Study On Electrocatalytic Degradation Of Benzoxalone And Vanillin With PbO₂-CeO₂ Composite Electrode

In this paper,PbO₂-CeO₂ composite anode was used as the anode for electrocatalytic degradation of metamitron and vanillin by electrocatalytic oxidation technology,and the changes in degradation time were monitored by UV spectrophotometer,HPLC and HPLC-MS.The main studies are as follows:The PbO₂-CeO₂ composite anode was used to remove the metamitron in an aqueous solution by electrocatalysis.The factors such as the current density,the initial metamitron concentration,the p H value,and the supporting electrolyte concentration were tested for the metamitron degradation experiment.Under different influencing factors,the electrocatalytic degradation of metamitron conforms to the quasi-first-order kinetic model.Under the experimental conditions,with the initial concentration of metamitron decreased,the p H value decreased and the current density increased,the removal rate of metamitron increased.However,with the increase of Na₂SO₄ concentration,the removal rate of metamitron increased first and then decreased.Under the optimal conditions of Na₂SO₄ concentration of 0.2 mol L^-1,metamitron concentration of 45 mg L^-1,current density of 90 m A cm^-2 and p H value of 5.0,the removal rate of metamitron reached 98.99%after electrolysis for 120 min.The key role of hydroxyl radical in the degradation of metamitron was also verified.According to the intermediates of HPLC-MS analysis,13kinds of intermediate products produced in the degradation process of metamitron were identified.According to the relationship between the upstream and downstream substances,the degradation pathway was proposed,and the degradation pathway was divided into two sub-pathways according to the different initial attack sites of hydroxyl radicals on benzidinoxone.PbO₂-CeO₂ composite anode was used to remove the vanillin in the aqueous solution by electrocatalytic oxidation.The effects of current density,initial vanillin concentration and supporting electrolyte concentration on the degradation of vanillin were investigated.The experimental results showed that vanillin in PbO₂-CeO₂ composite electrode on the efficiency of catalytic oxidation is a efficient,conform to the standard first order reaction kinetics model,when the concentration of Na₂SO₄ was 0.1 mol L^-1,vanillin concentration of 30 mg L^-1,current density of 50 m A cm^-2,electrolytic after 120 min of vanillin removal rate reached 98.03%,which was equivalented to completely remove vanillin.Under the experimental conditions of vanillin in electrical catalytic degradation process by HPLC and HPLC-MS analysis of intermediates and the degradation path to explore,9 intermediate products were analyzed based on the mass spectrum;according to hydroxyl free radical of vanillin initial attack position is different,the degradation path is divided into three sub way,finally these small molecular intermediates are electrical catalytic degradation ore into H₂O and CO₂.