Influence of Calcite Solids and Dissolved Calcium on U(VI) Sorption and Desorption in Hanford Subsurface Sediments
We have investigated U(VI) sorption and desorption with batch experiments conducted on core samples from the Hanford, WA, site as well as on sub-fractions of these materials and laboratory-grade calcite. In these studies, [U(VI)] was varied between 10- 7 and 10-5 and pH between 7.2 to 10, at constant I (=0.05) and constant PCO2 (10-3.5 atm), using water that was saturated with respect to calcite. A carbonate-free (acetic acid- treated) fraction of silt/clay material showed higher sorption than untreated material, suggesting that carbonates block access to higher affinity sites. Of particular interest was that U(VI) sorption on untreated material was maximum at pH=8.4, with substantially less sorption at lower and higher pH and in contrast to results from calcite free studies, which show strong sorption at pH {approx} 5 to 8. U(VI) speciation results suggest that aqueous-phase Ca2UO2(CO3)3 was the source of the otherwise unexpectedly low sorption at pH <8.4.
- Research Organization:
- Johns Hopkins University, Baltimore, MD (US)
- Sponsoring Organization:
- USDOE Office of Science (SC) (US)
- DOE Contract Number:
- FG07-02ER63498
- OSTI ID:
- 825902
- Country of Publication:
- United States
- Language:
- English
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