Spectroscopic confirmation of uranium(VI)-carbonato adsorption complexes on hematite

Journal Article · Thu Jul 15 04:00:00 EDT 1999 · Environmental Science and Technology

DOI:https://doi.org/10.1021/es990048g· OSTI ID:6192004

Bargar, J R ^[1]; Reitmeyer, R; Davis, J A ^[2]

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1. Stanford Linear Accelerator Center, CA (United States). Stanford Synchrotron Radiation Lab.
2. Geological Survey, Menlo Park, CA (United States). Water Resources Div.

Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)-carbonato complexes on oxide minerals. The existence of such complexes has not been demonstrated, and little is known about their compositions and reaction stoichiometries. The authors have used attenuated total reflectance Fourier transform infrared (ATR-FTIR) and extended X-ray absorption fine structure (EXAFS) spectroscopies to probe the existence, structures, and compositions of [triple bond]FeO[sub surface]-U(VI)-carbonato complexes on hematite throughout the pH range of uranyl uptake under conditions relevant to aquifers. U(VI)-carbonato complexes were found to be the predominant adsorbed U(VI) species at all pH values examined, a much wider pH range than previously postulated based on analogy to aqueous U(VI)-carbonato complexes, which are trace constituents at pH < 6. This result indicates the inadequacy of the common modeling assumption that the compositions and predominance of adsorbed species can be inferred from aqueous species. By extension, adsorbed carbonato complexes may be of major importance to the groundwater transport of similar actinide contaminants such as neptunium and plutonium.

• Sponsoring Organization: DOE; NATRC; USDOE, Washington, DC (United States); National Research Council, Washington, DC (United States)
• OSTI ID: 6192004
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Vol. 33:14; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

053002* -- Nuclear Fuels-- Environmental Aspects-- Radioactive Effluents-- (1992-)
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
ACTINIDES
ADSORPTION
CARBON COMPOUNDS
CARBONATES
CHALCOGENIDES
CHEMISTRY
ELEMENTS
ENVIRONMENTAL TRANSPORT
FOURIER TRANSFORMATION
GROUND WATER
HEMATITE
HYDROGEN COMPOUNDS
INTEGRAL TRANSFORMATIONS
IRON COMPOUNDS
IRON ORES
IRON OXIDES
MASS TRANSFER
METALS
MINERALS
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
RADIONUCLIDE MIGRATION
SORPTION
SPECTROSCOPY
TRANSFORMATIONS
TRANSITION ELEMENT COMPOUNDS
URANIUM
WATER
WATER CHEMISTRY
X-RAY SPECTROSCOPY