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RESEARCH PRODUCT

Preparation and characterization of Al2O3 supported TiO2 catalysts employed for 4-nitrophenol photodegradation in aqueous medium

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Abstract In this paper the preparation and some bulk and surface characterizations of set of Al2O3 supported TiO2 photocatalysts are reported. The powders were home prepared by a wet impregnation method using titanium (IV) isopropylate. The impregnation was followed by thermal treatments and this procedure was repeated several times in order to obtain samples with different amounts of TiO2. The solids were characterized by X-ray diffraction, specific surface area determination, scanning electron microscopy coupled with an electron microprobe used in an energy-dispersive mode and diffuse reflectance spectroscopy. Moreover, all of them were tested as photocatalysts by using different kinds of batch photoreactors for 4-nitrophenol photodegradation in aqueous medium chosen as a ‘probe’ reaction. The characterization results indicate that a layer of anatase TiO2 formed on the surface of Al2O particles, its extent depending on the number of impregnations. The photoactivity of the powders increased by increasing the number of impregnations up to seven times. For samples obtained by impregnating seven times, the photoreactivity was higher, but not much different from that observed by using samples impregnated five times. The photoactivities of the samples obtained with five and seven impregnations were found to be not much lower than that of a pure home prepared TiO2 sample, but quite lower than that of a Degussa P25 TiO2 sample. Finally, it is worth noting that the alumina supported TiO2 catalysts are easily separated from water by decantation and no significant deactivation due to disaggregation of the particles and/or erosion of their surface was shown to occur in some of the used experimental conditions, i.e. when photoreactors coupled with an electric impeller were used.