SOLID-STATE NMR STUDIES OF THE IMPACT OF TANK WASTE LEACHATES IN THE ENVIRONMENT
Open Access
- Author:
- Strepka, Caleb
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- March 02, 2010
- Committee Members:
- Karl Todd Mueller, Dissertation Advisor/Co-Advisor
Karl Todd Mueller, Committee Chair/Co-Chair
James David Kubicki, Committee Member
Alan James Benesi, Committee Member
Albert Welford Castleman Jr., Committee Member
Barbara Jane Garrison, Committee Member - Keywords:
- NMR
montmorillonite
hanford
zeolite - Abstract:
- Using a combination of analytical spectroscopy and wet chemistry techniques, we are investigating the coupling between mineral weathering from caustic waste release and contaminant fate/transport in waste-impacted sediments from the Hanford DOE site. We have examined a range of related samples including montmorillonite, homogeneous precipitates, and Hanford sediments, each reacted with or formed from a simulated tank waste leachate (STWL) containing varying concentrations of Sr and/or Cs. Batch and column studies have been performed, with reaction times varying from 1 day to 1.5 years. In this work, 27Al magic-angle spinning and 29Si magic-angle spinning nuclear magnetic resonance (MAS NMR) and spectral deconvolutions provide kinetic data allowing us to compare and contrast results from homogenous precipitates, model clay systems, and more complex Hanford sediment samples reacted under similar conditions. Neophase formation is governed by the dissolution of parent clay/sediment and free Si in solution, allowing for the formation of new tetrahedrally-coordinated Al species. More recalcitrant phases form with longer reaction times, as studied from samples washed with acidic ammonium oxalate solutions. Four new phases form containing tetrahedrally-coordinated Al which vary in amount based upon weathering time, contaminant present, or (in the case of homogenous studies) amount of silica present in solution.