Electrocatalytic nitrate removal by non-precious three-dimensional Fe/Ni foam cathode: Experimental study and mechanism verification

Developing efficient electrocatalysts has been considered a promising method for nitrates polluted wastewater treatment. Herein, we designed and prepared a non-precious three-dimensional (3D) Fe/Ni foam via an electrodeposition method and explored it as cathode for electrocatalytic nitrate removal. Electrochemical experiments indicated that vertical arrays of Fe-containing nanosheets greatly enhanced the electrochemical properties, specifically its catalytic activity towards nitrate. Notably, at a current density of 25 mA/cm(2), the 3D Fe/Ni foam cathode achieved a remarkable nitrate removal efficiency of 98.0 % within 60 min, far surpassing the 3.2 % efficiency observed for a Ni foam electrode. The outstanding performance can be attributed to the electrode 's improved electrochemical activity, enriched catalytic active sites and high nitrate affinity. Moreover, complete total nitrogen (TN) removal was achieved with the addition of Cl- in the simulated wastewater. The effects of operating parameters, complex environmental conditions and system stability on nitrate removal were also investigated. Additionally, the specific energy consumption (SEC) was calculated to be 82.2 kWh/kg NO3- reduced at the current density of 25 mA/cm(2) after 60 min electrolysis. Based on comprehensive characterizations, control experiments, scavenging tests and electrochemical analyses, we propose a mechanism for nitrate reduction and TN removal. Real natural water and pretreated textile wastewater were employed to verify the practical application. This study provides new insight into the fabrication of non-precious electrodes and their application in electrocatalytic nitrate removal.