A study has been carried out to establish the effectiveness of various membrane systems for the separation of anolyte (aqueous FeSO4+ H2SO4) and catholyte (aqueous CuSO4+ H2SO4) in a lab-scale copper electrowinning cell based on reactive electrodialysis. With a single anion membrane, there was a small but significant unwanted transport of both copper and iron through the membrane. Separation effectiveness increased by increasing the number of membranes, but so did the cell voltage, which implies a higher energy cost. For the most effective system (2 type B membranes), the unwanted transport rates were 4 × 10-4mol h-1m-2for Cu and 17 × 10-4mol h-1m-2for Fe. The corresponding cell voltage was 0.774 V. The difference in the transport rates for Fe and Cu may be explained by the ion transport mechanisms in the studied systems. © 2004 Elsevier Ltd. All rights reserved.