This work examines the properties of selected cation and anion exchange membranes for use in the electrochemical separation of sodium sulfate into sodium hydroxide and sulfuric acid. The effect of membrane type, electrolyte composition and ion exchange membrane thickness on the current efficiency was investigated. A decrease in current efficiency was observed due to ion migration under the influence of the electric field, and, to a lesser extent, diffusional losses. Increasing the membrane thickness improves the current efficiency at the cost of higher power due to the higher cell potential.