Biophysical Environmental Chemistry Group, Department of Chemistry, University of Montreal, C.P. 6128 Succursale Centre-ville, Montreal, H3C 3J7, Canada.
Biophysical Environmental Chemistry Group, Department of Chemistry, University of Montreal, C.P. 6128 Succursale Centre-ville, Montreal, H3C 3J7, Canada.
Environ Pollut. 2019 Apr;247:206-215. doi: 10.1016/j.envpol.2018.12.042. Epub 2019 Jan 4.
Determinations of the mobility of metals from tailings is a critical part of any assessment of the environmental impacts of mining activities. The leaching of thorium and uranium from the tailings of different processing stages of a niobium mine was investigated for several pH, ionic strengths and concentrations of natural organic matter (NOM). The pH of the leaching solution did not have a noticeable impact on the extraction of Th, however, for pH values below 4, increased U mobilization was observed. Similarly, only a small fraction of Th (0.05%, ≤15 μg kg) and U (1.22%, ≤6 μg kg) were mobilized from the tailings in the presence of environmentally relevant concentrations of Ca, Mg or Na. However, in the presence of 10 mg L of fulvic acid, much higher concentrations of ca. 700 μg kg of Th and 35 μg kg of U could be extracted from the tailings. Generally, colloidal forms of Th and dissolved forms of U were mobilized from the tailings, however, in the presence of the fulvic acid, both dissolved and colloidal forms of the two actinides were observed. Single Particle ICP-MS was used to confirm the presence of Th (and U) containing colloids where significant numbers (up to 10 mL) of Th and U containing colloids were found, even in 0.2 μm filtered extracts. Although mass equivalent diameters in the range of 6-13 nm Th and 6-9 nm for U could be estimated (based upon the presence of an oxyhydroxide), most of the colloidal mass was attributed to larger (>200 nm) heterocomposite particles.
确定尾矿中金属的迁移性是评估采矿活动对环境影响的关键部分。研究了不同铌矿加工阶段尾矿在不同 pH 值、离子强度和天然有机质 (NOM) 浓度下的钍和铀浸出情况。浸出液的 pH 值对 Th 的提取没有明显影响，但在 pH 值低于 4 时，观察到 U 的迁移量增加。同样，只有一小部分 Th（0.05%，≤15μg/kg）和 U（1.22%，≤6μg/kg）在存在环境相关浓度的 Ca、Mg 或 Na 时从尾矿中迁移出来。然而，在存在 10mg/L 腐殖酸的情况下，从尾矿中可以提取出高达约 700μg/kg 的 Th 和 35μg/kg 的 U。通常，从尾矿中迁移出胶体形式的 Th 和溶解形式的 U，但在腐殖酸存在的情况下，观察到两种放射性元素的溶解和胶体形式。单颗粒 ICP-MS 用于确认含 Th（和 U）胶体的存在，即使在 0.2μm 过滤提取物中，也发现了大量（多达 10mL）含 Th 和 U 的胶体。虽然可以估计 Th（范围为 6-13nm）和 U（范围为 6-9nm）的质量等效直径（基于存在氧氢氧化物），但大部分胶体质量归因于较大的（>200nm）异质复合颗粒。
