Dye-sensitized photodegradation of the fungicide carbendazim and related benzimidazoles.
Chemosphere
; 65(2): 237-44, 2006 Oct.
Article
en En
| MEDLINE
| ID: mdl-16643984
The present work studies the visible-light-promoted photodegradation of the colorless fungicide carbendazim (methyl 2-benzimidazolecarbamate) and several 2-substituted benzimidazoles (SBZ's), in water or water-methanol solution, in the presence of air and, as a photosensitizer, the synthetic xanthene dye Rose Bengal (RB) or the natural pigment riboflavin (Rf). The results indicate that the degradation of each particular SBZ depends on its chemical structure and on the sensitizer employed. In the presence of RB, the degradation always operates via a singlet molecular oxygen (O(2)((1)Delta(g)))-mediated mechanism, through a highly efficient process, as deduced from the comparison of the rate constants for physical and chemical quenching of O(2)((1)Delta(g)). In the presence of Rf, the visible-light irradiation of any of the studied SBZ's produces a series of competitive processes that depend on the relative concentrations of Rf and SBZ. These processes include the quenching of excited singlet and triplet Rf states by the SBZ and the generation of both O(2)((1)Delta(g)) and superoxide radical anion (O(2)(-)), the latter generated by electron transfer from excited Rf species to the dissolved oxygen. The overall result is the photodegradation of the SBZ and the photoprotection of the sensitizer.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Fotólisis
/
Fármacos Fotosensibilizantes
/
Colorantes
/
Fungicidas Industriales
Idioma:
En
Revista:
Chemosphere
Año:
2006
Tipo del documento:
Article
País de afiliación:
Argentina
Pais de publicación:
Reino Unido