Electrochemical Properties and Specific Selectivity of Ion-Exchange Membranes in Borate-Nitrate Electrolyte Solutions

Abstract

Electrochemical characteristics of heterogeneous cation- and anion-exchange Ralex membranes and the mechanism of transfer of ions of salt, boric acid and its anions through membranes at different pH values have been investigated by the method of rotating membrane disk (RMD). It is shown that boric acid is transported mainly through an anion exchange membrane. At pH 9.5, the limiting stage of anion transfer through the anion exchange membrane is the reaction of tetrahydroxyborate \({\text{B}}\left( {{\text{OH}}} \right)_{4}^{ - }\) anion formation. The study of the electrodialysis separation of a solution of sodium nitrate and boric acid has shown that the electrodialysis method makes it possible to effectively separate the components of the mixture, while the value of the specific selectivity coefficient \({{P}_{{{{\text{B}} \mathord{\left/ {\vphantom {{\text{B}} {{\text{NaN}}{{{\text{O}}}_{{\text{3}}}}}}} \right. \kern-0em} {{\text{NaN}}{{{\text{O}}}_{{\text{3}}}}}}}}}\) = (0.02–0.06), depending on the voltage on the electrodialyzer.