The characteristics of polyamide membranes with respect to interfacial polymerization of diamine mixtures with trimesoyl chloride (TMC) are studied using two-parameter model of Extended Nernst-Planck Equation. The investigation provided the information about the effect of TMC content and reaction time on the diffusive and convective flow of ions through the membrane. These indirectly reflected structural properties such as effective skin thickness, pore size and structural integrity of membrane. Membrane flux and rejection are related to the TMC content and reaction time, when NaCl and CuSO4 are used as testing solutes. The diffusive transport, -f(1)'Delta C-1 and convective transport, J(v)C(1,0)(1 - R-1') contributions are successfully determined by fitting the model to the experimental data to get A and R, parameters. It was found that at high TMC content the contribution of convective transport over diffusion transport is increased due to the increase of effective thickness. However, for smaller size and higher diffusive solute like Na+, the ratio of diffusive flow over convective flow is increased at high TMC and high reaction time. This indicated that numbers of tightened pores membrane are increased. An optimum membrane with high flux and high copper ion rejection could be obtained by incorporating 0.1% (w/v) of TMC in the polymerization reaction mixture under reaction time period of 5 s. (c) 2005 Elsevier B.V. All rights reserved.