SALT REJECTION AND FLUX IN REVERSE-OSMOSIS WITH COMPACTIBLE MEMBRANES

The theory of reverse osmosis in bilayer membranes is extended. At high fluxes the selectivity of the layer on the high pressure side dominates the salt rejection also in case this layer has the lowest selectivity. Theoretical concentration profiles are given for both orientations. Experimentally, irreversible compaction of the membrane is controlled by a pressure treatment. For the remaining reversible compaction the transport equations can be corrected. It turns out that reversible compaction affects the flux but not the salt rejection. Correspondingly structural changes occur in the layer of low selectivity. © 1979.