THE BEHAVIOR OF ION-EXCHANGE MEMBRANES IN ELECTROLYSIS AND ELECTRODIALYSIS OF SODIUM-SULFATE

There is an increasing interest in the electro-chemical splitting of sodium sulphate into caustic soda solution and sulphuric acid by means of ion exchange membranes. Adaptation of the product properties to the demands of recycling requires the use of cation exchange membranes, anion exchange membranes or a combination of both. Application of available membranes results in product concentrations which are below usual industrial standards. Extensive measurements prove that the current efficiency is either dependent on concentrations of the anode region (sulphuric acid, sodium sulphate) or on the concentrations of the cathode region (caustic soda, sodium sulphate) with regard to the range of concentrations. In order to explain these phenomena a model of an "acid" and an "alkaline" state of the membrane has been developed, which can be applied both for cation and anion exchange membranes. This model is a valuable help in optimizing the concentrations of sodium sulphate, sulphuric acid and caustic soda.