Asymmetric ion-exchange membranes were prepared for dehydrating a water/ethanol mixture by pervaporation. The ion-exchange membranes (Na-PSF) were prepared by exchanging sodium ion with various degree of sulfonation polysulfone. It was observed that the charged membranes showed a significant improvement on pervaporation performance and also showed a strongly enhancement on the hydrophilic properties of Na-PSF membranes. It was found that the membrane formation pathways were only slightly affected by increasing the sodium content in the casting solution during the membrane formation process. The improvements in the separation performance were mainly contributed by both of the enhancement on hydrophilicity and degree of swelling during the permeate transport through the charged membranes. The operating temperature also showed a significant influence on the separation performance of Na-PSF membranes due to the abating hydration behavior at the higher temperatures. Amount the charged Na-PSF membrane, the 0.58 is best optimum sodium substitution ratio for the charged membranes with a flux of 600 g m2 h 1 and a selectivity of 150 for the feed concentration of 90% ethanol solution at 25 �C.