Study On Vis-photocatalytic Degradation Of Imidacloprid Via H₃PW₁₂O₄₀/TiO₂-M?M=CuO,In₂O₃,In₂S₃? And Polyimide

Three series of modified TiO₂/H₃PW₁₂O₄₀ semiconductor composite photocatalysts(Type ?H₃PW₁₂O₄₀/TiO₂-CuO,Type ? H₃PW₁₂O₄₀/TiO₂-In₂O₃,Type ? H₃PW₁₂O₄₀/TiO₂-In₂S₃)were prepared by sol-gel method.PI polymer photocatalysts were prepared by thermal polymerization.The crystal,morphology,composition and optical properties of the photocatalysts were analyzed,respectively.The effects of the ratio of compounds,the calcination temperature and the catalyst dosage on the photocatalytic activity were studied by orthogonal test.The optimal conditions for the preparation of Type ? H₃PW₁₂O₄₀/TiO₂-CuO:30 wt%H₃PW₁₂O₄₀,5 wt%CuO,450?.When the catalyst dosage was 160 mg and the degradation time was 5 h,the photocatalytic degradation efficiency of imidacloprid by H₃PW₁₂O₄₀/TiO₂-CuO was 18.57%and the degradation rate constant was 0.0360 h^-1,.The optimal conditions for the preparation of Type ? H₃PW₁₂O₄₀/TiO₂-In₂O₃:30 wt%H₃PW₁₂O₄₀,5 wt%In₂O₃,450?.Under the catalyst dosage was 180 mg and the degradation time was 5 h,the photocatalytic degradation efficiency of imidacloprid by H₃PW₁₂O₄₀/TiO₂-In₂O₃ was 83.21%and the degradation rate constant was 0.3361 h^-1.The optimal conditions for the preparation of Type ? H₃PW₁₂O₄₀/TiO₂-In₂S₃:20 wt%H₃PW₁₂O₄₀,5 wt%In₂S₃,450?.When the catalyst dosage was 100 mg and the degradation time was 5 h,the photocatalytic degradation efficiency of imidacloprid by H₃PW₁₂O₄₀/TiO₂-Inn2S3 was 82.65%and the degradation rate constant was 0.3483 h--.The effects of the type of precursor,the ratio of precursor,polymerization temperature and catalyst dosage on the photocatalytic activity of polyimide were studied by orthogonal test.The optimal conditions for the preparation of polyimide:Urea-Melem,1:2,290 ?.Under the catalyst dosage was 120 mg and the degradation time was 5 h,the photocatalytic degradation efficiency of imidacloprid by polyimide was 93.87%and the degradation rate constant was 1.1089 h^-1.The mechanism of photocatalysts was studied by constructing the process of photoexcitation and photon excitons transfer and the reactive species trapping experiments.About Type I H₃PW₁₂O₄₀/TiO₂-CuO,in the process of photoexcitation and photon excitons transfer,the photo-generated excitons will focus on CuO simultaneously.Oniy the photogenerated h+ is active species in photocatalytic degradation of imidacloprid by H₃PW₁₂O₄₀/TiO₂-CuO.After the photoexcitation of Type II H₃PW₁₂O₄₀/TiO₂-In₂O₃,the photo-generated excitons will focus on the CB of H₃PW₁₂O₄₀ and the VB of In₂O₃,respectively.In the photocatalytic degradation of imidacloprid by H₃PW₁₂O₄₀/TiO₂-In₂O₃,photogenerated h+ and OH were the main active species.Type ?H₃PW₁₂O₄₀/TiO₂-In₂S₃ retains the photon excitons on the VB of TiO₂ and the CB of In₂S₃ by sacrificing partial quantum efficiency.All of the photogenerated h+,e-and ·OH were the main active species in the photocatalytic degradation of imidacloprid by H₃PW₁₂O₄₀/TiO₂-In₂S₃.The photo-generated excitons were separated on the Melem and acid anhydride moieties of the polyimide structure.The photogenerated h+,e-and OH are all active species in the photocatalytic degradation of imidacloprid by polyimide.Note that the photogenerated h+ was the major active specie.