The Fenton Reaction. Dependence of the Rate on pH

Abstract

The pH dependence of the evolution of O2 in the Fenton reaction has been studied by using an indirect method for measuring [O2]. The results confirmed observations of previous workers, namely, that the evolution of O2 diminished as the pH was lowered. A quantitative analysis of the dependence of [O2] and [Fe2+] during the reaction as a function of time showed that the pH dependence of the course of the reaction can be accounted for by assuming an acid base reaction of the active intermediate: FeO2+ + H+ ⇌ FeOH3+. FeOH3+ is the active entity in the reaction with Fe2+ to produce Fe3+ ions, while the other form FeO2+ is involved in reactions leading to O2 evolution.