Basic Principles of Membrane Technolog by Marcel Mulder Center for Membrane Science and Technology, University oftwente, Enschede, The Netherlands ff KLUWER ACADEMIC PUBLISHERS DORDRECHT / BOSTON / LONDON
CONTENTS 1. 1 Separation processes 1 1.2 to membrane processes 7 I. 3 History 9 I 4 Definition of a membrane 12 1. 5 Membrane processes 14 1.6 Solved problems 18 I. 7 19 1. 8 20 Materials and material properties 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Polymers Stereoisomerism Chain flexibility Molecular weight Chain interactions State of the polymer Effect of polymeric strueture on Tg Glass transition temperature depression Thermal and chemical stability Mechanical properties Elastomers Thermoplastic elastomers Polyelectrolytes Polymer blends Membrane polymers. 16.1 Porous membranes. 16.2 Nonporous membranes Inorganic membranes. 17.1 Thermal stability. 17.2 Chemical stability. 17.3 Mechanical stability Biological membranes. 15.1 Synthetic biological membranes Solved problems 22 22 24 26 27 29 31 33 40 41 44 45 47 47 49 51 52 59 60 60 61 61 62 66 67 67 69
I Preparation of synthetic membranes I. 1 71 I. 2 Preparation of synthetic membranes 72 I. 3 Phase inversion membranes 75 I. 3.1 Preparation by evaporation 76 I. 3.2 Precipitation.from the vapour phase 76 I. 3.3 Precipitation by controlled evaporation 76 I. 3.4 Thermal precipitation 76 I. 3.5 Immersion precipitation 77 I. 4 Preparation techniques for immersion precipitation 77 I. 4.1 Fiat membranes 77 I. 4.2 Tubulär membranes 78 I. 5 Preparation techniques for composite membranes 81 I. 5.1 Interfacial polymerisation 82 I. 5.2 Dip-coating 83 I. 5.3 Plasma polymerisation 86 I. 5.4 Modification of homogeneous dense membranes 87 I. 6 Phase Separation in polymer Systems 89 I. 6.1 89 I. 6.1.1 Thermodynamics 89 I. 6.2 Demixing processes 99 I. 6.2.1 Binary mixtures 99 I. 6.2.2 Ternary Systems 102 I. 6.3 Crystallisation 104 I. 6.4 Gelation 106 I. 6.5 Vitrification 108 I. 6.6 Thermal precipitation 109 I. 6.7 Immersion precipitation 110 I. 6.8 Diffusional aspects 114 I. 6.9 Mechanism of membrane formation 117 I. 7 Influence of various parameters on membrane morphology 123 I. 7.1 Choice of solvent-nonsolvent System 123 I. 7.2 Choice of the polymer 129 I. 7.3 Polymer concentration 130 I. 7.4 Composition of the coagulation bath 132 I. 7.5 Composition of the casting Solution 133 I. 7.6 Preparation of porous membranes - summary 134 I. 7.7 Formation of integrally skinned membranes 135 I. 7.7.1 Dry-wet phase Separation process 136 I. 7.7.2 Wet-phase Separation process 137 I. 7.8 Formation of macrovoids 138 I. 8 Inorganic membranes 141 I. 8.1 Thesol-gelprocess 141 I. 8.2 Membrane modification 144 I. 8.3 Zeolite membranes 144 I. 8.4 Glass membranes 146 I. 8.5 Dense membranes 147 I. 9 Solved problems 147
I. 10 I. 11 147 154 Characterisation of membranes IV.. 1 IV..2 IV..3 IV..4 IV.5 IV.6 IV.7 IV.8 \ Membrane characterisation Characterisation of porous membranes IV. 3.1 IV. 3.1.1 IV. 3.1.2 IV. 3.1.3 IV. 3.1.4 IV. 3.1.5 IV. 3.1.6 IV. 3.2 IV. 3.2.1. IV. 3.2.2 IV. 3.2.3 IV. 3.2.4 IV. 3.2.5 Microfiltration Electron microscopy Atomic force microscopy Bubble-point method Bubble-point with gas permeation Mercury intrusion method Permeability method Ultrafiltration Gas adsorption-desorption Thermoporometry Permporometry Liquid displacement Solute rejection measurements Characterisation of ionic membranes IV. 4.1 Electrokinetic phenomena IV. 4.2 Electro-osmosis Characterisation of nonporous membranes IV. 5.1 Permeability methods IV. 5.2 Physical methods IV. 5.2.1 DCS/DTA methods IV. 5.2.2 Density measurements IV. 5.2.2.1 Density gradient column IV. 5.2.2.2 Density determination by the Archimedes principle IV. 5.2.3 Wide-angle X-ray diffraction (WAXD) IV. 5.3 Plasma etching IV. 5.4 Surface analysis methods Solved problems 157 158 160 162 162 164 165 167 168 169 172 173 176 179 181 183 188 189 192 192 194 195 195 197 197 198 198 199 201 204 204 208 Transport in membranes V. 1 210 V. 2 Driving forces 212 V.3 Nonequilibrium thermodynamics 214 V. 4 Transport through porous membranes 224 V. 4.1 Transport of gases through porous membranes 225 V. 4.1.1 Knudsenflow 226 V. 4.2 Friction model 228
.5.6.7.8.9.8 Transport V. 5.1 V. 5.1.1 V. 5.1.2 V. 5.1.3 V.5.2 V. 5.2.1 V. 5.2.2 V. 5.2.3 V. 5.2.4 V. 5.2.5 V. 5.3 through nonporous membranes Transport in ideal Systems Determination of the diffusion coefficient Determination of the solubility coefficient Effect of temperature on the permeability coefficient Interactive Systems Free volume theory Clustering Solubility of liquid mixtures Transport of Single liquids Transport of liquid mixtures Effect of crystallinity Transport through membranes. A unified approach V.6.1 Reverse osmosis V.6.2 Dialysis V.6.3 Gas permeation V. 6.4 Pervaporation Transport in ion-exchange membranes Solved problems 232 239 243 244 246 248 251 254 255 257 258 259 260 264 266 266 267 267 271 272 278 VI Membrane processes. 1.2.3 Osmosis Pressure driven membrane processes 280 282 284 VI. 3.1 VI. 3.2 VI. 3.2.1 Microfiltration Membranes for microfiltration 284 286 288 VI. 3.2.2 Industrial applications 292 VI. 3.2.3 Summary of microfiltration 292 VI. 3.3 Ultrafiltration 293 VI. 3.3.1 Membranes for Ultrafiltration 294 VI. 3.3.2 295 VI. 3.3.3 Summary of Ultrafiltration 296 VI. 3.4 Reverse osmosis and nanofiltration 297 VI. 3.4.1 Membranes for reverse osmosis and nanofiltration 299 VI. 3.4.2 301 VI. 3.4.3 Summary of nanofiltration 302 VI. 3.4.3 Summary of reverse osmosis 303 VI. 3.5 Pressure retarded osmosis 303 VI. 3.5.1 Summary of pressure retarded osmosis 305 VI. 3.6 Piezodialysis 305 VI. 3.6.1 Summary of piezodialysis 306 VI. 4 Concentration as driving force 307 VI. 4.1 307 VI. 4.2 Gas Separation 308
VI. 4.2 VI. 4.2.1 VI. 4.2.2 VI. 4.2.3 VI. 4.2.4 VI. 4.2.5 VI. 4.2.6 VI. 4.2.7 VI. 4.3 VI. 4.3.1 VI. 4.3.2 VI. 4.3.3 VI. 4.3.4 VI. 4.4 VI. 4.4.1 VI. 4.4.2 VI. 4.4.3 VI. 4.4.4 VI. 4.4.5 VI. 4.4.6 VI. 4.4.7 VI. 4.5 VI. 4.5.1 VI. 4.5.2 VI. 4.5.3 VI. 4.5.4 VI. 4.6 VI. 4.6.1 VI. 4.6.2 Gas Separation Gas Separation in porous membranes Gas Separation in nonporous membranes Aspects of Separation Joule - Thomson effect Membranes for gas Separation Summary of gas Separation Pervaporation Aspects of Separation Membranes for pervaporation Summary of pervaporation Carrier mediated transport Liquid membranes Aspects of Separation Liquid membrane development Choice of the organic solvent Choice of the carrier Summary of carrier mediated transport Dialysis Transport Membranes Summary of dialysis Diffusion dialysis Summary of diffusion dialysis Thermally driven membrane processes VI. 5.1 VI. 5.2 VI. 5.2.1 VI. 5.2.2 VI. 5.2.3 VI. 5.2.4 Membrane contactors VI. 6.1 VI. 6.1.1 VI. 6.2 VI. 6.2.1 VI. 6.3 VI. 6.4 VI. 6.5 Electncally VI. 7.1 VI. 7.2 VI. 7.2.1 VI. 7.2.2 Membrane distillation Process parameters Membranes Summary of membrane distillation Gas-liquid contactor Liquid-liquid contactors Nonporous membrane contactors Summary of membrane contactors Thermo-osmosis driven membrane processes Electrodialysis Process parameters Membranes for electrodialysis 308 308 309 311 317 319 323 324 325 327 333 336 339 339 340 347 352 353 355 357 357 358 359 360 360 361 361 363 364 364 364 365 367 370 370 373 373 375 375 377 377 378 379 380 380 380 382 385
VI. 7.2.3 387 VI 7.2.3.1 Separation of amino acids 387 VI 7.2.4 Summary of electrodialysis 388 VI 7.3 Membrane electrolysis 388 VI 7.3.1 The 'chlor-alkali' process 389 VI 7.3.2 Bipolar membranes 390 VI 7.4 Fuelcells 391 VI 7.5 Electrolytic regeneration of mixed-bed ion-exchange resin 393 VI. 8 Membrane reactors and membrane bioreactors 394 VI. 8.1 Membrane reactors 395 VI. 8.2 Non-selective membrane reactor 396 VI. 8.3 Membrane reactor in liquid phase reactions 398 VI. 8.4 Membrane bioreactors 400 VI. 9 Solved problems 400 VI. 10 402 VI. 11 412 V Polarisation phenomena and fouling V. 1 416 V. 2 Concentration Polarisation 418 V. 2.1 Concentration profiles 423 V. 3 Turbulence Promoters 424 V. 4 Pressure drop 426 V. 5 Characteristic flux behaviour in pressure driven membrane Operations 427 V. 6 Gel layer model 429 V. 7 Osmotic pressure model 431 V. 8 Boundary layer resistance model 436 V. 9 Concentration Polarisation in diffusive membrane separaüons 440 V. 10 Concentration Polarisation in electrodialysis 442 V. 11 Temperature polarisation 444 V. 12 Membrane fouling 447 V. 12.1 Fouling tests in reverse osmosis 451 V. 13 Methods to reduce fouling 453 V. 14 Compaction 456 V. 15 Solved problems 456 V. 16 457 V. 17 463 VI Module and process design VI VI VI VIH vin VI l 2 3 4 5 6 Plate-and-frame model Spiral wound module Tubulär module Capillary module Hollow fiber module 465 '466 468 469 470 472
VI. 7 VI. 8 VI. 9 VI. 10 VI. 11 VI. 12 VI. 13 VI. 14 VI. 15 VI. 16 VI. 17 VI. 18 VI. 19 VI. 20 VI. 21 VI. 22 VI. 23 Comparison of the module configurations System design Cross-flow Operations Hybrid dead-end/cross flow System Cascade Operations Some examples of System design VI. 12.1 Ultrapure water VI.12.2 Recovery of organic vapours VI. 12.3 Desalination of seawater VI. 12.4 Dehydration ofethanol VI.12.5 Economics Process parameters Reverse osmosis Diafiltration Gas Separation and vapour permeation VI.16.1 Gas Separation under complete mixing conditions VI.16.2 Gas Separation under cross-flow conditions Pervaporation VI.17.1 Complete mixing in pervaporation VI.17.2 Cross-flow in pervaporation Pervaporation Dialysis Energy requirements VI. 20.1 * Pressure driven processes VI. 20.2 Partial pressure driven processes VI. 20.3 Concentration driven processes Solved problems 473 474 475 478 479 480 481 482 483 484 485 486 487 491 493 494 496 498 498 500 501 503 505 506 507 508 509 511 519 Appendix 1 Appendix 2 Answers to i exercises: solved problems Answers to i exercises: unsolved problems List of symbols 522 523 525 547 553 Index 557