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

Ozonation of drinking water: part I. Oxidation kinetics and product formation.

Advanced oxidation processes are defined as those which involve the generation of hydroxyl radicals in sufficient quantity to affect water purification. The theoretical and (practical yield of OH from O3 at high pH, 03/H202, O3/UV and H2O2/UV systems is reviewed. New data is presented which illustrates the importance of direct photolysis in the O3/UV process, the effect of the H202:03 ratio in the O3/H2O2 process, and the impact of the low extinction coefficient of H2O2 in the H202/UV process.

The Chemistry of Water Treatment Processes Involving Ozone, Hydrogen Peroxide and Ultraviolet Radiation

Superoxide ion (O2•–) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2•– is rather scarce. In addition, numerous studies on O2•– were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2•– reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2•– so as to enable researchers to venture into future research. It comprises the main characteristics of O2•– followed by generation methods. The reaction types of O2•– are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2•– environmental chemistry is also discussed. The detection methods of O2•– are categorized and elaborated. Special attention is given to the f...

Superoxide Ion: Generation and Chemical Implications

Advanced oxidation processes (AOPs), defined as those technologies that utilize the hydroxyl radical (·OH) for oxidation, have received increasing attention in the research and development of wastewater treatment technologies in the last decades. These processes have been applied successfully for the removal or degradation of toxic pollutants or used as pretreatment to convert recalcitrant pollutants into biodegradable compounds that can then be treated by conventional biological methods. The efficacy of AOPs depends on the generation of reactive free radicals, the most important of which is the hydroxyl radical (·OH). The authors summarize the formation reactions of ·OH and the mechanisms of pollutants degradation. They cover six types of advanced oxidation processes, including radiation, photolysis and photocatalysis, sonolysis, electrochemical oxidation technologies, Fenton-based reactions, and ozone-based processes. Controversial issues in pollutants degradation mechanism were discussed. They review t...

Advanced Oxidation Processes for Wastewater Treatment: Formation of Hydroxyl Radical and Application

The lifetime of the ferryl ion FeO2+, (minutes at pH below 1) is reduced by a factor of 50 at pH above 3. This is rationalized in terms of an acid-base equilibrium between two different hydrolytic forms of this species (Fe(OH)++2 and Fe(OH)+3) with a pKa=2.0. The rate constants for reactions between FeO2+ and selected compounds found in cloud water were measured in acid solutions by stopped-flow technique. For inorganic reactants: kHNO2=1.1×104 M−1 s−1, kNO2−≤105 M−1 s−1, kCl−=1.0×102 M−1 s− 1, kHSO3−=2.5×105 M−1 s−1, kSO2=4.5×105 M−1 s−1, and kMn(II)=1.0×104 M−1 s−1 were obtained and for the organic reactants: kHCOOH=160 M−1 s−1, kHCOO−=3×105 M−1, kCH3COOH=3.1 M−1 s−1, kCH2(OH)2=400 M−1 s−1, kCH3COCH3=16 M−1 s−1, kCH3CH20H=2.5×103 M−1 s−1, kC6H5OH=4.0×103 M−1 s−1, and kC6H5COOH=80 M−1 s−1 were obtained. A good correlation between log(k) and the standard one electron reduction potential (E°) indicates that the reactions of inorganic compounds proceed by electron transfer. The reaction mechanisms in case of organic compounds are very similar to the reactions of the OH radical, i.e., H-abstraction, and a fairly good correlation between log(k) and the bond dissociation energy BDE was obtained. Activation parameters were measured for the reaction of FeO2+ with HNO2 (Ea=34.5 kJ/mol); Mn2+ (Ea=21.3 kJ/mol); HCOOH (Ea=22.3 kJ/mol); CH2 (OH)2 (Ea=44.5 kJ/mol); and C6H5 OH (Ea=28.1 kJ/mol). © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 215–221, 1998.

Reactions of the ferryl ion with some compounds found in cloud water

In slightly alkaline solution the ozonide radical ion, O/sub 3//sup -/, forms as a product of the hydroxyl radical reaction with ozone For each O/sub 3//sup -/ formed, two O/sub 3/ molecules are consumed In acid solution the product of this reaction is the perhydroxyl radical, HO/sub 2/, formed from one O/sub 3/ molecule Our results are consistent with the gas-phase reaction where the products are HO/sub 2/ and O/sub 2/ A rate constant of (11 +/- 02) x 10/sup 8/ dm/sup 3/ mol/sup -1/ s/sup -1/ is found for the reaction OH + O/sub 3/ --> HO/sub 2/ + O/sub 2/ This rate constant was obtained by three systems, by buildup of O/sub 3//sup -/ in basic solutions, by competition of the OH radical with the carbonate ion, and directly by O/sub 3/ consumption in acid solution The rate constant for the reaction of HO/sub 2/ with O/sub 3/ is very low, < 10/sub 4/ dm/sup 3/ mol/sup -1/ s/sup -1/ At pH greater than or equal to 1, HO/sub 2/ reacts with O/sub 3/ preferentially in its dissociated form, O/sub 2//sup -/ No spectroscopic evidence has been found for the HO/sub 3/ and HO/sub 4/ free-radical intermediates 24more » references, 4 figures, 2 tables« less

A Pulse Radiolytic Study of the Reaction OH + O3 in Aqueous Medium

The radical cations of methylated benzene decompose in acid solution into the corresponding methylbenzyl radical and a proton. The rate constant for this reaction decreases by three orders of magnitude as the number of methyl groups increases from one to five. The rate constants can be correlated with the ionization potential of the parent compound. In neutral solution the reverse reaction to the acid-catalyzed OH adduct conversion occurs and the radical cations react with water to form the OH adduct. In slightly alkaline solution the radical cations of the higher methylated benzenes (n greater than or equal to 3) react with hydroxide ions forming the OH adduct.

Reactions of the radical cations of methylated benzene derivatives in aqueous solution

Pulse radiolytic experiments in strong alkaline solution (pH 13-14) on the formation and the decay of the ozonide ion radical, O/sub 3//sup -/, are reported. The high-pressure cell technique was used applying 4 MPa of nitrous oxide and 0.1 MPa of oxygen. The spectrum of O/sub 3//sup -/ in the uv was measured and the decay product was identified as the peroxy radical ion, O/sub 2//sup -/. A complete mechanism for the decay of O/sub 3//sup -/ is based on the following reactions: O/sub 3//sup -/ + O/sup -/ ..-->.. 2O/sub 2//sup -/ and O/sub 2//sup -/ + O/sup -/ + H/sub 2/O ..-->.. O/sub 2/ + 2OH/sup -/. A computer simulation of the high-pressure system as well as the atmospheric-pressure oxygenated system supports this mechanism and yields a rate constant, k/sub (O/sub 3//sup -/ + O/sup -/)/ of (7.0 +- 1.0) x 10/sup 8/ dm/sup 3/ mol/sup -1/s/sup -1/. As a consequence of our mechanism, a k/sub (O/sub 2//sup -/ + O/sup -/)/ of (6.0 +- 1.0) x 10/sup 8/ dm/sup 3/ mol/sup -1/ s/sup -1/ is also derived from the computations.

Ultraviolet spectrum and decay of the ozonide ion radical, O3-, in strong alkaline solution

Pulse radiolysis studies of intramolecular electron transfer in model peptides and proteins. 7. Trp-->TyrO radical transformation in hen egg-white lysozyme. Effects of pH, temperature, Trp62 oxidation and inhibitor binding.

Jerzy Holcman

Papers

Reactions of the ferryl ion with some compounds found in cloud water

A Pulse Radiolytic Study of the Reaction OH + O3 in Aqueous Medium

Reactions of the radical cations of methylated benzene derivatives in aqueous solution

Ultraviolet spectrum and decay of the ozonide ion radical, O3-, in strong alkaline solution

Pulse radiolysis studies of intramolecular electron transfer in model peptides and proteins. 7. Trp-->TyrO radical transformation in hen egg-white lysozyme. Effects of pH, temperature, Trp62 oxidation and inhibitor binding.