Synthesis of TiO2/SiO2@Fe3O4 magnetic microspheres and their properties of photocatalytic degradation dyestuff

The TiO2/SiO2@Fe3O4 photocatalysts were synthesized via two steps. First, the SiO2@Fe3O4 particles were synthesized using Fe3O4 as the core and tetraethoxysilane (TEOS) as silica source. Second, the anatase TiO2 was coated on the SiO2@Fe3O4 particle surface using tetrabutyl titanate (TBOT) as titanium source. The synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N-2 adsorption-desorption techniques and vibration sample magnetometer (VSM). The catalytic activity of TiO2/SiO2@Fe3O4 catalysts for the photocatalytic degradation of Rhodamine (RhB) was evaluated under ultraviolet (UV) irradiation. The results indicated that the mean size of the 6%SiO2@Fe3O4 particles was about 75-80 nm and thickness of the homogeneous SiO2 layer was about 2-3 nm. The diameter of 50%TiO2/6%SiO2@Fe3O4 microspheres was about 100 nm and thickness of the homogeneous anatase TiO2 layer was about 8-10 nm. The saturation magnetization and specific surface area of 50%TiO2/6%SiO2@Fe3O4 catalysts were 48.6 emu/g and 495.3 m(2)/g, respectively. The 50%TiO2/6%SiO2@Fe3O4 microspheres exhibited the best photocatalytic performance. The conversion of RhB achieved up to 98.1% after 60 min UV irradiation, and the photocatalytic reaction apparent rate constant k(a) was 0.05288 min(-1). After used for 8 times, it also maintained high degradation rate and catalyst recovery. (C) 2011 Elsevier B.V. All rights reserved.