Study On Preparation Of Ti/SnO₂-Sb/La-PbO₂ Electrode And Degradation Mechanism Of Fluconazole Using Low Frequency Ultrasound Assisted Electrocatalytic Oxidation

The production and use of Pharmaceuticals and personal care products is increasing.They are frequently detected in the environments and their detected concentration is constantly increasing.This will pose a serious threat to human life and health and the natural eological environment.Antimicrobial drug fluconazole is highly toxic and difficult to biodegrade.Currently,degradation methods for this kind of drug are limited.To solve the above problems,this paper used Ti/SnO₂-Sb/PbO₂ anode was prepared in this study and the low frequency ultrasonic assisted electrocatalytic oxidation mechanism of fluconazole in water was studied.The main research contents and results of this paper are as follows:（1）Ti/SnO₂-Sb/PbO₂ electrodes were prepared by sol-gel method and electrothermal deposition,and modified by adding La（NO₃）₃ into electrodeposition solution.The results showed that lanthanum was successfully incorporated into PbO₂layer,and the grain size on the electrode surface was smaller and more compact and ordered.The electrochemical test results showed that doped lanthanum into PbO₂ layer could enhance the electron transfer ability between electrode and solution,improve the oxygen evolution potential and reduce the charge transfer resistance.When 3 g/L La（NO₃）₃ was added into the electrodeposition solution,the degradation performance of Ti/SnO₂-Sb/La-PbO₂ electrode was the best,and the degradation kinetic constant(k=0.196 min^-1)was improved by 115.3%compared with Ti/SnO₂-Sb/PbO₂ electrode(k=0.091 min^-1).（2）Low-frequency ultrasound could effectively enhance the mass transfer efficiency of pollutants,·OH yield and electron transfer ability on anode surface during electrocatalysis oxidation process.The degradation kinetic constant of fluconazole increased from 0.134 min^-1 to 0.180 min^-1,the degradation kinetic constant was increased by 34.3%,and the degradation energy consumption decreased by 29.03%.When the ultrasonic power increased from 26 W to 130 W,the electron transfer ability and mass transfer efficiency of pollutants on the anode surface were effectively enhanced,the degradation kinetic constant of fluconazole was increased by 42.68%,and the degradation energy consumption was reduced by 35.06%.When the current density increases from 2 m A/cm² to 20 m A/cm²,the·OH yield can be improved effectively and some pollutants can be oxidized directly at the anode,and the degradation kinetic constant of fluconazole was increased by 24 times.Increasing the initial concentration of fluconazole would produce more intermediates competing with Fluconazole for·OH,and the initial concentration of fluconazole was inversely related to its degradation efficiency.Increasing the initial concentration of Na₂SO₄ can improve the solution conductivity and effectively reduce the anode potential.（3）·OH is the main active oxidizing substance for fluconazole degradation,The contribution ratios of·OH to fluconazole degradation were 85.71%and 82.45%,respectively,and the yields of·OH were 19.70 mmol/（L·min·m²）and 35.84mmol/（L·min·m²）,respectively,in the electrocatalytic and ultrasond-electrocatalytic systems.The·OH yield of electrocatalytic system was increased by 81.93%with the help of low-frequency ultrasound and the mineralization kinetic constant was increased by 29.03%.The main degradation processes of fluconazole are bond breaking,defluorination,cyclization and oxidation.In the degradation process,intermediate products such as TP302,TP284,TP268,TP224,TP152,TP85,TP83 and TP69 are generated,and finally oxidation into small molecular products such as oxalic acid,formic acid,NO₃^-and F^-.