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Sulfidation of magnetite with incorporated uranium

DOI: 10.1016/j.chemosphere.2021.130117 DOI Help

Authors: Luke T. Townsend (The University of Manchester) , Katherine Morris (The University of Manchester) , Robert Harrison (The University of Manchester) , Bianca Schacherl (Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal (KIT-INE)) , Tonya Vitova (Karlsruhe Institute of Technology, Institute for Nuclear Waste Disposal (KIT-INE)) , Libor Kovarik (Pacific Northwest National Laboratory) , Carolyn I. Pearce (Pacific Northwest National Laboratory) , J. Frederick W. Mosselmans (Diamond Light Source) , Samuel Shaw (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemosphere , VOL 363

State: Published (Approved)
Published: February 2021
Diamond Proposal Number(s): 13559 , 17376 , 17243

Abstract: Uranium (U) is a radionuclide of key environmental interest due its abundance by mass within radioactive waste and presence in contaminated land scenarios. Ubiquitously present iron (oxyhydr)oxide mineral phases, such as (nano)magnetite, have been identified as candidates for immobilisation of U via incorporation into the mineral structure. Studies of how biogeochemical processes, such as sulfidation from the presence of sulfate-reducing bacteria, may affect iron (oxyhydr)oxides and impact radionuclide mobility are important in order to underpin geological disposal of radioactive waste and manage radioactively contaminated land. Here, this study utilised a highly controlled abiotic method for sulfidation of U(V) incorporated into nanomagnetite to determine the fate and speciation of U. Upon sulfidation, transient release of U into solution occurred (∼8.6 % total U) for up to 3 days, despite the highly reducing conditions. As the system evolved, lepidocrocite was observed to form over a period of days to weeks. After 10 months, XAS and geochemical data showed all U was partitioned to the solid phase, as both nanoparticulate uraninite (U(IV)O2) and a percentage of retained U(V). Further EXAFS analysis showed incorporation of the residual U(V) fraction into an iron (oxyhydr)oxide mineral phase, likely nanomagnetite or lepidocrocite. Overall, these results provide new insights into the stability of U(V) incorporated iron (oxyhydr)oxides during sulfidation, confirming the longer term retention of U in the solid phase under complex, environmentally relevant conditions.

Journal Keywords: Sulfidation; Uranium; Iron (oxyhydr)oxide; GDF; XASHR-XANES

Subject Areas: Chemistry, Earth Science, Environment

Instruments: I20-Scanning-X-ray spectroscopy (XAS/XES)

Added On: 01/03/2021 11:32

Discipline Tags:

Earth Sciences & Environment Desertification & Pollution Nuclear Waste Materials Science Radioactive Materials

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)