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Title: Influence of Dynamical Conditions on the Reduction of UVI at the Magnetite-Solution Interface

The heterogeneous reduction of UVI to UIV by ferrous iron is a potentially key process influencing the fate and transport of U in the environment. The reactivity of both sorbed and structural FeII has been studied for numerous substrates, including magnetite. The results from UVI-magnetite experiments have been variable, ranging from no reduction to clear evidence for the formation of UIV. In this contribution, we used XAS and high resolution (+cryogenic) XPS to study the interaction of UVI with nano-particulate magnetite. The results indicated that UVI was partially reduced to UV with no evidence of UIV. However, thermodynamic calculations indicated that mixed-valence U phases with average oxidation states below (V) should have been stable, indicating that the system was not in redox equilibrium. A reaction pathway that involves incorporation of U and stabilization of UV and UVI in secondary phases is invoked to explain the observations.
Authors:
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Publication Date:
OSTI Identifier:
974920
Report Number(s):
PNNL-SA-66737
19823; KC0303020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Environmental Science & Technology, 44(1):170-176
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
magnetite; pentavalent uranium; reduction; Environmental Molecular Sciences Laboratory