The Reduction of Uranyl and Chromate to Insoluble Species by Green Rust and Other Ferrous Hydroxides Surfaces
EMSL Project ID
12701b
Abstract
Electron transfer reactions play an important role in determining of the fate of many environmental contaminants. Reduction from high-oxidation states (+5/+6), where the metal is stabilized in solution as an oxo-anion, to mid-oxidation states, where the metal is insoluble (+3/+4) are of particular importance for uranium and chromate. Iron is a particularly effective reductant for these metals in alkaline conditions, where hydroxide ligands lower the Fe2+/Fe3+ redox couple and ferrous hydroxides and green rust can be found. Molecular-scale factors controlling the magnitude of the thermodynamic driving force and the kinetics of step-wise reduction of uranium and chromium through the 'unstable' oxidation states are poorly understood. We propose to examine the electron transfer kinetics in the reduction of uranium and chromium by green rust materials and analogues using computational molecular modeling methods. Our work will entail use of the EMSL computing resources and NWChem. This study will focus on the computational evaluation of the rates of intermediate electron transfer steps, concentrating on the atomic and electronic structure changes between soluble and insoluble forms of the metal (e.g., U5+  U4+). Effects of solvation and hydrolysis, as well as proton transfer coupling to electron transfer, will be explicitly considered using state-of-the-art molecular modeling tools.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-06-01
End Date
2008-06-01
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.