Oxidative Degradation of 2,4‐Dihydroxybenzoic Acid by the Fenton and Photo‐Fenton Processes: Kinetics,Mechanisms, and Evidence for the Substitution of H2O2 by O2 |
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| Authors: | Ménana Haddou Florence Benoit‐Marquié Marie‐Thérèse Maurette Esther Oliveros |
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| Affiliation: | 1. Laboratoire des IMRCP, UMR CNRS 5623, Université de Toulouse III (Paul Sabatier), 118 route de Narbonne, F‐31062, Toulouse cédex 9, (phone: +33‐561‐556968;2. fax: +33‐561‐558155) |
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| Abstract: | The kinetics and mechanisms of the oxidative degradation of 2,4‐dihydroxybenzoic acid (2,4‐DHBA) by the Fenton and photo‐Fenton processes were investigated in detail by a combination of HPLC, IC, and TOC analyses. The formation of 2,3,4‐trihydroxybenzoic acid (2,3,4‐THBA) at an early oxidation stage shows that hydroxylation of the aromatic ring is the first step of the process. This intermediate was able to reduce FeIII and to contribute to the recycling of FeII. Complete mineralization could only be achieved under irradiation (photo‐Fenton). A detailed study of the dependence of the rate of mineralization on the concentration of H2O2 and dissolved O2 was carried out. It was found that, even at a low initial concentration of H2O2, mineralization by the photo‐Fenton process was complete in a relatively short time, provided that the O2 concentration was high enough, indicating that O2 may, at least in part, substitute H2O2. Channeling reaction pathways toward O2 rather than H2O2 consumption is of particular interest for the technical development of the photo‐Fenton process. |
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| Keywords: | Oxidative degradation Fenton process Photo‐Fenton process Benzoic acid derivatives Hydroxylation Mineralization Kinetics |
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