Preparation of three dimensional bimetallic Cu–Ni/NiF electrodes for efficient electrochemical removal of nitrate nitrogen

It still remains a hotspot and great challenge to efficiently remove the nitrate nitrogen from high salt wastewater. Herein, a novel three dimensional porous bimetallic copper-nickel alloy electrode was fabricated with Ni foam (NiF) as substrate. The physicochemical and electrochemical characterization results showed Cu-Ni/NiF electrode possessed the smaller particle size (0.3-1.0 μm) and electrode film resistance comparing with Ni/NiF and Cu/NiF electrodes. Besides, higher double layer capacitance (Cdl) for Cu-Ni/NiF electrode indicated more electrochemical active sites could be used in the electrochemical nitrate nitrogen (NO3--N) removal. The electrochemical experiments showed the Cu-Ni/NiF electrode had the optimal NO3--N reduction ability and almost 100% NO3--N removal could be achieved with 30 min. All NO3--N removal processes were in accord with the pseudo-first-order reaction kinetics completely. The gaseous nitrogen selectivity for Cu-Ni/NiF electrode could reach 80.9% within 300 min. Stability assessment experiments indicated the Cu-Ni/NiF electrode all kept an excellent stability with Na2SO4 or NaCl electrolyte and the Cl- addition could significantly improve the gaseous nitrogen selectivity. Finally, a possible removal mechanism of NO3--N was proposed. This work offered a direction for designing non-noble bimetallic electrodes for nitrate removal.