Uraninite oxidative dissolution at under slightly acidic conditions relevant to the Savannah River Site subsurface: microfluidic and spectroscopic studies
EMSL Project ID
48879
Abstract
The objective of this work is to utilize the micromodels from EMSL’s Subsurface Flow and Transport Laboratory to evaluate the rate and extent of reductive precipitation and subsequent oxidative dissolution of UO2(s,uraninite) in systems representative of porous media. This work will build upon previous studies conducted at EMSL examining uranyl phosphate precipitation within microfluidic systems (Fanizza et al., 2013). A novel aspect of this work will be incorporation of oxidation/reduction reactions into the experimental plan to monitor uranium precipitation and dissolution. Uraninite will be formed within the micromodel by in situ reduction of U(VI) with dithionite. After monitoring the initial formation of uraninite, the influent solution will be changed to a pH 4.5 or 5.5, oxygen saturated 10 mM NaCl solution representative of the ionic strength and pH conditions of the Savannah River Site subsurface. Micromodel experiments will be run with and without iron coatings on the micromodel substrate to determine the influence of iron on uranium oxidation and reduction. We propose that the differences in uranium speciation in pH 4-6 systems relative to pH 6-9 systems will influence rate and extent of uraninite oxidative dissolution. The micromodel work proposed at EMSL will be supported by parallel Attenuated Total Reflectance - Fourier Transform Infrared Spectroscopy (ATR-FTIR), X-ray Absorption Fine Structure Spectroscopy (EXAFS), and Transmission Electron Microscopy (TEM) studies characterizing the chemical and physical interactions of uraninite with hematite and quartz which will be performed at Clemson University (or the Stanford Synchrotron Light Source for EXAFS work). This work is part of a larger overarching DOE Office of Science funded project which will examine the mobility of several radionuclides under laboratory and field conditions relevant to the Savannah River Site subsurface. The intent is to begin experiments with uranium in this proposal and expand to other radionuclides over time as tools for autoradiographic imaging of radionuclides within micromodels are developed through collaboration between Clemson and EMSL.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2015-10-01
End Date
2017-09-30
Status
Closed
Released Data Link
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