Structure and photocatalytic performance of TiO2/clay nanocomposites for the degradation of dimethachlor

Abstract

In the present study TiO2/clay composites were synthesized by dispersion of TiO2 on the surfaces of a natural montmorillonite and a synthetic hectorite in order to increase the sorption ability of TiO2 and therefore its photocatalytic action. Six materials with different loading in TiO2 (15, 30 and 55wt%) were prepared and characterized by several analytical techniques including XRD, BET and SEM analysis. The synthetic procedure allows the development of delaminated layers for hectorite–TiO2 samples, while in the case of montmorillonite–TiO2 composites we have the formation of a more lamellar-like aggregation. It was found that, the greater the percentage of TiO2, the greater the pore volume and the specific surface area of the montmorillonite–TiO2 samples. On the contrary, in the case of hectorite–TiO2 samples, as the content of TiO2 increases, the surface area and pore volume decreases. The photocatalytic efficiency of the nanocomposite catalysts was evaluated using a chloroacetanilide herbicide (dimethachlor) in water as model compound. The primary degradation of dimethachlor followed pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. All supported catalysts exhibit good photodegradation efficiency and their overall removal efficiency per mass of TiO2 was better than that of bare TiO2 produced by the sol–gel method. In conclusion, together with their good sedimentation ability the composite materials could be considered as a promising alternative for the removal of organic water contaminants.