Efficient removal of ammonia nitrogen via a coupled system of Ni1Cu0.2-Se-T/CP anode and copper foam cathode

Abstract

Direct electrochemical oxidation is a green, clean and promising process for the treatment of ammonia nitrogen (NH4+-N) wastewater. Nevertheless, drawbacks of slow reaction kinetics and large overpotential greatly limit the ammonia oxidation reaction. To address the issue, Ni1Cu0.2-Se-T/CP was synthesized by the combination of heteroatom doping and in situ electrochemical oxidation (ISEO). Physical characterization shows that there are homogeneous and dense microscopic nanosphere particles on the electrode surface, which provide good attachment sites for the adsorption of reactants. Electrochemical tests further show that this catalytic electrode exhibits not only a high current density (37.17 mA·cm−2) at 0.65 V vs.Hg/HgO but also has the low Tafel slope (92.25 mV·dec−1) to ammonia oxidation reaction. Then, Ni1Cu0.2-Se-T/CP was applied as anode with copper as cathode to construct a coupled system. The area ratio of cathode/anode was optimized to improve the removal effect of ammonia nitrogen. The NH4+-N conversion efficiency of 100% was obtained at a constant anode potential of 0.65 V vs.Hg/HgO for 15 h when the cathode/anode area was 1:4. The system N2 selectivity up to 77.55%. This work provides a promising process for the green and efficient degradation of ammonia nitrogen wastewater.