from first principles PP-I-1

OY-V-1Kinetic Study of p-Nitrophenol Photodegradationwith Modified TiO 2 XerogelsTasseroul L. 1 , Pirard S.L. 1 , Lambert S.D. 1 , Páez C.A. 1 , Poelman D. 2 , Pirard J.-P. 1 , Heinrichs B. 11 University of Liège, Laboratoire de Génie chimique, B6a, B-4000 Liège, Belgium2 University of Ghent, Department of Solid State Sciences, Krijgslaan 281, S1, B-9000 Ghent,Belgiumltasseroul@ulg.ac.beAdvanced oxidative processes represent new technologies for waste water treatment, becausenew compounds in effluents are not readily degraded by the conventional treatments.Oxidative processes can completely destroy organic pollutants (alkanes, pesticides, etc.) ormicroorganisms (bacteria, viruses, fungi, etc.). TiO 2 is widely studied in photocatalyticoxidation processes for environmental applications but it is activated with UV light only [1].In this study, TiO 2 xerogels were sensitized in one step by the in situ introduction of nickel(II) tetra(4-carboxyphenyl)porphyrin (TCPPNi) into the TiO 2 matrix during sol-gel synthesisin order to extend TiO 2 activation to the visible light region of the solar spectrum. Crystallinephotoactive phase TiO 2 -anatase was obtained without high thermal treatments and wascharacterized by X-ray diffraction. The photoactivity of xerogels was evaluated forp-nitrophenol degradation in aqueous medium at 20 °C. Results showed that porphyrin dopedTiO 2 degrades more than 40% of the p-nitrophenol whereas non doped TiO 2 xerogel degradesonly 10% of the compound. Moreover, porphyrin was found to improve the photoactivity ofTiO 2 xerogels in a similar way to UV-A pretreatment. A kinetic study on p-nitrophenoldegradation was then performed with variations both in initial p-nitrophenol concentrationand in temperature. Results were adjusted on a physico-chemical model based on a sequenceof elementary steps. They showed that one type of active site corresponding to the hole ofelectron-hole pairs is created at the TiO 2 surface by light and that the rate determining step isthe reaction between the adsorbed p-nitrophenol molecule and the adsorbed OH • radical. Theapparent activation energy was found to be equal to 12 kJ mol -1 [2].[1] P. Gogate, Adv. Environ. Res. 8 (2004) 501-551.[2] L. Tasseroul, S.L. Pirard, S.D. Lambert, C.A. Páez, D. Poelman, J.-P. Pirard, B. Heinrichs, Chem.Eng. J.109