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International Journal of Photoenergy
Volume 2 (2000), Issue 2, Pages 81-86

Photolysis of dicamba (3,6-dichloro-2-methoxybenzoic acid) in aqueous solution and dispersed on solid supports

1Laboratoire de Photochimie Moléculaire et Macromoléculaire, UMR-CNRS 6505, Aubière Cedex F-63177, France
2Laboratoire de Photocatalyse, Catalyse et Environnement, Ecole Centrale de Lyon, BP 163, F-69131 Ecully Cedex, France

Copyright © 2000 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Dicamba (3,6-dichloro-2-methoxybenzoic acid) was exposed to UV light in aqueous solution. It was also irradiated in the solid phase without support or adsorbed on laponite (a synthetic clay) and ferric oxide.

Two main photoproducts (1) and (2) were identified in irradiated aqueous solutions. Both involve the substitution of chlorine by OH. The unexpected product (2) is formed through a kinetic reaction of primary product; it results from an oxidation and it is not formed in the absence of oxygen.

A huge number of intermediate products were simultaneously formed when dicamba is irradiated in the solid phase in presence of laponite. They correspond to methylation, decarboxylation, chlorination, dechlorination, and hydroxylation reactions. The latter is probably due to the presence of water in clays, whereas methylation, chlorination and decarboxylation have been attributed to the cage effect and to an energy transfer process. Without support or with ferric oxide, no decarboxylation occurs. The nature of the inorganic support also modify the kinetics of dicamba photolysis.