Preparation Of Rare Earth Doped TiO₂-SiO₂ Catalyst And Photocatalytic Degradation Of Rhodamine B

Photocatalytic degradation technology is a new high efficiency and energy saving modern treatment technology.TiO₂-based photo catalysts have a variety of promising applications including waste treatment and gas purification,owing to their novel stability,non-toxicity,low cost and highly active properties.However,the application and efficiency of TiO₂ as photocatalytic material is limited because of its only ultraviolet light absorption,hydrophilic hydrophobic oil properties.In addition,as powder,TiO₂ flows with the air and floats on liquid surface easily.Hence,the TiO₂treatment technology has become research focus in recent years.This paper describes the structure of TiO₂ photocatalytic materials and their photocatalytic mechanism,mainly reviews the research progress of several kinds of mature treatment technology,The review includes the introduction of photocatalysis,the summary of TiO₂ properties,the loading modification of TiO₂,as well as its application,and the prospect of future research.The specific research contents are as follows:TiO₂-SiO₂ doped with butyl titanate,TEOS and rare earth ions was prepared by simple and controllable sol-gel method using nitrate as a raw material,and characterized by Uv-vis diffuse reflectance spectroscopy,x-ray diffraction（XRD）,infrared Fourier transform（FTIR）,fluorescence（pl）and scanning electron microscopy（SEM）.The results shows:（1）Firstly,the peparation and experimental conditions of undoped TiO₂-SiO₂,concluded that SiO₂ load gives TiO₂ mechanical strength,through different calcination temperature found that lead to increased after decreased degration;From the XRD characterization analysis,the rise of temperature of700℃under the formation of the Ti-O-Si keys can be stable anatase phase,but reaches 800℃,the lattice fracture results in the formation of rutile phase,reduce the rate of photocatalysis.FT-IR verify the formation of Ti-O-Si keys,and found the surface of the catalyst under the 700℃calcination hydroxy most,so the highest catalytic activity;Through different calcination time,it is found that the catalytic rate increases first and then decreases.The optimum calcination time is 2h.The low degradation rate of less than 2h is due to inadequate calcination by scanning electron microscopy,After 2 hours,the degradation rate decreased slightly because of the aggregation of titanium dioxide and silicon dioxide,and the aggregation was caused by the fracture of Ti-O-Si bond caused by excessive calcination;The results showed that the aging time had no significant effect on the activity of the catalyst.In order to make the material more stable,24 hours were chosen to prepare the catalyst;When the amount of catalyst is more than 0.03g,the catalytic rate does not increase but decreases because of the limited light source and the scattering effect of particles;It was found that the degradation reaction was the strongest within 1 hour,and the degradation rate tended to be flat when the illumination time was more than 3 hours.Therefore,the following experiments were carried out under the optimum conditions:the samples aged for 24 hours were calcined for 2 hours at 700℃,and the photocatalytic reaction was carried out for 3 hours with 0.03g catalyst.（2）After doping different rate earth elements,no new luminescence phenomenon is ccaused and ideal anatase crystal are formed.The insertion of rate earth elements promotes the effective separation of photogenerated electrons and improves quantum efficiency.The doping of La can effrctively inhibit lattice transformation,and the doping of Ce can improve the absorption intensity of visible light.After that no new luminescence phenomena could be observed after doption of Sm and ideal anatase crystals were formed.The incorporation of samarium promoted the efficient separation of photogenerated electrons,as well as improving the quantum efficiency.The catalytic degradation of rhodamine B by catalysts doped with different mass percentages of Sm（signed as x%Sm@TiO₂-SiO₂）under xenon lamp irradiation was compared.The results showed that the catalysts doped with samarium had inhibitory effect onα-R phase transformation compared to undoped catalysts,which was beneficial to the formation of small-grain anatase.The degradation rate of rhodamine B catalyzed by2%Sm@TiO₂-SiO₂ catalyst reached 96%under 3 hours irradiation.（3）Finally,by compared,two superior rate earth metals were salacted for bimetallic doping at different ratios.When the doping ratio was Sm:La=1:3,the catalyst showed the best effect:the irradiation degradation rate reached 99%.The results of UV-Vis and PL spectra showed that the band gap of TiO₂-SiO₂ matrix was reduced by co-doping,and the catalytic rate of TiO₂-SiO₂ matrix was greatly increased.The doped metals are all bonded with the matrix by chemical bond by infrared spectrum analysis.The X-ray diffration pattern showed that the existence of La-O-Ti and Sm-O-Ti bonds could effectively inhibit the lattice growth,which confirmed the conclusion of the infrared spectrum.