Preparation And Photocatalytic Performance Of HSn_0.25CsPW/TiO₂ Composite Material

In this paper,tin-doped phosphonium phosphotungstate salt was prepared by hydrothermal process,and further prepared a novel composite of HSn_0.25CsPW/TiO₂.Moreover,SEM-EDS,BET,XRD,UV-diffuse reflectance spectra and EIS were used to analyze the morphology,size,surface area and photoelectrochemical properties of the as prepared catalysts,respectively.Tetracycline and pesticide dimethoate were chosen as the targeted model pollutants.The photocatalytic degradation effects of HSn_0.25CsPW₁₂O₄₀0 and HSn_0.25CsPW/TiO₂ on contaminants were also studied.The catalytic activity of the catalyst,influencing factors of the reaction,photocatalytic oxidation mechanism,recycling performance and photocatalytic reaction kinetics were furher studied.Some main results were concluded as follows:?1?Through various characterizations,the prepared composite material has the following characteristics:HSn_0.25CsPW/P25 composite material is a nano-sized sphere with a uniform particle size distribution and an apparent particle size of about 28 nm.Where HSn_0.25CsPW is the Keggin structure,TiO₂ is a mixed crystal of anatase and rutile,grain diameter was 17.71nm.The doped HSn_0.25CsPW catalyst has a BET surface area of 76.26 m² g^-1 and an average pore diameter of 0.523 nm.Due to the doping of phosphotungstate,the band gap energy of the composite photocatalyst is reduced?the band gap is 2.87 eV?.Its absorption wavelength is redshift at the edge of the band and absorbs some visible light.The Nyquist curve of the composite photocatalyst has a smaller arc radius,reveal that the composite photocatalyst has a lower charge transfer resistance,a faster photoelectron transfer rate,and exhibits superior photoelectrochemical performance and higher optical activity.?2?The Sn⁴⁺and Cs⁺doped phosphotungstate photocatalyst was prepared by hydrothermal method.The photocatalytic oxidation of tetracycline showed that the catalyst had good photocatalytic activity.The doping amount of Sn⁴⁺,dosage of the catalyst,initial concentration of the solution and pH value are all important factors affecting the photocatalytic degradation effect.When the catalyst HSn_0.25CsPW was added in an amount of50 mg,initial pH of the solution was 3.5,and initial concentration of tetracycline solution was50 mg/L,the effect of ultraviolet light for 2.5 h was the best,and removal rate was 93.3%.The degradation process of photocatalytic degradation of tetracycline by HSn_0.25CsPW accords with the first-order kinetic reaction,and its first-order reaction kinetic equation is ln?C₀/C_t?=0.7023t.The photooxidation removal rate after five cycles of tetracycline can still exceed 80%.?3?The dimethoate degradation rate?93%?of HSn0.25CsPW/P25 composites was 21%higher than that of P25?72%?under UV irradiation.HSn_0.25CsPW₁₂O₄₀ plays a key role in improving the photocatalytic activity of HSn_0.25CsPW/TiO₂,increased UV absorption,improved charge transfer process,and slowed electron hole recombination rate.The effects of experimental parameters on the degradation efficiency were investigated,including HSn_0.25CsPW₁₂O₄₀ loadings,catalyst concentration and dimethoate concentration.The optimal synergistic effect happened when the doping amount of HSn_0.25CsPW₁₂O₄₀ was 38%.This new complex can be easily recycled and reused several times with little change in degradation rate.