In this work, separation of toluene/n-heptane mixtures via pervaporation using a composite membrane was investigated. Effects of operating conditions such as feed temperature, feed composition and downstream pressure on the membrane performance were studied. Experimental results were obtained at different feed compositions (10-40 wt.%), operating temperatures (25-85 degrees C) and downstream pressures (2-32 mbar g). The membrane selectivity for toluene was found to be greater than that for n-heptane. According to the results, it was observed that increasing toluene concentration in the feed and operating temperature enhance the membrane swelling and increase the polymeric chain mobility. Therefore, feed concentration and temperature have the same effects on toluene selectivity and permeation flux of the membrane. Permeation flux increases and toluene selectivity decreases with increasing feed concentration and temperature. In contrary, the membrane performance enhances with decreasing downstream pressure. It was found out that for a feed with 10 wt.% of toluene, at a temperature of 85 degrees C and a downstream pressure of 2 mbar g, the highest PSI value of 18.371 kg/m(2) h (in which permeation flux = 4.610 kg/m(2) h and toluene selectivity = 4.985) is achieved. (C) 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.