Colloid and Interface Science

519 Pages·2009·7.995 MB·English

by  Ghosh Pallab

COLLOID AND
INTERFACE SCIENCE
PALLAB GHOSH
Associate Professor
Department of Chemical Engineering
Indian Institute of Technology Guwahati
New Delhi-110001
2009
About the cover illustration: The background depicts the waves created at the air–water interface induced
by external forces (e.g. when a rain drop falls on a calm water surface); (top left) petroleum oil-spill on sea
that can cause extensive environmental hazard; (middle) gas bubbles fascinate us with their shape and
colour, and they also constitute an integral part of gas–liquid dispersions; (bottom right) water-drops on
hydrophobic tree-leaves depicting the wetting phenomena; (top right) carbon-nanotube catalytic reactor
depicting the production of ethanol [taken from the work of Pan, X., Fan, Z., Chen, W., Ding, Y., Luo, H. and
Bao, X., “Enhanced Ethanol Production Inside Carbon-Nanotube Reactors Containing Catalytic Particles”,
Nature Materials, 6, 507 (2007), reproduced by permission from Macmillan Publishers Ltd., © 2007]
Rs. 425.00
COLLOID AND INTERFACE SCIENCE
Pallab Ghosh
© 2009 by PHI Learning Private Limited, New Delhi. All rights reserved. No part of this book
may be reproduced in any form, by mimeograph or any other means, without permission in
writing from the publisher.
ISBN-978-81-203-3857-9
The export rights of this book are vested solely with the publisher.
Published by Asoke K. Ghosh, PHI Learning Private Limited, M-97, Connaught Circus,
New Delhi-110001 and Printed by Rajkamal Electric Press, Plot No. 2, Phase IV, HSIDC,
Kundli-131028, Sonepat, Haryana.
Contents
Preface xi
SI Units xiii
1. BASIC CONCEPTS OF COLLOIDS AND INTERFACES .....................................1–23
1.1 Introduction ..................................................................................................................................2
1.2 Examples of Interfacial Phenomena..............................................................................................3
1.2.1 Capillary Action..................................................................................................................3
1.2.2 Tears of Wine......................................................................................................................4
1.3 Solid–Fluid Interfaces...................................................................................................................5
1.4 Colloids ........................................................................................................................................6
1.4.1 Colloids and Interfaces .......................................................................................................7
1.4.2 Classification of Colloids....................................................................................................9
1.4.3 Electrical Charge on Colloid Particles..............................................................................10
1.4.4 Stability of Colloids..........................................................................................................11
1.4.5 Kinetic and Thermodynamic Stabilities............................................................................13
1.4.6 Preparation of Colloids.....................................................................................................13
1.4.7 Parameters of Colloid Dispersions....................................................................................17
Summary..............................................................................................................................................19
Keywords.............................................................................................................................................19
Notation...............................................................................................................................................20
Exercises .............................................................................................................................................21
Numerical and Analytical Problems...................................................................................................21
Further Reading..................................................................................................................................22
2. PROPERTIES OF COLLOID DISPERSIONS.......................................................24–68
2.1 Introduction ................................................................................................................................25
2.2 Sedimentation under Gravity......................................................................................................25
2.3 Sedimentation in a Centrifugal Field..........................................................................................28
(cid:2)(cid:2)(cid:2)
(cid:2)(cid:3) (cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:5)(cid:7)
2.4 Brownian Motion........................................................................................................................30
2.5 Osmotic Pressure........................................................................................................................32
2.6 Optical Properties.......................................................................................................................36
2.6.1 Determination of Molecular Weight by Light Scattering..................................................39
2.6.2 Transmission Electron Microscopy (TEM) and
Scanning Electron Microscopy (SEM) .............................................................................42
2.6.3 Dynamic Light Scattering (DLS)......................................................................................42
2.6.4 Small-Angle Neutron Scattering (SANS).........................................................................43
2.7 Electrical Properties....................................................................................................................43
2.7.1 Reciprocal Relationships..................................................................................................48
2.7.2 (cid:2)-potential Obtained from Different Techniques...............................................................49
2.8 Some Properties of Lyophilic Sols..............................................................................................49
2.8.1 Hofmeister Series .............................................................................................................49
2.8.2 Viscosity of Lyophilic Sols...............................................................................................50
2.8.3 Gelation............................................................................................................................51
2.8.4 Imbibition.........................................................................................................................51
2.8.5 Syneresis...........................................................................................................................51
2.8.6 Gold Number....................................................................................................................52
2.9 Rheological Properties of Colloid Dispersions...........................................................................52
2.9.1 Einstein’s Equation of Viscosity .......................................................................................55
2.9.2 Mark–Houwink Equation for Polymer Solutions..............................................................56
2.9.3 Deborah Number ..............................................................................................................57
2.9.4 Peclet Number..................................................................................................................57
Summary..............................................................................................................................................58
Keywords.............................................................................................................................................59
Notation...............................................................................................................................................60
Exercises .............................................................................................................................................62
Numerical Problems............................................................................................................................63
Appendix..............................................................................................................................................66
Further Reading..................................................................................................................................66
3. SURFACTANTS AND THEIR PROPERTIES.......................................................69–94
3.1 Introduction ................................................................................................................................70
3.2 Surfactants and their Properties ..................................................................................................70
3.2.1 Anionic Surfactants.........................................................................................................71
3.2.2 Cationic Surfactants........................................................................................................72
3.2.3 Zwitterionic Surfactants..................................................................................................72
3.2.4 Nonionic Surfactants.......................................................................................................72
3.2.5 Gemini Surfactants..........................................................................................................73
3.2.6 Biosurfactants.................................................................................................................73
3.2.7 Micellisation of Surfactants............................................................................................74
3.2.8 Thermodynamics of Micellisation ..................................................................................83
3.2.9 Krafft Point and Cloud Point...........................................................................................84
3.2.10 Liquid Crystals................................................................................................................84
3.2.11 Hydrophilic–Lipophilic Balance.....................................................................................86
3.3 Emulsions and Microemulsions..................................................................................................88
3.4 Foams .........................................................................................................................................89
(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:5)(cid:7) (cid:3)
Summary..............................................................................................................................................90
Keywords.............................................................................................................................................90
Notation...............................................................................................................................................91
Exercises .............................................................................................................................................91
Numerical Problems............................................................................................................................92
Further Reading..................................................................................................................................93
4. SURFACE AND INTERFACIAL TENSION.........................................................95–142
4.1 Introduction ................................................................................................................................96
4.2 Surface Tension...........................................................................................................................96
4.2.1 Effect of Temperature on Surface Tension ....................................................................103
4.3 Interfacial Tension ....................................................................................................................106
4.4 Contact Angle and Wetting.......................................................................................................108
4.5 Shape of the Surfaces and Interfaces.........................................................................................109
4.5.1 Radius of Curvature......................................................................................................109
4.5.2 Young–Laplace Equation..............................................................................................112
4.5.3 Pendant and Sessile Drops............................................................................................115
4.5.4 Capillary Rise or Depression ........................................................................................118
4.5.5 The Kelvin Equation.....................................................................................................120
4.6 Measurement of Surface and Interfacial Tension......................................................................122
4.6.1 The Drop-Weight Method.............................................................................................122
4.6.2 du Noüy Ring Method ..................................................................................................124
4.6.3 Wilhelmy Plate Method................................................................................................126
4.6.4 Maximum Bubble Pressure Method..............................................................................127
4.6.5 Spinning-Drop Method.................................................................................................128
4.7 Measurement of Contact Angle ................................................................................................130
Summary............................................................................................................................................132
Keywords...........................................................................................................................................133
Notation.............................................................................................................................................134
Exercises ...........................................................................................................................................136
Numerical and Analytical Problems.................................................................................................137
Appendix............................................................................................................................................138
Further Reading................................................................................................................................140
5. INTERMOLECULAR AND SURFACE FORCES..............................................143–200
5.1 Introduction ..............................................................................................................................143
5.2 van der Waals Forces ................................................................................................................145
5.2.1 van der Waals Force between Two Macroscopic Bodies...............................................149
5.2.2 Derjaguin Approximation .............................................................................................151
5.2.3 The Hamaker Constant..................................................................................................152
5.2.4 Estimation of Surface Tension from Hamaker Constant ...............................................157
5.2.5 van der Waals Force in Electrolyte Solutions................................................................157
5.2.6 Disjoining Pressure.......................................................................................................158
5.2.7 Experimental Determination of van der Waals Force....................................................158
5.3 Electrostatic Double Layer Force .............................................................................................160
5.3.1 The Models of Electrostatic Double Layer ...................................................................162
5.3.2 Mathematical Modelling of the Diffuse Double Layer .................................................164
5.3.3 The Stern Layer ............................................................................................................171
5.3.4 Double Layer around Spherical Particles......................................................................173
(cid:3)(cid:2) (cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:5)(cid:7)
5.3.5 Electrostatic Double Layer Repulsion between Two Surfaces......................................174
5.3.6 The Derjaguin Approximation ......................................................................................177
5.3.7 The Zeta Potential.........................................................................................................177
5.3.8 Limitations of the Poisson–Boltzmann Equation..........................................................179
5.4 The DLVO Theory....................................................................................................................180
5.5 Non-DLVO Forces....................................................................................................................184
5.5.1 Hydration Force............................................................................................................184
5.5.2 Hydrophobic Interaction...............................................................................................186
5.6 Steric Forces due to Adsorbed Polymer Molecules...................................................................186
Summary............................................................................................................................................188
Keywords...........................................................................................................................................189
Notation.............................................................................................................................................190
Exercises ...........................................................................................................................................192
Numerical and Analytical Problems.................................................................................................194
Appendix 5A......................................................................................................................................195
Appendix 5B......................................................................................................................................197
Further Reading................................................................................................................................198
6. ADSORPTION AT INTERFACES .....................................................................201–238
6.1 Introduction ..............................................................................................................................202
6.2 The Gibbs Dividing Surface .....................................................................................................202
6.3 Gibbs Adsorption Equation.......................................................................................................204
6.4 Langmuir and Frumkin Adsorption Isotherms..........................................................................207
6.5 Surface Equation of State (EOS) ..............................................................................................208
6.6 Effect of Salt on Adsorption of Surfactants...............................................................................210
6.7 Adsorption Isotherms Incorporating the Electrostatic Effects...................................................215
6.8 Calculation of Free Energy of Adsorption ................................................................................217
6.9 Adsorption of Inorganic Salts at Interfaces...............................................................................218
6.10 Dynamics of Adsorption of Surfactants at the Interface............................................................219
6.11 Adsorption at Solid–Fluid Interfaces........................................................................................221
6.11.1 Henry, Freundlich and Langmuir Adsorption Isotherms .............................................222
6.11.2 The Brunauer–Emmett–Teller (BET) Theory..............................................................224
6.11.3 Adsorption Hysteresis.................................................................................................226
6.12 Direct Experimental Techniques for Measurement of Adsorption ............................................228
Summary............................................................................................................................................229
Keywords...........................................................................................................................................229
Notation.............................................................................................................................................230
Exercises ...........................................................................................................................................232
Numerical and Analytical Problems.................................................................................................232
Appendix............................................................................................................................................235
Further Reading................................................................................................................................236
7. INTERFACIAL RHEOLOGY..............................................................................239–269
7.1 Introduction ..............................................................................................................................239
7.2 Surface Shear Viscosity ............................................................................................................240
7.2.1 Molecular Theory of Newtonian Surface Viscosity.......................................................242
7.2.2 Boussinesq Number......................................................................................................243
7.2.3 Measurement of Surface Shear Viscosity......................................................................243
(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:5)(cid:7) (cid:3)(cid:2)(cid:2)
7.3 Interfacial Tension Gradient and Marangoni Effect..................................................................250
7.4 Surface Dilatational Viscosity...................................................................................................252
7.4.1 Measurement of Surface Dilatational Viscosity............................................................254
7.5 Boussinesq–Scriven Model.......................................................................................................257
7.6 Importance of (cid:3)S and (cid:4)S ............................................................................................................258
7.7 Interfacial Turbulence...............................................................................................................259
7.8 Motions of Drops in a Liquid....................................................................................................261
Summary............................................................................................................................................264
Keywords...........................................................................................................................................264
Notation.............................................................................................................................................264
Exercises ...........................................................................................................................................266
Numerical and Analytical Problems.................................................................................................266
Further Reading................................................................................................................................268
8. MONOLAYERS AND THIN LIQUID FILMS .....................................................270–315
8.1 Introduction ..............................................................................................................................271
8.2 Surfactant Monolayers and their Applications..........................................................................271
8.3 Properties of Monolayers..........................................................................................................272
8.3.1 Measurement of Surface Pressure.................................................................................273
8.3.2 Surface Pressure Isotherm.............................................................................................274
8.3.3 Model of Gas-Phase Monolayer....................................................................................276
8.3.4 Surface Potential...........................................................................................................278
8.3.5 Monolayers at Liquid–Liquid Interfaces.......................................................................279
8.4 Langmuir–Blodgett Films.........................................................................................................279
8.5 Surface Diffusion......................................................................................................................282
8.5.1 The Apparatus...............................................................................................................283
8.5.2 Measurement Procedure................................................................................................284
8.5.3 Determination of D ......................................................................................................285
s
8.6 Thin Liquid Films.....................................................................................................................286
8.6.1 Critical Film Thickness.................................................................................................287
8.6.2 Hydrostatics of Thin Liquid Films................................................................................292
8.6.3 Drainage of Liquid Films..............................................................................................293
8.6.4 The Lubrication Flow....................................................................................................295
8.6.5 Film-Drainage Time......................................................................................................298
8.6.6 Stability of Thin Liquid Films.......................................................................................302
8.6.7 Black Films...................................................................................................................303
Summary............................................................................................................................................306
Keywords...........................................................................................................................................307
Notation.............................................................................................................................................307
Exercises ...........................................................................................................................................309
Numerical and Analytical Problems.................................................................................................310
Appendix............................................................................................................................................311
Further Reading................................................................................................................................312
9. EMULSIONS, MICROEMULSIONS AND FOAMS ...........................................316–371
9.1 Introduction ..............................................................................................................................317
9.2 Emulsions.................................................................................................................................317
9.2.1 Preparation of Emulsions..............................................................................................318
(cid:3)(cid:2)(cid:2)(cid:2) (cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:5)(cid:7)
9.2.2 Stability of Emulsions...................................................................................................319
9.2.3 Ostwald Ripening .........................................................................................................321
9.2.4 Flocculation and Coalescence of Drops........................................................................324
9.2.5 Phase Inversion.............................................................................................................338
9.2.6 Application of Emulsions..............................................................................................339
9.3 Microemulsions........................................................................................................................340
9.3.1 Winsor’s Classification of Microemulsions ..................................................................340
9.3.2 Stability of Microemulsions..........................................................................................345
9.3.3 Rheology of Microemulsions........................................................................................351
9.3.4 Applications of Microemulsions...................................................................................353
9.4 Foams .......................................................................................................................................353
9.4.1 Preparation of Foams and Measurement of their Stability............................................355
9.4.2 Structure of Foams........................................................................................................356
9.4.3 Foam Drainage..............................................................................................................358
9.4.4 Applications of Foams..................................................................................................360
Summary............................................................................................................................................360
Keywords...........................................................................................................................................361
Notation.............................................................................................................................................362
Exercises ...........................................................................................................................................364
Numerical and Analytical Problems.................................................................................................366
Further Reading................................................................................................................................368
10. BIOLOGICAL INTERFACES.............................................................................372–409
10.1 Introduction ..............................................................................................................................372
10.2 Protein Adsorption at Interfaces................................................................................................373
10.2.1 Adsorption of Proteins at Solid–Liquid Interfaces......................................................374
10.2.2 Adsorption of Proteins at Fluid–Fluid Interfaces........................................................377
10.3 Biological Membranes..............................................................................................................381
10.4 Interfacial Forces......................................................................................................................384
10.4.1 van der Waals Force....................................................................................................385
10.4.2 Hydration Force..........................................................................................................385
10.4.3 Steric Forces ...............................................................................................................387
10.4.4 Electrostatic Double Layer Force................................................................................390
10.4.5 Hydrophobic Forces....................................................................................................392
10.5 Cell Adhesion ...........................................................................................................................393
10.6 Pulmonary Surfactant ...............................................................................................................396
10.7 Biomaterials..............................................................................................................................398
Summary............................................................................................................................................400
Keywords...........................................................................................................................................401
Notation.............................................................................................................................................401
Exercises ...........................................................................................................................................403
Numerical and Analytical Problems.................................................................................................404
Appendix............................................................................................................................................405
Further Reading................................................................................................................................406
11. NANOMATERIALS ............................................................................................410–451
11.1 Introduction ..............................................................................................................................411
11.2 Approaches for the Synthesis of Nanomaterials .......................................................................412
(cid:2)(cid:3)(cid:4)(cid:5)(cid:6)(cid:4)(cid:5)(cid:7) (cid:2)(cid:4)
11.3 Self-Assembly and Structure ....................................................................................................412
11.4 Synthesis of Nanoparticles........................................................................................................414
11.4.1 Homogeneous Nucleation...........................................................................................414
11.4.2 Microemulsion-Based Methods..................................................................................421
11.4.3 Synthesis of Carbon Fullerenes...................................................................................422
11.5 Synthesis of Nanowires, Nanorods and Nanotubes...................................................................425
11.5.1 Nanowires and Nanorods............................................................................................425
11.5.2 Nanotubes...................................................................................................................429
11.6 Deposition of Thin Films..........................................................................................................435
11.7 Synthesis of Microporous and Mesoporous Materials..............................................................438
11.8 Lithographic Techniques...........................................................................................................442
11.9 Toxic Effects of Nanomaterials.................................................................................................444
Summary............................................................................................................................................445
Keywords...........................................................................................................................................445
Notation.............................................................................................................................................446
Exercises ...........................................................................................................................................446
Numerical and Analytical Problems.................................................................................................448
Further Reading................................................................................................................................448
12. INTERFACIAL REACTIONS .............................................................................452–493
12.1 Introduction ..............................................................................................................................452
12.2 Reactions at Solid–Fluid Interfaces ..........................................................................................453
12.2.1 Langmuir–Hinshelwood Model ..................................................................................455
12.2.2 External Transport Processes ......................................................................................460
12.2.3 Determination of Mass and Heat Transfer Coefficients ..............................................464
12.2.4 Internal Transport Processes .......................................................................................465
12.3 Interfacial Polycondensation.....................................................................................................469
12.4 Gas–Liquid and Liquid–Liquid Interfacial Reactions...............................................................476
12.5 Reactions at Biointerfaces ........................................................................................................477
12.6 Micellar Catalysis.....................................................................................................................481
12.7 Phase Transfer Catalysis...........................................................................................................484
Summary............................................................................................................................................485
Keywords...........................................................................................................................................486
Notation.............................................................................................................................................486
Exercises ...........................................................................................................................................489
Numerical and Analytical Problems.................................................................................................490
Further Reading................................................................................................................................492
INDEX .......................................................................................................................495–503