Electrocatalytic Degradation Of Methylene Blue By Modified Lead Dioxide Electrode

With the development of global industry,the discharge of various refractory wastewater is increasing,including dye wastewater.Conventional treatment methods such as adsorption,chemical oxidation and biological treatment have some limitations on dye wastewater treatment.Electrocatalytic oxidation has attracted much attention because of its high oxidation performance and no secondary pollution,and anode materials are the key factors that affect the remove efficiency of organic pollutants.Although Ti/Pb O₂ electrode has the advantages of low cost,ease of preparation and high oxygen evolution potential,it also has the problem of poor catalytic performance and stability.In this study,a novel modified Ti/Pb O₂ electrode was prepared,the performance of modified electrode was analyzed by various ways,and the degradation of methylene blue（MB）dye wastewater was studied by the modified electrode.The main parts were as follows:（1）The modified PbO₂ electrode co-doped with Bi and Ce elements were prepared by electrodeposition technique,and the doping ratio was determined.The fluorescence spectrum showed that the Blue-Bi/Ce-Pb O₂electrode has stronger capability of hydroxyl radical（·OH）generation than other electrodes.Scanning electron microscopy（SEM）observed that the Blue-Bi/Ce-Pb O₂ electrode had a dense surface structure.The β-PbO₂crystal phase was detected by X-ray Diffraction（XRD）,and the Blue-Bi/Ce-Pb O₂ electrode had the smallest crystal size calculated by Scherrer formula.X-ray photoelectron spectroscopy（XPS）confirmed that Bi and Ce elements had been successfully doped into the Blue-Bi/Ce-Pb O₂electrode.Cyclic voltammetry（CV）and voltammetric charge analysis showed that the Blue-Bi/Ce-Pb O₂ electrode had higher oxidation peak response current（0.088 A）and larger electrochemical activity surface area,respectively.The linear sweep voltammetry（LSV）showed that the oxygen evolution potential of doped Pb O₂ electrode was higher than that of undoped electrode.The electrochemical impedance spectroscopy（EIS）curves and equivalent fitting circuit indicated that the charge transfer resistance of Blue-Bi/Ce-Pb O₂ electrode was the smallest（13.58Ω/cm²）.The accelerated service life of Blue-Bi/Ce-Pb O₂ electrode was 1.3,1.5,1.7and 5.7 times that of Ti O₂-Bi/Ce-Pb O₂,Blue-Bi-Pb O₂,Blue-Ce-Pb O₂ and Blue-Pb O₂ electrodes,respectively.（2）MB was degraded by Blue-Bi/Ce-Pb O₂ electrode,the effects of different factors on the removal efficiency and degradation kinetics of MB were systematically analyzed.The degradation conditions were optimized by response surface methodology.Under the optimized conditions:the current density was 29 m A/cm²,the electrolyte concentration was 0.14mol/L,the distance between the electrodes was 2.0 cm,the removal efficiency of 100 mg/L MB was 96.5%,the instantaneous current efficiency（ICE）was 7.68%and the energy consumption（EC）was 0.21k Wh/mg COD after 60 min degradation.The Blue-Bi/Ce-Pb O₂ electrode can remove more than 90%of MB after 15 times reused,and the XRD patterns showed that the crystal structure of the electrode had not changed,indicating that the electrode had good re-usability.The dissolution concentration of Pb ions was much lower than 0.01 mg/L.（3）The radical trapping test results demonstrated that ·OH was the dominant active substance in the reaction system.Ultraviolet-visible（UV-Vis）absorption spectrum showed that the molecular structure of MB was constantly destroyed in the process of degradation.The degradation intermediates of MB were analyzed by high performance liquid chromatography-mass spectrometry（HPLC-MS）,and a hypothetical degradation pathway was proposed.