Nitrate Electrochemical Reduction Process Using Bipolar Metal Particles For Groundwater Remediation

Groundwater is an important and precious resource in the world, playing a vital role in the human’s living and production. With the rapid development of economy, excessive human activities cause the nitrate contamination in groundwater, which is an environmental issue of common concern all over the world. Nitrate contamination in groundwater is mainly due to the excessive use of nitrogen fertilizer, domestic and industrial wastewater discharge, sewage irrigation, and solid waste leachate infiltration. High levels of nitrate in groundwater poses a potential threat to human’s health. Thus, it’s curial to remove nitrate from groundwater to meet standards. Electrochemical reduction of nitrate has attracted the extensive attention due to its short cycle of treatment, environmental friendlessness, and low investment cost. Nevertheless, promotions and applications of electrochemical process are limited by high energy consumption and low capacity.This study was based on the electrochemical reduction of nitrate in groundwater, we added metal particles into a conventional electrochemical system using Ti cathode and Ti/Ir O2-Pt anode to develop an electrochemical process intensified by bipolar metal particles. The study aims to assess the influence of Na Cl dosage, current density, and metal particles materials on the developed system to determine the optimum operating condition, and then reveal the mechanism of bipolar metal particles and verify the intensification by comparing the difference of system performance with different configurations of metal particles. In addition, the mechanism of the developed system for nitrate removal was also further discussed so as to provide theoretical foundation for applications of electrochemical process intensified by bipolar metal particles for groundwater remediation. A Na Cl dosage of 0.5 g/L and a current density of 20 m A/cm2 were determined as the optimum operating condition, and Cu-Zn metal particles were the optimum packing material. Under this condition, nitrate removal efficiency reached 93.94% with the nitrogen selectivity of 80.43% and energy consumption was 58.60 k Wh/n-NO3--N. Meanwhile, nitrate removal rate increase by 62.36%~78.9% and the energy consumption reduce 3 ~ 5 times. By comparing systems performance with different configurations of metal particles, we got the conclusion that metal particles were polarized and worked as many individual electrochemical cell with reduction on the cathodic pole and simultaneous oxidation on the anodic pole. And thus, more active surface for nitrate removal was provided to increase the nitrate removal rate and current efficiency effectively as well as decrease energy consumption, which intensified the electrochemical system. Simultaneously, nitrate reduction and by-product oxidation occurred at the cathode and anode respectively.