Photo-Fenton and Riboflavin-photosensitized Processes of the Isoxaflutole Herbicide

Abstract

The proherbicide Isoxaflutole (IXF) hydrolyzes spontaneously to diketonitrile (DKN) a phytotoxic compound with herbicidal activity. In this work, the sensitized degradation of IXF using Riboflavin (Rf), a typical environmentally friendly sensitizer, Fenton and photo-Fenton processes has been studied. The results indicate that only the photo-Fenton process produces a significant degradation of the IXF. Photolysis experiments of IXF sensitized by Riboflavin is not a meaningful process, IXF quenches the Rf excited triplet (³ Rf*) state with a quenching rate constant of 1.5 · 10⁷ m^-1 s^-1 and no reaction is observed with the species O₂ (¹ Δ_g ) or $O_2^{·-}$ generated from ³ Rf*. The Fenton reaction produces no changes in the IXF concentration. While the photo-Fenton process of the IXF, under typical conditions, it produces a degradation of 99% and a mineralization to CO₂ and H₂ O of 88%. A rate constant value of 1.0 × 10⁹ m^-1 s^-1 was determined for the reaction between IXF and HO˙. The photo-Fenton process degradation products were identified by UHPLC-MS/MS analysis.