1,721,678 research outputs found
The role of the synthetic procedure of nano-crystalline TiO2 on the photodegradation of toluene
No full textBecause of its stability and nontoxicity TiO2 has been extensively investigated as an efficient photocatalyst for purifying water and air. The use of TiO2 in photocatalytic concrete and paints is very promising and intensively investigated.
In recent years a great deal of activity was dedicated, by the authors’ group, to the study of synthetic routes leading to nanocrystalline materials with tailored features, mainly in the case of titania. Sol-gel paths, combined with hydrothermal stages performed either in the presence or in the absence of surfactants, have led to nanocrystalline TiO2 with controlled enrichment in either anatase, brookite or rutile [1-4]. There is ample debate in the literature concerning the actual role played by either of the titania polymorphs with respect to the photocatalytic activity of the material [5].
In this work the authors report on the activity of nanocrystalline titania, prepared by a multi-step sol-gel procedure, with respect to the photodegradation of toluene used as a model compound. Samples with varying surface area and anatase/brookite/rutile content are fully characterized and then tested and their photoactivity is compared with that of the most commonly commercial TiO2 photocatalysts.
The photodegradation of toluene is investigated both in aqueous and in gas phase. In the former case the composition of the reacting mixture, in terms of side products, is followed by HPLC and MS-GC and the total mineralization by TOC. In the latter case the reactor is equipped with an online micro-GC.
[1] T. Boiadjieva, G. Cappelletti, S. Ardizzone, S. Rondinini, A. Vertova, Phys. Chem. Chem. Phys., 5 (2003) 1689.
[2] G. Cappelletti, C. Ricci, S. Ardizzone, C. Parola, A. Anedda, J. Phys. Chem. B., 109 (2005) 4448.
[3] C.L. Bianchi, S. Ardizzone, G. Cappelletti, Dekker Encyclopedia of Nanoscience and Nanotechnology Marcel Dekker (New York), 2006, pp. 1-10, DOI: 10.1081/E-ENN-120042107
[4] G.Cappelletti, C.L.Bianchi, S. Ardizzone, Appl. Surf. Sci., 253 (2006) 519-524
[5] J. Krysa, M. Keppert, J. Jirkovsky, V. Stengl, J. Subrt, Mater. Chem. Phys., 86 (2004) 333
Bulk, surface and double layer properties of zirconia polymorphs subjected to mechanical treatments
No full textZirconia (ZrO2) may exist in different polymorphs. At low pressures and for temperatures as high as ∼-1150 °C only the stable phase has the monoclinic structure; tetragonal and cubic oxides form however, as metastable phases together with the monoclinic in the lower temperature region (up to ca. 600 - 800 °C). By combining stages of calcination (of a hydrothermal precursor) with severe grinding treatments of the powders it was possible to obtain pure phase monoclinic oxides (S. Ardizzone, G. Bassi, G. Liborio, Colloids and Surfaces 51 (1990) 207). This paper reports results concerning the effects specifically induced by the severe grinding on the phase composition, on the state of the surface and on the interfacial electrostatic reactivity of the powders. The effects produced by ageing, calcinations and further mechanical treatments of the samples are also examined by the same techniques i.e. by X-ray diffraction, XPS determinations and surface charge measurements. © 1991
La terapia immunosoppressiva long-term nelle malattie infiammatorie croniche intestinali
No full textSono gli immunosoppressori convenzionali i farmaci di prima scelta nel trattamento delle malattie infiammatorie croniche intestinali?
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Artt. 163-169
No full textAnalisi della evoluzione dottrinale e giurisprudenziale in materia di sospensione condizionale e di perdono giudiziale. Valutazione in chiave critica della funzione dell'istitut
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