PERVAPORATION OF WATER-ETHANOL MIXTURES THROUGH SULFONATED POLYSTYRENE MEMBRANES PREPARED BY PLASMA GRAFT-POLYMERIZATION

Different membranes which permeate water selectively from water-ethano l mixtures were prepared by plasma graft-polymerization of styrene ont o porous poly(vinylidene fluoride) (PVDF) films, by sulfonation of the grafted membranes, and by ionization of the sulfonated membranes, res pectively. The permselectivities of the grafted (g-PS), sulfonated (g- PSS) and sodium salt form of sulfonated (g-PSS-Na+) membranes were inv estigated in view of the feed composition of the water-ethanol mixture and the grafted amount of polystyrene (PS). It was found that the per mselectivity increased with the ethanol concentration in the feed and that the grafted amount should be controlled for optimum separation of water. The g-PSS-Na+ membrane with a grafted amount of PS of 0.14 mg/ cm(2) was found to have a high permeation rate of 6.6 kg/m(2)h, and a separation factor of 21 for the pervaporation of aqueous 60 wt% ethano l solution at 50 degrees C.