PHOTOCATALYTIC DECOMPOSITION OF TRICLOPYR OVER AQUEOUS SEMICONDUCTOR SUSPENSIONS

The photocatalytic degradation of 3,5,6-trichloro-2-pyridinyloxyacetic acid (Triclopyr), a pyridine analogue of the phenoxy herbicides, has been investigated in aqueous heterogeneous solutions containing TiO2 o r ZnO as photocatalyst. The disappearance of the organic molecule foll ows approximately a pseudo-first kinetic order according to the Langmu ir-Hinselwood model. As mineralization products, CO2 and Cl- ions have been identified, whereas the nitrogen atom forms only NH4+ ions. Vari ous commercial photocatalysts were compared with respect to their over all efficiency, as well as the production of CO2. The effect of pH and H2O2 on the reaction rate was ascertained. The photooxidation of Tric lopyr has also been monitored with FTIR spectroscopy. (C) 1998 Elsevie r Science S.A. All rights reserved.