PNNL

Abstract

We used high-resolution x-ray photoelectron spectroscopy to demonstrate that reduction of aqueous U6+ at ferrous mica surfaces at 25oC preserves U5+ as the dominant sorbed species over a broad range of solution compositions. Polymerization of sorbed U5+ with sorbed U6+ and U4+ is identified as a possible mechanism for how mineral surfaces circumvent the rapid disproportionation of aqueous U5+. The general nature of this mechanism suggests that U5+ could play an important, but previously unidentified, role in the low–temperature chemistry of uranium in reducing, heterogeneous aqueous systems.