Photodegradation of pyrene on solid phase

Abstract

Photodegradation of 1% weight ratio pyrene on different model supports SiO2CaCO3 and montmorillonite was investigated. The kinetic studies show that the pyrene pseudo half-lives depend on the nature of the support, and on the presence of water: on dry support, t1/2 =3 h on SiO2, 3 h on CaCO3, and 6 h on montmorillonite whereas, in presence of water, t1/2 =9.9 h, 9.9 h, and 221 h, respectively. The irradiation of pyrene revealed degradation products such as 1-hydroxypyrene, 4,5-dihydro-4,5-dihydroxypyrene, 1,6 and/or 1,8-dihydroxypyrene, 1,6 and/or 1,8-pyrenequinone and 1,1′-bipyrene. Given (i) the byproducts identified, (ii) the inhibition of pyrene transfer S 1→T1 with HgCl2 and (iii) an oxidation non photosensitized by rose bengal, a possible degradation pathway is proposed which involves the formation of a pyrene radical cation via the singlet state of pyrene. © 2005 Springer-Verlag Berlin Heidelberg.