Publication
539
J. Electroanal.
Chem., 507 (1-2), 96-102, 2001
DOI: 10.1016/S0022-0728(01)00369-2 |
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Production of hydroxyl radicals by electrochemically assisted Fenton's
reagent. Application to the mineralization of an organic micropollutant,
pentachlorophenol
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Mehmet A. Oturan,
Nihal Oturan, Claude Lahitte
and Stéphane Trevin
Laboratoire d'Electrochimie
Moléculaire, Université Paris 7, 2 place Jussieu, 75251 Paris Cedex 05,
France Laboratoire de Géomatériaux, Université
de Marne la Vallée, 5 Boulevard Descartes, bāt. IFI, Champs/Marne, 77454 Marne
la Vallée Cedex 2, France, and EDF, Division
Recherche et Développement, Site des Renardières, Route de Sens-Ecuelles, 77818
Moret sur Loing Cedex, France
Hydroxyl radicals are very powerful oxidizing agents. They are involved in
hydroxylation reactions, in biological and atmospheric phenomena. A recent
application of these radicals is their use in decontamination of water polluted
by toxic organic substances like pesticides. Chemically, these radicals are
produced by the use of a mixture of
(H2O2+Fe2+), the so called Fenton's reagent. In
this work Fenton's reagent is generated by electrochemistry in a catalytic way.
The reaction of the hydroxyl radicals with pentachlorophenol (PCP) was studied.
These radicals generated in situ in aqueous solution react with PCP and thus
lead to its degradation. The evolution of the composition of the solution was
followed by chromatographic analysis, COD analysis and the measurement of the
total organic carbon (TOC) of the studied aqueous solution.
Tetrachloro-o-benzoquinone and tetrachloro-p-benzoquinone (TCBQ)
are the only aromatic intermediates identified. They result from the oxidation
of the corresponding tetrachlorohydroquinones (TCHQ). Just like PCP, the TCBQs
are degraded and disappear in their turn. The mineralization of the initial
toxic substrate is confirmed on the one hand, by the regular decrease in
quantity of the total organic carbon of the solution (TOC analysis) and on the
other hand, by the quantitative release of chloride ions according to the
electrical charge passed during electrolysis. The degradation of PCP appears
relatively slow compared to that of the other organic pollutants studied by the
electro-Fenton process and also to the degradation of other less substituted
chlorophenols. The kinetic rate of the appearance of chloride ions is slower
than that in the degradation of PCP. This phenomenon highlights the formation of
chlorated aliphatic intermediates. |