Polystyrene-heterojunction semiconductor composite spheres prepared by a hydrothermal synthesis process: a recyclable photocatalyst under visible light irradiation for removing organic dyes from aqueous solution.

A composite photocatalyst, with a BiOI/TiO2 heterojunction supported on carboxyl polystyrene spheres, was prepared using a two step hydrothermal reaction method. The products were characterized by X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results show that the polystyrene microspheres were covered with smaller-sized BiOI microspheres, while nano-sized TiO2 particles were deposited on the surface of the flower-like BiOI microspheres. As an internal electric field exists when BiOI is hybridized with TiO2, the photogenerated carriers could be separated effectively and the resulting composite photocatalyst PS/BiOI/TiO2 had better performance for degrading rhodamine B in aqueous solution under visible-light irradiation with a 40 W incandescent lamp than that of PS/BiOI. Meaningfully, the composite photocatalyst can be recycled easily by filtering.