Structural formula of uraninite

Janeczek, Janusz; Ewing, Rodney C.

doi:10.1016/0022-3115(92)90082-v

Cited by 154 publications

(108 citation statements)

References 10 publications

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“…Both factors could accelerate oxidative dissolution rather than retard it, making the observed stability of Mnreacted uraninite all the more remarkable. The conclusion that Mn-reacted uraninite is less soluble and more resistant to dissolution than unreacted uraninite is consistent with the reported increase in stability conferred by impurities to geological uraninites [8,10,11]. A recent study of the effect of Ca 2+ on biogenic uraninite has shown that contrary to Mn 2+ , this cation does not affect the kinetics of uraninite oxidation (25).…”

Section: Figure 1 U L Iii -Edge Spectra For Abiotic and Naoh-treatedsupporting

confidence: 82%

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

Veeramani

Schofield

Sharp

et al. 2009

Environ. Sci. Technol.

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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.

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Section: Figure 1 U L Iii -Edge Spectra For Abiotic and Naoh-treatedsupporting

confidence: 82%

“…Cation impurities reported in sedimentary uraninites include Ca 2+ and Pb 2+ . These cations are thought to occur as lattice substituents for U 4+ with charge balance provided by highervalent U (hyperstoichiometry) and/or excess oxygens (11).…”

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.

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“…The term uraninite is used to denote compositionally complex, nonstoichiometric, and generally cation-substituted forms of UO 2 observed in nature (Janeczek and Ewing 1992). Uraninite exhibits a rich structural chemistry, which derives its properties from its open fluorite structure.…”

Section: Structure and Composition Of Geological Uraninitementioning

confidence: 99%

“…denotes an oxygen-vacancy pair (Janeczek and Ewing 1992). Notably, natural uraninite is stable at redox conditions at which stoichiometric UO 2 corrodes.…”

Section: Structure and Composition Of Geological Uraninitementioning

confidence: 99%

Biogenic Uraninite Nanoparticles and Their Importance for Uranium Remediation

et al. 2008

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Biogenic uraninite is of interest to geoscientists for its importance to bioremediation strategies, remarkably small particle size, and biological origin. Recent studies have begun to illuminate the chemical/structural complexities of this important natural nanomaterial. Intriguingly, in spite of its incredibly diminutive size, the molecular-scale structure, energetics, and surfacearea-normalized dissolution rates of hydrated biogenic uraninite appear to be similar to those of coarser-particle, abiotic, stoichiometric UO 2 . These findings have important implications for the role of size as a moderator of nanoparticle aqueous reactivity and for the bioremediation of subsurface U(VI) contamination.

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“…The cracks that are dark in BSE (on Fig. 1a) are probably newly formed due to the sub-recent oxidation-hydration weathering of uraninite, connected with volume changes (see Janeczek and Ewing 1992).…”

Section: Primary (Hypogene) Mineralizationmentioning

confidence: 99%

The recent weathering of uraninite from the Červená vein, Jáchymov (Czech Republic): a fingerprint of the primary mineralization geochemistry onto the alteration association

Plášil¹,

Sejkora²,

Škoda³

et al. 2014

Jour. Geosci.

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Uraninite and the supergene minerals from the Červená hydrothermal uranium vein (Jáchymov ore district, Czech Republic) were studied. These supergene minerals represent alteration products of the joint weathering of uraninite and hypogene sulfide minerals, connected to the acid-mine drainage (AMD) systems. The complex geochemistry of the hypogene mineralization provided a unique environment for formation of chemically diverse supergene phases. Among other features, the weathering system is characterized by the high activity of Cu 2+ and REE, which control the composition of the resulting supergene minerals: commonly occurring are Cu-dominant uranyl sulfates of the zippeite group (pseudojohannite, Cu-rabejacite), Cu-dominant uranyl silicates (cuprosklodowksite) or Y-and REE-containing uranyl-sulfate mineral sejkoraite-(Y). The high activity of Cu 2+ and REE is also reflected by the fact that both elements enter minerals, which are nominally Cu-or REE-free (marécottite, rabejacite, tyuyamunite, and compreignacite). The alteration association was evaluated with regard to the crystal-chemical properties of each mineral using the bond-valence approach, documenting distinct evolutionary trends during weathering.

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Structural formula of uraninite

Cited by 154 publications

References 10 publications

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

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

Biogenic Uraninite Nanoparticles and Their Importance for Uranium Remediation

The recent weathering of uraninite from the Červená vein, Jáchymov (Czech Republic): a fingerprint of the primary mineralization geochemistry onto the alteration association

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