Effect Of SiO₂ Microsphere Surface Treatment On The Preparation Of SiO₂-TiO₂ Composite Photocatalyst And Its Performance

Titanium dioxide is the most widely used typical semiconductor photocatalytic material.Loading nano-TiO₂ on the surface of the carrier is an important way to solve the problems of particle agglomeration and reuse.SiO₂ as the carrier has certain advantages and development prospects.In order to improve the carrier function of SiO₂ and realize the efficient utilization of resources,amorphous SiO₂ microspheres,a by-product of zirconia produced by industrial electrofusion method,are used as raw materials to carry out surface treatment.Nano-TiO₂ composite photocatalyst was prepared by using the treated SiO₂ microspheres as the carrier,and its properties were studied in depth.The surface of SiO₂ microspheres was treated by NaOH etching,Na₂SiO₃hydrolysis deposition and NaAlO₂ hydrolysis deposition respectively.Three kinds of treated products,SiO₂?NaOH?,SiO₂?Na₂SiO₃?and SiO₂?NaAlO₂?,were obtained respectively.After surface treatment,SiO₂ microspheres have less surface impurities,smoother morphology,and the number of hydroxyl groups on the surface increased from 0.38/nm² before treatment to 0.93,1.64 and 0.86/nm²,respectively,which laid a foundation for improving the performance of SiO₂ supported nano-TiO₂ composite photocatalyst.Using SiO₂?NaOH?,SiO₂?Na₂SiO₃?and SiO₂?NaAlO₂?as carriers,the preparation of supported nano-TiO₂ composite photocatalyst by sol-gel method was studied.The obtained composite photocatalyst has strong degradation ability to methyl orange solution,and is significantly better than the product after loading TiO₂on SiO₂ microspheres without surface treatment.the degradation efficiency is SiO₂?Na₂SiO₃?-TiO₂>SiO₂?NaOH?-TiO₂>SiO₂?NaAlO₂?-TiO₂>SiO₂?None?-TiO₂.Among them,the degradation rate of methyl orange by SiO₂?Na₂SiO₃?-TiO₂ under the optimal loading condition is 98.91%after 30 min of UV irradiation and 100%after 40min of UV irradiation.The structure,morphology and composite mechanism of the composite photocatalyst prepared by loading nano-TiO₂ onto surface-treated SiO₂ microspheres were studied.The results show that the composite photocatalyst is characterized by TiO₂ particles adhering to the surface of SiO₂ microspheres,TiO₂ is anatase phase,and the surface treatment of SiO₂ results in a significant reduction of TiO₂ particle size,with an average particle size of 14.8 nm and a minimum particle size of 12 nm.Si-O-Ti bond is used between SiO₂ microspheres and nano TiO₂.UV-Vis DRS and PL show that the loading of nano-TiO₂ and surface-treated SiO₂ microspheres does not significantly change the forbidden band width,but inhibits the recombination between photogenerated electrons and holes.Kinetics of degradation of methyl orange by SiO₂?NaOH?-TiO₂ and SiO₂?Na₂SiO₃?-TiO₂ were studied.The results show that both of them conform to the L-H model,the reaction rate constants k_LHH are 0.50 and 0.47 mg·L^-1·min^-11 respectively,and the apparent adsorption equilibrium constants K are 0.17 and 0.68 L mg^-1respectively.