Preparation Of Modified Lead Dioxide Electrode And Electrocatalytic Degradation Of Benzoquinone

In recent years,environmental pollution problem has become increasingly serious,and the problem of water pollution is particularly prominent.Electrocatalytic oxidation is widely used in the treatment of refractory organic wastewater because of its good environmental compatibility,low secondary pollution,high processing efficiency,easy operation,and easy automation.The key of electrocatalytic oxidation is obviously the availability of electrode materials with good stability,high catalytic activity,and low cost.good electrical conductivity,corrosion inhibition,high oxygen evolution over-potential and strong oxidation capacity.However,the PbO₂ electrode exhibits brittleness during use,and the active layer has low adhesion,easy to fall off,and poor stability.For this reason,the Ti/PbO₂ electrode was prepared by replacing the planar titanium substrate with porous titanium,and the Pb-TiO_xNWs intermediate layer was prepared in the porous Ti by ion substitution and followed calcination process.,and the Ti/Pb-TiO_xNWs/PbO₂ electrode was prepared by electrodeposition.The electrode stability and catalytic activity were evaluated by accelerated life test and simulated wastewater degradation test.The cause of electrode failure was estimated by analyzing the surface and profile of the electrode after failure.In addition,in view of the high toxicity of benzoquinone,its difficulty in electro-oxidative degradation and low current efficiency,this paper studied the effects of different inorganic salt electrolytes on electrocatalytic degradation of benzoquinone simulated wastewater,and determined the optimum process conditions for benzoquinone degradation.At the same time,the intermediate products of degraded benzoquinone wastewater were analyzed.The main conclusions of the paper are as follows:?1?The morphology and crystal structure of pl-Ti matrix PbO₂ coating electrode and po-Ti matrix PbO₂ coating electrode were compared by SEM and XRD.The PbO₂electrode with po-Ti as matrix was compared with pl-Ti/PbO₂ electrode.The particles are more refined,the surface is denser,and the edges and vertices are more pronounced.?2?Electrochemical anodic polarization curves,cyclic voltammetry curves,AC impedance spectroscopy and other analytical tests were carried out,as well as electrocatalytic degradation of benzoquinone and accelerated life testing.The electrochemical properties,catalytic activity and stability of the electrodes were characterized.The results show that the accelerated lifetimes of pl-Ti/PbO₂,po-Ti/PbO₂,po-Ti/TiO₂NWs/PbO₂ and po-Ti/Pb-TiO_xNWs/PbO₂ are 12h,14h,19h and25h,respectively.The lifetime of the po-Ti/Pb-TiO_xNWs/PbO₂ electrode is twice that of pl-Ti/PbO₂.Compared with the other three electrodes,the po-Ti/Pb-TiO_xNWs/PbO₂electrode with Pb-TiO_xNWs composite intermediate layer is oxygenated.The overpotential was higher,reaching 2.19V;the electrocatalytic degradation of 3h benzoquinone COD had the best removal rate of 53.8%,and the oxygen evolution resistance?21.59?·cm²?and oxide film resistance?485.8?·cm²?were the smallest.By analyzing the phase and profile of the surface of the electrode after failure,it is found that the surface of the electrode has a strong characteristic peak of titanium dioxide after the failure,the active layer dissolves and falls off,and the substrate may leak out locally.It is known that the main cause of electrode failure is the dissolution of the active layer and passivation of the substrate.?3?The effects of different types of intermediate layers on the stability of PbO₂electrodes were investigated.The results show that the accelerated lifetimes of po-Ti/MnO₂/PbO₂,po-Ti/?-PbO₂/PbO₂ and po-Ti/Pb-TiO_x NWs/PbO₂ electrodes are17h,22h and 25h,respectively,indicating po-Ti/Pb-TiO_xNWs/PbO₂ electrode has better stability.?4?In the process of electrocatalytic degradation of benzoquinone wastewater,the inorganic salts contained in the wastewater solution have an important effect on the electro-oxidative degradation of benzoquinone.Compared with sulfates,nitrates and fluorides,NaCl can significantly promote the removal of benzoquinone and COD.The effects of chloride ion concentration,electrolysis temperature,current density,initial pH value and chloride ion dosing method on COD removal rate and active chlorine content of benzoquinone simulated wastewater were investigated.It was found that the degradation of benzoquinone is very sensitive to chloride ions,and the presence of a small amount of chloride ions can cause a significant increase in oxidation efficiency.The higher the chloride ion concentration,the higher the COD removal rate of the benzoquinone simulated wastewater.However,when the chloride ion concentration is higher than 0.3mol/L,the COD removal rate decreases.The acidity and alkalinity of the solution has a great influence on the electro-oxidation treatment of chloride-containing organic wastewater.The weak alkaline environment with pH 8 is more favorable for the electro-oxidative degradation of chlorine-containing benzoquinone wastewater.Increasing the current density increases the COD removal rate;however,increasing the temperature decreases the COD removal rate;the larger the initial concentration of benzoquinone,the lower the energy consumption per unit of COD removal.Chloride ion dosing has little effect on the COD removal of benzoquinone.Under the conditions of pH 8,NaCl concentration of 0.3 mol/L,current density of 10 mA/cm² and temperature of 20°C,the initial concentration of 100 mg/L benzoquinone was degraded by electrochemical oxidation for 3 h.The COD removal rate can reach 80.9%.The intermediate products of electrooxidation degradation of benzoquinones were analyzed by high performance liquid chromatography?HPLC?.It was found that the degradation rate of benzoquinones increased significantly in the presence of chloride ions.Benzoquinone oxidative degradation pathway:the main intermediate products of benzoquinone oxidation ring opening are paramene dicarboxylic acid and antibutene dicarboxylic acid,and finally form carbon dioxide and water.