Preparation And Properties Of TiO₂-SiO₂ Based Photocatalysts

TiO₂-SiO₂ composites not only have the thermal stability and mechanical stability of SiO₂,but also have the catalytic properties of TiO₂.They have broad application prospects in the field of catalysis,but the wide band gap and electron-hole recombination of TiO₂ hinder its wide application.Therefore,TiO₂-SiO₂ composites were prepared and modified by loading AgBr,Ag and g-C₃N₄.The specific research contents are as follows:（1）The TiO₂-SiO₂ composites were prepared by sol-gel method,and their photocatalytic degradation properties for methylene blue（MB）dyes were studied.The results indicate that using 500 W xenon lamp as the light source for 1 h,TiO₂-SiO₂ prepared with a molar ratio of SiO₂ to TiO₂ of 0.1 can degrade nearly 70%of MB.TiO₂-SiO₂prepared with a PEG molecular weight of 20,000 can degrade nearly 70%of MB.TiO₂-SiO₂ prepared using deionized water as a hydrothermal solvent can degrade about90%of MB.The TiO₂-SiO₂ prepared by adding FA in an amount of 2 mL can degrade about 90%of MB.The addition of PEG to 1g of prepared TiO₂-SiO₂ can degrade about90%of MB.The prepared TiO₂-SiO₂ was used repeatedly for 5 times to maintain the degradation rate of MB at 70%or more.The·OH produced by TiO₂-SiO₂ is the most active species that degrade MB.（2）AgBr/TiO₂-SiO₂ materials with different mass ratios were obtained by loading AgBr on TiO₂-SiO₂ materials,and the photocatalytic degradation properties of MB and reactive red 2 dyes were studied.The results indicate that using 500 W xenon lamp as light source for 1 h,10%AgBr/TiO₂-SiO₂ can degrade 95%of MB and about 100%of active red2 dye,and the visible light catalytic activity is better than P25,and the COD value of degraded actual wastewater decreased by 77.8%,the degradation rate of MB was kept above 80%after repeated use for 5 times,and the resulting·OH and·O₂^-were the most active species for degrading MB and active red 2,respectively.（3）Ag/TiO₂-SiO₂ materials with different mass ratios were obtained by loading Ag on TiO₂-SiO₂ materials,and the photocatalytic degradation properties of MB and reactive red2 dyes were studied.The results indicate that using 500 W xenon lamp as light source for 1h,5%Ag/TiO₂-SiO₂ can degrade about 95%of MB and about 60%of reactive red 2 dye,its visible light catalytic activity is better than P25,and the COD value of degraded actual wastewater decreased by 78.2%,the degradation rate of MB was kept above 80%after repeated use for 5 times,the resulting·OH is the most active species to degrade MB.10%Ag/TiO₂-SiO₂ generated holes and·O₂^-is the degradation of active red 2 active species.（4）The g-C₃N₄/TiO₂-SiO₂ material was synthesized by calcination,and its photocatalytic degradation performance for MB and reactive red 2 dye was studied.The results show that using 500 W xenon lamp as light source for 1 h,20%g-C₃N₄/TiO₂-SiO₂can degrade about 100%MB and 60%active red 2 dye,and its visible light catalytic activity is better than P25,and the COD value of degraded actual wastewater decreased by83.7%,and its degradation rate of MB was maintained above 80%after repeated use for 5times,the resulting·OH is the most active species that degrade MB,and the resulting holes and·O₂^-are the most active species that degrade active red 2.