Non-specific degradation of chloroacetanilide herbicides by glucose oxidase supported Bio-Fenton reaction

Abstract

Bio-Fenton reaction supported by glucose oxidase (GOx) for producing H₂O₂ was applied to degrade persistent chloroacetanilide herbicides in the presence of Fe (Ⅲ)-citrate at pH 5.5. There were pH decrease to 4.3, the production of 8 mM H₂O₂ and simultaneous consumption to produce •OH radicals which non-specifically degraded the herbicides. The degradation rates followed the order acetochlor ≈ alachlor ≈ metolachlor > propachlor ≈ butachlor with the degradation percent of 72.8%, 73.4%, 74.0%, 47.4%, and 43.8%, respectively. During the Bio-Fenton degradation, alachlor was dechlorinated and filtered into catechol via the production of intermediates formed through a series of hydrogen atom abstraction and hydrogen oxide radical addition reactions. The current Bio-Fenton reaction leading to the production of •OH radicals could be applied for non-specific oxidative degradation to various persistent organic pollutants under in-situ environmental conditions, considering diverse microbial metabolic systems able to continuously supply H₂O₂ with ubiquitous Fe(II) and Fe(III) and citrate.

Keywords: Alachlor; Bio-Fenton reaction; Chloroacetanilide herbicide; Hydrogen peroxide; Hydroxyl radicals.