Preparation And Photocatalytic Activity Of Rare Earth Ytterbium And Erbium Doped TiO 2 Photocatalyst

This thesis mainly adopted the sol-gel method, then Yb-doped TiO₂, Er-doped TiO₂ and Yb-Er co-doped TiO₂ photo-catalyst were synthesized respectively. And Er-doped TiO₂ photo-catalyst was synthesized by microwave-hydrothermal synthesis method. Sol-gel method was mainly heated by microwave radiation for synthesis 1-butyl 3- methylimidazolium hexafluorophosphate（[Bmim]PF6） ionic liquids（ILs）. Then the ionic liquids was added into the solution of absolute ethyl alcohol and tetrabutyl titanate. In order to improve the performance of TiO₂, the TiO₂ was carried out by selecting Yb（NO3）3 and Er（NO3）3 as doping reagents. The sol-gel method was discussed the effects of the doping quantity of ytterbium and erbium（the amount of material percentage）, quantity of ILs and other factors which affect the activity of TiO₂ catalyst respectively. Then the microwave-hydrothermal synthesis method discussed the effects of the doping quantity of erbium（the amount of material percentage）, reaction temperature and other factors of affecting the activity of TiO₂ catalyst respectively. The main results are summarized as follows: 1. Sol-gel methodThe ionic liquids was added into the solution of absolute ethyl alcohol and tetrabutyl titanate. In order to improve the performance of TiO₂, the TiO₂ was carried out by selecting Yb（NO3）3 and Er（NO3）3 as doping reagents. Using the way of microwave drying Yb-doped Ti O2 photo-catalysts, Er-doped Ti O2 photo-catalysts and Yb-Er co-doped TiO₂ photo-catalysts. Then methyl orange as simulated pollutants which examined the quantity of ytterbium doped and erbium doped quantity, the amount of the ionic liquids on the photo-catalytic activity of TiO₂. 50 mL Methyl Orange was added into a beaker which contain 50 mg Ti O2 photo-catalysts, then put it in the home-made degradation device（high pressure mercury lamp of 300 W） reaction 60 min. After orthogonal and single factor experiments, the best reaction condition was selected, then In the ultraviolet and microwave ultrasonic combined catalytic synthesis, use TiO₂ photocatalyst degradation of methyl orange 50 min under the condition of MW, UV, MW-UV or separate MW-UV. The experimental results showed that as follows:（1）Yb-doped TiO₂ catalyst activity was higher than without doping element or without ionic liquids TiO₂ catalyst. When the Yb/Ti mole ratio of TiO₂-Yb was 0.08 %, the amount of ionic liquids was 3.0 mL, the microwave power was 210 W, microwave time was 20 min and calcined at 650 ℃for 3 h, the degradation rate of methyl orange was 96.8% in home-made device. In the ultraviolet and microwave ultrasonic combined catalytic synthesis, the degradation rate of methyl orange were respectively 3.9 %, 97.0 % and 98.1 % under the three kinds of condition. Because of the synergy effect of MW and UV, the catalytic activity for photo-catalysts had always been MW- UV > UV > MW under the three kinds of condition.（2）Er-doped TiO₂ catalyst activity was higher than doping element or without ionic liquids catalyst. When the Er/Ti mole ratio of TiO₂-Er was 0.4 %, the amount of ionic liquids was 3.0 m L, the microwave power was 70 W, microwave time was 10 min and calcined at 650 ℃ for 3 h, the degradation rate of methyl orange was 97.2 % in home-made device. In ultraviolet and the microwave ultrasonic combined catalytic synthesis, the degradation rate of methyl orange was 98.5 % under the MW- UV condition.（3）Yb and Er co-doped Ti O2 catalyst activity was higher than Yb-doped or Er-doped TiO₂ catalyst activity. When Yb/Ti mole ratio was 0.08 % and Er/Ti mole ratio was 0.2 % of TiO₂-Yb-Er, the amount of ionic liquids was 2.0 mL, the microwave power was 210 W, microwave time was 20 min and calcined at 650 for 3 h,℃ the degradation rate of methyl orange rate was 98.0 % in home-made device. In the ultraviolet and ultraviolet and microwave ultrasonic combined catalytic synthesis, the degradation rate of methyl orange was 99.3 % under the MW- UV condition.（4）Microwave auxiliary ionic liquid in the preparation of three kinds of doped TiO₂ photo-catalysts TiO₂-Yb, TiO₂-Er and TiO₂-Yb-Er always had high photo-catalytic activity, the catalytic activity of the three kinds of photo-catalysts had always been TiO₂-Yb-Er>TiO₂-Er>Ti O2-Yb in the same degradation condition. 2. Microwave-hydrothermal synthesis methodThe Erbium nitrate was added into the solution of absolute ethyl alcohol and tetrabutyl titanate, then the white sol was put into the high-pressure reaction kettle. When the Er/Ti mole ratio of TiO₂-Er was 0.4 %, reaction temperature was 160 ℃, the microwave power of the process of the reaction was 600 W, reaction time was 3h, and calcined at 650 ℃for 3h, the degradation rate of methyl orange was 99.1 % in home-made device; when the microwave was combined with UV lamp, the degradation rate of methyl orange was 100 %. And more the degradation rate of methyl orange with microwave-hydrothermal synthesis method was all along the higher than the sol-gel method. 3. Catalyst structure testing and characterizationIn order to obtain the structure of the TiO₂-Yb, TiO₂-Er and Ti O2-Yb-Er catalysts, the XRD, SEM, IR, BET, PL and ICP-AES methods were used for testing analysis and characterization respectively. The results showed that the particle size of three kinds of catalyst were 12.45, 10.65 and 10.80 nm respectively by the sol-gel method. Among them the particle size of TiO₂-Er catalyst which compouded by the microwave hydrothermal synthesis method was 9.35 nm. Because their crystallization and dispersion were well, the morphology of particles were spherical and the surface had a lot of hydroxyl, the TiO₂-Yb, TiO₂-Er and Ti O2-Yb-Er catalysts had high catalytic activity.In this article, the sol-gel method and microwave-hydrothermal synthesis method synthesised the doped TiO₂ photo-catalysts which had high photo-catalytic activity. Sol-gel method which doped ionic liquids provided few new ideas and methods for the preparation and modification of TiO₂ catalyst, and more expands the application range of the ionic liquids. When the traditional hydrothermal synthesis method combined with microwave field, microwave heating makes a reaction to the environment of high temperature and high pressure, usually difficult soluble or insoluble substances dissolved and the catalysts prepared by recrystallization separation and heating treatment. The microwave-hydrothermal synthesis method is a new method of doped TiO₂ catalyst for the preparation of high catalytic activity, and more this method enriches the research content of microwave chemistry.