Thin film composite (TFC) polyamide membranes for reverse osmosis (RO) were successfully prepared via interfacial polymerization of m-phenylenediamine (MPD), 2,2'-benzidinedisulfonic acid (BDSA) and trimesoyl chloride (TMC) on a polysulfone support. The physico-chemical characteristics of the membranes were determined using ATR-FTIR, XPS, zeta potential measurement, SEM and AFM. Membrane performance experiments were investigated using NaCl and MgCl2 salt solutions. The near region spectra show that the active layer of TFC membrane is an aromatic polyamide, with carboxyl and amino groups, as seen in the ATR-FTIR result. The sulfonyl group addition from the BDSA monomer is evident from the higher sulfur concentration as illustrated in the XPS results and due to more negative zeta potential values. Also, the SEM and AFM pictures show that the surface morphology became smoother as the BDSA content was increased. Due to the modification of the active layer, pure water permeability and rejection of NaCl and MgCl2 salts were significantly enhanced. (C) 2012 Elsevier B.V. All rights reserved.