Atomistic Simulations of Uranium Incorporation into Iron (Hydr)Oxides
Atomistic simulations were carried out to characterize the coordination environments of U incorporated in three Fe-(hydr)oxide minerals: goethite, magnetite, and hematite. The simulations provided information on U-O and U-Fe distances, coordination numbers, and lattice distortion for U incorporated in different sites (e.g., unoccupied versus occupied sites, octahedral versus tetrahedral) as a function of the oxidation state of U and charge compensation mechanisms (i.e., deprotonation, vacancy formation, or reduction of Fe(III) to Fe(II)). For goethite, deprotonation of first shell hydroxyls enables substitution of U for Fe(III) with a minimal amount of lattice distortion, whereas substitution in unoccupied octahedral sites induced appreciable distortion to 7-fold coordination regardless of U oxidation states and charge compensation mechanisms. Importantly, U-Fe distances of ~3.6 Å were associated with structural incorporation of U and cannot be considered diagnostic of simple adsorption to goethite surfaces. For magnetite, the octahedral site accommodates U(V) or U(VI) with little lattice distortion. U substituted for Fe(III) in hematite maintained octahedral coordination in most cases. In general, comparison of the simulations with available experimental data provides further evidence for the structural incorporation of U in iron (hydr)oxide minerals.
- Research Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 1012853
- Report Number(s):
- PNNL-SA-76491; 39953; KC0303020
- Journal Information:
- Environmental Science & Technology, 45(7):2770-2776, Journal Name: Environmental Science & Technology, 45(7):2770-2776 Journal Issue: 7 Vol. 45; ISSN 0013-936X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Reoxidation of Reduced Uranium with Iron(III) (Hydr)Oxides under Sulfate-Reducing Conditions
Reduction of Uranium(VI) under Sulfate-reducing Conditions in the Presence of Fe(III)-(hydr)oxides