Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling
Sulfidation and Reoxidation of U(VI)-Incorporated Goethite: Implications for U Retention during Sub-Surface Redox Cycling
Stagg, O.; Morris, K.; Townsend, L. T.; Kvashnina, K.; Baker, M. L.; Dempsey, R.; Abrahamsen-Mills, L.; Shaw, S.
Abstract
Over 60 years of nuclear activity have resulted in a global legacy of contaminated land and radioactive waste. Uranium (U) is a significant component of this legacy and is present in radioactive wastes and at many contaminated sites. U-incorporated iron (oxyhydr)oxides may provide a long-term barrier to U migration in the environment. However, reductive dissolution of iron (oxyhydr)oxides can occur on reaction with aqueous sulfide (sulfidation), a common environmental species, due to the microbial reduction of sulfate. In this work, U(VI)-goethite was initially reacted with aqueous sulfide, followed by a reoxidation reaction, to further understand the long-term fate of U species under fluctuating environmental conditions. Over the first day of sulfidation, a transient release of aqueous U was observed, likely due to intermediate uranyl(VI)-persulfide species. Despite this, overall U was retained in the solid phase, with the formation of nanocrystalline U(IV)O2 in the sulfidized system along with a persistent U(V) component. On reoxidation, U was associated with an iron (oxyhydr)oxide phase either as an adsorbed uranyl (approximately 65%) or an incorporated U (35%) species. These findings support the overarching concept of iron (oxyhydr)oxides acting as a barrier to U migration in the environment, even under fluctuating redox conditions.
Keywords: iron (oxyhydr)oxides; persulfide; sulfidation; uranium; XAS
Beteiligte Forschungsanlagen
- Rossendorf Beamline an der ESRF DOI: 10.1107/S1600577520014265
Verknüpfte Publikationen
- DOI: 10.1107/S1600577520014265 is cited by this (Id 34962) publication
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Environmental Science and Technology 56(2022)24, 17643-17652
DOI: 10.1021/acs.est.2c05314
Cited 3 times in Scopus
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