ABSTRACTTiO2 organoclays are potential adsorbents for aqueous pollutants and subsequently they could favour the photocatalysis of them. For this reason, the study of their surface and textural characteristics is important for the improvement of those processes. In this work TiO2 pillared organoclays were studied. The surfactant (hexadecyltrimethilammonium bromide) was introduced post-pillaring or during the pillaring process. The effect of the use of different acids of hydrolysis and different surfactants ratios was investigated. The clays were characterized by thermogravimetric analysis, infrared spectroscopy and nitrogen sorptometry. It was found that the highest adsorption capacity post-pillaring of the surfactant is near to 0.5 times the CEC of the original pillared clay, independently of the amount of surfactant offered. An increment in the amount of the surfactant introduced only increased the ratio adsorbed as ionic pair. In these samples the CEC measured after the adsorption was between 0.26 and 0.47 times the original CEC. It was observed a decrease in the total pore volume and the BET surface for every sample. The surface hydrophobicity of the samples with post-pillaring adsorption was higher than in those with co-adsorption. In conclusion, it was demonstrated that the incorporation of surfactant modifies the surface and textural properties of the material in different extent in accordance with the incorporation stage and the amount of surfactant used.

abstractIn this research TiO2 modified with nitrogen has been prepared. The synthesis method used was sol gel from the hydrolysis of titanium tetrabutoxide with urea solution, combined with a low temperature treatment at atmospheric pressure. The theoretical mole ratio N/Ti was equal to 0.5 and the theoretical mole ratio HNO3/TiO2 was equal to 0.5. The solid obtained was calcined at different temperatures in static air with high heating rate and residence time of 1 hour. The samples were characterized by X-ray diffraction, FTIR Raman and diffuse reflectance spectroscopy, thermodifferential and thermogravimetric analysis and specific surface area. All calcined solids exhibit absorption in the visible range. The Raman spectroscopy and X-ray diffraction revealed for all the heat treatments, the presence of crystalline phases corresponding to anatase and brookite polymorphism. The photocatalytic activity of the catalysts was tested in degradation of an artificial dye under visible light, yielding the best results for the sample treated at 250°C. Our results allow to say that this behaviour is due to the absorption of visible light, good efficiency for the adsorption of the dye and presence of two crystalline phases that decreases the recombination of photogenerated electrons and holes. The synthesis technique used allows obtaining solids with textural and attractive photocatalytic properties.

This study aims to synthesize and characterize organoclays developed from an Argentinian montmorillonite (Bent) using hexadecyltrimethylammonium bromide (HDTMA-Br) as the intercalation agent. Subsequently, an adsorption mechanism is proposed. The obtained organoclays were more hydrophobic than the starting clay. Surfactant molecules were adsorbed initially through cation exchange in sites placed in the interlayer space of the clay. Adsorption in such sites continued until the interlayer space was saturated. Depending on the surfactant loading introduced during the intercalation process, different organizations of surfactant in the interlayer were obtained. Further adsorption of surfactant occurred in the mesopores generated by tactoids in the "house of cards" organization. This process kept surfactant molecules relatively free and out of the interlayer space.