summary 44
References 45
2 Ion Exchange Fundamentals 50
2.1 Physical Realities 50
2.2 Swelling/Shrinking: Ion Exchange Osmosis 51
2.3 Ion Exchange Equilibrium 55
2.3.1 Genesis of Non-Ideality 57
2.4 Other Equilibrium Constants and Equilibrium Parameters 59
2.4.1 Corrected Selectivity Coefficient 59
2.4.2 Selectivity Coefficient, K IXse 60
2.4.3 Separation Factor (a A B) 60
2.4.4 Separation Factor: Homovalent Ion Exchange 61
2.4.5 Separation Factor: Heterovalent Exchange 62
2.4.6 Physical Reality of Selectivity Reversal: Role of Le Châtelier's Principle 65
2.4.7 Equilibrium Constant: Inconsistencies and Potential Pitfalls 66
2.5 Electrostatic Interaction: Genesis of Counterion Selectivity 69
2.5.1 Monovalent-Monovalent Coulombic Interaction 69
2.6 Ion Exchange Capacity: Isotherms 73
2.6.1 Batch Technique 75
2.6.2 Regenerable Mini-Column Method 79
2.6.3 Step-Feed Frontal Column Run 81
2.7 The Donnan Membrane Effect in Ion Exchanger 84
2.7.1 Coion Invasion or Electrolyte Penetration 84
2.7.2 Role of Cross-linking 90
2.7.3 Genesis of the Donnan Potential 90
2.8 Weak-Acid and Weak-Base Ion Exchange Resins 92
2.8.1 pKa Values of Weak Ion Exchange Resins 94
2.8.2 Weak-Acid and Weak-Base Functional Groups 96
2.9 Regeneration 98
2.9.1 Selectivity Reversal in Heterovalent Ion Exchange 100
2.9.2 pH Swings 101
2.9.3 Ligand Exchange with Metal Oxides 105
2.9.4 Use of Co-Solvent 106
2.9.5 Dual-Temperature Regeneration 108
2.9.6 Carbon Dioxide Regeneration 111
2.9.7 Regeneration with Water 112
2.10 Resin Degradation and Trace Toxin Formation 112
2.10.1 Formation of Trace Nitrosodimethylamine (NDMA) from Resin Degradation 114
2.11 Ion Exclusion and Ion Retardation 115
2.11.1 Ion Exclusion 115
2.11.2 Ion Retardation 116
2.12 Zwitterion and Amino Acid Sorption 118
2.12.1 Interaction with a Cation Exchanger: Role of pH 119
2.13 Solution Osmotic Pressure and Ion Exchange 121
2.14 Ion Exchanger as a Catalyst 124
Summary 126
References 127
3 Trace Ion Exchange 130
3.1 Genesis of Selectivity 130
3.2 Trace Isotherms 136
3.3 Multi-Component Equilibrium 138
3.4 Agreement with Henry's Law 140
3.5 Multiple Trace Species: Genesis of Elution Chromatography 143
3.5.1 Determining Separation Factor from Elution Chromatogram 143
3.6 Uphill Transport of Trace Ions: Donnan Membrane Effect 149
3.7 Trace Leakage 151
3.8 Trace Fouling by Natural Organic Matter 153
3.9 Ion Exchange Accompanied by Chemical Reaction 156
3.9.1 Precipitation 156
3.9.2 Complexation 157
3.9.3 Redox Reaction 157
3.10 Monovalent-Divalent Selectivity 158
3.10.1 Effect of Charge Separation: Mechanistic Explanation 158
3.10.2 Nitrate/Sulfate and Chloride/Sulfate Selectivity in Anion Exchange 160
3.10.3 Genesis of Nitrate-Selective Resin 162
3.10.4 Chromate Ion Selectivity 164
3.11 Entropy-Driven Selective Ion Exchange: The Case of Hydrophobic Ionizable Organic Compound (HIOC) 166
3.11.1 Focus of the Study and Related Implications 167
3.11.2 Nature of Solute-Sorbent and Solute-Solvent Interactions 169
3.11.3 Experimental Observations: Stoichiometry, Affinity Sequence, and Cosolvent Effect 173
3.11.4 Energetics of the Sorption Process 177
3.11.5 Unifying Hydrophobic Interaction: From Gas-Liquid to Liquid-Solid System 179
3.11.6 Effect of Polymer Matrix and Solute Hydrophobicity 182
3.12 Linear Free Energy Relationship and Relative Selectivity 183
3.13 Simultaneous Removal of Target Metal Cations and Anions 186
3.14 Deviation from Henry's Law 188
3.14.1 Ions Forming Polynuclear Species 188
3.15 Tunable Sorption Behaviors of Amphoteric Metal Oxides 192
3.16 Ion Sieving 195
3.17 Trace Ion Removal 201
3.17.1 Uranium(VI) 201
3.17.2 Radium 203
3.17.3 Boron 204
3.17.4 Perchlorate (ClO - 4) 205
3.17.5 Emerging Contaminants of Concern and Multi-Contaminant Systems 208
3.17.6 Arsenic and Phosphorus: As(V), P(V), and As(III) 210
3.17.7 Fluoride (F -) 214
Summary 215
References 216
4 Ion Exchange Kinetics: Intraparticle Diffusion 224
4.1 Role of Selectivity 224
4.2 State of Water Molecules inside Ion Exchange Materials 232
4.3 Activation Energy Level in Ion Exchangers: Chemical Kinetics 235
4.3.1 Activation Energy Determination from Experimental Results 236
4.4 Physical Anatomy of an Ion Exchanger: Gel, Macroporous and Fibrous Morphology 242
4.4.1 Gel-Type Ion Exchanger Beads 242
4.4.2 Macroporous Ion Exchanger Beads 243
4.4.3 Ion Exchange Fibers 246
4.5 Column Interruption Test: Determinant of Diffusion Mechanism 248
4.6 Observations Related to Ion Exchange Kinetics 250
4.6.1 Effect of Concentration on Half-time (t 1/2) 251
4.6.2 Major Differences in Ion Exchange Rate 252
4.6.3 Chemically Similar Counterions with Significant Differences in Intraparticle Diffusivity 252
4.6.4 Effect of Competing Ion Concentrations: Gel versus Macroporous 254
4.6.5 Intraparticle Diffusion during Regeneration 255
4.6.6 Shell Progressive Kinetics versus Slow Diffusing Species 255
4.7 Interdiffusion Coefficients for Intraparticle Diffusion 257
4.8 Trace Ion Exchange Kinetics 264
4.8.1 Chlorophenols as the Target Trace Ions 264
4.8.2 Intraparticle Diffusion inside a Macroporous Ion Exchanger 266
4.8.3 Effect of Sorption Affinity on Intraparticle Diffusion 268
4.8.4 Solute Concentration Effect 271
4.9 Rectangular Isotherms and Shell Progressive Kinetics 272
4.9.1 Anomalies in Arrival Sequence of Solutes 274
4.9.2 Quantitative Interpretation 275
4.10 Responses to Observations in Section 4.6 276
4.10.1 Effect of Concentration on Half-time (t 1/2) 276
4.10.2 Slow Kinetics of Weak-Acid Resin 277
4.10.3 Chemically Similar Counterions: Drastic Difference in Intraparticle Diffusivity 277
4.10.4 Gel versus Macroporous 278
4.10.5 Intraparticle Diffusion during Regeneration 278
4.10.6 Shrinking Core or Shell Progressive Kinetics 279
4.11 Rate-Limiting Step: Dimensionless Numbers 280
4.11.1 Implications of Biot Number: Trace Ion Exchange 281
4.12 Intraparticle Diffusion: From Theory to Practice 284
4.12.1 Reducing Diffusion Path Length: Short-Bed Process and Shell-Core Resins 285
4.12.2 Development of Bifunctional Diphonix ® Resin 288
4.12.3 Ion Exchanger as a Host for Enhanced Kinetics 289
Summary 292
References 293
5 Solid- and Gas-Phase Ion Exchange 297
5.1 Solid-Phase Ion Exchange 297
5.1.1 Poorly Soluble Solids 297
5.1.2 Desalting by Ion Exchange Induced Precipitation 303
5.1.3 Separation of Competing Solid Phases 305
5.1.4 Recovery from Ion Exchange Sites of Soil 306
5.1.5 Composite or Cloth-like Ion Exchanger (CIX) 307
5.1.6 Heavy Metals (Me 2+) with Solids Possessing High Buffer Capacity 309
5.1.7 Ligand-Induced Metal Recovery with a Chelating Exchanger 315
5.2 Coagulant Recovery from Water Treatment Sludge 317
5.2.1 Development of Donnan IX Membrane Process 318
5.2.2 Alum Recovery: Governing Donnan Equilibrium 318
5.2.3 Process Validation 322
5.3 Gas Phase Ion Exchange 323
5.3.1 Sorption of Acidic and Basic Gases 324
5.3.2 CO2and SO2 Capture with Weak-Base Anion (WBA) Exchanger 325
5.3.3 Effect of Ion Exchanger Morphology 327
5.3.4 Redox Active Gases: Hydrogen Sulfide and Oxygen 330
5.4 CO2 Gas as a Regenerant for IX Softening Processes: A Case Study 334
Summary 339
References 340
6 Hybrid Ion Exchange Nanotechnology (HIX-Nanotech) 345
6.1 Magnetically Active Polymer Particles (MAPPs) 347
6.1.1 Characterization of MAPPs 351
6.1.2 Factors Affecting Acquired Magnetic Activity 353
6.1.3 Retention of Magnetic Activity and Sorption Behavior 355
6.2 Hybrid Nanosorbents for Selective Sorption of Ligands (e.g., HIX-NanoFe) 357
6.2.1 Synthesis of Hybrid Ion Exchange Nanomaterials 359
6.2.2 Characterization of Hybrid Nanosorbents 361
6.2.3 Parent Anion Exchanger versus Hybrid Anion Exchanger (HAIX-NanoFe(III)): A Comparison 363
6.2.4 Support of Hybrid Ion Exchangers: Cation versus Anion 365
6.2.5 Efficiency of Regeneration and Field Application 369
6.2.6 Hybrid Ion Exchange Fibers: Simultaneous Perchlorate and Arsenic Removal 370
6.3 HAIX-NanoZr(IV): Simultaneous Defluoridation and Desalination 376
6.3.1 Field-Scale Validation 377
6.4 Promise of HIX-Nanotechnology 381
Summary 383
References 384
7 Heavy Metal Chelation and Polymeric Ligand Exchange 391
7.1 Heavy Metals and Chelating Ion Exchangers 391
7.1.1 Heavy Metals: What are They? 391
7.1.2 Properties of Heavy Metals and Separation Strategies 393
7.1.3 Emergence of Chelating Exchangers 395
7.1.4 Lewis Acid-Base Interactions in Chelating Ion Exchangers 398
7.1.5 Regeneration, Kinetics and Metals Affinity 402
7.2 Polymeric Ligand Exchange 405
7.2.1 Conceptualization and Characterization of the Polymeric Ligand Exchanger (ple) 406
7.2.2 Sorption of Polymeric Ligand Exchangers 407
7.2.3 Validation of Ligand Exchange Mechanism 410
Summary 413
References 413
8 Synergy and Sustainability 417
8.1 Waste Acid Neutralization: An Introduction 417
8.1.1 Underlying Scientific Concept 418
8.1.2 Mechanical Work through a Cyclic Engine 421
8.2 Improving Stability of Anaerobic Biological Reactors 423
8.2.1 Potential Use of Selective Ion Exchanger 424
8.2.2 Ion Exchange Fibers: Characterization and Performance 424
8.3 Sustainable Aluminum-Cycle Softening for Hardness Removal 429
8.3.1 Current Status and Challenges 429
8.3.2 Sodium-Free Approaches and Alternatives to Na-Cycle Softening 429
8.3.3 Underlying Scientific Approach of Al-cycle Cation Exchange 430
8.3.4 Comparison in Performance: Na-Cycle versus Al-Cycle 432
8.3.5 Regeneration Efficiency and Calcium Removal Capacity 436
8.3.6 Sustainability Issues and New Opportunities 438
8.4 Closure 438
Summary 439
References 440
A Commercial Ion Exchangers 445
B Different Units of Capacity, Concentration, Mass, and Volume 457
B.1 Capacity 457
B.2 Concentration (Expressed as CaCO 3) 457
B.3 Mass 458
B.4 Volume 458
C Table of Solubility Product constants at 25 ° c 459
D Acid and Base dissociation constants at 25 ° c 461
Periodic Table and Atomic Weights of Elements 463
Index 467
Chapter 1
Ion Exchange and Ion Exchangers: An Introduction
1.1 Historical Perspective
Evolution is traditionally viewed to occur in a slow but continuous manner for living organisms and creatures gradually acquiring new traits. To the contrary, many areas of "science" undergo periods of rapid bursts of fast development separated by virtual standstill with no significant activity. The first historically recorded use of ion exchange phenomenon is from the Old Testament of the Holy Bible in Exodus 15:22-25 describing how Moses rendered the bitter water potable by apparently using the process of ion exchange and/or sorption. Another often quoted ancient reference is to Aristotle's observation that the salt content of water is diminished or altered upon percolation through certain sand granules. From a scientific viewpoint, however, the credit for recognition of the phenomenon of ion exchange is attributed to the English agriculture and soil chemists, J.T. Way and H.S. Thompson. In 1850, these two soil scientists formulated a remarkably accurate description of ion exchange processes in regard to removal of ammonium ions from manure by cation exchanging soil [1, 2]. They essentially simulated the following naturally occurring cation exchange reactions as follows:
1.1 1.2Some of the fundamental tenets of ion exchange resulted from this work: first, the exchange of ions differed from true physical adsorption; second, the exchange of ions involved the exchange in equivalent amounts; third, the process is reversible and fourth, some ions were exchanged more favorably than others.
As often with many groundbreaking inventions, the findings of Way and Thompson cast doubts, disbeliefs and discouragement from their peers. In the following years, these two soil scientists discontinued persistent research in this field. As a result, the evolution of ion exchange process progressed rather slowly due to the difficulties in modifying or manipulating naturally occurring inorganic clayey materials with low cation exchange capacities.
Inorganic zeolites (synthetic or naturally occurring aluminosilicates) later found wide applications in softening hard waters, that is, removal of dissolved calcium and magnesium through cation exchange. However, the anion-exchange processes remained unexplored and practically unobserved. Even at that time, it was not difficult to conceptualize that the availability of both cation exchangers and anion exchangers in the ionic forms of hydrogen and hydroxyl ions, respectively, would create a new non-thermal way to produce water free of dissolved solids as indicated below:
1.3The biggest obstacle to realize this concept was to identify and/or synthesize ion exchangers which will be chemically stable and durable under the chemically harsh environments at very high and low pH. The immense potential of ion exchange technology scaled a new height when the first organic-based (polymeric) cation exchanger was synthesized by Adams and Holmes [3]. In less than ten years, D'Alelio prepared the first polymeric, strong/weak cation and anion exchangers [4-6]. Since then, synthesis of new ion exchangers never seemed to slow down and application of ion exchange technology in industries as diverse as power utilities, biotechnology, agriculture, pharmaceuticals, pure chemicals, microelectronics, etc. are continually growing. No specialty grows in isolation; ion exchange fundamentals, ion exchange resins and ion exchange membranes continue to find new and innovative applications globally. Figure 1.1 includes the number of ion exchange related US patents issued during the last three decades, illustrating continued inventions in new products and processes.
Figure 1.1 Number of patents per year for "anion exchange" and "cation exchange" per a Google Patents search.
Source: Data taken with permission from Google [7, 8].
Ironically, the Second World War and, more specifically, the race for nuclear technology helped catalyze the growth and maturity of the field of ion exchange at an accelerated pace. Ion exchange was found to be a viable process for separating some of the transuranium elements and, for understandable reasons, its application aroused a great deal of interest. In fact, some of the most fundamental works on ion exchange equilibria and kinetics were carried out during the Second World War period by Boyd et al. and reported afterwards in the open literature [9-11]. All along, the scientific understanding of ion exchange fundamentals consistently lagged well behind its applications. Table 1.1 attempts to summarize milestones in regard to the development and application of ion exchange technology over time.
Table 1.1 Historical milestones in ion exchange
Year Description Patent # Authors 1850 Discovery of ion exchange properties of soil N/A Thompson and Way [1, 2] 1876 Zeolites or aluminosilicates recognized for base exchange and equivalence of exchange is proved N/A Lemberg [12, 13] 1906-1915 Industrial manufacture of sodium permutit for hardness removal 914,405;943,535;
1,131,503 Gans [14] 1934 Invention of sulfonated condensation polymers as cation exchangers 2198378A Ellis 1935 First synthetic organic ion exchangers 2104501A,
2151883A Adams and Holmes [15] 1938 Mixed-bed ion exchange process or duplex ion exchanger 2275210A Stemen, Urbain, and Lewis 1939 Invention of sulfonated polystyrene polymerization as cation exchangers
Invention of aminated polystyrene polymerization as anion exchangers 2283236A
2304637A Soday
Vernal 1942 Cation exchange resin beads made from polymerized acrylic acids
Cation exchange resins with sulfonated, polymerized poly-vinyl aryl parent resin
Anion exchange resins with aminated, polymerized poly-vinyl aryl parent resin 2340110A, 2340111A
2366007A
2366008A D'Alelio 1947 Element 61 (Promethium) was discovered by ion exchange of the by-products of fission N/A Marinsky, Glendenin, and Coryell [16] 1953 Use of zeolites as molecular sieves
Magnetic ion exchange resin for NOM removal (MIEX process)
Invention of weak acid cation exchangers
First countercurrent ion exchange using suspended/agitated beds of resin 2882243A
2642514A
2838440A
N/A Milton
Herkenhoff
Thurmon
Swinton and Weiss [17] 1954 Higgins countercurrent ion exchange contactor invented 2815322A Higgins [18] 1955 Ligand exchange 2839241A Albisetti 1956 Pellicular ion exchange resin 2933460A Richter and McBurney 1958 Agitated bed contactor for semicontinuous ion exchange
Ion exchange in drug delivery N/A
2990332A Arden, Davis, and Herwig [19]
Keating 1958 (publicly released) Uranium separation, intraparticle diffusion (Manhattan Project) 2956858A Powell 1959-1960 The book on "Ion Exchange" by Friedrich Helfferich was printed and laid the theoretical foundations for the field of ion exchange N/A Helfferich [20] 1962-1971 Cloete-Streat countercurrent contactor invented 3551118A (1962)
3738814A (1969)
3957635A (1971) Cloete and Streat [21] 1964 Cellulosic ion exchange fibers synthesized 3379719A Rulison 1965 Sirotherm process - thermally regenerable ion exchange resins 274-029; 59,441/65
(Australia) Bolto, Weiss, and Willis Partially functionalized cation exchange (shallow-shell technology) 3252921A Hansen and McMahon 1966 Macroporous ion exchange resin 3418262A Grammont and Werotte 1968 Boron selective resin 20110108488A1 Chemtob 1969 Development of poly(methyl methacrylate) anion exchange resins or macroreticular polymers that reduced fouling by natural organic manner N/A Kressman and Kunin [22, 23] 1971 Continuous moving bed ion exchange 3751362A Probstein, Schwartz, and Sonin 1972 Phenolic ion exchange fibers 3835072A Economy and Wohrer 1973 Iminodiacetic acid chelating resin
Metal-selective...
