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

Combination of Advanced Oxidation Processes and biological treatments for wastewater decontamination—A review

Advanced oxidation processes (AOPs) constitute a promising technology for the treatment of wastewaters containing non-easily removable organic compounds. Chlorophenols (CPs) are a group of special interest due to their high toxicity and low biodegradability. Data concerning the degradation of CPs by means of AOPs reported during the period 1995–2002 are evaluated in this work. Among the AOPs, the following techniques are studied: processes based on hydrogen peroxide (H2O2+UV, Fenton, photo-Fenton and Fenton-like processes), photolysis, photocatalysis and processes based on ozone (O3, O3+UV and O3+catalyst). Half-life times and kinetic constants for CP degradation are reviewed and the different mechanistic degradation pathways are taken into account.

Degradation of chlorophenols by means of advanced oxidation processes: a general review

http://repository.ias.ac.in/39608/1/49_pub.pdf

A review of imperative technologies for wastewater treatment I: oxidation technologies at ambient conditions

Degradation and removal methods of antibiotics from aqueous matrices--a review.

The decomposition of fenuron (1,1-dimethyl-3-phenylurea), a herbicide regarded as a priority pollutant, was carried out in batch reactors by means of ozone, UV radiation, and Fenton's reagent as single oxidants and by the advanced oxidation processes formed by the following combinations:  UV radiation plus H2O2, UV radiation plus Fenton's reagent (photo-Fenton system), ozone plus UV radiation, and ozone plus UV radiation and H2O2. In all cases, the decomposition levels were determined and the apparent pseudo-first-order rate constants were evaluated by linear regression to compare the efficiencies of the processes. The rate constants for the reactions of fenuron with ozone and with hydroxyl radicals were determined as well as the efficiencies for the photodecomposition by direct UV radiation. Finally, in the combined systems, the contributions to the overall decomposition caused by the radical reactions were established by calculating the radical rate constants.

Kinetics of Fenuron Decomposition by Single-Chemical Oxidants and Combined Systems

The chemical oxidation of two herbicide derivatives of the phenylurea group—diuron and isoproturon—has been carried out by means of chlorine, in the absence and in the presence of bromide ion. Apparent second-order rate constants for the reactions between chlorine and the herbicides were determined to be below 0.45 L mol−1 s−1. Hypobromous acid reacts faster with the investigated herbicides, especially with isoproturon (kapp = 24.8 L mol−1 s−1 at pH 7). While pH exerts a negative effect on the bromination rate, the maximum chlorination rate was found to be at circumneutral pH. In a second stage, the oxidation of each compound was conducted in different natural waters, in order to simulate the processes which take place in water purification plants. Again, chlorine was used as an oxidant, and bromide ion was added in some experiments with the aim of producing the more reactive HOBr oxidant. The herbicide oxidation rate was inversely proportional to the organic matter content of the natural water. However, the formation of trihalomethanes (THMs) was directly proportional to the organic matter content and constitutes a limitation for the application of chlorine during drinking water treatment. Finally, the evolution of herbicide concentration was modeled and predicted by applying a kinetics approach based on the rate constants for the reactions between the herbicides and the active oxidants. Copyright © 2007 Society of Chemical Industry

Kinetics of reactions between chlorine or bromine and the herbicides diuron and isoproturon

Removal of phenyl-urea herbicides in natural waters by UF membranes : Permeate flux, analysis of resistances and rejection coefficients

The photooxidation of several herbicides belonging to the acetamides group (specifically propachlor, metolachlor and butachlor) by means of a monochromatic UV irradiation in ultrapure water was studied. In the case of propachlor, the quantum yield for its photolysis was evaluated directly, and a value 0.127 ± 0.01 mol Eins−1 was obtained independent of the pH. The quantum yields for the photolysis of metolachlor and butachlor were determined by using a competition kinetic model which used propachlor as reference compound, and values of 0.56 ± 0.05 and 0.78 ± 0.04 mol Eins−1 were deduced respectively for metolachlor and butachlor. In a second step, the elimination of the selected herbicides in some natural and mineral waters was studied by means of several oxidation systems: UV radiation alone, and UV radiation combined with hydrogen peroxide and ozone. The influence of the operating variables in these processes (acetamide type, presence or absence of tert-butyl alcohol and types of waters) are discussed as a consequence of the amounts of herbicides removed. Two different kinetic studies were carried out for the oxidation of the herbicides: the first one for UV radiation alone and UV radiation combined with H2O2; the second one for the combination UV radiation plus ozone. In these studies, the specific rate constants were evaluated in every process. Finally, kinetic models for the prediction of the elimination of these herbicides in the natural waters selected by the different oxidation systems are proposed. The values of concentrations predicted by these models agree well with the experimental results obtained. Copyright © 2004 Society of Chemical Industry

Modeling of photooxidation of acetamide herbicides in natural waters by UV radiation and the combinations UV/H2O2 and UV/O3

The degradation of the herbicide cyanazine in aqueous solution by ozone and UV radiation separately have been developed. In the ozonation process, the influence of the operating variables is observed, the stotchiometric ratio for the reaction is obtained, and a free radical reaction mechanism is proposed. The kinetic study establishes that the process is controlled by the chemical reaction, which takes place in the very slow kinetic regime. The reaction rate constants are determined as a function of temperature and pH.

F. Javier Benitez

Papers

Kinetics of Fenuron Decomposition by Single-Chemical Oxidants and Combined Systems

Kinetics of reactions between chlorine or bromine and the herbicides diuron and isoproturon

Removal of phenyl-urea herbicides in natural waters by UF membranes : Permeate flux, analysis of resistances and rejection coefficients

Modeling of photooxidation of acetamide herbicides in natural waters by UV radiation and the combinations UV/H2O2 and UV/O3

Degradation By Ozone and UV Radiation of the Herbicide Cyanazine