Simultaneous electrocatalytic removal of inorganic nitrogen compounds in groundwater: Modeling and mechanistic studies

The use of biological and chemical methods for the simultaneous removal of inorganic nitrogen compounds containing nitrate, ammonia, and nitrite in groundwater typically cannot achieve synchronous oxidation and reduction in an undivided reactor. In the present study, with the strict regulation of the oxidation reaction in the anode zone and reduction reaction in the cathode zone, simultaneous removal of nitrate, ammonia, and nitrite was achieved in an undivided electrochemical system. Our results indicated that ammonia and nitrite had been completely removed, and the concentration of nitrate was reduced to 8.58 mg N/L with initial nitrate, ammonia, and nitrite concentrations of 50.00, 10.00 and 5.00 mg N/L, respectively. Cyclic voltammetry (CV) and potentiostatic electrolysis revealed that the electrode surface reaction process, that is, nitrate, ammonia, and nitrite in the system, could be converted into nitrogen via ClO− generated from Cl− produced from the electrochlorination process during multiple cycle attenuation. Moreover, both CV and Density functional theory (DFT) calculations revealed the inhibitory effect of coexisting ammonia and nitrite on the electrochemical reduction of nitrate on the Cu cathode. This strategy opens a paradigm for the simultaneous efficient electrocatalytic removal of nitrate, nitrite, and ammonia in an undivided single reactor.