TiO2/palygorskite composite nanocrystalline films prepared by surfactant templating route: Synergistic effect to the photocatalytic degradation of an azo-dye in water

Microfibrous palygorskite clay mineral and nanocrystalline TiO2 are incorporating in the preparation of nanocomposite films on glass substrates via sot-gel route at 500 degrees C. The synthesis involves a simple chemical method employing nonionic surfactant molecule as pore directing agent along with the acetic acid-based sot-gel route without direct addition of water molecules. Drying and thermal treatment of composite films lead to the elimination of organic material while ensure the formation of TiO2 nanoparticles homogeneously distributed on the surface of the palygorskite microfibers. TiO2 nanocomposite films without cracks consisted of small crystallites in size (12-16 nm) and anatase crystal phase was found to cover palygorskite microfibers. The composite films were characterized by microscopy techniques, UV-vis, IR spectroscopy, and porosimetry methods in order to examine their structural properties. Palygorskite/TiO2 composite films with variable quantities of palygorskite (0-2 w/w ratio) were tested as new photocatalysts in the photo-discoloration of Basic Blue 41 azo-dye in water. These nanocomposite films proved to be very promising photocatalysts and highly effective to dye's discoloration in spite of the small amount of immobilized palygorskite/TiO2 catalyst onto glass substrates. 3:2 palygorskite/TiO2 weight ratio was finally the most efficient photocatalyst while reproducible discoloration results of the dye were obtained after three cycles with same catalyst. It was also found that palygorskite showed a positive synergistic effect to the TiO2 photocatalysis. (c) 2011 Elsevier B.V. All rights reserved.