Institut de Minéralogie et de Physique des Milieux Condensés (IMPMC), UMR 7590 CNRS-UPMC/Paris VI-IRD, Case 115 , 4 place Jussieu, 75252 Paris Cedex 05, France.
Environ Sci Technol. 2013 Nov 19;47(22):12695-702. doi: 10.1021/es401437y. Epub 2013 Oct 29.
The speciation of uranium was studied in the mill tailings of the Gunnar uranium mine (Saskatchewan, Canada), which operated in the 1950s and 1960s. The nature, quantification, and spatial distribution of uranium-bearing phases were investigated by chemical and mineralogical analyses, fission track mapping, electron microscopy, and X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopies at the U LIII-edge and Fe K-edge. In addition to uranium-containing phases from the ore, uranium is mostly associated with iron-bearing minerals in all tailing sites. XANES and EXAFS data and transmission electron microscopy analyses of the samples with the highest uranium concentrations (∼400-700 mg kg(-1) of U) demonstrate that uranium primarily occurs as monomeric uranyl ions (UO2(2+)), forming inner-sphere surface complexes bound to ferrihydrite (50-70% of the total U) and to a lesser extent to chlorite (30-40% of the total U). Thus, the stability and mobility of uranium at the Gunnar site are mainly influenced by sorption/desorption processes. In this context, acidic pH or alkaline pH with the presence of UO2(2+)- and/or Fe(3+)-complexing agents (e.g., carbonate) could potentially solubilize U in the tailings pore waters.
研究了 20 世纪 50 年代至 60 年代在加拿大萨斯喀彻温省 Gunnar 铀矿的尾矿中铀的形态。通过化学和矿物分析、裂变径迹测绘、电子显微镜以及铀 LIII 边和铁 K 边的 X 射线吸收近边结构（XANES）和扩展 X 射线吸收精细结构（EXAFS）光谱研究了含铀相的性质、定量和空间分布。除了矿石中的含铀相外，铀主要与所有尾矿点中的含铁矿物有关。具有最高铀浓度（约 400-700mgkg(-1)的 U）的样品的 XANES 和 EXAFS 数据和透射电子显微镜分析表明，铀主要以单体铀酰离子（UO2(2+)）的形式存在，形成与水铁矿（占总 U 的 50-70%）结合的内球表面络合物，并在较小程度上与绿泥石（占总 U 的 30-40%）结合。因此，Gunnar 场址铀的稳定性和迁移性主要受吸附/解吸过程的影响。在这种情况下，酸性 pH 或碱性 pH 以及存在 UO2(2+)和/或 Fe(3+)络合剂（例如碳酸盐）可能会使尾矿孔隙水中的 U 溶解。
