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.