PHYSICOCHEMICAL CHARACTERIZATION OF WO3 ZRO2 AND WO3/NB2O5 CATALYSTS AND THEIR PHOTOACTIVITY FOR 4-NITROPHENOL PHOTOOXIDATION IN AQUEOUS DISPERSION/

Two different photo-catalysts consisting of tungsten oxide supported o n zirconia and niobia have been studied. The photoactivity of the samp les has been investigated in both the absence and presence of H2O2 for the photo-oxidation of 4-nitrophenol in aqueous suspensions and compa red to that of WO3 and of the pure ZrO2 and Nb2O5 supports. Both catal ysts were found to be photoactive, although no beneficial influence of the presence of tungsten oxide on the reaction rate was observed in t he absence of H2O2. The presence of hydrogen peroxide was observed to be beneficial for all of the samples. Scanning electron microscopy, X- ray diffraction, diffuse reflectance and laser Raman spectroscopies, s urface area and porosity determination, as well as Fourier transform i nfra-red spectroscopy monitoring of surface acidity were used to chara cterize the catalysts.