Ammonia recovery from nitrate-rich wastewater using a membrane-free electrochemical system

Electrocatalytic nitrate reduction has great potential for simultaneously achieving ammonia recovery and nitrate-rich wastewater treatment. However, the complexity of wastewater matrices has long hampered its implementation and commercialization in the wastewater treatment industry. Here we develop a membrane-free electrochemical system, called electrochemical NO3− conversion synchronized with NH3 recovery (ECSN), which synchronizes nitrate reduction with ammonia recovery for treating real nitrate-rich wastewater. Key components of this system include a 3D-printed metallic glass decorated Cu–Ni (MPCN) working electrode bearing good corrosion resistance and a UV-assisted stripping unit. When treating real electroplating wastewater, the ECSN system converts over 70% of nitrate into high-purity ammonia chloride. Long-term stability test demonstrates the robustness of the ECSN system in treating real wastewater. Further, the economic feasibility and environmental benefits of this system are evidenced by technoeconomic analysis and life-cycle analysis. Overall, this work brings the electrocatalytic nitrate reduction process one step closer to practical application, contributing to both environmental protection and the circularity of anthropogenic nitrogen flow. Recovering ammonia from wastewater via electrochemical nitrate reduction would support a circular economy. Here the authors develop a membrane-free electrochemical system that allows efficient and robust ammonia recovery from real nitrate-rich wastewater.