Article Metrics


Online attention

Nanoscale mechanism of UO2 formation through uranium reduction by magnetite

DOI: 10.1038/s41467-020-17795-0 DOI Help

Authors: Zezhen Pan (École Polytechnique Fédérale de Lausanne) , Barbora Bartova (École Polytechnique Fédérale de Lausanne) , Thomas Lagrange (École Polytechnique Fédérale de Lausanne) , Sergei M. Butorin (Uppsala University) , Neil C. Hyatt (University of Sheffield) , Martin C. Stennett (University of Sheffield) , Kristina O. Kvashnina (ESRF – The European Synchrotron; Helmholtz Zentrum Dresden-Rossendorf (HZDR)) , Rizlan Bernier-latmani (École Polytechnique Fédérale de Lausanne)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Communications , VOL 11

State: Published (Approved)
Published: August 2020
Diamond Proposal Number(s): 20581 , 15955

Open Access Open Access

Abstract: Uranium (U) is a ubiquitous element in the Earth’s crust at ~2 ppm. In anoxic environments, soluble hexavalent uranium (U(VI)) is reduced and immobilized. The underlying reduction mechanism is unknown but likely of critical importance to explain the geochemical behavior of U. Here, we tackle the mechanism of reduction of U(VI) by the mixed-valence iron oxide, magnetite. Through high-end spectroscopic and microscopic tools, we demonstrate that the reduction proceeds first through surface-associated U(VI) to form pentavalent U, U(V). U(V) persists on the surface of magnetite and is further reduced to tetravalent UO2 as nanocrystals (~1–2 nm) with random orientations inside nanowires. Through nanoparticle re-orientation and coalescence, the nanowires collapse into ordered UO2 nanoclusters. This work provides evidence for a transient U nanowire structure that may have implications for uranium isotope fractionation as well as for the molecular-scale understanding of nuclear waste temporal evolution and the reductive remediation of uranium contamination.

Journal Keywords: Environmental chemistry; Geochemistry

Subject Areas: Earth Science, Chemistry

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

Other Facilities: BM20 at ESRF