The Preparation Of La,Eu And Zn-Eu Doped TiO₂ Photocatalysts By Microwave Hydrothermal Method And Their Photocatalytic Activity

In this paper,lanthanum,europium single doped and zinc-europium co-doped TiO₂ photocatalyst TiO₂-La,TiO₂-Eu and TiO₂-Zn-Eu were prepared by microwave hydrothermal method,the photocatalytic degradation activity of three photocatalyst was investigated under the conditions of self-made ultraviolet lamp,microwave?MW?,microwave-ultraviolet?MW-UV?,microwave-ultrasound-ultraviolet?MW-UT-UV?and visible light irradiation,in order to investigate the effect of the preparation conditions on the photocatalytic activity of the catalyst.The effects of element doped amount,microwave hydrothermal power,microwave hydrothermal temperature,microwave hydrothermal time,calcination temperature and calcination time on the photocatalytic activity of the catalyst were investigated.By means of XRD,FESEM,XPS,N₂ adsorption-desorption,TG-DTG,ICP-AES,FTIR and PL test and analysis,the structure of the doped TiO₂ photocatalyst was characterized,the influence of the structure of the catalyst on its photocatalytic activity was discussed,and the main results were as follows:1.Preparation of La-doped TiO₂Photocatalyst and Its Photocatalytic Activity by Microwave Hydrothermal MethodThe optimum conditions for the preparation of TiO₂-La by microwave hydrothermal method is n(La³⁺):n(Ti⁴⁺)=0.12%,microwave hydrothermal synthesis power 650 W,microwave hydrothermal synthesis temperature 150?,microwave hydrothermal synthesis time 2.5 h,the calcination temperature 600?,and the calcination time 3 h.Photocatalytic degradation of methyl orange solution was performed by TiO-La photocatalyst under three degradation conditions of MW,MW-UV and MW-UT-UV for 35 min,and the degradation rates were 9.8%,99.2%and 100%,respectively.In addition,the methyl orange solution was degraded by self-made UV lamp for 30 min,and the degradation rate of methyl orange was 97.4%.The methyl orange solution was degraded for 4 h,and the methyl orange was almost completely degraded under the irradiation of visible light.XRD,FESEM and N₂ adsorption-desorption test analysis showed that TiO₂-La has a single crystal form,high crystallinity,small particle size and uniform distribution,and TiO₂-La is a mesoporous material with uniform pore size and large specific surface area,therefore,TiO₂-La has higher photocatalytic activity.EDS,XPS and ICP-AES test analysis showed that the main elements of TiO₂-La were Ti and O,and a small amount of La element was loaded,La was mainly present on the surface of TiO₂ in the form of+3 valence oxide.FTIR analysis showed that there were more surface hydroxyl groups on the surface of TiO₂-La than pure TiO₂,and the presence of hydroxyl groups was beneficial to the improvement of photocatalytic activity.The incorporation of La improves the crystal phase composition,specific surface area and surface active components of TiO₂ to enhance the photocatalytic degradation activity of TiO2 catalyst.2.Preparation of Eu-doped TiO₂ Photocatalyst by Microwave Hydrothermal Method and Its Photocatalytic ActivityThe optimum conditions for the preparation of TiO₂-Eu by microwave hydrothermal method is n(Eu³⁺):n(Ti⁴⁺)=0.08%,microwave hydrothermal synthesis power 700 W,microwave hydrothermal synthesis temperature 150?,microwave hydrothermal synthesis time 2.5 h,the calcination temperature 600?,and the calcination time 3 h.The photocatalytic degradation of methyl orange solution was carried out under MW,MW-UV and MW-UT-UV conditions using TiO₂-Eu photocatalyst for 35 min,and the degradation rates were 9.9%,99.7%and 100%,respectively.In addition,the methyl orange solution was degraded by self-made UV lamp for 35 min,and the degradation rate of methyl orange was 96.7%.The methyl orange solution was degraded for 4 h,and the methyl orange was almost completely degraded under the irradiation of visible light.XRD,FESEM and N₂ adsorption-desorption test analysis showed that TiO₂-Eu has a single crystal form,high crystallinity,small particle size,uniform distribution,large specific surface area and regular pore structure,therefore,TiO₂-Eu has higher photocatalytic activity.EDS,XPS and ICP-AES test analysis showed that the main elements of TiO₂-Eu are Ti and O,and a small amount of Eu is supported,and Eu is mainly present in the form of+3 valence oxide on the surface of TiO₂,the oxide of Eu can be Forming electron or hole trapping wells on the surface of TiO₂,so that electrons and holes are effectively separated.FTIR analysis showed that there were more surface hydroxyl groups on the surface of TiO₂-Eu than pure TiO₂,and the presence of hydroxyl groups was beneficial to the improvement of photocatalytic activity.The incorporation of Eu improves the crystal phase composition,specific surface area and surface active component of TiO₂ to enhance the photocatalytic degradation activity of TiO2 catalyst.3.Preparation of Zn-Eu Co-doped TiO₂ Photocatalysts by Microwave Hydrothermal Method and Their Photocatalytic ActivityThe optimum conditions for the preparation of TiO₂-Zn-Eu by microwave hydrothermal method is n(Zn²⁺):n(Ti⁴⁺)=0.06%,n(Eu³⁺):n(Ti⁴⁺)=0.12%,microwave hydrothermal synthesis power 600 W,microwave hydrothermal synthesis temperature150?,microwave hydrothermal synthesis time 2.5 h,calcination temperature 575?,calcination time 3 h.The photocatalytic degradation of methyl orange solution was carried out under MW,MW-UV and MW-UT-UV conditions using TiO₂-Zn-Eu photocatalyst for 35 min,and the degradation rates were 9.4%,99.0%and 100%,respectively.In addition,the methyl orange solution was degraded by self-made UV lamp for 30 min,and the degradation rate of methyl orange was 98.6%.The methyl orange solution was degraded by visible light for 3.5 h,and the methyl orange was almost completely degraded.XRD,FESEM and N₂ adsorption-desorption test analysis showed that TiO₂-Zn-Eu has a single crystal form,high crystallinity,small particle size,uniform distribution,large specific surface area and regular pore structure,therefore,TiO₂-Zn-Eu has higher photocatalytic activity.EDS,XPS and ICP-AES test analysis shows that the main elements of TiO₂-Zn-Eu are Ti and O,and a small amount of Zn and Eu elements are also loaded,Zn and Eu exist in the form of oxides of+2 and+3valence,respectively,on the surface of TiO₂,and form electron or hole trapping wells,so that electrons and holes are effectively separated.FTIR analysis showed that there were more surface hydroxyl groups on the surface of TiO2-Zn-Eu than pure TiO2,and the presence of hydroxyl groups was beneficial to the improvement of photocatalytic activity.The co-doping of Zn and Eu improves the crystal phase composition,specific surface area and surface active components of TiO₂,and further enhances the photocatalytic degradation activity of TiO₂ catalyst.The results show that the photocatalytic activity of TiO₂ catalysts is improved by microwave hydrothermal method for the preparation of lanthanum,europium single doped and zinc-europium co-doped TiO₂ photocatalysts.The synergistic effect of microwave and ultrasound further enhances the photocatalytic activity of the three doped photocatalysts.The microwave hydrothermal method combines the traditional hydrothermal synthesis method with the microwave field,and uses the high temperature and high pressure reaction environment to dissolve some hardly soluble substances,and then prepares the photocatalyst after recrystallization,separation and high temperature calcination treatment.It provides an energy-saving,efficient and environmentally friendly green pathway for the preparation of doped TiO₂photocatalysts,promotes the practical application of TiO₂ photocatalysts,and enriches the research content of microwave chemistry.