Studies On The Preparation And Catalytic Performance Of Titanium Dioxide Based Magnetic Photocatalyst

Titanium dioxide photocatalyst has been widely concerned because of its chemical stability, cheapness, nontoxicity, high catalytic efficiency, and has good prospect in the research and application of photocatalyst. But the scale-up application of TiO2 catalyst also faces two major problems:first, disadvantages of easy recombination of photoinduced electron-hole pairs and weak visible light absorption ability; second, hardly recycling use of TiO2 photocatalyst due to forming stable colloid solution. In this thesis the preparation of magnetic particle Fe3O4 and core-shell structure SiO2/Fe3O4 were studied. The visible magnetic photocatalyst composing of AgBr/TiO2 and SiO2/Fe3O4 carrier with shell-core structures were studied.We prepared three kinds of magnetic Fe3O4 particles and coated it by SiO2. The characterization results of TEM and XRD showed that the magnetic carrier of Fe3O4 and SiO2/Fe3O4 particles with particle size of about 200nm prepared by solvothermal exhibited regular sphere-like morphology and well dispersion. The Fe3O4 particles prepared by sol-gel process are small particles and serious agglomerates.The composite magnetic photocatalysts were prepared by coprecipitation and sol-gel method at low temperatures using tetrabutyl titanate as precursor, Fe3O4 and SiO2/Fe3O4 as magnetic carriers, respectively. We used X-ray diffraction(XRD) and transmission electron microscope(TEM) and scanning electron microscope(SEM) with energy dispersive X-ray analysis(EDX) to characterize phase composition, morphology, particle size and element distribution of the TiO2/Fe3O4 photocatalyst and studied the effects of different calcination temperatures and molar ratios of TiO2 to Fe3O4 on photocatalytic degradation activity of Rhodamine B. The results indicated that the activity order of these samples is of TiO2/Fe3O4 (100℃)>TiO2/Fe3O4 (300℃)>TiO2/Fe3O4 (450℃), among which the TiO2/Fe3O4 photocatalyst prepared at lowest tempreture of 100℃shows a higher photocatalytic activity because the number of combination center of electron-hole pairs was decreased due to inhibiting the diffusion of Fe3+ and Fe2+ into TiO2 lattice. The both of photocatalytic activity and magnetic recyclation performance of the magnetic photocatalysts with the TiO2 contents of 67.3%-73% are best. The photocatalyst of TiO2/Fe3O4 (100℃,70%) has the decolorization ratio up to 99% and recovery rate up to 90%. Magnetic visible photocatalyst was prepared by loading AgBr/TiO2 composite catalyst on core-shell structure SiO2/Fe3O4 carrier. The phase composition, particle morphology, size, microstructure and magnetic property of these samples were characterized by XRD, TEM, SEM, HERTEM, XPS and VEM. The results of photocatalytic degradation to methylene blue showed that the activity order of these samples is of ATSF(3.35:1)> ATSF(5:1)> ATSF (1:1). Multicomponent ATSF(3.35:1) catalysts have the highest degradation activity and superior magnetic recycling performance. HRTEM results show that the AgBr/TiO2 with heterojunction microstructure is well loaded on the carrier of SiO2/Fe3O4 with obvious core-shell structure.