New method for electrochemical ion separation (ElONS) for chloride/nitrate separation using Ag/AgCl electrodes with a cation exchange membrane

Electrochemical ion separation (EIONS) is attracting attention as a new ion separation technology because no by-products are generated during the process. However, conventional EIONS systems have lower selectivity for anions; it has limitations in its application to selective anion extraction. Therefore, it is necessary to develop a new EIONS system with high selectivity for specific anions. In this study, we introduce a highly selective EIONS for Cl- extraction from a mixed solution of Cl- and NO3- using silver/silver-chloride electrodes with a cation exchange membrane. This technique is based on the principle that Ag/AgCl electrodes starts to react with Cl- at a specific potential to remove Cl- from the mixture. As a result, this system removed Cl- with 80 times higher selectivity than its removal of NO3- even at the low cell voltage of 0.3 V. Furthermore, it was found that this system could be operated at a current density as high as 5 mA cm−2, suggesting for rapid extraction. We believe that this system can be feasible for separating Cl- and NO3- electrochemically. [Display omitted] •Chloride and Nitrate were electrochemically separated using silver/silver chloride electrodes and a cation exchange membrane.•In this system, chloride was extracted with remarkably high selectivity, up to about 80 times higher that of nitrate.•This system can operate at very low cell voltages of 0.3 V or less.•The electrochemical separation performance of the system was evaluated.