The transport of vanadium(III) and iron(II) ions through the Nafion 117 cation-exchange membrane in the presence of picolinic acid was investigated by simulating the equilibrium distribution of ionic species as a function of pH, and by electrodialyzing the simulated waste solution. From distribution calculations of the model reaction systems it could be predicted that at pH 1.6 most vanadium ions exist predominantly in the form of the V-III(Pic(-))(2)(+) complex, and this form of complex permeates across the cation-exchange membrane during electrodialysis. The experimental results, including variations in the color and cation concentrations of the catholyte, confirm the existence of the vanadium(III) picolinate complex. Iron ions permeated into the catholyte were converted to their hydroxide precipitates, which could be formed at the high; pH condition resulting from the reduction of hydrogen ions and the production of OH- ions by water electrolysis at the cathode. It was also found that the in-situ precipitation of iron in the electrodialyzer could be self-modulated by shifting the catholyte pH from the acidic state to the alkaline state during electrodialysis operation.