SEPARATION OF LIQUID-MIXTURES BY USING POLYMER MEMBRANES .5. WATER-ALCOHOL SEPARATION BY PERVAPORATION THROUGH POLY(VINYL ALCOHOL)GRAFT-POLY(STYRENE-CO-MALEIC ANHYDRIDE) MEMBRANES

Graft copolymerization of styrene-maleic anhydride copolymer (ST-co-MA ) onto poly(vinyl alcohol) (PVA) was carried out by a condensation-cou pling reaction through esterification. The ST-co-MA copolymer was obta ined by the copolymerization of MA and ST in dimethyl sulfoxide (DMSO) , using azoisobutyronitrfle as initiator. The structure of the reactio n products was confirmed by infrared analysis. The dependence of compo sition, viscosity and yield of the graft terpolymers on the concentrat ion of the reactants are presented in detail. Mechanical properties of membranes with different compositions were measured over a wide range of composition. It was found that water was permeated through the mem branes preferentially in all ranges of feed compositions. The permeati on decreased and the selectivity increased with increasing ethanol con centration in the feed and with increasing PVA content in the membrane . The effect of the molecular size of the permeating species on both p ermeation and separation is also discussed.