Enhancement of nitrate removal from a solution of mixed nitrate, chloride and sulfate ions using a nitrate-selective carbon electrode

A nitrate-selective carbon electrode (NSCE) was fabricated to remove nitrate ions selectively from a solution of mixed anions. The NSCE was prepared by coating anion-exchange resin powder with a high selectivity toward nitrate ions on a carbon electrode surface. We performed desalination experiments on a solution of mixed chloride, nitrate and sulfate ions using a CDI cell (NSCE cell) constructed with the NSCE. The desalination results were compared with the results obtained in a CE cell containing an uncoated carbon electrode (CE). According to the adsorption equilibrium tests, the BHP55 resin had a preference for ions in the order nitrate ≫ sulfate > chloride. The desalination experiments were performed by applying a constant current until the cell potential reached 1.0 V. The total amount of ions adsorbed in the NSCE cell was approximately 34% higher than that in the CE cell. The amount of nitrate ions adsorbed in the NSCE cell was approximately 2-fold higher value than that in the CE cell. However, the amount of adsorbed chloride and sulfate ions was similar in the two cells. These results show that the fabricated NSCE was effective at enhancing the removal of nitrate ions from a mixed solution.