Efficient ammonia removal promoted in a bifunctional system constructed with NiCu–S/DSA electrodes

Currently, the treatment of ammonia in wastewater, one of the main causes of eutrophication in water bodies, has received widespread attention. In this work, a novel electrocatalytic bifunctional system was constructed to achieve efficient degradation of ammonia. It consists of Ni₁Cu_0.25-S/DSA electrodes with both anode and cathode, which is prepared by a combination of electrodeposition and electrochemical tuning strategies. The crystalline phases and oxidation states of the nano-textured particulate metal oxides were determined by using a series of physical characterizations. The Ni₁Cu_0.25-S/DSA electrode with the best electrocatalytic performance was screened by electrochemical analysis, which has good stability and reliability when processing ammonia nitrogen. The efficiency of electrodes for ammonia removal was verified by running denitrification of synthetic and real wastewater. The results showed that the NH₄⁺-N removal efficiency could approach up to 99%. Kinetically, compared with the monofunctional system, the bifunctional system obtained a higher NH₄⁺-N degradation rate of 45.5 mg L⁻¹ h⁻¹, increased the rate of N₂ generation by more than 10 times, and reduced the rate of NO₃⁻-N and NO₂⁻-N generation by one-third on average. The possible reaction mechanism of anodic ammonia oxidation and cathodic nitrate reduction in the bifunctional system was proposed.