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

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 55 wt%) 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. (c) 2007 Elsevier B.V. All rights reserved.