Study On The Preparation Of Ag And Sm Doped TiO₂ Photo-catalyst By Microwave Hydro-thermal Method And Its Photo-catalytic Activity

In this paper,TiO₂-Ag,TiO₂-Sm and TiO₂-Ag-Sm were prepared by microwave-hydrothermal method.At the same time,TiO₂-Ag catalyst was prepared by sol-gel method with [Bmim]PF6 ionic liquid used as the reaction medium.First,the influence of preparation conditions such as doping ratio,microwave reaction power,hydrothermal reaction temperature,reaction time,calcination temperature and calcination time on the photocatalytic activity of the catalyst was investigated by using the L18?37?orthogonal experiment design of 3 level 7 factors.Second,the effect of the preparation conditions on the photocatalytic activity of the catalyst was further optimized by using methyl orange as simulated contaminants under microwave?MW?,ultraviolet?UV?,microwave-ultraviolet?MW-UV?or microwaveultraviolet-ultrasound?MW-UV-UT?.Finally,the structure of the doped catalyst was analyzed by XRD,SEM,TG-DSC-DTG,BET,UV-Vis,PL and IR.The reason for the influence of the structure of the catalyst on the photocatalytic activity was discussed by the above characterization means.The main findings are as follows.??Preparation of TiO₂-Ag Catalyst and It's Photocatalytic ActivityFist,the optimum conditions for the preparation of TiO₂-Ag catalyst by microwave-hydrothermal method were as follows: n?Ag+?: n?Ti4+?= 0.2%,microwave reaction power 600 W,reaction temperature 140 ?,reaction time 3 h,calcination temperature 550 ? and calcination Time 3 h.And the optimum conditions for the preparation of TiO₂-Ag catalyst by sol-gel method were as follows: n?Ag+?: n?Ti4+?= 0.3%,V?[Bmim]PF6?= 3 mL,microwave drying power 210 W,microwave drying time 20 min,calcination temperature 650 ? and calcination time 3 h.Second,the degradation rate of TiO₂-Ag catalyst prepared by microwave-hydrothermal method was 9.75%,90.76%,95.05% and 100% after degradation of methyl orange solution for 35 min at the degradation conditions of MW,UV,MW-UV and MW-UV-UT respectively,but the degradation rate of the TiO₂-Ag catalysts prepared by sol-gel method were 3.89%,88.05%,93.98% and 100% at the same condition.The photocatalytic activity of TiO₂-Ag catalyst prepared by microwave-hydrothermal method was higher than that of TiO₂-Ag catalyst prepared by sol-gel method under various degradation conditions.The photocatalytic activity of TiO₂-Ag catalyst could be further enhanced by increasing the ultrasonic or microwave condition under the condition of ultraviolet light degradation,which indicated that the photocatalytic degradation of TiO₂-Ag catalyst was enhanced by microwave and ultrasonic.Finally,the ultrasonic vibration could expand the contact surface between the catalyst and the organic pollutants and the microwave radiation could inhibit the photo-generated electrons and hole pairs.Therefore,the three synergies could generate stack effect when the degradation of organic pollutants was enhanced by microwave radiation and ultrasonic vibration under the ultraviolet light,which made the time for photocatalytic reaction was shortened and the degradation rate increased in unit time.??Preparation of TiO₂-Sm Catalyst and it's Photocatalytic ActivityThe optimum conditions for the preparation of TiO₂-Sm catalyst by microwave-hydrothermal method were as follows: n?Sm3+?: n?Ti4+?= 0.3%,microwave power 450 W,reaction temperature 170 ?,reaction time 3 h,calcination temperature 700 ? and calcination time 3 h.The degradation rate of TiO₂-Sm catalyst was 11.51%,96.53% and 99.50% and 100% under the conditions of MW,UV,MW-UV and MW-UV respectively.??Preparation of TiO₂-Ag-Sm Catalyst and it's Photocatalytic ActivityThe optimum conditions for the preparation of TiO₂-Sm catalyst by microwave-hydrothermal method were as follows: n?Ag+?: n?Ti4+?= 0.3%,n?Sm3+?:n?Ti4+?= 0.3%,microwave power 600 W,reaction temperature 150 ?,reaction time 3 h,calcination temperature 650 ? and calcination time 3 h.The degradation rate of TiO₂-Ag-Sm catalyst was 11.87%,97.40%,98.72% and 100% under the conditions of MW,UV,MW-UV and MW-UV respectively.??The structural analysis and characterization of TiO₂-Ag,TiO₂-Sm and TiO₂-Ag-Sm CatalystsFirst,the results of XRD,SEM,TG-DSC-DTG and BET analysis shown that the three catalysts prepared by microwave-hydrothermal method had higher crystallinity,smaller grain size,uniform particle size distribution,larger specific surface area and so on.The addition of silver or samarium in the catalyst extended the temperature range of the amorphous TiO₂ phase to the rutile phase,thereby the phase transition temperature of the anatase to rutile increased and the growth of the grains inhibited,as a result photocatalytic activity of the TiO₂ catalyst was improved.Second,the results of UV-Vis,PL and IR show that the addition of silver or samarium effectively inhibited the recombination of photo-generated electron-hole pairs,extended the response range of the catalyst to the visible region and increased the hydroxyl content of the catalyst surface,as a result the photocatalytic activity of the doped TiO₂ catalyst was improved.Then,the results of elemental characterization of EDS and ICP-AES shown that the main elements of the three catalysts were Ti,O and doping elements,indicated that the doped element silver or samarium was indeed supported on the TiO₂ photocatalyst.In addition,the photocatalysts prepared by microwave-hydrothermal method had more photoactive sites and higher silver doping amount for TiO₂-Ag catalysts,which indicated that microwave-hydrothermal method was superior to sol-gel method.The results of paper shown that the TiO₂-Ag,TiO₂-Sm and TiO₂-Ag-Sm catalysts prepared by microwave-hydrothermal method that have high photocatalytic activity.Microwave and ultrasonic could enhanced the photocatalytic activity of TiO₂ catalyst.Microwave-hydrothermal method combined the traditional hydrothermal synthesis method with the microwave field,and used its high temperature and high pressure reaction environment to dissolve some of the difficult substances,and then photocatalyst was prepared by recrystallization,separation and calcination at high temperature.This provides an energy-saving,high-efficiency and environment-friendly green pathway for the preparation of doped TiO₂ photocatalyst,which promotes the practical application of TiO₂ photocatalyst and enriches the research content of microwave chemistry.