Natural kaolinite modified black titanium dioxide for efficient visible light assisted photocatalysis

A novel black TiO2/kaolinite composite (bTK) was prepared by the hydrothermal method and tested as a photocatalyst. Morphology and structure of samples were systematically characterized by field emission scanning electronic microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that black TiO2 (bT) nanoparticles formed point defects were successfully coated as thin layers on the surface of kaolinite. The bTK composite had a narrower band gap and higher specific surface area. XPS results showed that Ti3+ and oxygen vacancies (Vo) existed in bT. The photocatalytic removal performance of bTK composite on methylene blue (MB) was near to 100% in 2 h, which was 32.1% higher than that of bT. Kinetic studies reveal that MB degradation process by the bTK corresponded well to zero-order kinetic.