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

Guohui Wang, Wooyong Um, Zheming Wang, Estela Reinoso-Maset, Nancy M. Washton, Karl T. Mueller, Nicolas Perdrial, Peggy A. O'Day, Jon Chorover

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Abstract

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 (Hanford, WA). 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 2.67 × 10-12 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 1.05-2.42 × 10-10 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 the prediction of contaminant transport. These results suggest that phosphate minerals may be a good candidate for uranium remediation approaches at contaminated sites.

Original languageEnglish (US)
Pages (from-to)11011-11019
Number of pages9
JournalEnvironmental Science and Technology
Volume51
Issue number19
DOIs
Publication statusPublished - Oct 3 2017

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ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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