Highly selective electrochemical reduction of nitrate via CoO/Ir-Nickel foam cathode to treat wastewater with a low C/N ratio

• Published in: Journal of hazardous materials 2024-02, Vol.463, p.132813-132813, Article 132813
• Main Authors: Wang, Youke, Ji, Zehua, Pei, Yuansheng
• Format: Article
• Language: English
• Subjects: CoO; electrochemical nitrate reduction; hydrogen radical; proton enhancement effect
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2023.132813

Thorough nitrate removal from reclaimed water by biological techniques without carbon sources is difficult. Flexible, controllable electrochemical nitrate reduction is widely researched. Herein, ultrathin CoO nanosheets were constructed through amino group induction and orientation. The interfacial electron transfer resistance of two-dimensional CoO was 43.4% lower than that of one-dimensional nanoparticles, resulting in higher current density and improved nitrate reduction efficiency. Nickel foam and IrO2-Nickel foam electrodes have almost no effect on nitrate reduction. It is worth noting that iridium loading on CoO (nanosheet) regulated the electronic band structure and generated active atomic H*. The nitrate removal rate increased from 45.1% (CoO (nanoparticle)-Nickle foam) and 63.8% (CoO (nanosheet)-Nickle foam) to 94.64% (CoO/Ir10wt%-Nickle foam). The proton enhancement effect improved indirect nitrate reduction by atomic H* and increased the NO3--N removal rate to 99.8%. Active chlorine species generated by Cl- in the wastewater selectively converted more than 99% of nitrate to N2, exceeding previous Co-based cathode results. In situ DEMS indicated that electrochemical reduction of nitrate included deoxidation (NO3-→*NO2-→*NO→*N/*N2O→N2) and hydrogenation (*NH2→*NH3→NH4+). The NO3--N removal rate of CoO/Ir10wt% exceeded 65% during treatment of wastewater treatment plant effluents, verifying the feasibility of electrochemical nitrate reduction with the CoO/Ir10wt% cathode. A strategy for designing electrochemical nitrate reduction electrocatalysts with excellent potential for full-scale application to treat wastewater treatment plant effluent is provided. Nitrate accumulation in water environments as a result of the heavy use of chemical fertilizers. The excessive discharge of industrial wastewater poses a significant threat to natural aquatic environments and human health. In addition, nitrate is also a potential carcinogen. This study focused on nitrate in wastewater as the target pollutant and applied electrochemical technology to completely remove nitrate from the effluent of a sewage plant to solve the problems of secondary pollution and reduce the risk to human health. This study showed excellent potential for the full-scale application of electrochemical nitrate reduction of effluent from municipal sewage treatment plants. [Display omitted] •Constructing 2D materials enables facile electron transfer of CoO nanosheets.•Ir loading regulated the