Sulfidation and reoxidation of U(VI)-incorporated goethite: implications for U retention during sub-surface redox cycling

DOI: 10.1021/acs.est.2c05314

Authors: Olwen Stagg (The University of Manchester) , Katherine Morris (The University of Manchester) , Luke T. Townsend (The University of Manchester) , Kristina O. Kvashnina (ESRF-The European Synchrotron; Helmholtz Zentrum Dresden Rossendorf (HZDR)) , Michael L. Baker (The University of Manchester at Harwell) , Ryan L. Dempsey (he University of Manchester) , Liam Abrahamsen-Mills (National Nuclear Laboratory (UK)) , Samuel Shaw (The University of Manchester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Environmental Science & Technology , VOL 2

State: Published (Approved)
Published: November 2022
Diamond Proposal Number(s): 21441 , 24074

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.

Journal Keywords: sulfidation; uranium; iron (oxyhydr)oxides; XAS; persulfide

Subject Areas: Environment, Earth Science, Chemistry


Instruments: B18-Core EXAFS , I20-Scanning-X-ray spectroscopy (XAS/XES)

Other Facilities: BM20 at ESRF

Added On: 05/12/2022 08:35

Documents:
acs.est.2c05314.pdf

Discipline Tags:

Earth Sciences & Environment Radioactive Materials Mineralogy Materials Science Nuclear Waste Geology Geochemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)