Showing papers by "Marta I. Litter published in 2002"
TL;DR: In this paper, three commercially available TiO2-catalysts, namely Degussa P25, Sachtleben Hombikat UV100 and Millennium TiONA PC50, were platinized by a photochemical impregnation method in two ratios of platinum deposits (0.5 and 1.5 ).
Abstract: In the present work, three commercially available TiO2-catalysts, namely Degussa P25, Sachtleben Hombikat UV100 and Millennium TiONA PC50, were platinised by a photochemical impregnation method in two ratios of platinum deposits (0.5 and 1 wt.%). The physical characterisation of the new synthesised catalysts was carried out by measurements of the BET-surface area, the light absorption properties and the adsorption of the model compounds. The photocatalytic activities of these samples were determined using three different model compounds: EDTA, 4-chlorophenol (4-CP), and dichloroacetic acid (DCA). While in the case of EDTA its disappearance was studied, total mineralisation was measured for 4-CP and DCA. In all cases, the photocatalytical activity was found to increase with rising amounts of Pt, e.g., the photonic efficiency for DCA degradation increased from 12.2% for pure Hombikat UV100 to 32.1% for Hombikat UV100/0.5 wt.% Pt and to 42.7% for Hombikat UV100/1 wt.% Pt. Promising results were also achieved for the total mineralisation of 4-CP. The photonic efficiency rised from 0.82% using unmodified PC50 to 1.14% with PC50/0.5 wt.% Pt (zero-order kinetics assumed in all cases). Similar results were obtained with the other new synthesised catalyst samples and for the model compound EDTA. No immediate relationship between the photocatalytic activity of the catalyst samples and their physical properties (surface area, adsorption of pollutants, absorption of light) could be observed.
223 citations
TL;DR: In this article, the effect of platinum on titania was analyzed on the basis of proposed mechanisms, and the initial photonic efficiencies and conversion degrees have been calculated from kinetic profiles.
Abstract: Two commercial samples, namely Degussa P-25 and Sachtleben Hombikat UV 100, and platinized modifications of these samples have been tested comparatively as photocatalysts for EDTA oxidation and for Cr(VI) reduction in the absence and in the presence of EDTA. Platinized photocatalysts were prepared by photoimpregnation of H 2 PtCl 6 on TiO 2 by prolonged irradiation in the presence of methanol. Only slight differences in efficiency were found between both pure commercial forms, except for the Cr(VI) reduction in the presence of EDTA, where Hombikat UV 100 samples were more active. Platinized Hombikat UV 100 was found to be less active for Cr(VI) reduction in water. The concentration of dissolved molecular oxygen was crucial for EDTA oxidation and had no influence on Cr(VI) reduction. From kinetic profiles, initial photonic efficiencies ( ζ ) and conversion degrees have been calculated. Platinization did not improve Cr(VI) reduction but increased the initial photonic efficiency for EDTA oxidation. However, after prolonged irradiation, the conversion of EDTA was lower employing platinized samples instead of pure samples. The effect of platinum on titania was analyzed on the basis of proposed mechanisms.
187 citations
TL;DR: An advanced oxidation treatment was applied to an azo dye, Hispamin Black CA, widely used in the Peruvian textile industry and it has been found that the degradation rate increased until an optimum value, beyond which the reagent exerted an inhibitory effect.
171 citations
TL;DR: In this article, the degradation of EDTA at pH 3 was studied by the ferrioxalate/H2O2 process under solar irradiation and the final extent of degradation was found to decrease with higher oxalate concentrations, probably by competition of oxalates with EDTA or its degradation products.
Abstract: Degradation of ethylenediaminetetraacetic acid (EDTA; in the mmol/l range) at pH 3 was studied by the ferrioxalate/H2O2 process under solar irradiation. A rapid total organic carbon (TOC) removal was attained in all cases, reaching almost 100% after 1 h solar exposure under the best conditions. In order to attain a high TOC removal yield, the pH must be rigorously controlled. The reaction rate increased with H2O2 concentration; but its effect was not very marked. The final extent of degradation was found to decrease with higher ferrioxalate concentrations, probably by competition of oxalate with EDTA or its degradation products. In the absence of oxalate, EDTA could also be degraded to a reasonably good extent, with a TOC removal only slightly lower than when using ferrioxalate, which constitutes a good advantage from the economical point of view. The intensity of solar light was found to be a very important factor to improve the reaction.
77 citations
TL;DR: In this paper, the authors have analyzed the photocatalysis of 0.5mM mercuric aqueous solutions starting from Hg(NO 3 ) 2, Hg (ClO 4 ) 2 and HgCl 2 at different pH (3, 7 and 11) and in the presence or absence of oxygen.
57 citations
01 Jan 2002
TL;DR: In this article, the effect of platinization on titania was analyzed on the basis of proposed mechanisms and the initial photonic efficiencies and conversion degrees have been calculated from kinetic profiles, and the platinized modifications of these samples were tested comparatively as photocatalysts for EDTA oxidation and for Cr(VI) reduction in the absence and in the presence of EDTA.
Abstract: Two commercial samples, namely Degussa P-25 and Sachtleben Hombikat UV 100, and platinized modifications of these samples have been tested comparatively as photocatalysts for EDTA oxidation and for Cr(VI) reduction in the absence and in the presence of EDTA. Platinized photocatalysts were prepared by photoimpregnation of H2PtCl6 on TiO2 by prolonged irradiation in the presence of methanol. Only slight differences in efficiency were found between both pure commercial forms, except for the Cr(VI) reduction in the presence of EDTA, where Hombikat UV 100 samples were more active. Platinized Hombikat UV 100 was found to be less active for Cr(VI) reduction in water. The concentration of dissolved molecular oxygen was crucial for EDTA oxidation and had no influence on Cr(VI) reduction. From kinetic profiles, initial photonic efficiencies ( ζ ) and conversion degrees have been calculated. Platinization did not improve Cr(VI) reduction but increased the initial photonic efficiency for EDTA oxidation. However, after prolonged irradiation, the conversion of EDTA was lower employing platinized samples instead of pure samples. The effect of platinum on titania was analyzed on the basis of proposed mechanisms. © 2002 Published by Elsevier Science B.V.
15 citations
01 Jan 2002
TL;DR: In this article, the authors have analyzed the photocatalysis of 0.5 mM mercuric aqueous solutions starting from Hg(NO3)2, HgO4)2 and HgCl2 at different pH (3, 7 and 11) and in the presence or absence of oxygen.
Abstract: UV/TiO2 photocatalysis of 0.5 mM mercuric aqueous solutions has been analyzed starting from Hg(NO3)2, Hg(ClO4)2 and HgCl2 at different pH (3, 7 and 11) and in the presence or absence of oxygen. Profiles of Hg II concentration with time were characterized by a relatively rapid initial conversion followed by a decrease or an arrest of the rate, the shape of profiles changing with the conditions. Conversions at 60 min and initial quantum efficiencies have been found dependent on the initial conditions and type of mercuric salt. The faster transformation took place at pH 11 for all salts. A good transformation yield is observed also for HgCl2, which behaves differently to the other two salts, at pH 3 under nitrogen and pH 7 (N2 or O2). Inhibition by oxygen was observed in acid and neutral media but not at basic pH. When the conversion was 50% or more, pale or dark gray solids were deposited on the catalyst, identified as mixtures of Hg 0 , HgO or Hg2Cl2. A unique kinetic scheme could not be defined, which seemed to depend on the nature of the mercury salt, the ambient conditions and the type of deposit. Implications of the application of the technique to real systems are discussed. © 2002 Elsevier Science B.V. All rights reserved.
11 citations