Evaluation of a ceramic-polymer composite cation-selective membrane for sodium salt splitting

A RAIPORE polymeric cation-selective membrane was modified by deposition of a thin film of NASICON, a sodium superionic conducting ceramic, using pulsed laser deposition. The composite membrane was incorporated into an electrolysis system for the production of sodium hydroxide and sulfuric acid from sodium sulfate. Its performance was compared to the unmodified polymeric base membrane. The composite membrane showed a significantly higher selectivity for sodium over hydrogen ions compared to the unmodified polymeric base membrane, resulting in a higher current efficiency and a lower energy consumption for the production of sodium hydroxide. The composite,membrane was also found to be more resistant to fouling by ferric ion as compared to the polymeric membrane. Neither membrane was fouled by calcium or magnesium. The selectivity of the composite membrane for sodium over potassium ions was not found to improve by the deposition of the ceramic layer. (C) 1999 The Electrochemical Society. S0013-4651(98)04-057-9. All rights reserved.