Reactive transport of EDTA-complexed cobalt in the presence of ferrihydrite

Brooks, Scott C.; Taylor, Donald R.; Jardine, Philip M.

doi:10.1016/0016-7037(96)00064-6

Cited by 71 publications

(65 citation statements)

References 18 publications

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“…Ferrihydrite was prepared according to the method described by Brooks et al (32), and then coated quartz sand as reported previously (32,33). Iron concentration on the sand was approximately 10 g Kg -1 (1% by weight).…”

Section: Uranium(vi) Incorporation Experimentsmentioning

confidence: 99%

Stability of Uranium Incorporated into Fe (Hydr)oxides under Fluctuating Redox Conditions

Stewart

Nico

Fendorf

2009

Environ. Sci. Technol.

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Reaction pathways resulting in uranium bearing solids that are stable (i.e., having limited solubility) under both aerobic and anaerobic conditions will limit dissolved concentrations and migration of this toxin. Here we examine the sorption mechanism and propensity for release of uranium reacted with Fe (hydr)oxides under cyclic oxidizing and reducing conditions. Upon reaction of ferrihydrite with Fe(II) under conditions where aqueous Ca-UO 2 -CO 3 species predominate (3 mM Ca and 3.8 mM CO 3 -total), dissolved uranium concentrations decrease from 0.16 mM to below detection limit (BDL) after 5 to 15 d, depending on the Fe(II) concentration.In systems undergoing 3 successive redox cycles (15 d of reduction followed by 5 d of oxidation) and a pulsed decrease to 0.15 mM CO 3 -total, dissolved uranium concentrations varied depending on the Fe(II) concentration during the initial and subsequent reduction phases-U concentrations resulting during the oxic 'rebound' varied inversely with the Fe(II) concentration during the reduction cycle. Uranium removed from solution remains in the oxidized form and is found both adsorbed on and incorporated into the structure of newly formed goethite and magnetite. Our results reveal that the fate of uranium is dependent on anaerobic/aerobic conditions, aqueous uranium speciation, and the fate of iron.2

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Section: Uranium(vi) Incorporation Experimentsmentioning

confidence: 99%

Stability of Uranium Incorporated into Fe (Hydr)oxides under Fluctuating Redox Conditions

Stewart

Nico

Fendorf

2009

Environ. Sci. Technol.

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“…A subset of Al-doped ferrihydrite minerals were coated on quartz sand following the method of Brooks et al (1996) and as conducted previously (Hansel et al, 2003(Hansel et al, , 2004. Pure quartz sand (Unimin Corporation) was mixed with ferrihydrite slurry (10 mg Al-ferrihydrite per g quartz sand), excess water was decanted, and the mixture was allowed to evaporate at room temperature under convection with periodic stirring.…”

Section: Synthesis Of Fe(iii) (Hydr)oxidesmentioning

confidence: 99%

Contrasting effects of Al substitution on microbial reduction of Fe(III) (hydr)oxides

Ekstrom

Learman

Madden

et al. 2010

Geochimica et Cosmochimica Acta

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Aluminum, one of the most abundant elements in soils and sediments, is commonly found co-precipitated with Fe in natural Fe(III) (hydr)oxides; yet, little is known about how Al substitution impacts bacterial Fe(III) reduction. Accordingly, we investigated the reduction of Al substituted (0-13 mol% Al) goethite, lepidocrocite, and ferrihydrite by the model dissimilatory Fe(III)-reducing bacterium (DIRB), Shewanella putrefaciens CN32. Here we reveal that the impact of Al on microbial reduction varies with Fe(III) (hydr)oxide type. No significant difference in Fe(III) reduction was observed for either goethite or lepidocrocite as a function of Al substitution. In contrast, Fe(III) reduction rates significantly decreased with increasing Al substitution of ferrihydrite, with reduction rates of 13% Al-ferrihydrite more than 50% lower than pure ferrihydrite. Although Al substitution changed the minerals' surface area, particle size, structural disorder, and abiotic dissolution rates, we did not observe a direct correlation between any of these physiochemical properties and the trends in bacterial Fe(III) reduction. Based on projected Al-dependent Fe(III) reduction rates, reduction rates of ferrihydrite fall below those of lepidocrocite and goethite at substitution levels equal to or greater than 18 mol% Al. Given the prevalence of Al substitution in natural Fe(III) (hydr)oxides, our results bring into question the conventional assumptions about Fe (hydr)oxide bioavailability and suggest a more prominent role of natural lepidocrocite and goethite phases in impacting DIRB activity in soils and sediments.

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“…While EDTA generally enhances the solubility of 60 Co, the geochemical stability of Co-EDTA complexes, and thus the fate of 60 Co moving through the subsurface is strongly related to the oxidation state of cobalt (log K Co(II)-EDTA = 18.3; log K Co(III)-EDTA = 43.9) (Brooks et al, 1996(Brooks et al, , 1999. [Co(III)-EDTA] − is kinetically inert, resistant to ligand exchange reactions (Brooks et al, 1996), and thus promotes Co transport over a long distance. In contrast, [Co(II)-EDTA] 2− can dissociate more readily, allowing free cobalt ions to be sorbed onto oxide minerals, preventing further spreading in natural environment (Szecsody et al, 1994;Gorby et al, 1998;Brooks et al, 1999;Jardine et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

“…Radioactive 60 Co typically moves in ground water along with ethylenediaminetetraacetic acid (EDTA) (Riley et al, 1992;Brooks et al, 1996;Gao et al, 2010), a persistent organic compound used in cleaning and decontamination operations (Xue and Traina, 1996;Brooks et al, 1999). While EDTA generally enhances the solubility of 60 Co, the geochemical stability of Co-EDTA complexes, and thus the fate of 60 Co moving through the subsurface is strongly related to the oxidation state of cobalt (log K Co(II)-EDTA = 18.3; log K Co(III)-EDTA = 43.9) (Brooks et al, 1996(Brooks et al, , 1999. [Co(III)-EDTA] − is kinetically inert, resistant to ligand exchange reactions (Brooks et al, 1996), and thus promotes Co transport over a long distance.…”

Section: Introductionmentioning

confidence: 99%

[Cobalt(III)–EDTA]− reduction by thermophilic methanogen Methanothermobacter thermautotrophicus

et al. 2015

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a b s t r a c tCobalt is a metal contaminant at high temperature radioactive waste disposal sites. Past studies have largely focused on mesophilic microorganisms to remediate cobalt, despite the presence of thermophilic microorganisms at such sites. In this study, Methanothermobacter thermautotrophicus, a thermophilic methanogen, was used to reduce Co(III) in the form of [Co(III)-EDTA] − . Bioreduction experiments were conducted in a growth medium with H 2 /CO 2 as a growth substrate at initial Co(III) concentrations of 1, 2, 4, 7, and 10 mM. At low Co(III) concentrations (b4 mM), a complete reduction was observed within a week. Wet chemistry, X-ray absorption near-edge structure (XANES) and electron paramagnetic resonance (EPR) analyses were all consistent in revealing the reduction kinetics. However, at higher concentrations (7 and 10 mM) the reduction extents only reached 69.8% and 48.5%, respectively, likely due to the toxic effect of Co(III) to the methanogen cells as evidenced by a decrease in total cellular protein at these Co(III) concentrations. Methanogenesis was inhibited by Co(III) bioreduction, possibly due to impaired cell growth and electron diversion from CO 2 to Co(III). Overall, our results demonstrated the ability of M. thermautotrophicus to reduce Co(III) to Co(II) and its potential application for remediating 60 Co contaminant at high temperature subsurface radioactive waste disposal sites.

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Reactive transport of EDTA-complexed cobalt in the presence of ferrihydrite

Cited by 71 publications

References 18 publications

Stability of Uranium Incorporated into Fe (Hydr)oxides under Fluctuating Redox Conditions

Stability of Uranium Incorporated into Fe (Hydr)oxides under Fluctuating Redox Conditions

Contrasting effects of Al substitution on microbial reduction of Fe(III) (hydr)oxides

[Cobalt(III)–EDTA]− reduction by thermophilic methanogen Methanothermobacter thermautotrophicus

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