Dissertation
Synthesis, spectroscopic, and thermodynamic study of uranyl and neodymium phosphate solid phases
Washington State University
Doctor of Philosophy (PhD), Washington State University
12/2009
DOI:
https://doi.org/10.7273/000005974
Abstract
Hydrated uranyl phosphates comprise some of the most refractory U-bearing minerals in oxidizing environments. As such, these solids are expected to precipitate where in-situ phosphate amendments are employed in contaminant remediation scenarios. However, the structure, stability, and mechanisms by which these hydrated uranyl phosphates form are not well understood. The work presented herein is largely focused on (1) synthesis of a suite of hydrated uranyl phosphates, (2) characterization of these phases using a variety of analytical techniques, (3) analysis of the solution phases associated with the solids that form, and (4) development of thermodynamic data for these hydrated uranyl phosphates. In a related study, the uptake of the lanthanide cation neodymium onto hydroxylapatite (HA): Ca5(PO4)3OH was also investigated. The following novel contributions are presented in this study. 1. We synthesized, for the first time, the mixed actinide and lanthanide phosphate, francoisite-(Nd):Nd[(UO2)3OOH(PO4)2)]" H2O. 2. The transformation of chernikovite: H3O[(UO2)(PO4)]" H2O into triuranyl diphosphate tetrahydrate (TDT):(UO2)2(PO4)3" H2O was demonstrated. 3. The solubility of triuranyl diphosphate tetrahydrate (TDT) was measured at 23 and 50oC, and we report the first log Ksp data for elevated temperature. 4. The energetics of hydration were investigated for the natural meta autunite mineral (Ca[(UO2)(PO4)]2 " .5H2O and synthetic sodium autunite: Na2[(UO2)(PO4)]2 " H2O. 5. We show that the uptake mechanism of Nd onto HA is highly pH dependent. Whereas at high pH (ca. 10), isomorphic Nd-Ca substitution is observed, at lower pH (ca. 4), the precipitation of a discrete hydrated NdPO4 phase is evidenced
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Details
- Title
- Synthesis, spectroscopic, and thermodynamic study of uranyl and neodymium phosphate solid phases
- Creators
- Christopher Robert Armstrong
- Contributors
- Sue B. Clark (Chair)Ken Nash (Committee Member) - Washington State University, Department of ChemistryPeter R Griffiths (Committee Member)James O. Schenk (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Department of Chemistry
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 207
- Identifiers
- 99901055136301842
- Language
- English
- Resource Type
- Dissertation