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In situ AFM and XPS Investigation of U6+ Reduction by Fe2+ on Hematite and Pyrite

Published online by Cambridge University Press:  23 May 2012

Jingjie Niu ,
Udo Becker  and
Rodney Ewing
Jingjie Niu
Affiliation:
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109-1005, U.S.A.
Udo Becker
Affiliation:
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109-1005, U.S.A.
Rodney Ewing
Affiliation:
Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109-1005, U.S.A.
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Abstract

Uranyl adsorption/reduction by Fe2+ on hematite and pyrite has been studied at neutral pH under anoxic and CO2-free conditions. XPS results confirm that more U3O8 precipitates on hematite than on pyrite reacted for 24 h in 160 μM uranyl nitrate and 160 μM Fe2+ solution at initial pH 7.3. These results are explained in terms of co-adsorption energy and U atom Mulliken charge transfer by quantum mechanical calculations. Moreover, in situ fluid tapping-mode AFM experiments on hematite indicate a deceleration of the U reduction rate within 24 h due to the passivation of the surface caused by the formation of orthorhombic U3O8 crystals. In addition, crystals observed using AFM show morphologies of orthorhombic schoepite appearing on hematite after 5 h.

Keywords

Uadsorptionscanning probe microscopy (SPM)
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1444: Symposium S/Y – Actinides and Nuclear Energy Materials , 2012 , mrss12-1444-y10-15
Copyright
Copyright © Materials Research Society 2012

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