The interaction between uranium(VI) and magnetite surfaces: a combined STM and electron transfer calculation approach
EMSL Project ID
14392
Abstract
The interaction between iron-oxide mineral surfaces and uranium(VI) in solution is of interest because of the potential for reducing radionuclide mobility by sorption and/or reduction. The reduction of uranium(VI) in solution to the less soluble uranium(IV) phase upon contact with minerals bearing ferrous iron (Fe2+), such as magnetite (Fe3O4) and green rust (Fe(OH)2), has been observed experimentally. In order to investigate the mechanism by which this reduction process occurs, we will use atomic force microscopy (AFM) and scanning tunneling microscopy (STM) in order to characterize the (111) and (100) surfaces of bulk magnetite, both for topographic and electronic character. Subsequent exposure to uranium(VI) in solution will allow for changes in both surface topography and electronic structure to be observed under reducing environmental conditions (N2 atmosphere), or under vacuum if deemed necessary. We will be able to observe the most favorable surface sites for adsorption to occur (e.g. along step edges, kink sites, defects) and detect changes in the electronic nature (oxidized or reduced) of surface atoms and adsorbates based on changes in the atoms response to the tunneling current. Microscopy results will be complimented by quantum mechanical electron transfer calculations where different adsorption/reduction hypotheses will be tested to identify the most energetically favorable mechanism of uranium adsorption and reduction on magnetite surfaces.
Project Details
Project type
Exploratory Research
Start Date
2005-05-26
End Date
2007-06-01
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Abstract for the fall 2006 meeting of the American Chemical Society.
Presentation from the fall 2006 meeting of the American Chemical Society.
Quarterly summary of this research for the Dept. of Energy's Office of Science, Technology, and International division.