The ferryl generation by fenton reaction driven by catechol

• Published in: Chemosphere (Oxford) 2023-09, Vol.335, p.139155-139155, Article 139155
• Main Authors: Benítez, Francisca J., Melín, Victoria, Perez-Gonzalez, Gabriel, Henríquez, Adolfo, Zarate, Ximena, Schott, Eduardo, Contreras, David
• Format: Article
• Language: English
• Subjects: Fenton reaction driven by catechol; Ferryl; Semiquinone
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2023.139155

The Fenton and Fenton-like reactions are based on the decomposition of hydrogen peroxide catalyzed by Fe(II), primarily producing highly oxidizing hydroxyl radicals (HO∙). While HO∙ is the main oxidizing species in these reactions, Fe(IV) (FeO2+) generation has been reported as one of the primary oxidants. FeO2+ has a longer lifetime than HO∙ and can remove two electrons from a substrate, making it a critical oxidant that may be more efficient than HO∙. It is widely accepted that the preferential generation of HO∙ or FeO2+ in the Fenton reaction depends on factors such as pH and Fe: H2O2 ratio. Reaction mechanisms have been proposed to generate FeO2+, which mainly depend on the radicals generated in the coordination sphere and the HO∙ radicals that diffuse out of the coordination sphere and react with Fe(III). As a result, some mechanisms are dependent on prior HO∙ radical production. Catechol-type ligands can induce and amplify the Fenton reaction by increasing the generation of oxidizing species. Previous studies have focused on the generation of HO∙ radicals in these systems, whereas this study investigates the generation of FeO2+ (using xylidine as a selective substrate). The findings revealed that FeO2+ production is increased compared to the classical Fenton reaction and that FeO2+ generation is mainly due to the reactivity of Fe(III) with HO∙ from outside the coordination sphere. It is proposed that the inhibition of FeO2+ generation via HO∙ generated from inside the coordination sphere is caused by the preferential reaction of HO∙ with semiquinone in the coordination sphere, favoring the formation of quinone and Fe(III) and inhibiting the generation of FeO2+ through this pathway. [Display omitted] •Fe(IV) was produced at pH = 2.0 and 4.0 through two pathways by Fenton reaction.•In Fenton–like systems driven by catechol, Fe(IV) production is higher than in Fenton systems.•In Fenton-like systems, Fe(IV) is only produced by HO·-dependent pathways.