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

Decontamination and disinfection of water by solar photocatalysis: Recent overview and trends

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

A surface science perspective on TiO2 photocatalysis

Advanced oxidation processes (AOPs) constitute important, promising, efficient, and environmental-friendly methods developed to principally remove persistent organic pollutants (POPs) from waters and wastewaters. Generally, AOPs are based on the in situ generation of a powerful oxidizing agent, such as hydroxyl radicals (•OH), obtained at a sufficient concentration to effectively decontaminate waters. This critical review presents a precise and overall description of the recent literature (period 1990–2012) concerning the main types of AOPs, based on chemical, photochemical, sonochemical, and electrochemical reactions. The principles, performances, advantages, drawbacks, and applications of these AOPs to the degradation and destruction of POPs in aquatic media and to the treatment of waters and waste waters have been reported and compared.

Advanced Oxidation Processes in Water/Wastewater Treatment: Principles and Applications. A Review

The photoinduced degradation of an alkylphenol ethoxylate (APE) (Igepal CA 520) by Fe(III) in aqueous solution has been investigated. A complete characterization of the commercial product showed the presence of a mixture of compounds with various ethoxy and alkyl chain lengths. The photodegradation study was carried out with the major fraction of ethoxymers having an alkyl chain length of 8 carbon atoms and n ethoxy units E (C8PhEn). We have demonstrated that the Fe(III) sensitized degradation of this fraction occurs efficiently both at 365 nm and under sunlight. The rate of degradation depends on the concentration of Fe(OH)2+, the most photoreactive species in terms of •OH radical formation. The primary step of the decomposition of Igepal involves the hydrogen abstraction on one carbon of the ethoxy chain. The shortening of the ethoxylated chain all along the degradation process was observed. The identified photoproducts are aldehyde ethoxylates, formate ethoxylates, and octylphenol that is a persistent ...

Degradation Photoinduced by Fe(III): Method of Alkylphenol Ethoxylates Removal in Water

The degradation of dibutyl phthalate (DBP) photoinduced by Fe(III) in aqueous solution has been investigated under monochromatic irradiation and sunlight. Hydroxyl radicals OH, responsible of the degradation, are formed via an intramolecular photoredox process in excited Fe(III) aquacomplexes. The concentration in Fe(OH)2+ in the starting Fe(III) solution appears to be a controlling parameter of the degradation rate, as already stated in our previous works. The first step of the decomposition of DBP involves the hydrogen abstraction on the butyl chain mainly on the carbon in α-position to aromatic ring. The major primary photoproducts are hydroxy, dihydroxy and carboxylic derivatives. For prolonged irradiations, DBP and its photoproducts are completely mineralized due to the regeneration of the absorbing species and the continuous formation of OH radicals that confers a catalytic aspect to the process. Consequently, the degradation photoinduced by Fe(III) could be an efficient method of DBP removal from water.

Degradation of dibutyl phthalate by homogeneous photocatalysis with Fe(III) in aqueous solution

Iron (III) aquacomplexes as effective photocatalysts for the degradation of pesticides in homogeneous aqueous solutions.

The degradation of diuron photoinduced by iron(III) in aqueous solution has been investigated with different iron(III) species (monomeric species Fe(OH) 2+ , dimeric species Fe 2 (OH) 2 4+ and water-soluble oligomeric species) under monochromatic excitation at 365 nm and under sunlight. The rate of degradation depends on the concentration in Fe(OH) 2+ , the most reactive species in terms of . OH radical formation. The major photoproduct is 3-(3,4-dichlorophenyl)-1-formyl-1-methylurea which represents more than 60% of diuron disappearance. The mechanism only involves the attack by . OH radicals arising from iron(III) excited species. The half-lives of diuron when submitted to such a process in the environment were estimated to be 1-2 h and a few days according to the concentration of Fe(OH) 2+ (respectively 70% and <10% of total iron(III) concentration).

Degradation of Diuron Photoinduced by Iron(III) in Aqueous Solution

Degradation of citric acid (Cit) at relatively high concentrations by photocatalysis over TiO2 under air bubbling and near UV-light was tested under different conditions. The reaction was improved by addition of H2O2, Fe(III) or both. Minor amounts of H2O2 were effective to enhance the oxidation and the mineralization. H2O2 addition impacts more on the initial rate, while the effect of Fe(III) is more important after prolonged irradiation. The kinetic profiles were analyzed and compared, and the best ratio of reagents was found (1:1:1 H2O2/Cit/Fe molar ratio). However, a lower amount of Fe (1:1:0.2 H2O2/Cit/Fe ratio) was also effective. Similar experiments under the optimal conditions in the absence of TiO2 were performed for comparison. When both H2O2 and Fe(III) were present, the behavior with and without TiO2 was very similar. So far, 3-oxoglutaric acid was detected as a reaction intermediate. A mechanistic analysis is initiated to explain some features of these complex systems.

Photocatalytic degradation of citric acid under different conditions: TiO2 heterogeneous photocatalysis against homogeneous photolytic processes promoted by Fe(III) and H2O2

Michèle Bolte

Papers

Degradation Photoinduced by Fe(III): Method of Alkylphenol Ethoxylates Removal in Water

Degradation of dibutyl phthalate by homogeneous photocatalysis with Fe(III) in aqueous solution

Iron (III) aquacomplexes as effective photocatalysts for the degradation of pesticides in homogeneous aqueous solutions.

Degradation of Diuron Photoinduced by Iron(III) in Aqueous Solution

Photocatalytic degradation of citric acid under different conditions: TiO2 heterogeneous photocatalysis against homogeneous photolytic processes promoted by Fe(III) and H2O2