Fenton processes

Chan K-W, W Chu (2006) Model applications and intermediates quantification of atrazine degradation hy UV-enhanced Fenton process. J Agric Food Chem 54 1804-1813. 

Chakinala AG, Gogate PR, Burgess AE, Bremner DH (2008) Treatment of industrial waste-water effluents using hydrodynamic cavitation and the advanced Fenton process. Ultrason Sonochem 15 49-54... 

Oturan MA, Sires I, Oturan N (2008) Sonoelectro-Fenton process a novel hybrid technique for the destruction of organic pollutants in water. J Electroanal Chem 624 329-332... 

Lurascu B, Siminiceanu I, Vione D, Vicente MA, Gil A (2009) Phenol degradation in water through a heterogeneous photo-Fenton process catalyzed by Fe-treated laponite. Water Res 43 1313-1322... 

Segura Y, Molina R, Martmez F, Melero JA (2009) Integrated heterogeneous sono-photo Fenton processes for the degradation of phenolic aqueous solutions. Ultrason Sonochem 16 417 424... 

Devi LG, Kumar SG, Reddy KM, Munikrishnappa C (2009) Photodegradation of methyl orange an azo dye by advanced Fenton process using zero valent metallic iron Influence of various reaction parameters and its degradation mechanism. J Hazard Mater 164 459 167... 

S.-F. Kang, C.-H. Liao and M.-C. Chen, Pre-oxidation and coagulation of textile wastewater by the Fenton process. Chemosphere, 46 (2002) 923-928. 

In this chapter, the main mechanisms of the homogeneous catalysis of the Fenton s reagent are discussed and special attention is paid in their main drawback as an effective oxidant. Indeed, the catalytic activity ceases after a critical time because iron ions undergoes a chemical speciation during the Fenton process. In order to maintain for a longer time the catalytic activity of the iron ions, a heterogeneous catalyst is proposed. This approach is better because the control over iron ions during the oxidation reaction is improved. 

Reaetion (8) is still the main souree of hydroxyl radicals OH but most of the soluble ferric ions are forming complexes Fe(OH), FeOOH. Ferrous and ferric ions can be regenerated supporting the Fenton process, according to the following equations ... 

The fact that reaction (12) is much slower than reaction (8), implies that Fe is faster depleted from the solution. As a result, Fenton process is halted because the redox chain cannot be supported itself. In addition, it is accepted that (Pignatello 1992 Boye et al. 2003) the hydroperoxyl radical (HO2 ) has a much lower oxidant power than OH. In the presence of organics, Fenton chemistry is even more complex because hydroxyl radical, both iron cations and the oxidation products enter into a series of consecutive and parallel reactions. An example of the complexity of these reactions is discussed elsewhere (Gozzo 2001) but a brief description is given here. The initial step for an organic substrate (R-H) oxidation starts with the interaction of itself with OH, according to (Walling and Kato 1971) ... 

The tertiary and primaiy hydroxyalkyl radicals are produced in the ratio 7.2 1, respectively. The former is rapidly oxidized by Fe (supporting the Fenton process) while a big proportion of the latter is accumulated in solution and terminates the redox chain by dimerization, according to the reactions (15) and (16), respectively ... 

In order to verify if the color and COD abatement from the solution was due to degradation by Fenton process rather than by an adsorption process, some experiments were repeated for an aqueous solution consisting of 100 ml 50 mM Na2S04 + 0.06 mM RB5 + required amount of catalyst, pH 2.8 and room temperature. Hydrogen peroxide was not included to avoid the Fenton chemistry. Figure 17 shows the absorbance spectra for (a) the initial solution, (b) after 180 minutes of contact time (catalyst C1+ BR5) without H2O2, and (c) in the presence of H2O2 after 180 minutes of Fenton process. 

Figure 28. Degradation of 0.1 mM B02 by the heterogeneous Fenton process as a function of FI2O2 concentration with 0.01 g of C2-Ms at pH 3.

Kavitha, V Palanivelu, K. The role of ferrous ion in Fenton and photo-Fenton processes for the degradation of phenol. Chemosphere, 2004 55, 1235-1243. 

Cameiro, PA Pupo Nogueira, RF Zanoni, MVB. Homogeneous photodegradation of C.l. Reactive Blue 4 using a photo-Fenton process under artificial and solar irradiation. Dyes and Pigments, 2006 in press. 

Follow-up work by Sires et al. (2007) proposed combining BDD with Fenton processes as well as UV catalysts to favor the photodecomposition of complexes of Fe with the carboxylic acids that are generated. The Fe is regenerated, producing more OH from the photoreduction of Fe(OH) ... 

J. Ermfrio, F. Moraes, F. H. Quina, C. A. O. Nascimento, D. N. Silva, and O. Chiavone-Filho, Treatment of Saline Wastewater Contaminate with Hydrocarbons by the Photo-Fenton Process, Environ. Sci. Technol. 2004,... 

In another example of free radical formation known as the Fenton process, H202, in the presence of ferrous ions (Fe2+), decomposes into a harmless OH ion and a powerful OH radical. OH has the ability to attack stable organic structures (Equation 2, 3). This slow reaction process requires the presence of ferric ions which act as a catalyst. 

UV peroxide process Ozonolysis Peroxon process Fe3+-catalyzed photolysis Photoassisted Fenton process Photocatalysis... 

The three intermediate products that reached the highest concentrations in the case of quinoline degradation by the photo-Fenton process were in the order ... 

Regarding the main products corresponding to the opening of the pyridine moiety of quinoline, 2-aminobenzaldehyde and, to a lesser extent, its A -formyl derivative were formed by photocatalysis, whereas only traces of this latter product were detected when the photo-Fenton process was employed. Also, (2-formyl)phenyliminoethanol was detected only in the case of the degradation over Ti02. 

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