Uranium Release from Acidic Weathered Hanford Sediments: Single-Pass Flow-Through and Column Experiments

Journal Article · Thu Sep 21 04:00:00 EDT 2017 · Environmental Science and Technology

DOI:https://doi.org/10.1021/acs.est.7b03475· OSTI ID:1406774

Wang, Guohui ^[1]; Um, Wooyong ^[2]; Wang, Zheming ^[1]; Reinoso-Maset, Estela ^[3]; Washton, Nancy M. ^[1]; Mueller, Karl T. ^[1]; Perdrial, Nicolas ^[4]; O’Day, Peggy A. ^[3]; Chorover, Jon ^[5]

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1. Pacific Northwest National Laboratory, Richland, Washington 99354, United States
2. Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Pohang University of Science and Technology (POSTECH), Pohang, South Korea
3. Sierra Nevada Research Institute and School of Natural Sciences, University of California Merced, Merced, California 95343, United States
4. Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona 85721, United States; Department of Geology, University of Vermont, Burlington, Vermont 05405, United States
5. Department of Soil, Water and Environmental Science, University of Arizona, Tucson, Arizona 85721, United States

The reaction of acidic radioactive waste with sediments can induce mineral transformation reactions that, in turn, control contaminant fate. Here, sediment weathering by synthetic uranium-containing acid solutions was investigated using bench-scale experiments to simulate waste disposal conditions at Hanford’s cribs, USA. During acid weathering, the presence of phosphate exerted a strong influence over uranium mineralogy and a rapidly precipitated, crystalline uranium phosphate phase (meta-ankoleite [K(UO2)(PO4)·3H2O]) was identified using spectroscopic and diffraction-based techniques. In phosphate-free system, uranium oxyhydroxide minerals such as K-compreignacite [K2(UO2)6O4(OH)6·7H2O] were formed. Single-pass flow-through (SPFT) and column leaching experiments using synthetic Hanford pore water showed that uranium precipitated as meta-ankoleite during acid weathering was strongly retained in the sediments, with an average release rate of 2.67E-12 mol g-1 s-1. In the absence of phosphate, uranium release was controlled by dissolution of uranium oxyhydroxide (compreignacite-type) mineral with a release rate of 1.05-2.42E-10 mol g-1 s-1. The uranium mineralogy and release rates determined for both systems in this study support the development of accurate U-release models for prediction of contaminant transport. These results suggest that phosphate minerals may be a good candidate for uranium remediation approaches at contaminated sites.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1406774
• Report Number(s): PNNL-SA-128583; 47951; KP1702030
• Journal Information: Environmental Science and Technology, Journal Name: Environmental Science and Technology Journal Issue: 19 Vol. 51; ISSN 0013-936X
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Environmental Molecular Sciences Laboratory