SOME CONSIDERATIONS ON MASS-TRANSFER RESISTANCES IN SOLUTION DIFFUSION-TYPE MEMBRANE PROCESSES

The influence of feed-side concentration polarization and the resistan ce of the porous support on membrane processes where solution-diffusio n-type composite membranes are involved is discussed in this paper. Re verse osmosis, nanofiltration, gas permeation, prevaporation and vapor permeation represent the complete variation of liquid and gaseous sta te at the feed and permeat side and cover cases where the driving forc e is realized by increasing the feed-side potential and cases where th e permeate-side potential is decreased. In the calculations, the major parameters, especially feed-side concentration of the preferentially permeating components is varied over a wide range - from ''traces'' to ''fairly high''. The discussion of the results shows clearly the impo rtance or unimportance of the resistances relative to each other for e very process. Finally, the effect of transport resistances on module p erformance is discussed.