Study On Immobilization And Photocatalytic Properties Of Titanium Dioxid

It is difficult to treat the industrial and domestic wastewater with complex composition,high organic content,and large number of pathogens.The wastewater from traditional two-stage sewage treatment cannot be directly discharged or used in production and life.However,high energy-consuming membrane filtration and deep chemical treatment are commonly used in the third-stage wastewater treatment,which greatly increase the cost of wastewater treatment.Photocatalytic technology can degrade organic pollutants and pathogens in wastewater.Photocatalysts have photocatalytic activity for almost all organic substances.In this paper,titanium dioxide（TiO₂）with good photocatalytic activity and stability was selected as photocatalyst,and the catalyst was immobilized onto SiO₂aerogel and organic membrane by sol-gel technique.Methylene blue was used as the photocatalytic model to study the optimum technological conditions forpreparing composite photocatalysts.And the prepared photocatalysts were applied to the actual industrial and domestic wastewater.The specific research contents and results are as follows:Firstly,inorganic silicon-based TiO₂-SiO₂ photocatalyst was prepared by sol-gel method using SiO₂ aerogel as carrier.The surface morphology and spatial pore structure of the composite catalyst were characterized by scanning electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction pattern and specific surface area and pore structure analysis.The results showed that TiO₂particles were uniformly distributed on the surface of SiO₂ aerogels,and the catalyst has abundant spatial pore structure and good specific surface area.Based on the single factor experiments and the response surface optimization experiments,the optimal process conditions for preparing silicon-based catalysts are obtained as follows:the ratio of tetraethyl orthosilicate（TEOS）to water（V/V）is 4:1,and the concentration of TiO₂ in suspension was 2.21 g/L,the sol-gel time was 3.1 days,The removal rate of methylene blue was 99.1%after 24 hours degradation test.The repeatability experiment showed that the removal rate of methylene blue decreased from 76.70%to 53.74%after 5 times and 2 hours of repeatable degradation experiments.Secondly,organic photocatalyst films were prepared by sol-gel method using organic film as carrier.The surface morphology and crystalline structure of the catalyst film were characterized by different analytical methods.The results show that the structure of titanium dioxide on the surface of organic membranes is porous.There were more hydroxyl groups on the surface of the material,which improved the catalytic activity of the catalyst.On the basis of single factor experiments and response surface optimization experiments,the optimum technological conditions for preparing silicon-based catalysts were obtained as follows:the ratio of KH560 to water（V/V）was 3.86:1,and the concentration of TiO₂ in the mixture was 4.61 g/L.The amount of trisodium citrate added was 22.00 g/L,and the amount of sodium diphenylamine sulfonate added was 7.50 g/L.The removal rate of methylene blue was 96.6%after 24 hours degradation test.The repeatability experiment showed that the removal rate of methylene blue decreased from 55.80%to 52.15%after 5 times and 2 hours of repeatable degradation experiments.Finally,two kinds of composite catalysts were applied to the treatment of actual living and production wastewater,and the changes of COD and chromaticity values of wastewater with photocatalytic degradation were investigated.The experimental results showed that the catalyst had better effect on the treatment of wastewater with smaller chroma and COD.The inorganic silicon-based TiO₂-SiO₂ catalyst exhibits better adsorption due to its abundant pore structure,and there is a good synergistic effect between the adsorption of organic substances by the carrier and the degradation of organic pollutants by TiO₂;Stirring and hydrogen peroxide can improve the photocatalytic degradation efficiency of organic pollutants in wastewater.