Preparation Of Carbon-based Copper-nickel Bimetallic Three-dimensional Composite Electrode And Its Treatment Of Typical Nitrogen-containing Compounds In Water

With the rapid development of industry and agriculture,a large number of nitrogen-containing wastewater was released into the environment,so that the nitrogen content in a variety of water bodies continues to rise,which seriously destroyed the natural cycle of nitrogen,causing serious harm to human beings and the environment.Among nitrogen compounds,nitrate is one of the common inorganic nitrogen compounds,due to the use of nitrogen fertilizer,nitrogen emissions of industrial wastewater and domestic sewage of arbitrary emissions of human activity,which is discharged into the environment in large quantities.Nitrobenzene is one of the common organic nitrogenous compounds,which is an important raw material for the synthesis of polymers,dyes,drugs,pesticides,explosives,herbicides and synthetic rubber.It is widely used in industrial production.Electrocatalytic treatment technology has received extensive attention and research in recent years due to its advantages of high reaction efficiency,no dosage of agents and no secondary pollution.With the development of the power industry,the application prospect and market value of this technology are also continuously improving.In this paper,a new Cu-Ni bimetallic three-dimensional composite electrode Cu-Ni/G-GF was successfully prepared by electrodeposition method to treat typical compounds of nitrate and nitrobenzene,as well as organic practical waste water with high salt and high nitrogen content.The main research conclusions are as follows:（1）A new Cu-Ni/G-GF three-dimensional composite electrode was prepared by electrodeposition of graphene and Cu-Ni bimetallic on the surface of graphite felt,which was a three-dimensional carbon material.Through SEM/EDS,XRD,XPS,Raman and other characterization techniques,the graphene and Cu-Ni bimetallic are successfully loaded on the electrode surface,and the bimetallic Cu-Ni exists in the form of zero valence state.The excellent electrochemical performance of the electrode was proved by condition optimization and electrochemical characterization.（2）Cu-Ni/G-GF electrode was used to electrocatalyze the reduction of nitrate,When the reaction time is 3 h and the current is 10 m A/cm²,the nitrate removal rate is93%and the reaction rate is 0.014 min^-1,the electrocatalytic reduction of nitrate conforms to the quasi-first-order reaction kinetics.The effect of Cu-Ni/G-GF electrode on electrocatalytic reduction of nitrate is significantly better than that of GF,G-GF and Cu-Ni/GF electrodes.The loading of graphene and Cu-Ni metal can enhance the reactivity,improve the mass transfer capacity of electrode and reduce the electrode impedance.The reduction products of nitrate include nitrogen,ammonia nitrogen and nitrite,etc.,Cl^-has a great effect on the reduction products of nitrate at Cu-Ni/G-GF electrode,and can further improve the selectivity of nitrogen.The total nitrogen removal rate reaches 97%after 3 h under the condition of 10 m A/cm² and 5 g/L Na Cl.According to theoretical calculation,nitrogen atoms in Na NO₃ are vulnerable to attack by active species,that is,nitrogen atoms are vulnerable to attack by reducing hydrogen[H]and are reduced,thus transforming into ammonia nitrogen,nitrogen,nitrite and other products.The Cu-Ni/G-GF electrode has good stability in the process of nitrate degradation through repeated experiments and electrochemical characterization.（3）Cu-Ni/G-GF electrode was used for electrocatalytic reduction of nitrobenzene.When Cu-Ni/G-GF electrode was electrified for 90 min,the removal rate of nitrobenzene could reach nearly 100%,and the reaction process was in line with the quasi-first-order reaction kinetics,and the reaction rate was 0.034 min^-1.The electrocatalytic reduction of nitrobenzene by Cu-Ni/G-GF electrode is significantly better than that by GF,G-GF and Cu-Ni/GF electrode.The loading of graphene and Cu-Ni metal increases the reactivity,which can improve the mass transfer capacity of the electrode and reduce electrode impedance.Density functional theory calculation shows that in the reduction process,nitrogen atoms in nitro group are vulnerable to attack by active species,that is,they are reduced by attack of reducibility[H],the main product of reduction is aniline.The Cu-Ni/G-GF electrode has been proved to have good stability in the application of nitrobenzene reduction by repeated experiments and electrochemical characterization.（4）Cu-Ni/G-GF electrode was used to electrocatalyze the treatment of organic wastewater with high salt,high nitrogen and high concentration.By comparing three electrocatalytic processes of electrocatalytic reduction-oxidation,electrocatalytic oxidation-reduction,electrocatalytic oxidation-reduction and electrocatalytic oxidation,it is found that the electrocatalytic reduction-oxidation process has a better effect on the removal of actual wastewater.The TOC and COD removal rates of the actual wastewater after 2 hours of reduction and then 2 hours of oxidation are 33%and 42%,respectively,which proves that electrocatalytic reduction is beneficial to the mineralization degradation of organic matter by electrocatalytic oxidation.By comparing the effects of different cathode materials on the treatment of actual wastewater,it is found that the Cu-Ni/G-GF electrode has better performance compared with titanium plate and graphite felt.The reduction effects under different current densities were investigated.When the current density was 40 m A/cm²,the TOC and COD removal rates of the wastewater were 36% and 49%.