Removal of malodorous organic sulfides with molecular oxygen and visible light over metal phthalocyanine

Organic sulfides are malodorous compounds in environment. In this work, deodorization of model substrates, methyl phenyl sulfide, 2-mercaptobenzoic acid and benzyl 2-propenyl sulfide, have been studied in an aerated methanolic aqueous solution under visible light irradiation (lambda > 450 nm), using metal phthalocyanine sulfonate (MPcS, M = Al, Pd) as a photocatalyst. The result shows that all the representative sulfides could be efficiently oxidized, with concomitant formation of sulfoxide and sulfone as the main products. Kinetic study using sodium azide and benzoquinone as reactive species scavenger reveals that the sulfide oxidation is mainly initiated by singlet oxygen. It is also observed that the rate of sulfide oxidation increases with increasing the water content in the mixed solvent. Recycle experiments with immobilized PdPcS on organoclay or immobilized AlPcS on anionic resin demonstrates that the sensitizer could be repeatedly used, without significant loss in the photosensitization activity. (C) 2007 Published by Elsevier B.V.