Kinetics and mechanism of the autoxidation of iron(II) induced through chelation by ethylenediaminetetraacetate and related ligands

Zang, V.; Eldik, Rudi van

doi:10.1021/ic00334a023

Cited by 128 publications

(142 citation statements)

References 5 publications

(7 reference statements)

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“…It should be noted that bridged dimeric species of the form such as Fe(III)L(O 2− 2 )Fe(III)L, proposed to occur during O 2 -mediated oxidation by Seibig and Van Eldik (1997) for L = EDTA are not considered in the kinetic model as they are unimportant at the low Fe concentrations used here despite their demonstrated importance at millimolar concentrations of Fe(II) (Zang and Van Eldik, 1990b). The rate constants for O 2 -and H 2 O 2 -mediated oxidation of Fe(II)L (L = EDTA, DTPA) found here are generally consistent with previously determined values under similar conditions (see Supplementary Material Sections 4 and 5 for details).…”

Section: Verified As Discussed In Textmentioning

confidence: 99%

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

2016

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The reaction between Fe(II) and H 2 O 2 to yield hydroxyl radicals (HO • ), the Fenton reaction, is of interest due to its role in trace metal and natural organic matter biogeochemistry, its utility in water treatment and its role in oxidative cell degradation and associated human disease. There is significant dispute over whether HO • , the most reactive of the so-called reactive oxygen species (ROS), is formed in this reaction, particularly under circumneutral conditions relevant to natural systems. In this work we have studied the oxidation kinetics of Fe(II) complexed by L = citrate, ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA) and also measured HO • production using phthalhydrazide as a probe compound at pH 8.2. A kinetic model has been developed and utilized to confirm that HO • is the sole product of the Fe(II)L-H 2 O 2 reaction for L = EDTA and DTPA. Quantitative HO • production also appears likely for L = citrate, although uncertainties with the speciation of Fe(II)-citrate complexes as well as difficulties in modeling the oxidation kinetics of these complexes has prevented a definitive conclusion. In the absence of ligands at circumneutral pH, inorganic Fe(II) reacts with H 2 O 2 to yield a species other than HO • , contrary to the well-established production of HO • from inorganic Fe(II) at low pH. Our results suggest that at high pH Fe(II) must be complexed for HO • production to occur.

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Section: Verified As Discussed In Textmentioning

confidence: 99%

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

2016

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“…This change in the order in iron chelate appears to be a function of the concentration of ferrous chelate. 8,9 At low concentrations, the reaction seems to be first order in iron chelate, whereas the order changes to 2 at increasing Fe II (EDTA) concentrations. Mechanistic proposals have been put forward to explain this effect.…”

Section: Introductionmentioning

confidence: 99%

“…9 In addition, all studies imply that the reaction is first order with respect to oxygen. [5][6][7][8][9][10] This work describes a kinetic study on the reaction of C Fe II (EDTA) with oxygen under conditions relevant to the BiodeNOx process (C Fe II (EDTA) ) 15-60 mol/m 3 , P O2 ) 5-20 kPa, pH ) 5-8, T ) 298-328 K, and C NaCl ) 0-15 kg/m 3 ). Although various studies have been performed in the past, the results are not always reliable because of improper attention to mass transfer issues.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of the Reaction of Fe^II(EDTA) with Oxygen in Aqueous Solutions

Gambardella¹,

Ganzeveld

Winkelman³

et al. 2005

Ind. Eng. Chem. Res.

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The kinetics of the reaction of oxygen with aqueous Fe II (EDTA) solutions has been determined in a range of process conditions (C Fe II (EDTA) ) 15-60 mol/m 3 , P O2 ) 5-20 kPa, pH ) 5-8, T ) 298-328 K, C NaCl ) 0-15 kg/m 3 ) using a gas-liquid stirred cell reactor. The oxygen absorption rates were modeled using an expression derived by De Coursey using the penetration theory of mass transfer. Within the range of process conditions applied, the reaction was shown to be first order in oxygen and second order in iron chelate. The temperature dependence of the kinetic constant may be expressed as (pH ) 7, no salt addition): k 12 ) 5.3 × 10 3 e -4098/T m 6 /(mol 2 ‚s). The kinetic constant is essentially independent of the pH in the range 5 < pH < 8. When applying a NaCl concentration of 15 kg/m 3 , the kinetic constant increases ∼35% (T ) 328 K). The oxidation of Fe II (EDTA) to Fe III (EDTA) is not the sole oxygen-consuming reaction. The extent of side reactions, possibly related to EDTA ligand degradation, is a function of the pH and the oxygen concentration. A remarkable, unprecedented step change in the selectivity of the reaction was observed when the reaction was performed at a higher oxygen concentration.

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“…[1Ϫ12, 21] A number of test experiments on the [Fe II (cdta)] system We recently reported a detailed kinetic study of the oxishowed that its spectroscopic behavior is very similar to the dation kinetics of [Fe II (edta)] with molecular oxygen. [22] For [Fe II (edta)] system, which we investigated recently.…”

Section: Spectral Observationsmentioning

confidence: 99%

“…[4,6,7,10,12,21] text was their importance in several biochemical processes, for example the cleavage of DNA, the decomposition of H 2 O 2 or the dismutation of superoxide.…”

Section: Introductionmentioning

confidence: 99%

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

Seibig¹,

Eldik²

1999

Eur. J. Inorg. Chem.

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The complicated oxidation kinetics of the reaction of [FeII(cdta)] [cdta = 1,2‐(N,N′‐ cyclohexanediamine)tetraacetate] with molecular oxygen was investigated as a function of [FeII], [O2], pH, temperature and pressure. In the presence of an excess of [FeII(cdta)] three steps could be observed, for which the following rate constants were found at 25°C; k1 = 1080 ± 16 M−1 s−1, k2 = 103 ± 4 M−1 s−1 and k3 = 59 ± 5 M−1 s−1. These reaction steps can be accounted for in terms of the following mechanism: (1) [FeII(cdta)H2O]2– reacts with O2 by a substitution process to form [FeII(cdta)O2]2–; (2) electron‐transfer to form an FeIII‐superoxo species; (3) subsequent bridge formation followed by electron‐transfer to give [(cdta)FeIII‐O22–‐FeIII(cdta)]4–; and (4) a fast decomposition of the peroxide intermediate yielding the monomeric [FeIII(cdta)] and H2O2. Rate and activation parameters for these steps are reported and discussed in terms of the postulated mechanism and in reference to available literature data.

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Kinetics and mechanism of the autoxidation of iron(II) induced through chelation by ethylenediaminetetraacetate and related ligands

Cited by 128 publications

References 5 publications

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Kinetics of the Reaction of Fe^II(EDTA) with Oxygen in Aqueous Solutions

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

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Kinetics and mechanism of the autoxidation of iron(II) induced through chelation by ethylenediaminetetraacetate and related ligands

Cited by 128 publications

References 5 publications

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Importance of Iron Complexation for Fenton-Mediated Hydroxyl Radical Production at Circumneutral pH

Kinetics of the Reaction of FeII(EDTA) with Oxygen in Aqueous Solutions

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

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Kinetics of the Reaction of Fe^II(EDTA) with Oxygen in Aqueous Solutions