In this paper, electrodialysis (ED) process was modeled based on basic electrochemistry rules and copper ion separation experimental data. Experiments were conducted by Taguchi method as an experimental design. Then the same experiments were performed for zinc, lead and chromium ions. It was found that performance of an ED cell is almost independent on the type of ions and only depends on the operating conditions and the cell structure. With the aid of this valuable result, a model was used for total definite concentration of ion mixtures. The model starts from a differential equation of steady state mass balance. Neglecting resistances of ion exchange membranes compared with resistances of bulk solutions in dilute and concentrate compartments and deriving a relation for solution resistance as a function of concentration and temperature, the final one-parameter model was obtained. The model parameter was determined by experimental data. The approached model gives separation percent for various temperatures, concentrations, flow rates and voltages. In order to assess the reliability of the model, the calculated results were compared with measured experimental data. It was found that there is an acceptable agreement between the calculated results and experimental data. (C) 2004 Elsevier B.V. All rights reserved.