- Title
- The short-term reduction of uranium by nanoscale zero-valent iron (nZVI): role of oxide shell, reduction mechanism and the formation of U(v)-carbonate phases
- Creator
- Tsarev, Sergey; Collins, Richard N.; Ilton, Eugene S.; Fahy, Adam; Waite, T. David
- Relation
- Funding BodyARCGrant NumberFT110100067 http://purl.org/au-research/grants/arc/FT110100067
- Relation
- Environmental Science: Nano Vol. 4, Issue 6, p. 1304-1313
- Publisher Link
- http://dx.doi.org/10.1039/c7en00024c
- Publisher
- Royal Society of Chemistry
- Resource Type
- journal article
- Date
- 2017
- Description
- Nanoscale zero-valent iron (nZVI) is a potential remediation agent for uranium-contaminated groundwaters, however, a complete mechanistic understanding of the processes that lead to uranium immobilization has yet to be achieved. In this study, the short-term anoxic reaction of U(VI) with fresh, (anoxic) aged and corroded nZVI particles was investigated under aqueous conditions conducive to the formation of thermodynamically stable U(VI)-Ca-CO₃ ternary aqueous complexes. The first stage of the reaction between U(VI) and nZVI was assigned to sorption processes with the formation of surface U(VI)-carbonate complexes. Aged nZVI removed U(VI) faster than either fresh or corroded nZVI and it is hypothesized that U reduction initially occurs through the transfer of one electron from Fe(II) in the nZVI surface oxide layer. Evidence for reduction to U(V) was obtained through X-ray photoelectron spectroscopy and by determination of U-O bond distances of ~2.05 and 2.27 Å, using U LIII -edge X-ray absorption spectroscopy, which are similar to those observed for the U(v) site in the mixed U(v)/U(VI) carbonate mineral wyartite. Scanning transmission electron microscopy also demonstrated that U was present as a nanoparticulate phase after one day of reaction, rather than a surface complex. Further reduction to U(IV), as observed in previous studies, would appear to be rate-limiting and coincident with the transformation of this meta-stable U-carbonate phase to uraninite (UO).
- Subject
- nanoscale zero-valent iron; remediation agent; chemistry; uranium; contaminated groundwaters
- Identifier
- http://hdl.handle.net/1959.13/1385497
- Identifier
- uon:32238
- Identifier
- ISSN:2051-8153
- Language
- eng
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