A novel mixed-phase TiO 2/kaolinite composites and their photocatalytic activity for degradation of organic contaminants

Abstract

We successfully synthesized the TiO 2/kaolinite (TiO 2/Kao) composites with mixed phase TiO 2 using a simple method at low temperature. The as-prepared TiO 2/Kao composites were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), nitrogen adsorption/desorption measurements, Fourier transform infrared (FT-IR) spectroscopy and UV–vis diffuse reflectance spectra (DRS). The X-ray diffraction analysis indicated that the binary mixtures of anatase and rutile or the binary mixtures of anatase and brookite or the ternary mixtures of anatase, brookite, and rutile exist in the TiO 2/Kao composites. The specific surface area of the TiO 2/Kao composites is much higher than that of the kaolinite. The as-prepared samples exhibited strong photocatalytic activity for the removal of acid red G (ARG) and 4-nitrophenol (4-NP). The composites obtained at 70 °C showed the highest photocatalytic activity, in which the mixed phases of anatase and brookite existed. The high specific surface area and heterojunction microstructure could be responsible for the high photocatalytic activity.