Radiolytic degradation of pesticide 4-chloro-2-methylphenoxyacetic acid (MCPA) - Experimental data and kinetic modelling

The aqueous solutions of MCPA have been gamma-irradiated in different conditions, where particular active radical species from water radiolysis predominate. The obtained data confirmed that largest yield of radiolytic decomposition is obtained in oxidation processes, where oxidation is carried out with hydroxyl radicals. The obtained data have been compared with kinetic modelling. A fair agreement was obtained for degradation of MCPA in different experimental conditions, including also irradiation in the presence of hydrogen peroxide, that in optimised conditions can be used to enhance the yield of decomposition. The obtained data have also shown a strong effect of the presence of large amount of chloride on yield of MCPA decomposition, which can be attributed to strong oxidation properties of chlorine radicals formed. It is also shown that MCPA can be completely decomposed in industrial wastes from various stages of MCPA production, although this is not accompanied by satisfactory reduction of toxicity of examined wastes. (C) 2007 Elsevier Ltd. All rights reserved.