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Mechanistic study of the ZEA organic pollutant degradation system / Derek F. Laine in Industrial & engineering chemistry research, Vol. 47 N°17 (Septembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6502–6508 Titre : Mechanistic study of the ZEA organic pollutant degradation system : evidence for H2O2, HO•, and the homogeneous activation of O2 by feIIEDTA Type de document : texte imprimé Auteurs : Derek F. Laine, Auteur ; Alexander Blumenfeld, Auteur ; I. Francis Cheng, Auteur Année de publication : 2008 Article en page(s) : p. 6502–6508 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : ZEA  system  Electrochemical  model  Carbon  basket  electrode Résumé : The ZEA (zero valent iron, ethylenediaminetetraacetic acid (EDTA), and air) organic pollutant degradation system has been previously shown to degrade a variety of organic pollutants and chemical warfare agent surrogates; however, mechanistic details and reactive intermediates formed in this system have not been identified. It is hypothesized that the ZEA system produces reactive oxygen species (H2O2, HO•) by the reduction of oxygen by FeIIEDTA(aq). This hypothesis is examined through an electrochemical model of the ZEA system. A carbon basket electrode is used as the reducing agent in place of Fe(0). The FeIIIEDTA complex (0.5 mM) is electrochemically reduced to FeIIEDTA at an applied potential of −120 mV (vs Ag/AgCl) under aerobic conditions. Hydrogen peroxide was observed to form in the presence of the metal complex with a maximum concentration reaching 0.139 mM H2O2 after 3 h of electrolysis. In the absence of FeEDTA, 0.04 mM H2O2 is obtained by the direct reduction of O2 at the electrode surface. Electron resonance spectroscopy (ESR), along with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap and methanol as a radical scavenger confirms the formation of HO• produced via the Fenton reaction in the electrochemical system. Hydroxyl radical attack on EDTA caused the degradation of FeII/IIIEDTA to a steady-state concentration of 0.14 mM from 0.5 mM as observed by HPLC. The pH of the electrolysis solution increased from 2.64 to 9.25 during 6 h of reductive electrolysis which is indicative of the consumption of H+ during the reduction of O2 to form H2O2. These experiments provide evidence that the ZEA system uses atmospheric O2 to produce reactive oxygen species including those that deeply oxidize organics under room temperature and pressure conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701676q [article] Mechanistic study of the ZEA organic pollutant degradation system : evidence for H2O2, HO•, and the homogeneous activation of O2 by feIIEDTA [texte imprimé] / Derek F. Laine, Auteur ; Alexander Blumenfeld, Auteur ; I. Francis Cheng, Auteur . - 2008 . - p. 6502–6508. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6502–6508 Mots-clés : ZEA  system  Electrochemical  model  Carbon  basket  electrode Résumé : The ZEA (zero valent iron, ethylenediaminetetraacetic acid (EDTA), and air) organic pollutant degradation system has been previously shown to degrade a variety of organic pollutants and chemical warfare agent surrogates; however, mechanistic details and reactive intermediates formed in this system have not been identified. It is hypothesized that the ZEA system produces reactive oxygen species (H2O2, HO•) by the reduction of oxygen by FeIIEDTA(aq). This hypothesis is examined through an electrochemical model of the ZEA system. A carbon basket electrode is used as the reducing agent in place of Fe(0). The FeIIIEDTA complex (0.5 mM) is electrochemically reduced to FeIIEDTA at an applied potential of −120 mV (vs Ag/AgCl) under aerobic conditions. Hydrogen peroxide was observed to form in the presence of the metal complex with a maximum concentration reaching 0.139 mM H2O2 after 3 h of electrolysis. In the absence of FeEDTA, 0.04 mM H2O2 is obtained by the direct reduction of O2 at the electrode surface. Electron resonance spectroscopy (ESR), along with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as a spin trap and methanol as a radical scavenger confirms the formation of HO• produced via the Fenton reaction in the electrochemical system. Hydroxyl radical attack on EDTA caused the degradation of FeII/IIIEDTA to a steady-state concentration of 0.14 mM from 0.5 mM as observed by HPLC. The pH of the electrolysis solution increased from 2.64 to 9.25 during 6 h of reductive electrolysis which is indicative of the consumption of H+ during the reduction of O2 to form H2O2. These experiments provide evidence that the ZEA system uses atmospheric O2 to produce reactive oxygen species including those that deeply oxidize organics under room temperature and pressure conditions. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701676q