Pervaporation experiments were conducted to recover 1-butanol from model pharmaceutical aqueous waste using a surface modified poly(vinylidene difluoride) membrane. The surface modification of the membrane was made using silicone grease as an ultra-thin layer on the surface to improve the pervaporation performance of the membrane. The effect of operating variables such as feed composition, feed temperature and feed flow rate on permeation fluxes, separation factor and pervaporative separation index were studied in order to optimize the operating variables. The experimental results showed that surface modified poly(vinylidene difluoride) membrane was 1-butanol permselective, especially for low feed compositions. 1-Butanol separation factor of 6.4 and a total flux of 4.126 kg m(-2) h(-1) have been obtained at a feed composition of 7.5 wt%, feed temperature of 50 degrees C, feed flow rate of 600 mL min(-1) and permeate pressure of 50 mmHg. The total flux of the surface modified membrane increased with increasing the feed composition, feed temperature, feed flow rate of the mixture whereas the separation factor follows a reversed order except for flow rate. The influence of operating variables such as feed composition and temperature on partial flux and permeate composition was modelled based on Fick's first law to understand the process behaviour and it will be very useful for design purpose. These models will be used to predict the required membrane surface area for recovery of 1-butanol for the range of experimental feed compositions. (C) 2007 Elsevier Ltd. All rights reserved.