Composite nanofiltration membranes were prepared by incorporating single-walled carbon nanotubes (SWNTs) into polysulfone polymer via the phase inversion method. Addition of SWCNTs resulted in the reduction of the pore size due to nanosize (0.7-1.3 nm) diameter of SWCNTs used. The increase in carbon nanotubes makes the surface of the membranes smoother, although the solvent and nonsolvent exchange process becomes slower due to increase in viscosity of the blend solution. The addition of SWCNTs improved the rejection of metal ions, the oxidized functionalized C/PS composite membranes gave 96.8% removal for Cr(VI), 87.6% for As(III), and 94.2% removal for Pb(II) which was just 30.3%, 28.5%, and 28.3%, respectively, with unblended virgin polysulfone membrane.