U(VI) Adsorption on Aquifer Sediments at the Hanford Site
Aquifer core samples collected in three new groundwater wells in the 200-UP-1 operable unit at the Hanford Site were characterized and showed typical Ringold Formation Unit E dominated by gravel and sand. High iron-oxide content in iron (Fe) oxide/clay coatings caused the highest U(VI) adsorption as quantified by Kd values, indicating these hydrous iron oxides are the key solid adsorbent in the 200-UP-1 sediments that affect U(VI) fate and mobility. In batch adsorption tests with varying total U(VI) concentrations in spiked groundwater, a linear isotherm up to 1 ppm of total U(VI) concentration was observed. However, U(VI) adsorption decreased with increasing concentrations of dissolved carbonate, because strong anionic aqueous uranium-carbonate complexes formed at elevated pH and high carbonate conditions. A small amount of uranium desorption hysteresis was observed in a flow-through column experiment, suggesting that desorption Kd values for aged uranium-contaminated sediments at the Hanford Site can be larger than Kd values determined in short-term laboratory experiments and slow uranium release into the groundwater is expected.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 912983
- Report Number(s):
- PNNL-SA-50848; JCOHE6; 830403000; TRN: US0800620
- Journal Information:
- Journal of Contaminant Hydrology, 93(1-4):255-269, Vol. 93, Issue 1-4; ISSN 0169-7722
- Country of Publication:
- United States
- Language:
- English
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