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RESEARCH PRODUCT

ZrO2SiO2 mixed oxides: surface aspects, photophysical properties and photoreactivity for 4-nitrophenol oxidation in aqueous phase

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Abstract Mixed oxides of ZrO2 and SiO2 were synthesized by a sol-gel technique by using zirconyl chloride and commercial silica gel as starting materials. The paper reports some surface features of the powders and the photoreactivity results obtained in the oxidation of 4-nitrophenol in aqueous suspensions of powdered photocatalyst. The optical characterization of the suspension was also performed by measuring the photon flows reflected and absorbed by the reacting system. The photoactivity exhibited by the ZrO2SiO2 samples is very scarce especially if compared with that shown by a TiO2 sample tested at equal experimental conditions. The low photoreactivity can be justified on the basis of two main reasons: (i) the unfavourable optical features of ZrO2SiO2 suspensions in comparison with those of TiO2 ones; and (ii) the lower degree of hydroxylation of ZrO2SiO2 samples with respect to that of TiO2 and, consequently, the less significant oxygen adsorption.