Pervaporation dehydration of isopropanol/water using poly(hema)/poly acrylic acid composite membranes.

Abstract

Dehydration of alcohols by pervaporation is a growing industry which has many advantages over the high energy consuming and polluting distillation. Pervaporation is a unique membrane separation process that involves phase change. Poly (2-hydroxyethylmethacrylate) and polyacrylic acid were used to form a selective layer on top of polyacrylonitrile and polyethersulfone porous substrate membranes, to perform dehydration of isopropyl alcohol by pervaporation. In order to achieve the best performance, membranes were prepared under many casting variables including casting solution compositions, number of layers, curing temperatures and curing times. The fluxes of composite membranes based on polyethersulfone substrate were higher than those based on polyacrylonitrile substrate when the membranes were prepared under the same preparation conditions. On the other hand, selectivities of polyethersulfone based membranes were lower. Therefore, attempts were made to increase the flux of polyacryolonitrile composite membranes. The best flux and separation factor of polyethersulfone composite membranes were 0.126 kg/hr.m2 and 183.12, respectively, while for polyacrylonitrile composite membranes they were 0.038 kg/hr.m 2 and 1925, respectively. Cross-linking was necessary to prevent the swelling of the coated layer of poly (2-hydroxyethylmethacrylate), which was done by adding polyacrylic acid as a cross-linking agent. It was found that the pores of the substrate membrane shrunk during the cross-linking process.