Study On Degradation Mechanism Of Enrofloxacin By Photoelectrocatalysis Based On TiO₂

In recent years,antibiotics have been widely detected in the water environment,and their residual problems and potential hazards have attracted people’s attention.However,the traditional water treatment technology is not effective for the removal of antibiotics.Photocatalysis is a technology that can convert light energy into chemical energy,which can effectively remove refractory organic matter in water environment.Single photocatalysis technology has problems such as low conversion rate of light energy and slow reaction rate,while photocatalysis can reduce photogenerated carrier recombination by introducing external electric field.Thus,photocatalysis can improve energy utilization rate and reaction rate.Furthermore,most catalysts exist in powder form.Powder catalysts are difficult to recycle and reuse after use,which is easy to cause secondary pollution.Catalysts loaded on the certain supports by adhesive is prone to fall off.While unconventional methods have difficulties in operation and high energy consumption.In order to solve aforementioned problems,TiO₂ film was in-situ grown on Ti sheet by anodic oxidation method at a low oxidation voltage.Ti sheet was used as photoanode,and enrofloxacin,a fluoroquinolone antibiotic,was used as the target pollutant.The photocatalytic degradation efficiency,degradation kinetics and degradation path of enrofloxacin by TiO₂photoanode were investigated in this study.The main research results are as follows:（1）Three photoanodes（TiO₂–5 V,TiO₂–10 V and TiO₂–15 V）were prepared by changing the oxidation voltage.The crystal structure,surface morphology,optical absorption band gap,elemental composition and electrochemical performance of TiO₂ photoanodes were characterized by XRD,SEM,UV–Vis DRS,XPS and electrochemical workstation,respectively.The results showed that TiO₂ photoanode mixed with anatase phase and rutile phase had been successfully prepared,and the oxidation voltage played an important role in the surface morphology of TiO₂ photoanode.In addition,the electrochemical performance test showed that the impedance of TiO₂ photoanode gradually increased with the increase of oxidation voltage.（2）The influence factors of TiO₂ photoanode photocatalytic degradation of enrofloxacin were explored.The results showed that TiO₂–15 V had a higher degradation rate of enrofloxacin than TiO₂–5 V,and TiO₂–10 V.The degradation rate of enrofloxacin is 90.74%,and the first-order reaction rate constant is 0.0067 min^–1 at initial concentration of 10 mg/L,applied bias voltage of 1.2 V,supported electrolyte of 0.1 mol/L Na Cl,p H=7,light source of 350 W xenon lamp,and reaction time of 360 min,which is 3.04 times of that of single photocatalysis and 9.57 times of that of single photodegradation.When p H was acidic,the lower initial substrate concentration,the higher the photocatalytic degradation rate of enrofloxacin.There are optimal values for applied bias and electrolyte concentration,and both too high concentration and too low concentration will reduce the degradation rate of enrofloxacin.The repeatability and stability of TiO₂ photoanode are good.After four consecutive uses,there is no significant change in the photocatalytic degradation rate of enrofloxacin,indicating its good application.（3）By adding free radical quencher,it was found that·OH,h⁺and·O₂^–all played roles in the photocatalytic degradation of enrofloxacin,and the contribution to the enrofloxacin degradation was·O₂^–>h⁺>·OH.According to the degradation intermediate products,there may be three pathways for the degradation of enrofloxacin.The main degradation pathway was the oxidation of piperazine groups and the cracking of quinolone parts.