Electrocatalytic Reduction Of Nitrate On Cu-Sn-Bi Cathode

With the rapid development of modern industry and agriculture has led to the increasing nitrate pollution in groundwater of the country.As an important source of drinking water,groundwater has caused great harm to human health.Electrocatalytic methode has attracted extensive attention as environmentally friendly technology.However,most of electrodes are expensive for precious metal materials,which limits their applications.Therefore,development an efficient and low-cost electrode material is the current research focus.Multi-metal electrode has good prospect in nitrate treatment because of the interaction between its elements,which can promote nitrate reduction reaction.In this experiment,Cu-Sn-Bi electrode was prepared by electrodeposition method.The main research contents include:?1?Optimizing electrode preparation conditions,effect of the electrodepositiong time,temperature,current density and Bi content on performances of Cu-Sn-Bi electrode were investigated,the optimal electrode preparation conditions were determined and the best electrode was obtained.?2?Using the best electrode as the cathode to degrade nitrate wastewater,the factors of electrocatalytic reduction of nitrate were studied,and the optimal treatment conditions were determined.?3?Through cyclic voltammetry,linear voltammetry test methodes,and combined with the electrocatalytic reduction results of nitrate,the potential and path of nitrate reduction by the Cu-Sn-Bi electrode were preliminarily analyzed.Through the analysis and discussion of the above experimental research results,the following conclusions are obtained:?1?The effects of electrodeposition time,current density,temperature and Bi content on the performance of Cu-Sn-Bi electrodes were significant.The Cu-Sn-Bi electrode prepared by electrodeposition for 30 min at temperature of 35?and current density of 4 mA/cm² had better effect on electrocatalytic reduction of nitrate.Cu-Sn-Bi electrode with Bi content of 9%possessed the high crystallinity and electrochemical stability,the response current decayed slowly with time,the surface area and active sites were large,surface particle size was small,the electrocatalytic activity was high and the nitrate removal effect was the best.?2?Set the preparated Cu-Sn-Bi electrode as cathode,ruthenium iridium electrode as anode,the nitrate simulated wastewater was treated in the effective area 40 cm²,the spacing between electrode was 20 mm,nitrate initial concentration was 100 mg/L,Na₂SO₄ concentration was0.125 mol/L,current density was 6 mA/cm²,the pH was 7,under the condition of electrocatalytic reduction treatment for 5 h,nitrate removal rate was 88.43%,the nitrogen selectivity was 56.20%,the current efficiency was 28.21%,and the energy consumption was0.15 KWh/gNO₃^--N,when concentration of Cl^-was 0.5 g/L,nitrogen selectivity was 75.32%.?3?Electrochemical analysis results showed that the Cu-Sn-Bi electrode undergoed hydrogen evolution reaction at around-1.7 V,and the nitrate reduction reaction occurred before the hydrogen evolution reaction.The potential was about-0.7 V,NO₃^-was adsorbed on the cathode surface.It was reduced to NO₂^-and then further reduced to other products at around-1.5 V.The electrocatalytic reduction reaction of nitrate followed first-order kinetics,and the reduction reaction of nitrate was carried out step by step.The main process was NO₃^-?NO₂^-?N₂?NH₄⁺.