Electrochemical denitrification and kinetics study using Ti/IrO2–TiO2–RuO2 as the anode and Cu/Zn as the cathode

This study investigated the performance of electrochemical denitrification using Ti/IrO2–TiO2–RuO2 as the anode and Cu/Zn as the cathode in an undivided cell. The main product of nitrate reduction of cathode was ammonia and indirect oxidation of the chlorine/hypochlorite took place in anodic area. However, the anode also possessed capacity of direct oxidation. The results of single-factor assay revealed that the optimal current density and NaCl dosage were 15 mA/cm2 and 0.5 g/L, respectively. The model of Exponential Decay 2 can be used to simulate the reaction kinetics of nitrate to nitrogen (R2 > 0.983) at any NaCl dosage and current density. Reaction kinetics of nitrate reduction in cathode can be represented by pseudo first-order kinetics after 100 rounds fitting iterations of Levenberg–Marquardt. Moreover, it was found that the corrosion of cathode was neglectable in acid/neutral condition and Zn was less active than Cu for nitrate removal.

► The dominant oxidation style of Ti/IrO2–TiO2–RuO2 is indirect oxidation.
► High selectivity of nitrogen is obtained in the present NaCl.
► The optimal value of NaCl dosage and current density are recommended.
► Kinetics model combining cathodic reduction and anodic oxidation is presented.
► The highest electrodes efficiency can achieve 0.55 g NO3-–N m−2 A−1 h−1.