Preparation Of MnO₂/Graphite Composite Base Electrode And Study On The Properties Of Electrocatalytic Oxidation Of Phenol

Phenol containing wastewater is one of the typical representative of industrial wastewater,which contains phenol and phenols’derivatives will cause serious harm to the environment.Electrochemical oxidation is a commonly used advanced oxidation technology,with the advantages of simple operation,strong flexibility and strong functionality,which has attracted the attention of many water treatment workers.How to reduce the cost and improve the activity of electrode materials is the key of electrocatalytic water treatment technology.GP/PVDF electrode,MnO₂-GP/PVDF electrode and MnO₂@GP/PVDF electrode were prepared by combined method.The physical and electrochemical properties of the electrodes were characterized by XRD,SEM,CV,Tafel and polarization curves.XRD results show that the two kinds of nano MnO₂ areα-type.SEM observation showed that the graphite powder showed lamellar structure,nano MnO₂ in MnO₂-GP/PVDF electrode was rod-shaped stacking arrangement,nano MnO₂ dispersed on the surface of graphite or between graphite flakes,and the composite of low impedance binder improved the overall conductivity.The results show that nano MnO₂ in MnO₂@GP/PVDF electrode has more uniform distribution on the surface of graphite powder,better particle formability,closer combination with graphite powder,and more effective protection of electrode material.Through electrochemical characterization,it was found that the potential of phenol oxidation peak in CV Curve of MnO₂@GP/PVDF electrode was the highest,which was 0.97 V;Tafel curve showed that MnO₂@GP/PVDF electrode had the best corrosion resistance;In general,the performance of MnO₂@GP/PVDF electrode is better than the other two electrodes.Finally,the UV scanning analysis of the intermediate products in the process of phenol degradation proved that phenol was converted into benzoquinone first and then ring opening reaction took place.The effects of MnO₂ content,temperature,pH value,voltage,electrolyte concentration and initial phenol concentration on phenol degradation rate and current density were investigated.Under the same conditions,the degradation rate of phenol was 48.5 wt%at GP/PVDF electrode for 3 h,79.1 wt%at MnO₂-GP/PVDF electrode and 80.0 wt%at MnO₂@GP/PVDF electrode.In the service life of electrode,MnO₂@GP/PVDF electrode>MnO₂-GP/PVDF electrode>GP/PVDF electrode。Under different experimental conditions,the coulomb efficiency of GP/PVDF electrode for electrochemical oxidation of phenol is mostly in the range of 15%～30%;the coulomb efficiency of MnO₂-GP/PVDF electrode and MnO₂@GP/PVDF electrode modified by catalyst is mostly in the range of 25%～45%.The electrochemical oxidation of phenol by GP/PVDF electrode conforms to the second-order kinetic model,the rate constants k of GP/PVDF electrode was 3×10^-4 L·（mg·min）^-1;MnO₂-GP/PVDF electrode and MnO₂@GP/PVDF electrode are in accordance with the first-order kinetic model,the rate constants k of MnO₂-GP/PVDF electrode and MnO₂@GP/PVDF electrode were 8.4×10^-3 min^-1 and 8.9×10^-3 min^-1,respectively.