Study On Preparation Of Fe₃O₄-TiO₂Photocatalysts And Its Photocatalytic Degradation Of Alizarin Red S

The photocatalytic oxidation technology is a novel water treatment technology withthe advantages of high treatment efficiency, simple technical equipment, and degradationorganics pollution without secondary pollution. It’s well known that titanium dioxide(TiO2) has attracted much attention for environmental applications due to its chemicalinert and high catalytic activity. While TiO2powder is hard to separate from the reactionmedia and it has low efficiency under solar light.In this work, a composite catalyst with magnetite Fe3O4core and TiO2shell wasprepared by a new method, and then the high productivity and catalytic efficiency of itswere achieved through optimizing the preparation conditions. Firstly, the nanoparticletitanium dioxide was prepared by the sol-gel method, and then the surface of magnetiteFe3O4powder was pretreated by sodium citrate. After that, titanium dioxide was coated onFe3O4powder to obtain Fe3O4-TiO2core-shell nanocatalysts. The typical procedures forthe synthesis of magnetite nanoparticles are as follows: sodium citrate0.1M was used forthe surface pretreatment of Fe3O4. The modified magnetic Fe3O4were dispersed indeionised water whose pH equaled3. The molar ratio of Fe3O4to TiO2was kept to2.5.XRD and TEM were used to investigate structure and morphology of the samples. Theresults of XRD indicate that there only are Fe3O4and TiO2(anatase) particals in thecomposite. The absence of other diffraction peaks indicates that there was no new phaseformation at the interface between Fe3O4and TiO2. The average sizes of samples wereestimated from the main peaks by scherrer’s equation, which were about11.56nm forFe3O4, and18.381nm for TiO2nanoparticles. From the TEM pictures, it can be seen thatthe shell of TiO2is coated on the Fe3O4surface to form a core-shell structure.In addition, in this work, four main metal ions (Mg2+, Cr3+, Ce4+and Mn2+) wereselected to doping in the TiO2powders. Then, TiO2doped with ions were coated on thesurface of Fe3O4nanoparticles. The stability of the photocatalysts was measured. Theexperiments showed that doping metal ions except Mn2+can improve the catalystperformance.This work also used alizarin red S as the model pollution and discussed the degradation conditions. The result showed that when the dosage of the photocatalyst was0.24g, the degradation rate of100mg/L alizarin red S under nature pH can reach89%.The results indicated that doping appropriate concentrations of metal ions canincrease the catalyst performance and the degradation efficiency, because of thesynergistic effect, the photodegradation effect enhancing remarkably.