The separation performance of Na+, K+ Ca2+ and Mg2+ ions from ternary mixtures prepared from NaCl-CaCl2 and KCl-MgCl2 salts dissolved in deionized water were investigated by the electrodialysis (ED) method using batch mode of operation as a function of solution concentration, applied voltage and flow rate. TS-1-10 electrodialysis equipment (Tokuyama) was used in the experiments. During the unsteady-state run of the ED system, both inlet and outlet concentrations and conductivities of streams were measured at certain time intervals until the observed current dropped to 0.01 A. The separation performances of Na+ and K+ ions from prepared mixtures were compared with those of Ca2+ and Mg2+ ions. When concentration of monovalent salts decreased in ternary mixtures, removal of monovalent ions from the mixture sharply decreased at a voltage of 5 V, although this was not apparent at 10 V. Similar behavior was not observed for divalent salts.