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Published January 1, 2004 | public
Journal Article

Influence of Dissolved Sodium and Cesium on Uranyl Oxide Hydrate Solubility


The solubility of uranium-containing minerals can control the mobility of uranium in contaminated soil and groundwater. The identity and solubility of these minerals are strongly influenced by solution composition. The influence of dissolved sodium and cesium on the solubility of uranyl oxide hydrates has been investigated in a series of batch experiments conducted with synthetic metaschoepite ((UO_2)8O_2(OH)_(12)·10H_2O). During reaction of metaschoepite in NaNO_3, CsNO_3, and NaF solutions, an initial increase in the dissolved uranium concentration was followed by a decrease as uranium was incorporated into a secondary solid phase. Given sufficient reaction time, metaschoepite was completely transformed to a clarkeite-like sodium uranyl oxide hydrate or a cesium uranyl oxide hydrate that has not previously been described. These secondary solid phases exhibited X-ray diffraction patterns and Raman spectra that were distinct from those of the original metaschoepite. Dissolved uranium concentrations in equilibrium with the sodium and cesium uranyl oxide hydrates can be more than 2 orders of magnitude lower than those in equilibrium with metaschoepite. Initial changes in metaschoepite solubility may also result from particle growth induced by sodium and cesium incorporation into the solid phase.

Additional Information

© 2004 American Chemical Society. Received 6 June 2003. Date accepted 13 October 2003. Published online 26 November 2003. Published in print 1 January 2004. Yi-Ping Liu contributed to this work as part of a Summer Undergraduate Research Fellowship. Raman spectra were collected with the assistance of George Rossman and Liz Arredondo. During the completion of this work, D.E.G. was partially supported by a National Science Foundation Graduate Fellowship. The authors thank the four anonymous reviewers whose comments helped improve this manuscript.

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