Reactions and Transport of Toxic Metals in Rock-Forming Silicates at 25 degrees C

Abstract

Sorption-reduction of aqueous Uv' by ferrous micasThe primary objective of our work in the present grant period was to extend our earliest results to a wider range of solution and mica compositions, and reaction times. These objectives were pursued through a series of systematic, batch sorption experiments, performed under argon at 25C. Single crystal run products were analyzed by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The use of large single crystals and high waterhock ratios had advantages, but precluded changes in solution composition. The bulk of the data was determined by XPS of edge and basal plane orientations. Some of our results have been reported in Ilton et al. (2003) and Ilton and Simmons (2003). However, we made three unexpected discoveries that have expanded the possible pathways for sorption-reduction: 1) XAS has shown that uranyl may be reduced in the interlayer region, 2) XPS yielded evidence that pentavalent uranium is stabilized on the mica edge orientations, and 3) HRTEM recorded the presence of U/Fe-rich nano-scale zones on interior basal surfaces. All of our results are briefly summarized here.