Theoretical Treatment of the Kinetics of Uranium Reduction by Magnetite Surfaces
EMSL Project ID
12701
Abstract
Uranium redox chemistry plays an important role in determining its mobility and therefore its environmental impact. Previous experimental studies of abiotic Uranium reaction have shown that magnetite[1,2], like other iron oxides[3-5], is able to adsorb and reduce Uranium(VI) to U(IV). Carbonate thermodynamically enhances the stability of Uranium(VI) in solution[8, 9] but work on the uranyl carbonate system is even more limited in reduction studies than Uranyl ions. Prior theoretical work in this area has examined uranyl solvation[6] and reduction thermodynamics[7] but limitations in basis set size have hampered the accuracy of the treatment. Additionally, the application of Marcus Theory to understand electron transfer kinetics has not yet been attempted for this system.We propose to examine the electron transfer kinetics in the uranium/magnetite reaction system using theoretical calculations. The work will entail utilization of the EMSL computing resources of the MSCF, including the use of NWChem. This study will focus on computing factors controlling and rates of step-wise electron transfer from structural FeII in magnetite to surface-bound U(VI) via the U(V) intermediate, identifying any stable form(s) of the surface reaction product, and producing a kinetic model that describes the overall rate in the early stages of reaction. We will examine the (100) and (111) terminations of magnetite in equilibrium with an overlying bulk water phase. Adsorption trajectories and configurations will be simulated using classical molecular dynamics methods using periodic boundary conditions. Ab initio cluster methods will be used to compute the reorganization energy and electronic coupling matrix element for the electron transfer rate as laid out by Marcus.
No experimental instrumentation is needed. Access to EMSL computing resources is required. The study would be performed in collaboration with Kevin Rosso, who is the scientific point-of-contact.
References
1. Missana, T., C. Maffiotte, and M. Garcia-Gutierrez, Surface reactions kinetics between nanocrystalline magnetite and uranyl. Journal of Colloid and Interface Science, 2003. 261: p. 154-160.
2. Morris, D.E., Redox Energetics and Kinetics of Uranyl Coordination Complexes in Aqueous Solution. Inorganic Chemistry, 2002. 41: p. 3542-3547.
3. Missana, T., M. Garcia-Gutierrez, and C. Maffiotte, Experimental and modeling study of the uranium (VI) sorption on goethite. Journal of Colloid and Interface Science, 2003. 260: p. 291-301.
4. Liger, E., L. Charlet, and P.V. Cappellen, Surface catalysis of uranium(VI) reduction by iron(II). Geochimica et Cosmochimica Acta, 1999. 63(19/20): p. 2939-2955.
5. Ilton, E.S., et al., Heterogeneous reduction of uranyl by micas: Crystal chemical and solution controls. Geochimica et Cosmochimica Acta, 2004. 68(11): p. 2417-2435.
6. Moskaleva, L.V., et al., Role of Solvation in the Reduction of the Uranyl Dication by Water: A Density Functional Study. Inorganic Chemistry, 2004. 43: p. 4080-4090.
7. Privalov, T., et al., Reduction of Uranyl(VI) by Iron(II) in Solutions: An Ab Initio Study. Journal of Physical Chemistry A, 2003. 107: p. 587-592.
8. Noubactep, C., et al., Mitigating Uranium in Groundwater: Prospects and Limitations. Environmental Science and Technology, 2003. 37: p. 4304-4308.
9. Fredrickson, J.K., et al., Reduction of U(VI) in goethite (a-FeOOH) suspensions by a dissimilatory metal-reducing bacterium. Geochimica et Cosmochimica Acta, 2000. 64(18): p. 3085–3098.
Project Details
Project type
Capability Research
Start Date
2005-06-13
End Date
2005-12-08
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Matthew Wander "Environmental Redox Reactions of Iron" Stony Brook University PhD Dissertation, October 2007
Wander, Matthew C. F., Kevin M. Rosso, Martin A. A. Schoonen. “Green Rust Reduction of Chromium, Part 1: The Applicability of a Single Sheet Ferrous Hydroxide for Green Rust”. Journal of Physical Chemistry C, v. 111, no. 30, 2007, p. 11414-11423.
Wander, Matthew C. F., Sebastien Kerisit, Kevin M. Rosso, Martin A. A. Schoonen. “Kinetics of Triscarbonato Uranyl Reduction by Aqueous Ferrous Iron: A Theoretical Study”. Journal of Physical Chemistry A, v. 110, no. 31, August 10, 2006, p. 9691-9701.