Preparation Of Ti/SnO₂-Sb/Ce-GO-PbO₂ Electrode And Its Electro-oxidation Properties Of Phenolic Compounds

Phenolic compounds,as common organic chemical raw materials,are widely present energy and chemical sewage.The"Action Plan for Prevention and Control of Water Pollution"promulgated by China lists phenolic sewage as a class of toxic and harmful water body that needs to be addressed urgently,therefore,phenolic sewage needs to be treated effectively.This sewage is difficult to be degraded,and the treatment ability of biological technology is limited.Electrocatalytic oxidation is considered as an ideal technology for the treatment of phenolic sewage.The efficiency of electrocatalytic oxidation mainly depends on the activity and stability of electrode materials,and the electrocatalytic oxidation mechanism is also different for different pollutants.Therefore,in this thesis,a stable electrode material with high phenolic degradation activity was prapared,and the degradation mechanism of phenolic compounds was explored.Firstly,the traditional lead dioxide electrode was modified by surface doping,and a Ti/SnO₂-Sb/PbO₂ electrode co-doped with rare earth elements cerium（Ce）and graphene oxide（GO）（Ti/SnO₂-Sb/Ce-GO-PbO₂）was prepared by electrodeposition method.Compared with the undoped and the single-doped electrodes,the Ti/SnO₂-Sb/Ce-GO-PbO₂ electrode had stronger electrocatalytic activity and stability.The characterization results showed that after co-doping,the cracks on the electrode surface disappeared,the electrode surface was dense and orderly,and the grains showed a specific growth trend towards the（301）crystal plane.Meanwhile,higher oxygen evolution potential and lower mass transfer resistance were obtained.Compared with the Ti/SnO₂-Sb/PbO₂ electrode,the·OH free radicals generation rate,phenol removal rate and COD removal rate of Ti/SnO₂-Sb/Ce-GO-PbO₂ electrode were increased by 13.6%,15.2%and19.8%,respectively.In addition,the Ti/SnO₂-Sb/Ce-GO-PbO₂ electrode also had excellent working and chemical stability,and long service life.Furthermore,the dissolved concentration of lead ions in the treated solution was less than 0.01 mg/L,which met the allowable lead-containing sewage in discharge standard of surface water in China.Secondly,the highly toxic substance phenol with monocyclic structure and the endocrine disrupting substance bisphenol A with bicyclic structure were selected as two typical phenolic compounds.Ti/SnO₂-Sb/Ce-GO-PbO₂ electrode was used to explore the removal effect and degradation mechanism of phenolic compounds simulated sewage.The optimal process parameters were obtained by single factor experiments,and the removal rates of both substances were above 90%under the optimal condition.The results of radical quenching and capture experiments showed that indirect oxidation was the main way to remove the two substances.Among them,active chlorine and·OH free radicals had important contributions to the removal of phenol,but for bisphenol A,the contribution of active chlorine was much higher than·OH free radicals.Qualitative analysis of the intermediate products showed that the degradation of the two substances was mainly through the process of free radical reaction,ring opening and mineralization.Among them,·OH free radicals were prone to electrophilic substitution on the benzene ring of phenol,while the active chlorine was prone to attack the hydrogen atom on the benzene ring and intermediate structure of bisphenol A.Finally,the Ti/SnO₂-Sb/Ce-GO-PbO₂ electrode was used to inbestigate the degradation performance of actual coking sewage.By combining single factor and response surface experiments,the optimized reaction conditions were obtained:initial p H of 8.7,current density of 23.3m A/cm²,NaCl concentration of 0.09 mol/L and reaction time of 40 min.Under the optimal condition,the average COD removal rate was 71.5%,which was within the 95%confidence interval of the model prediction result.The three-dimensional fluorescence spectrum analysis of the treated solution showed that in addition to phenolic substances,the electrolysis system also had a good treatment effect on refractory organic substances such as humic acid and fulvic acid.The research results of this work enrich the types of high-performance anode materials in the field of electrocatalytic oxidation,and obtain the degradation laws of different phenolic compounds by electrocatalytic oxidation,which can provide basic data and theoretical guidance for the engineering practice of coking and other phenol-containing sewage treatment.