Influence of magnetite stoichiometry on U VI reduction

Drew E. Latta, Christopher A. Gorski, Maxim I. Boyanov, Edward J. O'Loughlin, Kenneth M. Kemner, Michelle M. Scherer

Research output: Contribution to journalArticle

89 Citations (Scopus)

Abstract

Hexavalent uranium (U VI) can be reduced enzymatically by various microbes and abiotically by Fe 2+-bearing minerals, including magnetite, of interest because of its formation from Fe 3+ (oxy)hydroxides via dissimilatory iron reduction. Magnetite is also a corrosion product of iron metal in suboxic and anoxic conditions and is likely to form during corrosion of steel waste containers holding uranium-containing spent nuclear fuel. Previous work indicated discrepancies in the extent of U VI reduction by magnetite. Here, we demonstrate that the stoichiometry (the bulk Fe 2+/Fe 3+ ratio, x) of magnetite can, in part, explain the observed discrepancies. In our studies, magnetite stoichiometry significantly influenced the extent of U VI reduction by magnetite. Stoichiometric and partially oxidized magnetites with x ≥ 0.38 reduced U VI to U IV in UO 2 (uraninite) nanoparticles, whereas with more oxidized magnetites (x < 0.38) and maghemite (x = 0), sorbed U VI was the dominant phase observed. Furthermore, as with our chemically synthesized magnetites (x ≥ 0.38), nanoparticulate UO 2 was formed from reduction of U VI in a heat-killed suspension of biogenic magnetite (x = 0.43). X-ray absorption and Mössbauer spectroscopy results indicate that reduction of U VI to U IV is coupled to oxidation of Fe 2+ in magnetite. The addition of aqueous Fe 2+ to suspensions of oxidized magnetite resulted in reduction of U VI to UO 2, consistent with our previous finding that Fe 2+ taken up from solution increased the magnetite stoichiometry. Our results suggest that magnetite stoichiometry and the ability of aqueous Fe 2+ to recharge magnetite are important factors in reduction of U VI in the subsurface.

Original languageEnglish (US)
Pages (from-to)778-786
Number of pages9
JournalEnvironmental Science and Technology
Volume46
Issue number2
DOIs
StatePublished - Jan 17 2012

Fingerprint

Ferrosoferric Oxide
stoichiometry
Stoichiometry
magnetite
Uranium
corrosion
uranium
Suspensions
Bearings (structural)
Iron
Hydroxides
suboxic conditions
Corrosion
iron
uraninite
maghemite
Steel
Spent fuels
X ray absorption
Nuclear fuels

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Environmental Chemistry

Cite this

Latta, D. E., Gorski, C. A., Boyanov, M. I., O'Loughlin, E. J., Kemner, K. M., & Scherer, M. M. (2012). Influence of magnetite stoichiometry on U VI reduction. Environmental Science and Technology, 46(2), 778-786. https://doi.org/10.1021/es2024912
Latta, Drew E. ; Gorski, Christopher A. ; Boyanov, Maxim I. ; O'Loughlin, Edward J. ; Kemner, Kenneth M. ; Scherer, Michelle M. / Influence of magnetite stoichiometry on U VI reduction. In: Environmental Science and Technology. 2012 ; Vol. 46, No. 2. pp. 778-786.
@article{ece1d4b1384f40ca8e6397fb7ca92c5f,
title = "Influence of magnetite stoichiometry on U VI reduction",
abstract = "Hexavalent uranium (U VI) can be reduced enzymatically by various microbes and abiotically by Fe 2+-bearing minerals, including magnetite, of interest because of its formation from Fe 3+ (oxy)hydroxides via dissimilatory iron reduction. Magnetite is also a corrosion product of iron metal in suboxic and anoxic conditions and is likely to form during corrosion of steel waste containers holding uranium-containing spent nuclear fuel. Previous work indicated discrepancies in the extent of U VI reduction by magnetite. Here, we demonstrate that the stoichiometry (the bulk Fe 2+/Fe 3+ ratio, x) of magnetite can, in part, explain the observed discrepancies. In our studies, magnetite stoichiometry significantly influenced the extent of U VI reduction by magnetite. Stoichiometric and partially oxidized magnetites with x ≥ 0.38 reduced U VI to U IV in UO 2 (uraninite) nanoparticles, whereas with more oxidized magnetites (x < 0.38) and maghemite (x = 0), sorbed U VI was the dominant phase observed. Furthermore, as with our chemically synthesized magnetites (x ≥ 0.38), nanoparticulate UO 2 was formed from reduction of U VI in a heat-killed suspension of biogenic magnetite (x = 0.43). X-ray absorption and M{\"o}ssbauer spectroscopy results indicate that reduction of U VI to U IV is coupled to oxidation of Fe 2+ in magnetite. The addition of aqueous Fe 2+ to suspensions of oxidized magnetite resulted in reduction of U VI to UO 2, consistent with our previous finding that Fe 2+ taken up from solution increased the magnetite stoichiometry. Our results suggest that magnetite stoichiometry and the ability of aqueous Fe 2+ to recharge magnetite are important factors in reduction of U VI in the subsurface.",
author = "Latta, {Drew E.} and Gorski, {Christopher A.} and Boyanov, {Maxim I.} and O'Loughlin, {Edward J.} and Kemner, {Kenneth M.} and Scherer, {Michelle M.}",
year = "2012",
month = "1",
day = "17",
doi = "10.1021/es2024912",
language = "English (US)",
volume = "46",
pages = "778--786",
journal = "Environmental Science & Technology",
issn = "0013-936X",
publisher = "American Chemical Society",
number = "2",

}

Latta, DE, Gorski, CA, Boyanov, MI, O'Loughlin, EJ, Kemner, KM & Scherer, MM 2012, 'Influence of magnetite stoichiometry on U VI reduction', Environmental Science and Technology, vol. 46, no. 2, pp. 778-786. https://doi.org/10.1021/es2024912

Influence of magnetite stoichiometry on U VI reduction. / Latta, Drew E.; Gorski, Christopher A.; Boyanov, Maxim I.; O'Loughlin, Edward J.; Kemner, Kenneth M.; Scherer, Michelle M.

In: Environmental Science and Technology, Vol. 46, No. 2, 17.01.2012, p. 778-786.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Influence of magnetite stoichiometry on U VI reduction

AU - Latta, Drew E.

AU - Gorski, Christopher A.

AU - Boyanov, Maxim I.

AU - O'Loughlin, Edward J.

AU - Kemner, Kenneth M.

AU - Scherer, Michelle M.

PY - 2012/1/17

Y1 - 2012/1/17

N2 - Hexavalent uranium (U VI) can be reduced enzymatically by various microbes and abiotically by Fe 2+-bearing minerals, including magnetite, of interest because of its formation from Fe 3+ (oxy)hydroxides via dissimilatory iron reduction. Magnetite is also a corrosion product of iron metal in suboxic and anoxic conditions and is likely to form during corrosion of steel waste containers holding uranium-containing spent nuclear fuel. Previous work indicated discrepancies in the extent of U VI reduction by magnetite. Here, we demonstrate that the stoichiometry (the bulk Fe 2+/Fe 3+ ratio, x) of magnetite can, in part, explain the observed discrepancies. In our studies, magnetite stoichiometry significantly influenced the extent of U VI reduction by magnetite. Stoichiometric and partially oxidized magnetites with x ≥ 0.38 reduced U VI to U IV in UO 2 (uraninite) nanoparticles, whereas with more oxidized magnetites (x < 0.38) and maghemite (x = 0), sorbed U VI was the dominant phase observed. Furthermore, as with our chemically synthesized magnetites (x ≥ 0.38), nanoparticulate UO 2 was formed from reduction of U VI in a heat-killed suspension of biogenic magnetite (x = 0.43). X-ray absorption and Mössbauer spectroscopy results indicate that reduction of U VI to U IV is coupled to oxidation of Fe 2+ in magnetite. The addition of aqueous Fe 2+ to suspensions of oxidized magnetite resulted in reduction of U VI to UO 2, consistent with our previous finding that Fe 2+ taken up from solution increased the magnetite stoichiometry. Our results suggest that magnetite stoichiometry and the ability of aqueous Fe 2+ to recharge magnetite are important factors in reduction of U VI in the subsurface.

AB - Hexavalent uranium (U VI) can be reduced enzymatically by various microbes and abiotically by Fe 2+-bearing minerals, including magnetite, of interest because of its formation from Fe 3+ (oxy)hydroxides via dissimilatory iron reduction. Magnetite is also a corrosion product of iron metal in suboxic and anoxic conditions and is likely to form during corrosion of steel waste containers holding uranium-containing spent nuclear fuel. Previous work indicated discrepancies in the extent of U VI reduction by magnetite. Here, we demonstrate that the stoichiometry (the bulk Fe 2+/Fe 3+ ratio, x) of magnetite can, in part, explain the observed discrepancies. In our studies, magnetite stoichiometry significantly influenced the extent of U VI reduction by magnetite. Stoichiometric and partially oxidized magnetites with x ≥ 0.38 reduced U VI to U IV in UO 2 (uraninite) nanoparticles, whereas with more oxidized magnetites (x < 0.38) and maghemite (x = 0), sorbed U VI was the dominant phase observed. Furthermore, as with our chemically synthesized magnetites (x ≥ 0.38), nanoparticulate UO 2 was formed from reduction of U VI in a heat-killed suspension of biogenic magnetite (x = 0.43). X-ray absorption and Mössbauer spectroscopy results indicate that reduction of U VI to U IV is coupled to oxidation of Fe 2+ in magnetite. The addition of aqueous Fe 2+ to suspensions of oxidized magnetite resulted in reduction of U VI to UO 2, consistent with our previous finding that Fe 2+ taken up from solution increased the magnetite stoichiometry. Our results suggest that magnetite stoichiometry and the ability of aqueous Fe 2+ to recharge magnetite are important factors in reduction of U VI in the subsurface.

UR - http://www.scopus.com/inward/record.url?scp=84855918489&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84855918489&partnerID=8YFLogxK

U2 - 10.1021/es2024912

DO - 10.1021/es2024912

M3 - Article

C2 - 22148359

AN - SCOPUS:84855918489

VL - 46

SP - 778

EP - 786

JO - Environmental Science & Technology

JF - Environmental Science & Technology

SN - 0013-936X

IS - 2

ER -

Latta DE, Gorski CA, Boyanov MI, O'Loughlin EJ, Kemner KM, Scherer MM. Influence of magnetite stoichiometry on U VI reduction. Environmental Science and Technology. 2012 Jan 17;46(2):778-786. https://doi.org/10.1021/es2024912