PERVAPORATION SEPARATION OF AQUEOUS ALCOHOL SOLUTION THROUGH ASYMMETRIC POLYCARBONATE MEMBRANE

In the present work the separation of aqueous alcohol mixtures through wet-phase inversion prepared polycarbonate membranes was studied by using the pervaporation process. The formation of asymmetric pervaporation membranes was discussed in terms of the presence of a nonsolvent in the casting solution, the polycarbonate concentration, and the kinds of coagulation media. The effects of feed composition, swelling degree, and the size of the alcohols on the pervaporation performances were investigated. The rate of liquid-liquid demixing increases with a decreasing number of carbon atoms of the alcohol coagulation medium. The permeation rate of the pervaporation process for the nonsolvent-added membrane was much higher than that of the membrane without nonsolvent additive. In binary alcohol mixtures, the permselectivities of small-sized alcohols through the asymmetric membrane are decided by two factors: preferential solubility of larger-sized alcohol and predominant diffusivity of small-sized alcohol.