Uranium Association with Iron-Bearing Phases in Mill Tailings from Gunnar, Canada

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• 作者：Guillaume Othmane ; Thierry Allard ; Guillaume Morin ; Madeleine S茅lo ; Jessica Brest ; Isabelle Llorens ; Ning Chen ; John R. Bargar ; Mostafa Fayek ; Georges Calas
• 刊名：Environmental Science & Technology
• 出版年：2013
• 出版时间：November 19, 2013
• 年：2013
• 卷：47
• 期：22
• 页码：12695-12702
• 全文大小：424K
• 年卷期：v.47,no.22(November 19, 2013)
• ISSN：1520-5851

文摘

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 L_III-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鈥?00 mg kg^鈥? of U) demonstrate that uranium primarily occurs as monomeric uranyl ions (UO₂²⁺), forming inner-sphere surface complexes bound to ferrihydrite (50鈥?0% of the total U) and to a lesser extent to chlorite (30鈥?0% 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 UO₂²⁺- and/or Fe³⁺-complexing agents (e.g., carbonate) could potentially solubilize U in the tailings pore waters.