Due to the carbon nanotubes unique one-dimensional tubular structure and superior mechanical and chemical properties, it has been used as a filler to prepare high performance flat sheet membranes. In this study, we explored if the incorporation of oxidized multi-walled carbon nanotubes (MWNTs) into polysulfone (PSU) hollow fiber membranes could enhance the membrane performance. Polyvinylpyrrolidone (PVP) was used as porogen and 1-methyl-2-pyrrolidinone (NMP) as the solvent in the phase inversion spinning process, and deionized water was used as bore fluid and coagulant. Purified and oxidized MWNTs in the mixed acid solution (H2SO4/HNO3 = 3/1 in volume) were used as fillers at concentrations ranging from 0 to 1 wt%. Results indicated that at three different PSU concentrations (15, 18, and 20 wt%), the pure water flux of all membranes increased first and then gradually decreased with increasing nanotube concentration. The optimized mixed matrix membranes showed a significant increase in pure water flux (60% to 100%) while maintaining a similar capability for solute rejection, and also an improved resistance to protein fouling. The water contact angle of the membrane decreased with increasing filler concentration, suggesting an increase in the membrane surface hydrophilicity that might have contributed to the improved membrane performance. (c) 2013 Elsevier B.V. All rights reserved.