Uraninite alteration by H2O2 solutions and formation of secondary phases: An in situ microRaman spectroscopy and synchrotron X-ray diffraction study

Uraninite alteration by H2O2 solutions and formation of secondary phases: An in situ microRaman spectroscopy and synchrotron X-ray diffraction study

The (111) surface of uraninite obtained by monolith cleavage was reacted in H2O2 solutions of increasing concentrations ([H2O2]) from 0.005 to 0.5 M. The reacted interface was characterized in situ by µRaman spectroscopy, or, for 0.5 M H2O2, Grazing-Incidence X-Ray Diffraction (GI-XRD). At low [H2O2], schoepite and studtite coexisted on the reacted surface. With increasing [H2O2], studtite predominated, and a pattern of black strips cross-cutting at 60° suggested control of the solid neoformation by the (111) surface structure. In situ GI-XRD for 0.5 M H2O2 revealed the presence of studtite only, with an initial anisotropy in particle orientation (c* axes parallel to the uraninite surface), and a subsequent reorientation of growing particles. Upon draining out the solution, the formation of schoepite was observed after a few hours of emersion. This result reveals that apparently benign post-experimental manipulations can lead to significant changes in the nature of observed secondary precipitates.

Schlegel M.L., Jégou C. - Uraninite alteration by H2O2 solutions and formation of secondary phases: An in situ microRaman spectroscopy and synchrotron X-ray diffraction study