J. Phys. IV France 123 (2005) 381–386 C  EDP Sciences, Les Ulis DOI: 10.1051/ jp4:2005123070 Preparation and caracterization of TiO 2 powder photocatalysts. Comparative studies of photocatalytic activity in the degradation of -naphthol S. Qourzal 1 , M. Tamimi 1 , A. Assabbane 1 , A. Nounah 1 , N. Maroufi 1 , A. Bouamrane 2 and Y. Ait Ichou 1 1 Laboratoire de Chimie Physique, Équipe de Photocatalyse et Environnement, Département de Chimie, Faculté des Sciences, Université Ibn Zohr, BP. 8106, Cité Dakhla,Agadir, Maroc 2 Laboratoire d´Analyse Environnementale des Procédés et Systèmes Industriels, LAEPSI INSA Lyon, 69562 Villeurbanne Cedex, France Abstract. Titanium dioxide TiO 2 powder photocatalysts were prepared at the laboratory by two methods: hydrolysis of titanium tetraisopropoxide (TTIP) and the precipitation of a precursor starting from titanium tetrachloride TiCl 4 in basic medium. The products obtained are calcined at temperatures around 800 ◦ C. Their characterization was carried out by both diffraction X-ray (XRD) and thermogravimetric analysis (TGA). The photocatalytic activity of the elaborate solids (TiO 2 ) is evaluated. It is compared with that given for commercial TiO 2 “Degussa P-25” in the degradation of -naphthol chosen as an model molecule in aqueous suspension. These reactions are done at room temperature in a photochemical reactor. Key words: Preparation; TiO 2 ; Photocatalysis; Photodegradation; -naphthol. 1. INTRODUCTION Heterogeneous photocatalysis by oxides is a fast growing field of basic and applied research, especially for the case of the oxidation processes of organic pollutants in waste waters, or in air [1-4]. In these processes, the semiconductor TiO 2 has been considered to be very promising because of its non-toxicity, low cost and high activity [5-7]. The principle of this technique is based on the illumination of a semiconductor. This illumination, with light energy equal to or greater than its band-gap (E bg ), causes an electron (e - ) to shift from the valence band to the conduction band, thereby creating holes (h + ) in the former [8-10]. Subsequently, charge carriers either recombine and dissipate the input energy as heat, get trapped in metastable surface states, or react with electron donors and acceptors adsorbed on the surface or bound within the electrical double layer [11]. The generation of the hydroxyl radical (OH ◦ ) which is a reactive intermediate and has a high oxidation potential. This OH ◦ attacks organic molecules by abstracting a hydrogen atom or by adding to the double bonds. Organic molecules are then transformed to more oxidized intermediates, carbon dioxide and water. This study is designed to improve the fundamental understanding of this type of process of water purification. However, it is necessary to know the factors that affect photocatalysis with oxides powders, in order to use the known photocatalysts more efficiently. Numerous studies have been devoted to investigate the synthesis of TiO 2 powders with improved photoactivity. In this work, we show the results of a comparative study between commercial TiO 2 photocatalyst “Degussa P-25” and titania samples prepared in laboratory, which have been widely chracterized, and tested in photocatalytic degradation of -naphthol selected as a model organic pollutant of the carboxylic type. Article published by EDP Sciences and available at http://www.edpsciences.org/jp4 or http://dx.doi.org/10.1051/jp4:2005123070