Electrochemical Removal Kinetics of Nitrate Ions on Copper from Acidic Medium

Abstract

The electrocatalytic activity of the copper electrode for nitrate electroreduction was performed in acidic medium. The mechanism of the reduction reaction was studied by cyclic voltammetry. One cathodic peak was detected at ca. -0.62 V/SCE, where the charge transfer reaction takes place. The number of electrons involved in the corresponding potential was determined to be eight. The ratedetermining step was concluded to be the reduction of nitrate to nitrogen dioxide. According to further analysis, the reduction reaction of NO 3 on the copper electrode proved to be an irreversible process, with diffusion as its limiting factor. At low concentrations ([NO 3 -]≤0.1 M), nitrate removal follows first-order kinetics, while it approaches zero at high concentrations ([NO 3 -]≥0.1 M). As a result, the adsorption phenomena associated with the nitrate reduction process follow a Langmuir isotherm adsorption with a -5.0 Kj mol -1 adsorption Gibbs free energy. The charge transfer due to nitrate reaction and hydrogen evolution was further verified by EIS measurements at different potentials, where the diffusion of nitrate ions limits the reaction process. Bulk electrolysis results revealed that current density has a significant effect on nitrate removal efficiency, as well as a percentage of nitrate destruction of up to 88% after 2h, indicating the high capacity of copper for nitrate removal.