Adsorption and photocatalytic bleaching of acid orange 7 on P25 titania

作者：O'Rourke Christopher; Mills Andrew^*

来源：Journal of Photochemistry and Photobiology A: Chemistry , 2010, 216(2-3): 261-267.

DOI：10.1016/j.jphotochem.2010.07.006

• Photocatalysis
• CD-MUSIC
• Adsorption
• Photobleaching
• Acid orange 7

The observed adsorption of acid orange 7, AO7(-), on P25 titania over a range of pH values (pH 2-8) gives a good fit to data generated using a charge distribution, multisite complexation, i.e. CD-MUSIC, model, modified for aggregated dye adsorption. For this system the model predicts that both the apparent dark Langmuir adsorption constant. K(L), and the number of adsorption sites, n(o), increase with decreasing pH, and are negligible above pH 6. At pH 2 the CD-MUSIC model predicts the fraction of singly co-ordinated sites occupied by the dye,f(AO7), is ca. 32% under the in situ monitoring experimental conditions used in this work to study the photocatalytic bleaching of AO7(-) under UV light illumination ([TiO(2)] = 20 mgdm(-3); [AO7(-)](total) = 4.86 x 10(-5) M). Although AO7(-) adsorption on P25 titania is insignificant above pH 6 and increases almost linearly and markedly below this pH, the measured initial rate of bleaching of AO7(-), photocatalysed by titania using UV appears to only increase modestly (<factor of 2) over the pH range 2-10 studied. Possible reasons for the lack of a strong dependency of initial rate of photobleaching, r(i), upon f(AO7) are discussed briefly. In contrast, the rate of bleaching of AO7(-) via a visible light driven, dye-sensitised process, shows some correlation with the CD-MUSIC model-calculated variation of f(AO7) as a function of pH. Such a correlation follows from the basic assumption that only dye molecules that are in direct contact with the surface can undergo photodegradation via a dye-sensitised route.

• 出版日期2010-12-15