Fenton electrochemical treatment of aqueous atrazine and metolachlor

A bench-scale Fenton electrochemical system was used to study the degradation of two widely used herbicides, atrazine and metolachlor. In this system the degradation of the herbicides occurs by attack of hydroxyl radicals which are produced from reaction of hydrogen peroxide with electrochemically generated ferrous iron. The goals of the study were to achieve degradation of the herbicides by optimizing reagent concentrations and to identify degradation pathways. Herbicide degradation was determined with respect to iron and hydrogen peroxide concentrations and their rate of addition. Effects of near-UV illumination and herbicide concentration on the degradation of the herbicides were also studied. Adding hydrogen peroxide in multiple smaller doses resulted in enhanced removal of the herbicides, especially metolachlor (greater than 99% degradation), as compared to adding it all at once at the beginning of the treatment. The degradation of atrazine, which was initially difficult, was enhanced (greater than 99% degradation) by using a small molar excess of hydrogen peroxide to iron (5:1) and maintaining the ratio for the entire period of treatment. Atrazine degradation in this system appears to be via N-dealkylation and dechlorination.