This study focuses on the surface modification of polyethersulfone (PES) ultrafiltration (UF) membranes using corona air plasma in order to reduce membrane fouling during separation of oil/water emulsions. The PES membranes were fabricated using polyvinylpyrrolidone (PVP) as a pore forming agent with various solvents including N,N-dimethylacetamide (DMAc), N,N-dimethyl-formamide (DMF), 1-methyl-2-pyrrolidone (NMP) and dimethyl sulfoxide (DMSO) by the phase inversion method. The effects of solvent in casting solution and corona treatment conditions on the surface properties, membrane morphology and separation performance of the membranes were investigated. The ATR-FTIR, SEM and AFM analyses were used to characterize the untreated and corona treated membranes. The results showed that viscosity of the casting solution and difference in solubility parameter between the solvent and non-solvent play an important role in the membrane structure and performance, however, the effect of viscosity is more pronounced. The corona treatment led to significant enhancement of the surface hydrophilicity, improvement of anti-fouling properties and oil/water flux in all membranes without significant changes in oil rejection. The effect of corona parameters on DMSO-solvent membrane indicated that the corona needs more time or higher power to ablate the surface, widening the pore distribution and enhancing permeation in case of membranes with a thicker dense layer. (C) 2012 Elsevier B.V. All rights reserved.