RESUMEN
The bandgap of solid-state TiO2 (3.2 eV) enables it to be a useful photocatalyst in the ultraviolet (lambda < 380 nm) region of the spectrum. A clean TiO2 surface in the presence of sunlight therefore enables the removal of harmful NOx gases from the atmosphere by oxidation to nitrates. These properties, in addition to the whiteness, relative cheapness and non-toxicity, make TiO2 ideal for the many de-NOX catalysts that are currently being commercially exploited both in the UK and Japan for concrete paving materials in inner cities. There is need, however, for further academic understanding of the surface reactions involved. Hence, we have used surface specific techniques, including X-ray photoelectron spectroscopy and Raman spectroscopy, to investigate the NOx adsorbate reaction at the TiO2 substrate surface.
Asunto(s)
Contaminantes Atmosféricos/química , Salud Ambiental , Óxidos de Nitrógeno/química , Titanio/química , Adsorción , Amoníaco/química , Catálisis , Microscopía Electrónica de Rastreo , Espectrometría por Rayos X , Espectrometría Raman , Rayos UltravioletaRESUMEN
Recent advances in understanding dynamic surface tensions (DSTs) of surfactant solutions are discussed. For pre-CMC solutions of non-ionic surfactants, theoretical models and experimental evidence for a mixed diffusion-kinetic adsorption mechanism are covered. For micellar solutions of non-ionics, up to approximately 100 x CMC, the DST behaviour can also be accounted for using a mixed mechanism model. Finally, the first reported measurements of the dynamic surface excess Gamma(t), using the overflowing cylinder in conjunction with neutron reflection, are described.
