https://nova.newcastle.edu.au/vital/access/ /manager/Index en-au 5 https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:32238 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 L_III -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).]]> Tue 15 May 2018 16:00:13 AEST ]]> https://nova.newcastle.edu.au/vital/access/ /manager/Repository/uon:24054 Sat 24 Mar 2018 07:09:41 AEDT ]]>