EFFECT OF SURFACE-MODIFYING MACROMOLECULES AND SOLVENT EVAPORATION TIME ON THE PERFORMANCE OF POLYETHERSULFONE MEMBRANES FOR THE SEPARATIONOF CHLOROFORM WATER MIXTURES BY PERVAPORATION

Polyethersulfone (PES) membranes using different evaporation periods w ere fabricated by the phase-inversion method. Pervaporation experiment s were conducted for chloroform/water mixtures to determine the select ivity of the PES membranes. It was found that chloroform could be conc entrated in the permeate from chloroform/water binary feed mixtures by PES membranes prepared using longer evaporation periods, and that the selectivity of PES membranes in pervaporation could be reversed by sh orter evaporation periods. This study also showed that by adding surfa ce-modifying macromolecules (SMM) up to 1 wt % into the casting soluti on, chloroform enrichment in the permeate could be increased by 50%. C hloroform enrichment increased with increasing SMM concentration until an optimal value, after which the enrichment decreased. (C) 1994 John Wiley and Sons, Inc.