A novel mixed-phase TiO2/kaolinite composites and their photocatalytic activity for degradation of organic contaminants

We successfully synthesized the TiO2/kaolinite (TiO2/Kao) composites with mixed phase TiO2 using a simple method at low temperature. The as-prepared TiO2/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 TiO2/Kao composites. The specific surface area of the TiO2/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.

► The mixed phase TiO2 supported on kaolinite was synthesized at low temperature.
► The heterojunction structures are formed in the as-prepared samples.
► The high specific surface area and bimodal mesoporous structure improve adsorbility.
► The TiO2/Kao composites show better adsorption and photocatalytic ability than P25.