Applied Catalysis B: Environmental, Vol.88, No.1-2, 194-203, 2009
Effect of sample preparation and humidity on the photodegradation rate of CEES on pure and Zn doped anatase TiO2 nanoparticles prepared by homogeneous hydrolysis
Pure titania and titania doped with Zn2+ were prepared by homogeneous hydrolysis in aqueous solution with urea and thioacetamide as precipitating agents. The materials were characterized by XRD, TEM, BET and BJH analysis, which show microporous, nanaocrytsalline anatase phase titania in the size range 45 nm and specific surface area 200-500 m(2)/g. Adsorption and photocatalytic decomposition of 2-chloroethyl ethyl sulfide (CEES) was measured on dry and water pre-covered titania surfaces, respectively. Illumination with UV light leads to rapid decomposition of CEES on all samples resulting in formation of surface bound ethoxy, chloro ethoxy, aldehydes, acetone and carboxylates. Volatile sulphur moieties (S=O) and isocyanate (Ti-NCO) are observed which is related to the synthesis methods employed. A procedure for removing residual synthesis products from the particles was devised and the intrinsic photodegradation rate was determined on the purified samples and compared with the as prepared samples. The photodegradation rate is notable higher for the purified TiO2 nanoparticles prepared by the urea route with respect to the "as prepared". In the case of the Zn doped TiO2 samples a diminution in photodegradation rate is observed after purification. The results are correlated with the amount of volatile residual synthesis products present on the different particles. All materials have comparable or higher photo-reactivity than P25 (Degussa). On a humidified surface, the effects from synthesis residues, in particular volatile sulphur moieties, are reduced due to reactions with water and improved photoreaction rates for all samples are observed. (C) 2008 Elsevier B.V. All rights reserved.
Keywords:CEES;TiO2;Photocatalysis;Homogeneous hydrolysis;Diffuse reflectance;Fourier transform infrared spectroscopy