Study On The Photocatalytic Degradation Of Antibiotics By ZnIn₂S₄ Modified By Conductive Polymers Under Visible Light

With the overall improvement of residents'medical standards,the mass use of drugs,especially antibiotics,results in residual antibiotic pollutants in the water environment in our country.The antibiotic wastewater has complex components and poor biodegradability.Meanwhile,the abuse of antibiotics in China is prominent,which leads to the problem of antibiotic resistance andfurther promotes the increase of the use of antibiotics.Photocatalytic technology has some advantages in many methods of treating antibiotics,among which the ternary catalyst ZnIn₂S₄ has the advantages of good visible light response,simple preparation method,high catalytic efficiency and so on.However,the photocatalytic degradation ability of ZnIn₂S₄ on antibiotic wastewater still needs to be improved.The modification of the photocatalyst can effectively improve the photocatalytic efficiency.The conductive polymer has been widely studied for the modification of photocatalystbecause of its flexible and tunable properties,whichcan be used as effective electron donor,electron transmitter and hole acceptorreceptor and transporter.In this study,polypyrrole?PPy?and 3,4-polyethylenedoxythiophene?PEDOT?were used to modify ZnIn₂S₄ in order to improve its ability to degrade antibiotic wastewater.In this paper,chloramphenicol and tetracycline hydrochloride were used as the targeted antibiotic pollutants.The conductivepolymer modified composite photocatalyst was prepared by hydrothermal method and the catalyst was characterized by SEM?XRD?TEM?BET?FT-IR?UV-vis?PL?XPS?EDS?EPR and so on.The photocatalytic degradation of chloramphenicol and tetracycline hydrochloride was investigated in a self-made reactor.The results showed that the photocatalytic removal rate and TOC removal rate of methylene blue and chloramphenicol by 4%PPy-Zn In₂S₄ under visible light were higher than that of pure ZnIn₂S₄,the removal rate of TOC is more than doubled.The characterization analysis showed that the crystal structure of the catalyst changed and the cubic crystal structure appeared.Uv-vis showed that the range of visible light absorption of the composite catalyst was enlarged.The degree of photocatalytic degradation of chloramphenicol was obviously increased over PPy-ZnIn₂S₄ composite photocatalyst,and the final product was decreased.The PEDOT-ZnIn₂S₄ composite photocatalyst was successfully synthesized.The XRD result showed that the crystal form and structure of the catalyst were not changed so much.The DRS analysis showed that the absorption of visible light was increased.The recombination of electron-hole pairs was suppressed,and the separation and transfer of photo-generated electrons and holes was enhanced.The degradation rate of TCH and the removal rate of toc were enhanced by the composite catalyst.The highest TOC removal rate of 56.13%was obtained when the pH of the initial TCH solution was 7.The results of radical scavenging experiments showed that superoxide radicals were the main active species of photocatalytic degradation.