Electroreduces Nitrate to Ammonia and Converts to Nitrogen Through Chloride Ions by CoO/GF Cathode: Performance, Regulation and Mechanism

With the development of cities, the issue of excess nitrate in wastewater has become increasingly severe. Electrochemical technology has garnered significant attention due to its straightforward operation and environmental sustainability. A CoO/GF cathode was successfully prepared by depositing CoO onto Graphite felt (GF) using an electrochemical deposition-calcination method. The effects of electrochemical reduction of nitrate (NO-N) using CoO/GF cathodes were investigated. The removal rate of NO-N achieved an impressive 98.6% with the CoO/GF cathode, and the formation rate of reduced ammonia (NH-N) was 100% within 2 h at -1.61 V vs. Ag/AgCl voltage. The optimal removal efficiency for NO-N occurred at a pH of 5. In addition, the electrode demonstrated excellent recyclability and stability. In the presence of Cl, N was produced instead of NH through mediated oxidation. NH-N was oxidized to N under the action of Cl. When the concentration of KCl reached 3000 mg/L, the total nitrogen removal rate achieved 98.63%. The reduction mechanism for NO reduction was confirmed through electrochemical analysis, scavenging experiments and XPS analysis: on the one hand, it was caused by the Co -Co -Co process. On the other hand, it was caused by indirect reduction mediated by H∗. This study presents an efficient and environmentally friendly method for converting NO-N to NH-N while simultaneously controlling NH-N production through chlorine addition, providing a theoretical foundation for the degradation of NO-N from wastewater.