Giammar Daniel E, Hering Janet G
California Institute of Technology, 1200 E. California Boulevard, Environmental Engineering Science, Pasadena, California 91125, USA.
Environ Sci Technol. 2004 Jan 1;38(1):171-9. doi: 10.1021/es0345672.
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 ((UO2)8O2(OH)12 x 10H2O). During reaction of metaschoepite in NaNO3, CsNO3, 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.
含铀矿物的溶解度能够控制铀在受污染土壤和地下水中的迁移性。这些矿物的种类和溶解度受溶液成分的强烈影响。通过一系列使用合成变水铀矿（(UO2)8O2(OH)12·10H2O）进行的批量实验，研究了溶解的钠和铯对氧化铀水合物溶解度的影响。在变水铀矿于硝酸钠、硝酸铯和氟化钠溶液中发生反应的过程中，溶解铀浓度最初会升高，随后随着铀被纳入次生固相而降低。在足够的反应时间后，变水铀矿完全转化为一种类似水铀钍矿的钠氧化铀水合物或一种此前未被描述过的铯氧化铀水合物。这些次生固相呈现出与原始变水铀矿不同的X射线衍射图谱和拉曼光谱。与钠和铯氧化铀水合物达到平衡时的溶解铀浓度可能比与变水铀矿达到平衡时的浓度低两个数量级以上。变水铀矿溶解度的初始变化也可能是由于钠和铯纳入固相所诱导的颗粒生长导致的。
