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International Journal of Photoenergy
Volume 2006, Article ID 26870, 8 pages
http://dx.doi.org/10.1155/IJP/2006/26870

Modelling of quantum yields in photocatalytic membrane reactors immobilising titanium dioxide

1Environmental Research Centre, University of Milan, Via C. Golgi 19, Milan 20133, Italy
2Research and Development Group, BIT srl, Milan 20121, Italy
3Department of Materials Science, University of Milano Bicocca, Milan 20126, Italy
4CNR, ISTM, Milan 20133, Italy

Received 19 February 2006; Revised 25 April 2006; Accepted 4 May 2006

Copyright © 2006 Ignazio Renato Bellobono et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

For some model molecules (methanoic and ethanoic acids, methane, and phenol), systematic investigations of quantum yields were carried out in the present paper, as a function of concentration and of absorbed radiant power. Quantum yields Φ, calculated from rates, followed an apparently Langmuirian function of initial concentration C0, by which Φ values at “infinite” concentration could be obtained. By having thus established that quantum yields of photomineralisation Φ are independent of radiation wavelength, within the absorption range of semiconductor, but depend on radiant power, such a dependency was experimentally investigated. For all the investigated molecules, the maximum allowable values reached in the low radiant power range clearly appeared as a plateau. On the contrary, at high radiant power values, another plateau, at a value of about 1/4-1/5 with respect to the maximum value, was evident. This was interpreted on the basis of a competition kinetics of hydroxyl radicals with themselves, leading to hydrogen peroxide formation, other than with substrate or intermediate molecules leading to full mineralisation. Modelling of quantum yields as a function of concentration and radiant power thus allows a fully consistent and trustworthy design of photoreactors.