Degradation Of Tetracycline Hydrochloride And Sulfamethoxazole In Water By Photocatalytic Activation Of Persulfate With ZnFe₂O₄-Based Materials

The extensive use of antibiotics has caused inestimable impact on water environment worldwide,so it is of great significance to develop economical and effective antibiotic treatment technology.Advanced oxidation technology has been proved to be effective in the treatment of various organic wastewater.In this context,the use of photocatalysis in conjunction with the advanced oxidation technology of persulfate can promote the formation of active free radical,further promoting the degradation of pollutants.Due to its simple chemical composition,high catalytic activity,stable structure and easy recovery,ZnFe₂O₄is often used to activate persulfate to degrade organic pollutants in water environment.However,ZnFe₂O₄catalyst has limited active sites,fast photogenerated charge recombination rate and low Fe（Ⅲ）/Fe（Ⅱ）conversion efficiency,which limit its further application in wastewater treatment.In this paper,a series of ZnFe₂O₄-based catalysts were prepared to study the performance and mechanism of catalyst activated persulfate to degrade antibiotics,and the structure-activity relationship between the improvement of catalytic performance and its physicochemical properties was discussed.The research work is mainly divided into the following three aspects:（1）ZnFe₂O₄（ZFO_V）with oxygen vacancy was prepared by simple heat treatment and applied to the degradation of tetracycline hydrochloride（TCH）by photoactivated perdisulfate（PDS）.It was found that ZFO_V/PDS/vis system had the best degradation performance for TCH,which was 1.23 times that of ZFO/PDS/vis system.Free radical capture experiments and EPR tests showed that e^-,h⁺,^·OH and^·O₂^-were involved in the degradation of TCH by ZFO_Vphotoactivation.On the one hand,the introduction of oxygen vacancy can improve the absorption of visible light and promote the separation of photogenerated electron holes;on the other hand,it can accelerate the redox of Fe（Ⅱ）/Fe（Ⅲ）through electron transfer,thus promoting the formation of^·OH and SO₄^·-.In addition,the effects of initial p H value,PDS concentration,humic acid,anions and cations on the degradation of TCH by ZFO_V/PDS/vis system were investigated,and the intermediates in the degradation process of TCH were determined by HPLC-MS,and the possible degradation pathways and mechanisms were proposed.（2）Cu-doped ZnFe₂O₄（ZFCO-X）was synthesized by a simple hydrothermal method and applied to photoactivated permonosulfate（PMS）to degrade the antibiotic sulfamethoxazole（SMX）.The experimental results showed that Cu doping significantly improved the catalytic activity of ZFO,and CZFO-12.5 showed the best catalytic performance in the degradation of SMX,and the degradation rate of 30 mg/L SMX reached77%within 30 min.The electrochemical test showed that Cu doping can improve the electron transfer efficiency and promote CZFO-12.5 photoactivation of PMS to generate active free radicals.In addition,the degradation mechanism of SMX by ZFCO-12.5photoactivated PMS was proposed through characterization tests and free radical capture experiments.（3）A novel PMS-based advanced oxidation system with Cu doped ZnFe₂O₄（ZFCO-12.5）as catalyst and hydroxylamine（HA）as reducing agent was constructed and used in photoactivated PMS to degrade the antibiotic sulfamethoxazole（SMX）.Experiments showed that the introduction of HA significantly improved the degradation efficiency of ZFCO-12.5photoactivated PMS on SMX.CZFO-12.5/PMS/HA/vis degradation rate of 50 mg/L SMX reached 88.1%within 40 min.In addition,the effects of initial p H value,pollutant concentration,humic acid concentration,anion and other factors on degradation performance were systematically discussed.And through the cycle experiment,ZFCO-12.5 has good reusability and stability.