Neptunium and Uranium Interactions with Environmentally and Industrially Relevant Iron Minerals
نویسندگان
چکیده
Neptunium (237Np) is an important radionuclide in the nuclear fuel cycle areas such as effluent treatment and geodisposal of radioactive waste. Due to neptunium’s redox sensitivity its tendency adsorb strongly mineral phases, iron oxides/sulfides, environmental mobility Np can be altered significantly by a wide variety chemical processes. Here, interactions with key minerals, ferrihydrite (Fe5O8H·4H2O), goethite (α-FeOOH), mackinawite (FeS), are investigated using X-ray Absorption Spectroscopy (XAS) order explore neptunyl(V) (Np(V)O2+) moiety (radioactive waste disposal) industrial (effluent plant) scenarios. Analysis LIII-edge Near-Edge Structure (XANES) Extended Fine (EXAFS) showed that upon exposure ferrihydrite, Np(V) adsorbed surface, likely inner-sphere complex. Interestingly, analysis only first two shells (Oax Oeq) EXAFS could modelled high degree confidence, there was no clear indication Fe or carbonate fits. When Np(V)O2+ added mackinawite-containing system, reduced Np(IV) formed nanocrystalline Np(IV)O2 solid. An analogous experiment also performed U(VI)O22+, similar reduction observed, U(VI) being uraninite (U(IV)O2). These results highlight may undergo speciation changes engineered systems whilst highlighting need for multi-technique approaches determination actinyl (for example, Np(V)O2+) species.
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ژورنال
عنوان ژورنال: Minerals
سال: 2022
ISSN: ['2075-163X']
DOI: https://doi.org/10.3390/min12020165