Eletrochemical Behaviors Of Copper Alloys And Nano-copper Cathode For Electrocatalytic Nitrate Removal

With the industrial development and the widespread use of synthetic fertilizers,there has been increasing concentration of nitrate in water.High concentration of nitrate can seriously impact to animal,plant and human.So nitrate contamination is urgently to resolve.electrocatalytic denitrification is highly efficient,simple to operate,and produces no secondary pollutants.Therefore,application of electrocatalytic denitrification to control nitrate pollution has become increasingly popular.The key to electrocatalytic denitrification is the electrode material.Good electrode materials should have a low cost,high catalytic activity,high stability,and good corrosion resistance.In this work,the electrocatalytic activities of a series of copper alloys and copper nanoparticles toward the reduction of nitrate were investigated.The surface morphology and chemical composition of different electrode materials were analyzed.Moreover,the electrons transfer and nitrate reduction reaction process were confirmed by electrochemical analysis and electrolysis experiments.The electrocatalytic activities of a series of copper alloys,Cu/Ni/Zn(Cu:Ni:Ni=60:15:25 wt%)and Cu/Zn(Cu:Zn=62:38 wt%),toward the reduction of nitrate were investigated,in comparison with that of pure copper.Electrochemical analysis showed that the copper alloy electrode exhibited higher electrochemical reduction rate of nitrate.The nitrate electrochemical reduction reaction is a diffusion-controlled process for this experimental setup,and nitrate is first reduced to nitrite and then to ammonia.The extreme difference(R)between the orthogonal experiments revealed that the NO3--N concentration was the main determinant of the removal percentage,followed by the current density and electrolyte concentration,while the impact of the initial pH was minimal.The conditions of the electrolysis experiments with Cu/Ni/Zn and Cu/Zn cathodes were optimized as follows:a current density of 8 mA/cm2,a NaCl concentration of 2.0 g/L,and an initial pH of 3.0.Under these conditions,the energy consumptions per kilogram of the converted nitrate of the Cu/Zn and Cu/Ni/Zn alloy electrodes were 145.1 and 153.0 kWh/kg of N,respectively.Therefore,copper alloy is a feasible option for practical application to the electrocatalytic reduction of nitrate.A fast and simple electrochemical method was developed to make composite electrodes containing monodispersed copper nanoparticles(Cu NPs)and reduced graphene oxide(rGO)for nitrate removal.The electrocatalytic denitrification with the prepared electrode was analyzed.Bulk electrolysis results showed the percentage of nitrate removal up to 96.8%after 3 h and the reaction rate constant of the Cu/rGO/GP electrode was 14.08,8.00 and 1.94 times higher than those of GP,GO/GP and Cu/GP electrodes,respectively.Further analysis revealed improvements in electron transfer,adsorption of the electroactive species and electrochemically active surface area,which all contributed to the enhancement of electrocatalytic nitrate reduction.Furthermore,the mechanism of nitrate reduction with the Cu/rGO/GP electrode studied in detail by cyclic voltammetry.The voltammogram profile of the Cu/rGO/GP electrode after 50 scanning cycles was similar to that of the initial cycle,and the percentage of nitrate removal was still at 92.4%after the eighth application,demonstrating the high stability of the composite electrode.Taking together,the promising application of graphene-based electrodes with copper nanoparticles in electrocatalytic denitrification for its low price and good performance.