New SnO2/MgAl-layered double hydroxide composites as photocatalysts for cationic dyes bleaching.

A new type of nanocomposite containing SnO(2) has been obtained by wet impregnation of dehydrated Mg/Al-hydrotalcite-type compounds with ethanolic solutions of SnCl(4).2H(2)O. Tin chloride hydrolysis was achieved using NaOH or NH(4)OH aqueous solutions, at pH around 9, followed by the conversion into corresponding hydroxides through calcinations. The powder X-ray diffraction (PXRD) and UV-Vis diffuse reflectance (UV-DR) methods confirmed the structure of as-synthesized solids. The chemical composition and morphology of the synthesized materials were investigated by energy dispersive X-ray analysis (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The as-synthesized materials were used for photocatalytic studies showing a good activity for methylene blue decolourization, which varies with SnO(2) content and used as a hydrolysing agent. The proposed mechanism is based on the shifting of flat band potential of SnO(2) due to the interaction with Mg/Al-LDH, this being energetically favourable to the formation of hydroxyl radicals responsible for methylene blue degradation.

Synthesis and characterization of TiO2-pillared Romanian clay and their application for azoic dyes photodegradation.

The synthesis and properties of metal oxide pillared cationic clays (PILCs) has been subject to numerous studies in the last decades. In order to obtain TiO(2)-pillared type materials, sodium montmorillonite from Romania-areal of Valea Chioarului, having the following composition (% wt): SiO(2)-72.87; Al(2)O(3)-14.5; MgO-2.15; Fe(2)O(3)-1.13; Na(2)O-0.60; K(2)O-0.60; CaO-0.90; PC-5.70 and cation exchange capacity, determined by ammonium acetate method, of 82 meq/100g, as matrix, was used. Sodium form of the clay was modified, primarily, by intercalation of cetyl-trimethylammonium cations between negatively charged layers which will lead to the expansion of the interlayer space. For the preparation of the TiO(2)-pillared clay, the alkoxide molecules, as titania precursor, were adsorbed onto/into clay samples (1 mmol Ti/g clay), in hydrochloric acid environment, the resulted species being converted into TiO(2) pillars by calcination. The as-prepared materials have been used as catalysts for Congo Red dye photodegradation, under UV. The photocatalytic activity of the pillared clays is a function of TiO(2) pillars size, their increase leading to the enhancement of the contact areas between dye solution and photoactive species present in the interlayer space. The structural characteristics and properties of the obtained materials were investigated by X-ray Diffraction, Thermogravimetry Analysis, UV-vis Diffuse Reflectance, Transmission Electron Microscopy and Energy Dispersive X-ray Analysis.