Separation of water-ethanol mixtures by pervaporation through hydrophilic-hydrophobic composite membranes

A new kind of polymer composite membrane, which we refer as hydrophilic-hydrophobic composite membrane, is prepared by the concentrated emulsion polymerization method and employed to separate permselectively ethanol-water mixtures. This composite contains polyacrylamide as the dispersed phase and crosslinked polystyrene as the continuous phase. The swelling in water of this composite membrane is around 4 g water/g polymer and its swelling in ethanol is negligible. The permeation of the composite membrane by pervaporation decreases with increasing ethanol concentration in the feed and increases with increasing polyacrylamide fraction in the composite. The rate of permeation is in the range of 30-103 g/m2 h. The selectivity of the membrane ranges with increasing feed temperature. The activation energy of permeation varies between 1.8 and 4.9 kcal/mol, depending upon the compositions of the feed and membrane.