Biogenic Uraninite Nanoparticles and Their Importance for Uranium Remediation

Bargar, John R.; Bernier‐Latmani, Rizlan; Giammar, Daniel E.; Tebo, Bradley M.

doi:10.2113/gselements.4.6.407

Cited by 156 publications

(106 citation statements)

References 44 publications

Supporting

Mentioning

100

Contrasting

Unclassified

Order By: Relevance

“…Similarly, biogenic UO 2 was produced via the enzymatic reduction of U(VI) by S. putrefaciens and G. sulfurreducens in the absence of Fe(III) and shows the same salient features as that of nanoparticulate UO 2 produced by biogenic magnetite in this study and reported elsewhere Bargar et al, 2008;Sharp et al, 2009;Veeramani et al, 2009).…”

Section: Discussionsupporting

confidence: 84%

“…Coupled with XANES analyses that suggest dominance of U(IV), an absence of distortion in the U-O shell is also suggestive of stoichiometric UO 2.00 , unlike nonstoichiometric UO 2+X which exhibits a split U-O shell (Conradson et al, 2004;Bargar et al, 2008;Schofield et al, 2008). We thus conclude that uranium reduction in the biogenic magnetite system leads to the formation of structurally ordered crystalline uraninite with a composition close to UO 2.00 .…”

Section: Discussionmentioning

confidence: 64%

See 1 more Smart Citation

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

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.

show abstract

Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 64%

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

show abstract

“…U L III -edge EXAFS spectra, fits, and associated Fourier transforms (FTs) for NaOH-treated biogenic uraninite are shown in Figure 1 and Table 2. The focus on NaOHtreated samples is necessary because for the untreated samples the presence of biomass-sorbed U(IV) partially obscures the signal for UO 2 EXAFS spectra and FTs of the NaOH-treated samples qualitatively resemble those of stoichiometric UO 2.00 ( Figure 1), notably including a strong O shell at 1.8 Å (R + dR) (corresponding to the O shell at 2.35 Å) and a strong U shell at 3.8 Å (R + dR) (corresponding to the 3.85 Å U-U distance in the uraninite structure). This conclusion is consistent with the SR-PD results ( Figure SI-5 (Figure 1 and ref 16).…”

Section: Resultsmentioning

confidence: 99%

“…A significant issue associated with uranium bioremediation is the susceptibility of biogenic uraninite, the product of microbial U(VI) reduction (2), to chemical oxidation by O 2 (3)(4)(5), nitrite (6), nitrate (4), and Fe(III) (hydr)oxides (7) and to biological oxidation coupled with nitrate reduction (8).…”

Section: Introductionmentioning

confidence: 99%

Effect of Mn(II) on the Structure and Reactivity of Biogenic Uraninite

Veeramani

Schofield

Sharp

et al. 2009

Environ. Sci. Technol.

View full text Add to dashboard Cite

The efficacy of a site remediation strategy involving the stimulation of microbial U(VI) reduction hinges in part upon the long-term stability of the product, biogenic uraninite, toward environmental oxidants. Geological sedimentary uraninites (nominal formula UO 2 ) reportedly contain abundant cation impurities that enhance their resistance to oxidation. By analogy, incorporation of common groundwater solutes into biogenic uraninite could also impart stability-enhancing properties. Mn(II) is a common groundwater cation, which has a favorable ionic radius for substitution reactions. The structure and reactivity of Mn(II)-reacted biogenic uraninite are investigated in this study. Up to 4.4 weight percent Mn(II) was found to be structurally bound in biogenic uraninite. This Mn(II) incorporation was associated with decreasing uraninite particle size and structural order. Importantly, the equilibrium solubility of Mn-reacted uraninite was halved relative to unreacted uraninite, demonstrating changes in thermodynamic properties, while the dissolution rate was up to 38-fold lower than that of unreacted biogenic uraninite. We conclude that structural incorporation of Mn(II) into uraninite has an important stabilizing effect, leading to the prediction that other groundwater solutes may similarly stabilize biogenic uraninite.

show abstract

“…[6,8,9] Under anoxic conditions, U can be present as molecular U IV , nano-uraninite, or the most stable and least soluble of the reduced forms, crystalline uraninite (UO 2 ). [10][11][12][13] Although U is less mobile in its reduced forms than in its oxidised forms, As is generally more mobile in its reduced form as As III . [14][15][16] Arsenic can adsorb to iron oxides under environmental pH as both As III (H 2 AsO 3 0 ) and As V (H 2 AsO 4 -).…”

Section: Introductionmentioning

confidence: 99%

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Troyer

Stone

2014

Environ. Chem.

View full text Add to dashboard Cite

Environmental context. Uranium and arsenic, two elements of human health concern, are commonly found at sites of uranium mining, but little is known about processes influencing their environmental behaviour. Here we focus on understanding the chemical and physical processes controlling uranium and arsenic transport at an abandoned uranium mine. We find that the use of sedimentation ponds limits the mobility of uranium; however, pond conditions at our site resulted in arsenic mobilisation. Our findings will help optimise restoration strategies for mine tailings.Abstract. Although As can occur in U ore at concentrations up to 10 wt-%, the fate and transport of both U and As at U mine tailings have not been previously investigated at a watershed scale. The major objective of this study was to determine primary chemical and physical processes contributing to transport of both U and As to a down gradient watershed at an abandoned U mine site in South Dakota. Uranium is primarily transported by erosion at the site, based on decreasing concentrations in sediment with distance from the tailings. Sequential extractions and U X-ray absorption near-edge fine structure (XANES) fitting indicate that U is immobilised in a near-source sedimentation pond both by prevention of sediment transport and by reduction of U VI to U IV . In contrast to U, subsequent release of As to the watershed takes place from the pond partially due to reductive dissolution of Fe oxy(hydr)oxides. However, As is immobilised by adsorption to clays and Fe oxy(hydr)oxides in oxic zones and by formation of As-sulfide mineral phases in anoxic zones down gradient, indicated by sequential extractions and As XANES fitting. This study indicates that As should be considered during restoration of uranium mine sites in order to prevent transport.

show abstract

Biogenic Uraninite Nanoparticles and Their Importance for Uranium Remediation

Cited by 156 publications

References 44 publications

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

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

Effect of Mn(II) on the Structure and Reactivity of Biogenic Uraninite

Effect of biogeochemical redox processes on the fate and transport of As and U at an abandoned uranium mine site: an X-ray absorption spectroscopy study

Contact Info

Product

Resources

About