Electrochemical degradation of a chlorophenoxy propionic acid derivative used as an herbicide at boron-doped diamond

Abstract

The electrochemical degradation of diclofop-methyl (DM), an herbicide deriving from aryloxy propionic acid, was carried out by galvanostatic electrolysis at boron-doped diamond electrode. The oxidation process leads in an early step to the cleavage of the aryloxy propionic ester bond and the formation of 4-(2,4-dichlorophenoxy) phenol (P1). The subsequent oxidation of P1 resulted in a quantitative mineralization of DM. Measuring the reduction in chemical oxygen demand and total organic carbon during the electrolysis shows that the mineralization efficiency increases with decreasing current densities. As a result, two mechanistic pathways were proposed for DM electrochemical degradation. The first one is a direct electro-oxidation of the starting molecule leading to the breakdown of aromatic ether bonds. A second evidenced competitive pathway uses electrogenerated hydroxyl radicals as mediators in the mineralization process of DM.

Keywords:

• BDD
• Diclofop-methyl
• Electrochemical degradation
• Hydroxyl radical

Acknowledgments

This work has been achieved with the financial support of the Ministère de l’Enseignemnt Supérieur et de la Recherche Scientifique (Tunisia). The authors thank Dr L. Monser for proof reading.