Currently, electrospun nanofibrous membrane (ENM) is classified as a microfiltration (MF) membrane, which upon further modification is used for nanofiltration (NF) applications. The objective of this study was to investigate the suitability of ENM for water treatment applications. Different fiber sizes were obtained by varying the concentration of polyacrylonitrile solution (namely 4, 6, 8 and 10 wt%) to explore the interplay between electrospun fiber size and rejected salt ions. When the fiber size was larger, its 'bubble-point' was higher and hence its pure water flux was also higher. In order to transform these MF membrane to NF membrane, an interfacial polymerization technique was used to coat a thin film on the surface of ENM. Separation of 2000 ppm of various salts was conducted on this developed thin film nanofibrous composite (TFNC) membrane. The results indicated that as the fiber size decreased, the pore-size also decreased, and the separation of salts increased, while at the expense of flux. When the cross-sectional thickness of the electrospun layer was decreased together with smaller pore-size, it resulted in the increased flux with high salt rejection. In addition, rejection efficiency of these TFNC membranes against PEG 300, PEG 600 and PEG 3400 were also studied. (C) 2011 Elsevier B. V. All rights reserved.