Fenton chemistry encompasses reactions of hydrogen peroxide in the presence of iron to generate highly reactive species such as the hydroxyl radical and possibly others. In this review, the complex mechanisms of Fenton and Fenton-like reactions and the important factors influencing these reactions, from both a fundamental and practical perspective, in applications to water and soil treatment, are discussed. The review covers modified versions including the photoassisted Fenton reaction, use of chelated iron, electro-Fenton reactions, and Fenton reactions using heterogeneous catalysts. Sections are devoted to nonclassical pathways, by-products, kinetics and process modeling, experimental design methodology, soil and aquifer treatment, use of Fenton in combination with other advanced oxidation processes or biodegradation, economic comparison with other advanced oxidation processes, and case studies.

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Advanced Oxidation Processes for Organic Contaminant Destruction Based on the Fenton Reaction and Related Chemistry

The reactions between peroxymonosulfate (PMS) and quinones were investigated for the first time in this work, where benzoquinone (BQ) was selected as a model quinone. It was demonstrated that BQ could efficiently activate PMS for the degradation of sulfamethoxazole (SMX; a frequently detected antibiotic in the environments), and the degradation rate increased with solution pH from 7 to 10. Interestingly, quenching studies suggested that neither hydroxyl radical (•OH) nor sulfate radical (SO4•–) was produced therein. Instead, the generation of singlet oxygen (1O2) was proved by using two chemical probes (i.e., 2,2,6,6-tetramethyl-4-piperidinol and 9,10-diphenylanthracene) with the appearance of 1O2 indicative products detected by electron paramagnetic resonance spectrometry and liquid chromatography mass spectrometry, respectively. A catalytic mechanism was proposed involving the formation of a dioxirane intermediate between PMS and BQ and the subsequent decomposition of this intermediate into 1O2. Accordi...

Activation of Peroxymonosulfate by Benzoquinone: A Novel Nonradical Oxidation Process

The corrosion of zero-valent iron (Fe0(s)) by oxygen (O2) can lead to the oxidation of organic compounds. To gain insight into the reaction mechanism and to assess the nature of the oxidant, the oxidation of methanol, ethanol, 2-propanol, and benzoic acid by the reaction of nanoparticulate zero-valent iron (nZVI) or ferrous iron (Fe[II]) with O2 in the absence of ligands was studied. At pH values below 5, Fe0(s) nanoparticles were oxidized by O2 within 30 min with a stoichiometry of approximately two Fe0(s) oxidized per O2 consumed. The yield of methanol and ethanol oxidation products increased from 1% at acidic pH to 6% at pH 7, relative to nZVI added. Product yields from 2-propanol and benzoic acid were highest under acidic conditions, with little oxidation observed at neutral pH. At pH values below 5, product formation was attributable to hydroxyl radical (OH·) production through the Fenton reaction, involving hydrogen peroxide and Fe(II) produced during nZVI oxidation. At higher pH values, the oxidati...

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Factors affecting the yield of oxidants from the reaction of nanoparticulate zero-valent iron and oxygen.

A review on Fenton process for organic wastewater treatment based on optimization perspective.

This study presents a critical review on the application of magnetite-based catalysts to industrial wastewater decontamination by heterogeneous Fenton oxidation. The use of magnetic materials in this field started only around 2008 and continues growing increasingly year by year. The potential of these materials derives from their higher ability for degradation of recalcitrant pollutants compared to the conventional iron-supported catalysts due to the presence of both Fe(II) and Fe(III) species. In addition, their magnetic properties allow their easy, fast and inexpensive separation from the reaction medium. The magnetic materials applied up to now can be classified in three general groups: magnetic natural minerals, in-situ-produced magnetic materials and ferromagnetic nanoparticles. A survey of the catalysts investigated so far is presented paying attention to their nature and competitive features in terms of activity and durability.

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Preparation of magnetite-based catalysts and their application in heterogeneous Fenton oxidation – A review

This work extends investigations into the development and use of a kinetic model to simulate and improve the iron-catalyzed oxidation of organic compounds using Fenton’s reagent. While a number of ...

pH effects on iron-catalyzed oxidation using Fenton's reagent.

In the remediation, water, and wastewater industries, an appropriate understanding of the chemical reactions governing the Fenton system allows the development of kinetic models to help design and ...

Process optimization of fenton oxidation using kinetic modeling.

The increased use of Fenton systems for the treatment of contaminated waters and wastewaters necessitates the development of kinetic models capable of accurately simulating key species concentrations in order to optimize system performance and efficiency. In this work a reaction mechanism in which the hydroxyl radical is nominated to be the active oxidant in Fenton systems is used to describe the oxidation of formic acid (HCOOH) under a variety of experimental conditions. A kinetic model based on this reaction mechanism is shown to adequately describe results of experiments in which starting concentrations of H202 and HCOOH varied over 1 and 4 orders of magnitude, respectively, under both air-saturated and deaerated conditions. The intermediate generated during HCOOH oxidation was observed to increase oxidation efficiency, especially at high initial organic concentrations [relative to Fe(II)], by assisting in the redox cycling of iron. In the presence of oxygen, however, such improvement was attenuated through competition for the organic intermediates. While mechanistic analysis and associated kinetic modeling is invaluable in optimization of Fenton systems, a clear understanding of reaction byproducts and their reactivity toward other species in the system is critical for accurate simulations.

Fenton-mediated oxidation in the presence and absence of oxygen.

As Fenton (and Fenton-like) chemistry is increasingly implicated in a variety of areas and applications, an understanding of the mechanism and rates governing the system becomes relevant for a growing number of disciplines and purposes. In this work a kinetic model capable of describing species concentrations measured experimentally during the Fenton-mediated oxidation of p-hydroxybenzoic acid (pHBA) is presented and discussed. Experiments were conducted in the dark at low pH using reagent and substrate concentrations ranging from 100 μM to 2 mM. Analysis of the experimental and modeling results reveals that redox reactions between Fe and quinone or quinone-like compounds are essential for the model to qualitatively predict species concentration profiles observed in the laboratory. The quinone and quinone-like compounds generated as byproducts during the oxidation of pHBA act as reducing agents toward Fe(III), thereby assisting the redox cycling of Fe and increasing degradation of the target substrate. Th...

Christopher K. Duesterberg

Papers

pH effects on iron-catalyzed oxidation using Fenton's reagent.

Process optimization of fenton oxidation using kinetic modeling.

Fenton-mediated oxidation in the presence and absence of oxygen.

Kinetic modeling of the oxidation of p-hydroxybenzoic acid by Fenton's reagent: implications of the role of quinones in the redox cycling of iron.