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International Journal of Photoenergy
Volume 2006, Article ID 39182, 12 pages
http://dx.doi.org/10.1155/IJP/2006/39182

The role of water in the photocatalytic degradation of acetonitrile and toluene in gas-solid and liquid-solid regimes

1Dipartimento di Ingegneria Chimica dei Processi e dei Materiali, Università degli Studi di Palermo, Viale delle Scienze, Palermo 90128, Italy
2Dipartimento di Chimica IFM and NIS Centre of Excellence, Università degli Studi di Torino, Via Pietro Giuria 7, Torino 10125, Italy

Received 25 June 2005; Revised 17 August 2005; Accepted 20 September 2005

Copyright © 2006 Maurizio Addamo 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

Photocatalytic degradation of acetonitrile and toluene was carried out both in gas-solid and in liquid-solid regimes by using commercial TiO2 samples (Merck and Degussa P25). The investigation was mainly aimed to study the influence of water present in the reaction environment on the mechanism and degradation rate of two probe molecules. In gas-solid regime, the reacting mixture consisted of toluene or acetonitrile, oxygen, nitrogen, and water vapour. The main degradation product of toluene was CO2 with small amounts of benzaldehyde. In the presence of water vapour, the activity of TiO2 Merck remained stable but greatly decreased if water was absent. TiO2 Degussa P25 continuously deactivated, even in the presence of water vapour. With both catalysts, the photodegradation products of acetonitrile were CO2 and HCN; the activity was stable and was independent of the presence of water vapour in the reacting mixture. The production of HCN represents a drawback of acetonitrile photocatalytic degradation but the elimination of HCN is not actually a problem. In liquid-solid regime, the main intermediates of toluene photodegradation were p-cresol and benzaldehyde; traces of pyrogallol and benzyl alcohol were also found. Benzoic acid, hydroquinone, and trans, trans muconic acid were detected only when TiO2 Merck was used. The photodegradation products of acetonitrile were cyanide, cyanate, formate, nitrate, and carbonate ions.