Investigation of the Iron–Peroxo Complex in the Fenton Reaction: Kinetic Indication, Decay Kinetics, and Hydroxyl Radical Yields

Abstract

The Fenton reaction describes the reaction of Fe(II) with hydrogen peroxide. Several researchers proposed the formation of an intermediate iron-peroxo complex but experimental evidence for its existence is still missing. The present study investigates formation and lifetime of this intermediate at various conditions such as different Fe(II)-concentrations, absence vs presence of a hydroxyl radical scavenger (dimethyl sulfoxide, DMSO), and different pH values. Obtained results indicate that the iron-peroxo complex is formed under all experimental conditions. Based on these data, stability of the iron-peroxo complex could be examined. At pH 3 regardless of [Fe(II)] decay rates for the iron-peroxo complex of about 50 s were determined in absence and presence of DMSO. Without DMSO and [Fe(II)] = 300 μM variation of pH yielded decay rates of about 70 s for pH 1 and 2 and of about 50 s at pH 3 and 4. Hence, the iron-peroxo complex becomes more stable with increasing pH. Furthermore, pH-dependent hydroxyl radical yields were determined to investigate whether the increasing stability of the intermediate complex may indicate a different reaction of the iron-peroxo complex which might yield Fe(IV) instead of hydroxyl radical formation as suggested in literature. However, it was found that hydroxyl radicals were produced proportionally to the Fe(II)-concentration.

Fenton-Like Oxidation of Antibiotic Ornidazole Using Biochar-Supported Nanoscale Zero-Valent Iron as Heterogeneous Hydrogen Peroxide Activator

“…Thirdly, the hydrolysis of iron ion at higher pH also had adverse effects on the formation of hydroxyl radicals due to the precipitation of FeOOH on the surface of nZVI [45,46]. Lastly, the iron-peroxo complex, which was the intermediate of Fenton reaction, becomes more stable with increasing pH and might yield less •OH for the degradation [47]. respectively.…”

Regulation of the Peroxidase‐Like Activity of nGO, MoS2 and WS2 Nanozymes by Using Metal Cations

“…They report the selectively towards ABTS over other chromogenic substrates like TMB, OPD is due to the electrostatic interactions between the UO 2 2+ and the negatively charged ABTS [27] . The Fenton reaction between Fe 2+ and H 2 O 2 generates OH radical that can oxidize ABTS [28–30] . The positive regulation of the ABTS radical formation with Fe 2+ is attributed to this phenomenon.…”

Cell phone and wireless radiation hazard on TRPV1 channel activation: A Scoping Review study

“…When H2O2 exceeds the normal level, it begins to interact with Fe, which results in the initiation of the Fenton reaction (Mostofa and Sakugawa 2016). In this reaction, H2O2 reacts with Fe 2+ and results in the production of Fe 3+ and • OH (Wiegand et al 2017). Then Fe 3+ results with H2O2 to produce HO2, hydroxyl radicals are also produced according to the Haber-Wiess reaction from the reaction of O 2and H2O2.…”