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

摘要

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.