Magnetic photocatalysts of cenospheres coated with Fe3O4/TiO2 core/shell nanoparticles decorated with Ag nanopartilces

A layer of magnetite Fe3O4 nanoparticles is first loaded onto the surfaces of cenospheres using ferric trichloride, ferrous chloride, and aqueous ammonia by a precipitation method, and then modified with silane coupling agent KH550. The modified Fe3O4 coated cenospheres are coated further with a film of anatase TiO2 nanoparticles under hydrothermal conditions, and finally decorated with Ag nanoparticles by electroless deposition. The surface morphology, chemical composition, crystalline structure, magnetic properties, and optical behaviors of cenosphere before and after treatments are determined by means of field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffractometry (XRD), vibrating sample magnetometry (VSM), and diffuse reflectance spectrum (DRS). The synthetic route for the formation of Ag decorated Fe3O4/TiO2 core/shell coating on cenosphere surfaces is established. The photocatalytic activity of the as-prepared cenospheres for the methylene blue degradation is measured under both ultraviolet and visible light irradiation. The results show that the Ag decorated Fe3O4/TiO2 coated cenospheres having a saturation magnetization of 21 emu g−1 are fabricated. After decoration with Ag the photocatalytic activity of the Fe3O4/TiO2 coated cenospheres is greatly improved under visible light irradiation because of the strong scattering and absorption properties of Ag nanoparticles. The silicon–oxygen interlayer between Fe3O4 core and TiO2 shell can be employed to prevent photodissolution of Fe3O4 during photocatalysis.