Preface .................................................................... v 1 Introduction ............................................................... 1 1.1 Importance of Clay Minerals ............................................ 1 2 Applications of Clays and Clay Minerals .................................... 5 2.1 Ceramics and Related Clay Products ..................................... 5 2.1.1 Bricks and other structural ceramic ware ......................... 5 2.1.2 Refractories ..................................................... 6 2.1.3 Earthenware ...................................................... 6 2.1.4 Porcelain ........................................................ 6 2.1.5 Pencil leads ..................................................... 8 2.2 Clay as Filler Material ................................................ 8 2.3 Agricultural Applications .............................................. 9 2.4 Clays as Adsorptive Materials .......................................... 9 2.4.1 Physical adsorption .............................................. 9 2.4.2 Ion exchange .................................................... 10 2.4.3 Zeolites as molecular sieves .................................... 10 2.5 Washing Scouring and Felting: Fuller's Earth .......................... 11 2.6 Talc and Its Uses ..................................................... 11 2.7 Smectites and Their Uses .............................................. 12 2.7.1 Uses of hydrophilic smectites ................................... 12 2.7.2 Bentones ........................................................ 13 3 Clay Minerals ............................................................. 15 3.1 Silicate Mineral Structures ........................................... 15 3.1.1 The polyhedral paradigm ......................................... 17 3.1.2 Polymerization of polyhedra ..................................... 19 3.2 Silicate Classification ............................................... 20 3.3 Structure of Phyllosilicates .......................................... 21 3.3.1 Layer types ..................................................... 21 3.3.2 Octahedral site occupancy ....................................... 25 3.3.3 Layer charge .................................................... 25 3.3.4 The interlayer .................................................. 28 3.3.5 Chemical variations ............................................. 36 3.4 Phyllosilicate Minerals ............................................... 39 3.4.1 1:1 minerals .................................................... 39 3.4.2 2:1 minerals .................................................... 41 3.4.3 2:1:1 minerals .................................................. 46 3.5 Interlayer Water ...................................................... 47 3.5.1 Structure of interlayer water ................................... 47 3.6 Intercalated Organic Molecules ........................................ 52 3.6.1 Organic complexes with vermiculite .............................. 54 3.6.2 Organic complexes with kaolinite ................................ 60 3.6.3 Summary of molecular-clay interactions .......................... 61 3.7 Origin of Clay Minerals ............................................... 64 3.7.1 Modes and environments of formation ............................. 64 3.7.2 Commercial deposits of clay minerals ............................ 66 4 Other Mineral Colloids .................................................... 69 4.1 Simple Oxides ........................................................ 72 4.2 Halides .............................................................. 79 4.3 Hydroxides ........................................................... 81 4.4 Nesosilicates ........................................................ 81 4.5 Cyclosilicates ....................................................... 84 4.6 Sorosilicates ........................................................ 87 4.7 Pyroxenes ............................................................ 87 4.8 Amphiboles ........................................................... 90 4.9 Silica Minerals ...................................................... 93 4.10 Feldspars ........................................................... 101 4.11 Carbonates .......................................................... 101 4.12 Phosphates .......................................................... 104 4.13 Sulphates ........................................................... 104 4.14 Asbestos ............................................................ 116 5 Theory of Colloids ....................................................... 119 5.1 The Hamaker Approximation ........................................... 119 5.2 The Lifshitz Approach ............................................... 121 5.3 Interfacial Lifshitz-van der Waals Interactions ..................... 123 5.4 Polar Forces ........................................................ 125 5.5 Lewis Acid-Base Interactions ........................................ 127 5.6 Polar Attractions and Repulsion ..................................... 129 5.7 Electrostatic Interactions .......................................... 130 5.8 Ionic Double Layer .................................................. 130 5.9 Electrokinetic Phenomena ............................................ 131 5.10 The ζ-Potential ..................................................... 132 5.10.1 Thick double layer ........................................... 132 5.10.2 Thin double layer ............................................ 133 5.10.3 Relaxation ................................................... 134 5.11 Energy Balance Relationships ........................................ 134 5.12 Decay with Distance ................................................. 135 5.12.1 LW interactions .............................................. 135 5.12.2 Polar interactions ........................................... 136 5.13 Electrostatic Interactions .......................................... 137 5.14 Energy Balance Diagrams ............................................. 138 5.14.1 Types of energy balance diagram .............................. 139 6 Measurement of Surface Thermodynamic Properties .......................... 141 6.1 The Young Equation .................................................. 142 6.2 The Young-Dupre Equation as a Force Balance ......................... 142 6.3 Concept of the Surface Tension of a Solid ........................... 144 6.4 Contact Angle Measurements on Heterogeneous Surfaces ................ 145 6.4.1 The Cassie equation ........................................... 145 6.4.2 The extent to which solid surfaces become heterogeneous by condensation of molecules evaporating from the liquid drop .... 146 6.5 Contact Angle Measurement on Solid, Flat Surfaces ................... 148 6.5.1 Advancing and retreating contact angles ....................... 148 6.5.2 Preparation of solid surfaces ................................. 149 6.5.3 Contact angles measured with liquid 1, immersed in liquid 2 ... 151 6.6 Other Approaches to the Interpretation of Contact Angle Data ........ 152 6.6.1 The Zisman approach ........................................... 152 6.6.2 The single polar parameter or γP approach ..................... 152 6.6.3 The "equation of state" ....................................... 153 6.7 Contact Angle Determination by Wicking and Thin Layer Wicking ....... 154 6.7.1 Determination of the average pore radius, R ................... 156 6.7.2 Derivation of contact angles from wicking measurements .................................................. 159 6.7.3 Other uses of wicking ......................................... 159 6.8 Solution of the Young-Dupre Equation from Contact Angle Measurements ........................................................ 162 6.8.1 Minimal solution .............................................. 162 6.8.2 The overdetermined case ....................................... 163 6.8.3 Estimation of errors in the γ values .......................... 163 6.9 Other Methods for Determining Surface Properties .................... 165 6.9.1 Stability of particle suspensions ............................. 165 6.9.2 Advancing freezing fronts ..................................... 166 6.9.3 Force balance ................................................. 167 6.9.4 Electrophoresis in monopolar organic solvents ................. 168 6.10 Surface Tension Measurement of Liquids .............................. 168 6.10.1 The Wilhelmy plate method .................................... 169 6.10.2 Pendant drop shape ........................................... 169 6.10.3 Interfacial tension between immiscible liquids ............... 169 6.10.4 Apolar and polar surface tension component liquids ........... 170 6.10.5 Determination of the polar surface tension parameters of liquids ................................................... 172 7 Electrokinetic Methods ................................................... 173 7.1 Electrophoresis ...................................................... 173 7.1.1 Particle microelectrophoresis .................................. 175 7.1.2 Electrophoresis in non-aqueous media ........................... 175 7.2 Electroosmosis ....................................................... 176 7.3 Streaming Potential and Sedimentation Potential ...................... 176 7.4 Link Between the Electrokinetic Potential and Electron Donicity ...... 178 7.4.1 The Schulze-Hardy rule ......................................... 178 8 Interactions Between Colloids ............................................ 181 8.1 Introduction ........................................................ 181 8.2 Lifshitz-van der Waals Interactions ................................. 181 8.3 Electrostatic Interactions .......................................... 182 8.4 Polar Interactions: Lewis and Bronsted Acid-Base Approaches ......... 182 8.4.1 Lewis acid-base properties of polar condensed-phase materials ..................................................... 183 8.4.2 Polar solids .................................................. 183 8.4.3 Polar solutes ................................................. 184 8.4.4 Polar liquids ................................................. 185 8.5 The Hydrophobic Effect: Hydrophobic Attraction ...................... 186 8.6 Hydrophilic Repulsion ............................................... 190 8.7 Definition of Hydrophobicity and Hydrophilicity ..................... 191 8.8 DLVO Approach, Including Lewis Acid-Base Energies ................... 193 8.8.1 Decay of interaction energies and forces as a function of distance ...................................................... 194 8.8.2 The extended DLVO (XDLVO) approach applied to aqueous media ... 195 8.8.3 Stability versus flocculation of aqueous particle suspensions ................................................... 195 8.8.4 Inadequacy of "steric" stabilization theories ................ 202 8.8.5 The extended DLVO approach in aqueous media; comparison with experimental data ............................................. 203 8.8.6 Comparison between DLVO and XDLVO plots of hectorite suspensions, as a function of ionic strength .................. 203 8.9 Influence of Plurivalent Cations on the Flocculation of Negatively Charged Particles: DLVO and XDLVO Analysis .......................... 204 8.10 Solubility .......................................................... 208 8.10.1 Solubility of electrolytes ................................... 209 8.10.2 Solubility of organic compounds .............................. 209 8.10.3 Solubility of surfactants and other ahiphipathic compounds ... 212 8.11 Adhesion and Adsorption ............................................. 213 8.11.1 Macroscopic scale adhesion and adsorption .................... 213 8.11.2 Adhesion and adsorption onto the water-air interface- flotation .................................................... 214 8.11.3 Macroscopic and microscopic-scale adsorption phenomena combined ..................................................... 215 8.11.4 Adsorption and adhesion kinetics ............................. 216 8.11.5 Adsorption and adhesion equilibrium .......................... 218 8.12 Net Repulsive Interactions .......................................... 218 8.12.1 Reversal of adsorption and adhesion .......................... 218 8.12.2 Temperature effects .......................................... 219 8.13 Nature of Clay-water Interactions ................................... 220 8.14 Structure of Bound Outer Layer Water ................................ 221 8.15 Swelling of Clays ................................................... 221 8.15.1 Nature of the swelling mechanism ............................. 221 8.15.2 Prerequisite properties of swelling clays .................... 223 8.15.3 Influence of steam on swelling clays ......................... 224 8.15.4 Hydrophobicity of talc and pyrophyllite ...................... 225 8.16 Special Properties of Kaolinite ..................................... 226 9 Surface Thermodynamic Properties of Minerals ............................. 229 9.1 Phyllosilicate Minerals .............................................. 229 9.1.1 Samples ........................................................ 229 9.1.2 Values ......................................................... 230 9.1.3 Generalities; clay minerals .................................... 235 9.1.4 Role of organic material adsorbed on clays ..................... 239 9.2 Other Minerals ....................................................... 244 9.2.1 Generalities; other minerals ................................... 248 10 Biological Interactions with Mineral Particles ........................... 251 10.1 Interactions with Biological Systems ................................ 251 10.2 Polymer Adsorption .................................................. 252 10.3 Protein Adsorption .................................................. 252 10.3.1 Protein adsorption onto hydrophobic surfaces ................. 253 10.3.2 Protein adsorption onto hydrophilic surfaces ................. 253 10.3.3 In vivo consequences of protein adsorption onto clay and mineral particles ........................................ 255 10.4 Pulmonary Pathogenesis .............................................. 256 10.4.1 Small, roughly spherical particles ........................... 256 10.5 Needle-shaped or Fibrous Particles .................................. 256 10.5.1 The most dangerous fibrous particles ......................... 256 10.5.2 The less dangerous fibrous (asbestos) particles .............. 257 10.5.3 A few proposed physical or chemical correlations with the pathogenicity of, e.g., amphiboles that turn out to be erroneous .................................................... 258 References .................................................................. 261 Index ....................................................................... 285