| With the development of industrialization,the problem of water pollution caused by the arbitrary discharge of organic matter has brought potential harm to the living environment and health of human beings.Because of the variety of pollutants,the traditional treatment of water pollution has been unable to be efficient.Therefore,we focused on the heterogeneous photo-Fenton degradation method,that is,the photocatalyst can generate electron hole pair under the light condition,and react with hydrogen peroxide and oxygen respectively to generate strong oxidizing substances,hydroxyl radicals and superoxide anions,and further degrade the organic pollutants,so that the final products are carbon dioxide and water,achieving complete mineralization objective.Due to the semiconductor characteristics of iron oxide,it has good photocatalytic performance,stable chemical properties,and good ferromagnetism,which can be recycled and used to improve its efficiency.Therefore,cobalt ferrite is selected as the substrate and different types of organic semiconductor materials are loaded on it,so as to further improve the catalytic performance and chemical stability of the intrinsic semiconductor and the catalytic ability of photocatalyst.The organic semiconductors selected in this paper are polyaniline,polypyrrole and carbon nitride.(1)Firstly,polyaniline was grown on cobalt ferrite by in-situ Fenton dissolution polymerization,and the core-shell structure with cobalt ferrite as the core was formed.The effects of hydrochloric acid concentration,hydrogen peroxide concentration and aniline concentration on the catalytic ability of the catalyst were investigated by changing the reaction conditions.The results showed that when the amount of H2O2 and HCl was 2 m L and1 m L respectively,the ratio of CoFe2O4 to aniline was 1:2,the catalytic ability of the catalyst can achieve the best.However,CoFe2O4@PANI synthesized by this method has weak binding ability.After ultrasonic stirring and other processes,PANI falls off to some extent,resulting in poor photocatalytic stability.After five cycles,the optical Fenton efficiency is only 66%.(2)In order to improve the stability of optical Fenton performance,we replaced the above-mentioned organic semiconductor PANI with PPy,using the same synthesis method tocoat polypyrrole on the outer layer of cobalt ferrite to form a uniform and stable core-shell structure.The composite material has the characteristics of cobalt ferrite and polypyrrole.It can generates photogenerated electrons under light conditions.The presence of polypyrrole improves the electron migration efficiency,while effectively preventing the dissolution of metal ions,achieving the purpose of high efficiency and environmental protection.A large number of repeated experiments prove that CoFe2O4@PPy has stable chemical properties and can degrade many organic pollutants.After two hours of photo-Fenton,5 mg/L of rhodamine B can be completely degraded.After five cycles,the degradation efficiency of CoFe2O4@PPy is still maintained at about 90%.This is due to the synergistic effect of cobalt ferrite and polypyrrole.CoFe2O4 takes full advantage of the electron-rich and multiple redox balance characteristics of PPy to enhance photo-Fenton activity by promoting electron transfer.(3)We also synthesized a composite of carbon nitride and iron oxide for photocatalysis.The urea is heated at high temperature to produce lamellar carbon nitride,and then the precursor of cobalt ferrite is added to mix with carbon nitride.By adjusting p H,it is deposited on urea and then dried and calcined.The iron oxide generated grows on carbon nitride,in which the iron oxide is cobalt ferrite and iron oxide,which is caused by the difference of KSP between iron and cobalt.The composite prepared by this method is simple,highly efficient and magnetic.After two hours of visible light irradiation,the organic compounds can be mineralized completely,and its stability is very high.The efficiency of five cycles test is as high as 98%.Compared with CoFe2O4@PANI and CoFe2O4@PPy,Fe2O3/CoFe2O4@g-C3N4 only needs to be irradiated with visible light to complete the photodegradation process of organic dyes,saving the use of photo-Fenton reagents and ensuring thoroughness and stability of the photodegradation process. |