Study Of NiCu/DSA Composite Electrode Construction And Denitrification Performance For Electrochemical Oxidation Of Ammonia Nitrogen

Currently,as one of the main causes of water eutrophication,ammonia nitrogen treatment in wastewater has received wide attention.Based on the characteristics of efficient and clean electrochemical oxidation method with little secondary pollution,this paper constructs Ni Cu/DSA composite electrode for ammonia nitrogen electrochemical oxidation and proposes a novel electrocatalytic bifunctional coupling system that uses the composite electrode as both cathode and anode.The indicators of NH₄⁺-N removal efficiency,N₂ selectivity,NO₃^--N generation efficiency,NO₂^--N generation efficiency,TN removal efficiency,Faraday efficiency,energy consumption and kinetics were investigated.The physical characterization,electrochemical characterization,denitrification performance and factors influencing the electrochemical oxidation of ammonia nitrogen of the catalytic electrode were systematically investigated to achieve efficient degradation of ammonia.The following main conclusions were obtained in this paper:（1）A sulfur-doped Ni Cu-S/DSA catalytic electrode was prepared using a combination of electrodeposition and electrochemical modulation strategies.A bifunctional system of Ni Cu-S/DSA electrode as both anode and cathode was constructed for the first time,aiming to promote the electrochemical ammonia oxidation reaction while inhibiting the peroxidation reaction to suppress the nitrate production.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%,the selectivity of N₂ could reach 68.3%.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.A possible reaction mechanism of anodic AOR and cathodic NO₃^--N reduction in the bifunctional system was proposed.（2）The Ni₁Cu_0.25-F/DSA catalytic electrode was prepared by electrodeposition and fluorination strategy,and was also used as a cathode to construct a bifunctional coupling system,aiming to facilitate the simultaneous removal of ammonia,nitrate and nitrite nitrogen from the actual wastewater.The optimal conditions for the preparation of Ni₁Cu_0.25-F/DSA electrode were screened,which exhibited excellent catalytic performance for AOR.Physical characterization analysis revealed the successful synthesis of Ni₁Cu_0.25-F/DSA electrode with porous sponge-like structure,converting the pristine metal fluoride to highly porous and amorphous metal oxide during alkaline electrochemical conditioning.The catalytic effect of Ni₁Cu_0.25-F/DSA cathode and anode was analyzed by electrochemical tests:strong ammonia oxidation effect existed at the anode and some nitrate reduction effect existed at the cathode.CV,i-t tests,and SEM characterization before and after denitrification showed that the electrode had superior stability.In the Ni₁Cu_0.25-F/DSA||Ni₁Cu_0.25-F/DSA bifunctional coupled system,the effects of potential between cathode and anode,initial p H and initial ammonia nitrogen concentration on the system were explored.The system was operated continuously in a large300 ml apparatus under the optimal conditions screened,with a more satisfactory denitrification effect,and the Ni₁Cu_0.25-F/DSA electrode was verified to be highly reusable.