title: Relative reactivity of biogenic and chemogenic uraninite and biogenic noncrystalline U(IV).
abstract: Aqueous chemical extractions and X-ray absorption spectroscopy (XAS) analyses were conducted to investigate the reactivity of chemogenic uraninite, nanoparticulate biogenic uraninite, and biogenic monomeric U(IV) species. The analyses were conducted in systems containing a total U concentration that ranged from 1.48 to 2.10 mM. Less than 0.02% of the total U was released to solution in extractions that targeted water-soluble and ion exchangeable fractions. Less than 5% of the total U was solubilized via complexation with a 0.1 M solution of NaF. Greater than 90% of the total U was extracted from biogenic uraninite and monomeric U(IV) after 6 h of reaction in an oxidizing solution of 50 mM K2S2O8. Additional oxidation experiments with lower concentrations (2 mM and 10 mM) of K2S2O8 and 8.2 mg L(-1) dissolved oxygen suggested that monomeric U(IV) species are more labile than biogenic uraninite; chemogenic uraninite was much less susceptible to oxidation than either form of biogenic U(IV). These results suggest that noncrystalline forms of U(IV) may be more labile than uraninite in subsurface environments. This work helps fill critical gaps in our understanding of the behavior of solid-associated U(IV) species in bioremediated sites and natural uranium ore deposits.
authors.affiliation: Department of Energy, Environmental, and Chemical Engineering, One Brookings Drive, Washington University , Saint Louis, Missouri 63130, United States.
authors.forename: José M
authors.initials: JM
authors.lastname: Cerrato
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Ashner
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Alessi
authors.forename: Juan S
authors.initials: JS
authors.lastname: Lezama-Pacheco
authors.forename: Rizlan
authors.initials: R
authors.lastname: Bernier-Latmani
authors.forename: John R
authors.initials: JR
authors.lastname: Bargar
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Giammar
mesh_terms: D018533:Biomass; D004784:Environmental Monitoring; D013058:Mass Spectrometry; D010084:Oxidation-Reduction; D011848:Radioactive Pollutants / Q000032:analysis / Q000737:chemistry*; D014501:Uranium / Q000032:analysis / Q000737:chemistry*; D017974:Uranium Compounds / Q000032:analysis / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
chemical_list: D011848:Radioactive Pollutants; D017974:Uranium Compounds; D014501:Uranium
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