Degradation of phenol by photocatalysis using TiO₂/montmorillonite composites under UV light

Composites of titanium (IV) oxide combined with montmorillonite (MMT) with various TiO₂/MMT were prepared for photocatalysis application. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), diffuse reflectance UV-visible spectroscopy, and X-ray photoelectron spectroscopy (XPS). The main influential factors such as the TiO₂/MMT dose, calcined temperature, and pH value of the solution were studied. The main intermediates of phenol degradation were determined by high performance liquid chromatography (HPLC). The results showed that the average size of TiO₂ nanoparticles was decreased from 22.51 to 10.66 nm through the immobilization on MMT. The components in the interlayer domain were replaced by titanium pillars, and the pillaring reaction proceeded in the interlayer domain, the basic skeleton of MMT was unchanged, and TiO₂ was dispersed on the surface of the MMT. When the initial concentration of phenol is 10 mg/L, the phenol solution pH is 6, and the UV light irradiation time is 240 min; the phenol degradation rate of 30%TiO₂/MMT composite is 89.8%, which is better than MMT (11.5%) and pure TiO₂ (58.8%). It shows that TiO₂ loaded on MMT improves its photocatalytic activity. The phenol reaction process detected by HPLC showed that it had undergone through hydroquinone and benzoquinone, and finally converted into maleic acid and carbon dioxide and small molecules. The possible photocatalysis mechanism is presented.