Competition between enzymatic and abiotic reduction of uranium(VI) under iron reducing conditions

Behrends, Thilo; Cappellen, Philippe Van

doi:10.1016/j.chemgeo.2005.04.007

Cited by 126 publications

(97 citation statements)

References 45 publications

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“…Biogenic Fe(II)-bearing minerals are of interest in the context of uranium redox cycling and bioremediation because they are formed under Fe-reducing conditions (Behrends and Van Cappellen, 2005). Previous studies that focused on chemogenic analogs may not have accounted for important properties characteristic of biogenic minerals such as their nano-size and associated enhanced reactivity (O'Loughlin et al, 2003;Regenspurg et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

“…Research thus far has demonstrated U(VI) reduction by Fe(II) sorbed onto a variety of iron oxides/oxyhydroxides (Charlet et al, 1998;Liger et al, 1999;Fredrickson et al, 2000;Jeon et al, 2004), Fe(II)-containing natural sediments (Behrends and Van Cappellen, 2005;Jeon et al, 2005), Fe(II)-containing carboxyl-functionalized microspheres (Boyanov et al, 2007), Fe(II) sorbed on corundum (Regenspurg et al, 2009) and Fe(II) sorbed on montmorillonite (Chakraborty et al, 2010). These studies primarily consider surface catalyzed processes that involved either concomitant or sequential adsorption of aqueous Fe(II) and U(VI) species onto a solid phase adsorbent or mineral to mediate abiotic U(VI) reduction.…”

Section: Introductionmentioning

confidence: 99%

“…doi: 10.1016/j.gca.2011.02.024 Subsurface uranium can be reduced by a number of abiotic (Behrends and Van Cappellen, 2005) and microbiallymediated processes (Abdelouas et al, 1998;Elias et al, 2003) including reductive immobilization of uranium by dissimilatory metal-reducing bacteria (DMRB) (Lovley, 1993). These bacteria catalyze U(VI) reduction using organic acids, alcohols or H 2 as electron donors and utilize Fe(III) as growth-supporting electron acceptors.…”

Section: Introductionmentioning

confidence: 99%

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Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

Veeramani

Alessi

Suvorova

et al. 2011

Geochimica et Cosmochimica Acta

138

122

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Reductive immobilization of uranium by the stimulation of dissimilatory metal-reducing bacteria (DMRB) has been investigated as a remediation strategy for subsurface U(VI) contamination. In those environments, DMRB may utilize a variety of electron acceptors, such as ferric iron which can lead to the formation of reactive biogenic Fe(II) phases. These biogenic phases could potentially mediate abiotic U(VI) reduction. In this work, the DMRB Shewanella putrefaciens strain CN32 was used to synthesize two biogenic Fe(II)-bearing minerals: magnetite (a mixed Fe(II)-Fe(III) oxide) and vivianite (an Fe(II)-phosphate). Analysis of abiotic redox interactions between these biogenic minerals and U(VI) showed that both biogenic minerals reduced U(VI) completely. XAS analysis indicates significant differences in speciation of the reduced uranium after reaction with the two biogenic Fe(II)-bearing minerals. While biogenic magnetite favored the formation of structurally ordered, crystalline UO 2 , biogenic vivianite led to the formation of a monomeric U(IV) species lacking U-U associations in the corresponding EXAFS spectrum. To investigate the role of phosphate in the formation of monomeric U(IV) such as sorbed U(IV) species complexed by mineral surfaces, versus a U(IV) mineral, uranium was reduced by biogenic magnetite that was pre-sorbed with phosphate. XAS analysis of this sample also revealed the formation of monomeric U(IV) species suggesting that the presence of phosphate hinders formation of UO 2 . This work shows that U(VI) reduction products formed during in situ biostimulation can be influenced by the mineralogical and geochemical composition of the surrounding environment, as well as by the interfacial solute-solid chemistry of the solid-phase reductant.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

Veeramani

Alessi

Suvorova

et al. 2011

Geochimica et Cosmochimica Acta

138

122

View full text Add to dashboard Cite

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“…Abiological U(VI) reduction in the presence of the Fe(III) oxide minerals requires aqueous Fe(II) species, and the Fe(II) monohydroxo surface complex Fe III OFe II OH 0 is considered to be a reductant in the reduction of U(VI) (Liger et al, 1999). Magnetite appears to be a more efficient component of U(VI) reduction than hematite under certain experimental conditions (Behrends and Van Cappellen, 2005).…”

Section: Abiological Processes That Control U Redox Transformationsmentioning

confidence: 99%

“…To date, all known processes for the abiological reduction of U(VI) CO 3 complexes involve Fe(III) oxide minerals Behrends and Van Cappellen, 2005;Jeon et al, 2005). Fe(III) oxide minerals involved in U reduction include magnetite (Fe 3 O 4 ), goethite (α FeOOH), and hematite (α Fe 2 O 3 ).…”

Section: Abiological Processes That Control U Redox Transformationsmentioning

confidence: 99%

Geomicrobiological factors that control uranium mobility in the environment: Update on recent advances in the bioremediation of uranium-contaminated sites

Suzuki

Suko

2006

Journal of Mineralogical and Petrological Sciences

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Understanding the behavior of uranium (U) in the environment is essential not only for the protection of aquifers from U contamination but also for predicting the fate of U and other actinides disposed of in deep geological settings. It has long been believed that the redox chemistry of U can be simply predicted by thermodynamics and that the development of a low redox potential is a sufficient condition for U reduction. However, recent studies have demonstrated that redox transformations of U are controlled by kinetic factors that are strongly influenced by microbial activity. Although abiological U oxidation proceeds efficiently under oxygenic conditions, abiological reduction of U is inhibited by the formation of negatively charged U(VI) CO 3 complexes that prevail in nature. Phylogenetically diverse microorganisms are capable of enzymatically reducing U(VI) CO 3 complexes to form U(IV) bearing minerals such as uraninite (UO 2+x ). The only abiological pathway currently known for the reduction of U(VI) CO 3 complexes involves the Fe(II) monohydroxo surface complex Fe III OFe II OH 0 . This complex is mainly produced by the microbial reduction of Fe(III) in natural systems. Thus, U(VI) reduction is controlled both directly and indirectly, at least in part, by microbial activity. Several mechanisms of U oxidation under anoxic conditions have been revealed recently by laboratory and field studies. U(IV) is abiologically oxidized by Fe(III) and Mn(IV) oxides. Microbial reduction of nitrate to molecular nitrogen, which occurs following the depletion of O 2 , produces nitrogen intermediates including nitrite (NO 2 -), nitrous oxide (NO), and nitric oxide (N 2 O). Although the nitrogen intermediates oxidize U(IV), poorly crystalline Fe(III) oxide minerals resulting from the oxidation of aqueous Fe(II) species by the nitrogen intermediates oxidize U(IV) more efficiently than the nitrogen intermediates alone. Remarkably, the formation of Ca U(VI) CO 3 complexes resulting from increased levels of Ca 2+ and/or HCO 3 -leads to the reoxidation of bioreduced U(IV) under reducing conditions. These geomicrobiological factors pose challenges in manipulating and/or predicting the mobility and fate of U in complex and heterogeneous environmental settings.

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