SEPARATION OF ISOPROPANOL FROM WATER BY PERVAPORATION USING SILICONE-BASED MEMBRANES

The separation of isopropanol from water by pervaporation was carried out using silicone-based membranes. It was found that both the homogenous poly (dimethyl siloxane) membrane and the symmetric silicone-polycarbonate copolymer membrane were selective to isopropanol, and the poly(dimethyl siloxane) membrane exhibited a quite large selectivity to low concentrations isopropanol. The ultrathin silicone-polycarbonate membrane used in this study was found to be slightly selective to water, which was presumably due to the influence of the support structure. This membrane was modified by coating a thin layer of silicone material on its surface, resulting in an isopropanol selective membrane. Mathematical modelling of the batch pervaporation process was also attempted. Starting from material balances, mathematical equations were developed and the applicability of these equations was examined with experimental data. For a given separation task, the product concentration and product recovery as well as the membrane area and batch time required to achieve the separation can be predicted, provided that the concentration dependence of the membrane permselectivity is known. On the basis of the model, the effects of the process parameters such as batch time and the quantity of the feed mixture to be treated per unit membrane area were analyzed.