Oxygenation of Ferrous Iron

Stumm, Werner; Lee, G. F.

doi:10.1021/ie50614a030

Cited by 755 publications

(451 citation statements)

References 10 publications

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“…One possible explanation is the lack of Fe(III) surface species at a pH of ∼5 owing to the slow oxidation kinetics of dissolved Fe(II). 41 The oxidation rate of noncrystalline U(IV) is limited relative to the control experiment in the absence of FeS (Table 1), likely because surface Fe(III) is absent or negligible, and DO levels are lowered by FeS consumption. Therefore, the pH-dependent oxidation pathway of FeS has potentially an important impact on noncrystalline U(IV) oxidation.…”

Section: Environmental Science and Technologymentioning

confidence: 98%

Rapid Mobilization of Noncrystalline U(IV) Coupled with FeS Oxidation

Stylo

Bernier‐Latmani

et al. 2016

Environ. Sci. Technol.

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The reactivity of disordered, noncrystalline U(IV) species remains poorly characterized despite their prevalence in biostimulated sediments. Because of the lack of crystalline structure, noncrystalline U(IV) may be susceptible to oxidative mobilization under oxic conditions. The present study investigated the mechanism and rate of oxidation of biogenic noncrystalline U(IV) by dissolved oxygen (DO) in the presence of mackinawite (FeS). Previously recognized as an effective reductant and oxygen scavenger, nanoparticulate FeS was evaluated for its role in influencing U release in a flowthrough system as a function of pH and carbonate concentration. The results demonstrated that noncrystalline U(IV) was more susceptible to oxidation than uraninite (UO 2 ) in the presence of dissolved carbonate. A rapid release of U occurred immediately after FeS addition without exhibiting a temporary inhibition stage, as was observed during the oxidation of UO 2 , although FeS still kept DO levels low. X-ray photoelectron spectroscopy (XPS) characterized a transient surface Fe(III) species during the initial FeS oxidation, which was likely responsible for oxidizing noncrystalline U(IV) in addition to oxygen. In the absence of carbonate, however, the release of dissolved U was significantly hindered as a result of U adsorption by FeS oxidation products. This study illustrates the strong interactions between iron sulfide and U(IV) species during redox transformation and implies the lability of biogenic noncrystalline U(IV) species in the subsurface environment when subjected to redox cycling events.

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Section: Environmental Science and Technologymentioning

confidence: 98%

Rapid Mobilization of Noncrystalline U(IV) Coupled with FeS Oxidation

Stylo

Bernier‐Latmani

et al. 2016

Environ. Sci. Technol.

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“…Stumm and Lee ( 1961) and Theis and Singer (1973) demonstrated that the organic ligands decrease the rate constant of Fe(II) oxidation. The differences in the degree of the rate constant of Fe(II) oxidation in the presence of complexing ligands has been attributed to the relative stability of the Fe(II)-ligand complex (Krishnamurti and Huang, 1990a).…”

Section: Introductionmentioning

confidence: 99%

“…In an aqueous weathering environment, the oxidation products of Fe(II) solutions are important, because Fe is commonly mobilized as Fe(II) during weathering under the Eh-pH regime of natural soil environments. The rate of Fe(II) oxidation at a constant rate of oxygen supply can be influenced by pH, temperature, and the presence of ions, such as Mn 2+, Cu 2+, Co 2+, and H2PO4- (Stumm and Lee, 1961), and, thus, it should influence the nature of the hydrolytic products in an oxidizing Fe(II) system. Fe(II) is capable of forming complexes with organic matter, and such ligand stabilization has been suggested as an explanation for the apparent presence of Fe(II) in oxic solutions that contain relatively high levels of organic matter (Morgan and Stumm, 1964).…”

Section: Introductionmentioning

confidence: 99%

Influence of Citrate on the Kinetics of Fe(II) Oxidation and the Formation of Iron Oxyhydroxides

Krishnamurti

Huang

1991

Clays and clay miner.

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Abstract--The rate of Fe(II) oxidation at a constant rate of oxygen supply in the presence of citrate was measured at pH 6.0 at various citrate/Fe(II) molar ratios at 23.5~ in 0.01 M ferrous perch/orate system. The kinetics followed a first-order reaction with respect to Fe(II) concentration at constant pH (6.0) and aeration (5 ml/min). The rate constant decreased exponentially from 41.3 x 10 -4 to 7.6 x 10-"/min with an increase in the citrate/Fe(II) molar ratio from 0 to 0.1.The nature of the hydrolytic products formed after 120 min of oxidation was arrived at by X-ray powder diffraction (XRD), infrared spectrometry (IR), and transmission electron microscopic (TEM) analyses. In the absence of citrate, goethite (a-FeOOH) and poorly crystalline lepidocrocite (7-FeOOH) were the oxidation products formed at pH 6.0. The formation of lepidocrocite was promoted at the expense of goethite at citrate/Fe(II) molar ratios of 0.0005 to 0.005. The formation of lepidocrocite was especially pronounced at a citrate/Fe(II) molar ratio of 0.001, as observed from the width at half height (WHH) and the area of the 020 XRD peak of lepidocrocite. At a citrate/Fe(II) molar ratio of 0.01, however, the crystallization was perturbed resulting in the formation of noncrystalline Fe oxides, and no precipitate was observed at a citrate/Fe molar ratio of 0.1. The strong complexation of Fe(II) with citrate retarded the kinetics of Fe(II) oxidation and the formation and hydrolysis of Fe(III). The complexation, electrostatic, and steric effects of the coexisting citrate anions in solution apparently influenced the oxygen coordination and the way by which the double rows of edge-sharing Fe(O,OH)6 octahedra linked during crystallization, resulting in the formation of lepidocrocite.

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“…Two experimental limitations have previously prevented characterization of Fez+ transport in multicellular roots: (a) Fez+ activity is difficult to control because of the rapid reoxidation of Fez+ to Fe3+ in aerobic environments (Stumm and Lee, 1961), and this makes it difficult to ascertain to what activity of Fez+ plants are exposed; and (b) 59Fe nonspecifically binds to cell walls, complicating measurements of Fe accumulation in roots. Thus, Fe influx into roots will be overestimated unless appropriate techniques are used to remove cell-wall Fe without compromising Fe transport into the symplasm.…”

mentioning

confidence: 99%

Direct Measurement of 59Fe-Labeled Fe2+ Influx in Roots of Pea Using a Chelator Buffer System to Control Free Fe2+ in Solution

et al. 1996

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Fe2+ transport in plants has been difficult to quantify because of the inability to control Fe2+ activity in aerated solutions and non-specific binding of Fe to cell walls. In this study, a Fe(II)-3-(2-pyridyl)-5,6-diphenyl-1,2,4-triazine-4[prime]4″-disulfonic acid buffer system was used to control free Fe2+ in uptake solutions. Additionally, desorption methodologies were developed to adequately remove nonspecifically bound Fe from the root apoplasm. This enabled us to quantify unidirectional Fe2+ influx via radiotracer (59Fe) uptake in roots of pea (Pisum sativum cv Sparkle) and its single gene mutant brz, an Fe hyperaccumulator. Fe influx into roots was dramatically inhibited by low temperature, indicating that the measured Fe accumulation in these roots was due to true influx across the plasma membrane rather than nonspecific binding to the root apoplasm. Both Fe2+ influx and Fe translocation to the shoots were stimulated by Fe deficiency in Sparkle. Additionally, brz, a mutant that constitutively exhibits high ferric reductase activity, exhibited higher Fe2+ influx rates than +Fe-grown Sparkle. These results suggest that either Fe deficiency triggers the induction of the Fe2+ transporter or that the enhanced ferric reductase activity somehow stimulates the activity of the existing Fe2+ transport protein.

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Oxygenation of Ferrous Iron

Cited by 755 publications

References 10 publications

Rapid Mobilization of Noncrystalline U(IV) Coupled with FeS Oxidation

Rapid Mobilization of Noncrystalline U(IV) Coupled with FeS Oxidation

Influence of Citrate on the Kinetics of Fe(II) Oxidation and the Formation of Iron Oxyhydroxides

Direct Measurement of 59Fe-Labeled Fe2+ Influx in Roots of Pea Using a Chelator Buffer System to Control Free Fe2+ in Solution

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