Kinetics of Photodegradation of MCPA Herbicide in Aqueous TiO2 Suspension

Abstract

The direct and catalytic photodegradations of toxic and widely used herbicide, 2-methyl-4-chlorophenoxyacetic acid (MCPA) were investigated under the artificial (UV and Visible) and solar source of radiation, in aqueous suspensions of TiO2 and ZnO. UV-Visible spectroscopy and High performance Liquid Chromatography (HPLC) were used to monitor changes of herbicides concentration.The degradation of MCPA in all experiments followed a pseudo-first order reaction .The reaction rate constants of the processes for UV/ TiO2 system was 0.369 min-1 and for UV/ZnO system was 0.0171 min-1. The effect of the initial herbicide concentration was investigated and was concluded that the rate of herbicide degradation can be described in terms of Langmuir-Hinshelwood kinetic model.