Abstract: An electrode for use in electrochemical ion exchange which includes a hydrolysable metal phosphate such as zirconium phosphate (Zr(HPO.sub.4).sub.2) which has been hydrolysed at least in part is regenerated. The electrode is made the anode of an electrochemical cell in which the electrolyte is an aqueous solution containing one or more phosphate ions provided, for example, by a dissolved salt (eg Na.sub.3 PO.sub.4, Na.sub.2 HPO.sub.4 or NaH.sub.2 PO.sub.4) or orthophosphoric acid, or both. Preferably, the electrolyte is acidic (eg pH 2). Operation of the cell reverses the hydrolysis reaction and enhances the performance of the electrode.