Tungstophosphoric acid supported on polycrystalline TiO2 for the photodegradation of 4-nitrophenol in aqueous solution and propan-2-ol in vapour phase

The present work reports the preparation of samples based on Millennium PC-500 TiO2 loaded with different amounts of tungstophosphoric acid (up to 30% in weight) and their characterisation by means of different physicochemical techniques: powder X-ray diffraction, N-2 adsorption-desorption at -196 degrees C, transmission electron microscopy, UV-vis and FT-IR spectroscopies and thermogravimetric analyses. The acidity of samples was evaluated by FTIR using pyridine as probe molecule, and the catalysts activity was tested for the photodegradation of 4-nitrophenol in aqueous solution and for the photo-oxidation of propan-2-ol in vapour phase. The results show a noticeable improvement (8 and 2.5 times faster in the photodegradation rate of 4-nitrophenol and propan-2-ol, respectively), in both regimes for these specific substrates, when tungstophosphoric acid is dispersed over the oxide up to a certain amount (20% in weight). A partial leaching of the polyoxometalate was also detected in solution for samples loaded with the largest amounts on this compound. (C) 2009 Elsevier B.V. All rights reserved.