Investigation On Preparation And Photocatalytic Activity Of Rare Earth Doped TiO₂ And α-Fe₂O₃ Nano-particles

In this study we described the resource, background and content of the project, then, the arsenic removal techniques in water and the current research status of TiO2 were reviewed. The detailed steps of sol-gel method were expounded and standard curve depending on the molybdenum blue spectrophotometric method were plotted.Re/TiO2(La、Ce、Pr、Nd、Y、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb、Lu)were synthesized by sol-gel method, and their crystal structures and morphology of catalyst were characterized by XRD and SEM respectively.The analysis results of XRD showed that pure TiO2 was composed of anatase phase and rutile phase and 0.5%Te/TiO2、0.8%Yb/TiO2、0.3%La/TiO2、0.1%Dy/TiO2 were composed of anatase phase. Meanwhile, the diffraction peaks of doped TiO2 were widened which indicated the thermostability were improved by doping. The particle size and lattice distortion were calculated by crystal formulae, element doping resulted in reducing of particle size and increasing of lattice distortion.The SEM analysis results showed that the particle sizes of Yb/TiO2、Te/TiO2、La/TiO2、 Dy/TiO2 and Pure TiO2 were all between 3-13μm.In order to analyze the effect of light intensity, dosage of catalyst, concentration of oxygen and initial arsenic on the photocatalytic activity of catalyst with constant pH value, an orthogonal experiment with four factors and three levels was carried out. The order of factors which affected photocatalytic activity was obtained through the orthogonal experiments:concentration of initial arsenic>light intensity>dosage of catalyst> concentration of oxygen.In the first stage of photocatalytic activity test, forty five Re/TiO2 (La、Ce、Pr、Nd、Y、 Sm、Eu、Gd、Tb、Dy、Ho、E、Tm、Yb、Lu) with different doping ratio(0.1%、0.5%、 1%) were tested. The test result indicated that the photocatalytic activity of Te/TiO2、 Yb/TiO2、La/TiO2 and Dy/TiO2 with three doping ratio were improved obviously. The test results of the second stage of photocatalytic activity test indicated that 0.5%Te/TiO2、 0.8%Yb/TiO2、0.3%La/TiO2 and 0.1%Dy/TiO2 were four kinds of catalysts with best photocatalytic activity among all samples. And the order was:0.8%Yb/TiO2> 0.3%La/TiO2>0.1%Dy/TiO2>0.5%Te/TiO2. First order kinetics model was used to describe the catalytic oxidation process of Re/TiO2 for As (Ⅲ) in the solution.In addition, polyhedral α-Fe2O3 nanoparticle was synthesized via hydrothermal process. The crystal structures, morphology were characterized by XRD and SEM respectively. The positions of the diffraction peaks indicated that all the nanocrystals were polycrystalline with a structure that belonged to the polyhedral α-Fe2O3 (JCPDS data card33-0664). It was observed that α-Fe2O3 nanoparticle was high dispersion and polyhedron from the SEM images. In this work, adsorption and catalysis of samples were measured, then, first order kinetics model was used to describe the catalytic oxidation process ofaαFe2O3 for As (Ⅲ) in the solution.