The removal of oil from oil-in-water (o/w) emulsion was investigated using a packed bed of an ion-exchange resin (Purolite OL 100) beads. Purolite OL 100 is an oleophilic resin which acts as a coalescing agent for the oil present in the o/w emulsion system. Preliminary experimental studies were performed to evaluate the operating parameters, which were then used for the determination of oil removal efficiency. The effect of four process parameters, namely pH, bed height, oil concentration and flow velocity on the removal efficiency of the resin bed were studied simultaneously. The process was optimized with respect to a single response, viz, oil removal efficiency, using Box-Behnken design of response surface methodology. The results indicate that the responses are predicted adequately and satisfactorily within the limits of input parameters being used. The optimum conditions for oil removal were found to be the initial oil concentration (30% (v/v)), bed height (100 mm), pH 6, and the emulsion flow velocity (127 x 10(-3) dm(3)/min) at which the oil removal efficiency was obtained as 83.4%. Analysis of variance on the experimental data showed a high correlation coefficient. (C) 2013 Elsevier B.V. All rights reserved.