The presence of excessive concentrations of nitrate in industrial wastewaters, agricultural runoff and some groundwaters constitutes a serious issue for both environmental and human health. As a result, there is considerable interest in the possibility of converting nitrate to the valuable product ammonia by electrochemical means. In this work, we demonstrate the efficacy of a novel flow cathode system coupled with ammonia stripping for effective nitrate removal and ammonia generation and recovery. Continuous nitrate reduction and ammonia recovery can be achieved by integrating the flat gas membrane (FGM) with the packed flow electrode system while recovering the electrode slurry by ultrafiltration (UF) column simultaneously. In our previous batch-mode study, a copper-loaded activated carbon slurry (Cu@AC), made by a simple, low-cost wet impregnation method, is used as the flow cathode in this novel electrochemical reactor. Use of a 3 wt% Cu@AC suspension at an applied current density of 20 mA cm<sup>−2</sup> resulted in almost complete nitrate removal with 97% of the nitrate reduced to ammonia and 70% of the ammonia recovered in the acid receiving chamber. A mathematical kinetic model was developed that satisfactorily describes the kinetics and mechanism of the overall nitrate electroreduction process. Overall, this study sheds light on an efficient, low-cost water treatment technology for simultaneous nitrate removal and ammonia generation and recovery.

Continuous electrochemical reduction of nitrate with simultaneous ammonia recovery using a flow cathode reactor

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