Contaminant Uranium Phases and Leaching at the Fernald Site in Ohio

Buck, Edgar C.; Brown, N. R.; Dietz, N.L.

doi:10.1021/es9500825

Cited by 158 publications

(101 citation statements)

References 15 publications

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“…These minerals are important in controlling the mobility of uranium in the contaminated subsurface. For example, the uranyl silicate, boltwoodite, and the uranyl phosphate, metatorbernite, have formed in contaminated sediments of the Hanford site [2][3][4], uranyl phosphates occur in contaminated soils of the Fernald site [5], and uranyl sulfates are common in altered mine tailings [6]. The interactions of these minerals with aqueous systems, and the details of how they dissolve and precipitate, are integral to understanding and predicting the mobility of uranium.…”

Section: Introductionmentioning

confidence: 99%

An integrated study of uranyl mineral dissolution processes: etch pit formation, effects of cations in solution, and secondary precipitation

Schindler¹,

Hawthorne

Mandaliev

et al. 2011

Radiochimica Acta

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Summary.Understanding the mechanism(s) of uraniummineral dissolution is crucial for predictive modeling of U mobility in the subsurface. In order to understand how pH and type of cation in solution may affect dissolution, experiments were performed on mainly single crystals of curite, PbSolutions included: deionized water; aqueous HCl solutions at pH 3.5 and 2; 0.5 mol L −1 Pb(II)-, Ba-, Sr-, Ca-, Mg-, HCl solutions at pH 2; 1.0 mol L −1 Na-and K-HCl solutions at pH 2; and a 0.1 mol L −1 Na 2 CO 3 solution at pH 10.5. Uranyl mineral basal surface microtopography, micromorphology, and composition were examined prior to, and after dissolution experiments on micrometer scale specimens using atomic force microscopy, scanning electron microscopy, and X-ray photoelectron spectroscopy. Evolution of etch pit depth at different pH values and experimental durations can be explained using a stepwave dissolution model. Effects of the cation in solution on etch pit symmetry and morphology can be explained using an adsorption model involving specific surface sites. Surface precipitation of the following phases was observed: (a) a highly-hydrated uranyl-hydroxy-hydrate in ultrapure water (on all minerals), (b) a Na-uranyl-hydroxy-hydrate in Na 2 CO 3 solution of pH 10.5 (on uranyl-hydroxy-hydrate minerals), (c) a Na-uranyl-carbonate on zippeite, (d) Ba-and Pb-uranylhydroxy-hydrates in Ba-HCl and Pb-HCl solutions of pH 2 (on uranophane), (e) a (SiO x (OH) 4−2x ) phase in solutions of pH 2 (uranophane), and (f) sulfate-bearing phases in solutions of pH 2 and 3.5 (on zippeite).

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Section: Introductionmentioning

confidence: 99%

An integrated study of uranyl mineral dissolution processes: etch pit formation, effects of cations in solution, and secondary precipitation

Schindler¹,

Hawthorne

Mandaliev

et al. 2011

Radiochimica Acta

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“…For example, U-phosphorus phases were identified in contaminated soil at the Fernald site in Ohio (17). The initial precipitates may be relatively unstable and subsequently transform to phases of greater stability (10,16,18,19).…”

Section: Introductionmentioning

confidence: 99%

Uranium Extraction From Laboratory-Synthesized, Uranium-Doped Hydrous Ferric Oxides

Smith

Douglas

Moore

et al. 2009

Environ. Sci. Technol.

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The extractability of uranium (U) from synthetic uranium-hydrous ferric oxide (HFO) coprecipitates has been shown to decrease as a function of mineral ripening, consistent with the hypothesis that the ripening process will decrease uranium lability. To evaluate this process, three HFO suspensions were coprecipitated with uranyl (UO 2 2+) and maintained at pH 7.0 ( 0.1. Uranyl was added to the HFO postprecipitation in a fourth suspension. Two suspensions also contained either coprecipitated silicate (Si-U-HFO) or phosphate (P-U-HFO). After precipitation of the HFOs, at time intervals of 1 week, 1 month, 6 months, 1 year, and 2 years, aliquots of each suspension were contacted with five extractant solutions for a range of time. Uranium was preferentially extracted over Fe in varying degrees from all coprecipitates, by all extractants. The preference was dependent on the duration of mineral ripening and adjunct anion. Micro-X-ray diffraction analysis provides evidence for the transformation from amorphous material to phases containing substantial proportions of crystalline goethite and hematite, except the P-U-HFO, which remained primarily amorphous. Analysis of the U-HFO coprecipitate by the Mössbauer technique and scanning electron microscopy provides confirmation of an increase in particle size and evidence of mineral ripening to crystalline phases.

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“…The speciation and bonding environment of U in soil, sediment, and clay minerals has been examined with a variety of spectroscopic techniques such as FT-infrared (FT-IR), FT-Raman, time-resolved luminescence, X-ray photoelectron and X-ray diffraction (XRD) (BURNS et al, 1997;BARGAR et al, 1999;CEJKA, 1999 and references therein;HANCHAR, 1999 and references therein;BUCK et al, 1996;MORRIS et al, 1996;CHISHOLM-BRAUSE et al, 1994;WERSIN et al, 1994;BIWER et al, 1990;HO and MILLER, 1986). Synchrotron-based techniques such as extended X-ray absorption fine-structure (EXAFS) and X-ray absorption near-edge structure (XANES) have been used to determine the identification, location and number of atoms in the local structural environment and the oxidation state of U within a variety of environmentally relevant media (MOYES et al, 2000;DUFF et al, 2000;BARGAR et al, 1999;DENECKE et al, 1998;THOMPSON et al, 1997;BURNS et al, 1997;ALLEN et al, 1996;MORRIS et al, 1996;BERTSCH et al, 1994;WAITE et al, 1994;WERSIN et al, 1994;DENT et al, 1992;FARGES et al, 1992).…”

Section: Introduction-the Geochemical Speciation Of Uranium Influencementioning

confidence: 99%

Uranium co-precipitation with iron oxide minerals

Duff

Coughlin

Hunter

2002

Geochimica et Cosmochimica Acta

418

266

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ABSTRACT-In oxidizing environments, the toxic and radioactive element uranium (U) is most soluble and mobile in the hexavalent oxidation state. Sorption of U(VI) on Fe-oxides minerals [such as hematite (α-Fe 2 O 3 ) and goethite (α-FeOOH)] and occlusion of U(VI) by Feoxide coatings are processes that can retard U transport in environments. In aged Ucontaminated geologic materials, the transport and the biological availability of U toward reduction may be limited by co-precipitation with Fe-oxide minerals. These processes also affect the biological availability of U(VI) species toward reduction and precipitation as the less soluble U(IV) species by metal-reducing bacteria.To examine the dynamics of interactions between U(VI) and Fe oxides during crystallization, indicated that almost all of the Fe in these solids was crystalline and that most of the U was associated with these crystalline Fe oxides. X-ray diffraction and Fourier-transform infrared (FT-IR) spectroscopic studies indicate that hematite formation is preferred over that of goethite when the amount of U in the Fe-oxides exceeds 1 mol % U (~4 wt % U). FT-IR and room temperature continuous wave luminescence spectroscopic studies with unleached U/Fe solids indicate a relationship between the mol % U in the Fe oxide and the intensity or existence of the spectra features that can be assigned to UO 2 2+ species (such as the IR asymmetric υ 3 stretch for O=U=O for uranyl). These spectral features were undetectable in carbonate-or oxalate-leached Molecular modeling studies reveal that U 6+ species could bond with O atoms from distorted Fe octahedra in the hematite structure with an environment that is consistent with the results of the XAFS. The results provide compelling evidence of U incorporation within the hematite structure.

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Contaminant Uranium Phases and Leaching at the Fernald Site in Ohio

Cited by 158 publications

References 15 publications

An integrated study of uranyl mineral dissolution processes: etch pit formation, effects of cations in solution, and secondary precipitation

An integrated study of uranyl mineral dissolution processes: etch pit formation, effects of cations in solution, and secondary precipitation

Uranium Extraction From Laboratory-Synthesized, Uranium-Doped Hydrous Ferric Oxides

Uranium co-precipitation with iron oxide minerals

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