INFLUENCE OF TUNGSTEN-OXIDE ON STRUCTURAL AND SURFACE-PROPERTIES OF SOL-GEL PREPARED TIO2 EMPLOYED FOR 4-NITROPHENOL PHOTODEGRADATION

A set of tungsten oxide/TiO2 polycrystalline samples (W/Ti) prepared b y the sol-gel method has been characterised using several techniques, namely thermogravimetric analysis, gas-chromatography, mass spectromet ry, thermogravimetric analysis combined with mass spectrometry or with gas chromatography/mass spectrometry, X-ray diffraction, X-ray photoe lectron spectroscopy, determination of specific surface area, scanning electron microscopy, Fourier-transform infrared spectroscopy and moni torisation of pyridine adsorption for surface acidity. Moreover the sa mples have been employed as catalysts for 4-nitrophenol photodegradati on in aqueous suspensions used as a 'probe' reaction. Characterisation results indicate that the surface of the W/Ti particles is enriched w ith homogeneously dispersed tungsten as well as microcrystalline or am orphous species. Maximum photoactivity for 4-nitrophenol photodegradat ion was achieved for a sample containing 1.7 mol W per 100 mol Ti.