Phototransformations of Atrazine Over Different Metal Oxide Particles

Abstract

The photocatalytic degradation of atrazine has been examined under simulated solar light irradiation of various semiconductors powders (TiO₂, ZnO, WO₃, SnO₂, and Fe₂O₃) and different titania specimens (nanometersize colloids, micrometer particles and millimeter spherical beads). Three major different degradation pathways operate in the photocatalyzed process: (a) dehalogenation, (b) dealkylation, and (c) deamination; the final product is cyanuric acid. Comparison of the results suggests that, amongst the different semiconductors, TiO₂ is the most efficient. Titania, ZnO and WO₃ degrade atrazine through the generation of active species which mainly promote the alkyl chain oxidation. Fe₂O₃ and SnO₂ behave similarly to Al₂O₃ (an insulator) through a slow surface-assisted hydrolysis at the chlorine substituent position. The activity and selectivity of titania definitely depends on the differently preparative modes used to make the titania specimens. The temporal distribution of intermediates changes significantly as a consequence of the manner by which the organic probe and the catalyst interact.