An atomic scale computational approach to understanding REDOX speciation of uranium on iron bearing minerals

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The proposed PhD research will use state of the art quantum chemical calculations and accompanying ongoing experimental studies to determinethe REDOX speciation of uranium with iron-bearing minerals, including reduction from uranyl(VI) to uranyl(V), U(IV) and disproportionationmechanisms on Fe(II) REDOX active minerals representative of those present at NDA sites. Outcomes will explicitly support the Land Qualitythematic area (NDA bursary call section C5). The specific objectives are to: 1. Employ quantum chemical calculations (density functional theory) toinvestigate uranyl(VI)-Fe(II) mineral interactions, complemented by experimental Raman, optical and X-ray absorption spectroscopy data. 2. Targetthe Fe(II) bearing minerals mackinawite, ferrihydrite, magnetite and pyrite. 3. Allow accurate prediction of the thermodynamic parameters andspectroscopic data (REDOX potentials, EXAFS, Raman, IR and optical spectra) to feed into geochemical models e.g. the ANDRA Specific InteractionTheory database and PHREEQC. 4. Investigate the mechanisms of uranyl(V) interaction with Fe(II) mineral surfaces. 5. Further examine the resultantreduced/oxidised species including key oligiomeric uranyl(V) aggregates that lead to disproportionation of uranyl(V), reforming uranyl(VI) andproducing U(IV) phases. 6. Establish thermodynamic parameters for sorption and desorption, including the energy profiles for approach of uranyl(VI)and (V) cations to a given mineral surface or crystallographic plane.