Étude Cinétique De La Dégradation Du Piclorame En Solution Aqueuse Par Photolyse Directe Et Par Photocatalyse

Abstract

The treatment of pesticides is a necessity in view of the stability and toxicity of the pesticides that generate them. The objective of this work is to study the degradation of picloram in aqueous medium under UV irradiation. It is a selective and systemic herbicide that can control woody plants and broadleaf weeds. The irradiations were carried out using a mercury vapor lamp of wavelength λ = 365 nm. A high performance liquid chromatograph equipped with a UV / visible detector was used to analyze the samples. The degradation of picloram in aqueous medium was carried out by direct photolysis and photocatalysis. In direct photolysis, a low rate of product degradation (6.9 %) was obtained after 225 min of irradiation. Photolysis in the presence of a catalyst (TiO2) accelerated the degradation of the molecule. Experiments demonstrating the effect of the concentration of the catalyst showed that the optimum concentration corresponding to a maximum degradation of picloram is 4 mg / L (62.68 %). The study of the influence of the pH of the solution on the degradation indicates that the molecule degrades better in an acid medium (pH = 5) with a rate of 62 % in 225 min  of irradiation. Apparent order 1 degradation kinetics were observed in all cases.