Identification of calcium carbonate in uranium mine tailings by X-ray spectroscopy and X-ray diffraction

自然资源部门是加拿大经济的一个重要领域。在已开采的许多自然资源中，铀矿开采集中在萨斯喀彻温省北部。铀矿体中除了铀氧化物外，还含有许多矿物相，需要负责任地处理。固体采矿废物可以放置在尾矿管理设施中，该设施旨在包含废物元素，并限制与外部环境的相互作用。为了了解尾矿设施在为尾矿管理设施提供燃料的采矿作业的整个生命周期内以及在该场地退役后的表现，重要的是了解尾矿的化学成分以及它们如何随时间变化。位于McClean Lake作业的Jeb尾矿管理设施包含许多从铀氧化物中分离出来的金属，包括铁(Fe)、砷(As)、钼(Mo)和铀(U)等元素。在这一持续的研究合作中，我们将研究尾矿设施中的样品，以更好地了解尾矿中发现的含钙物种。通过比较孔隙水样中溶解物种的浓度和尾矿中固体的分析，再加上尾矿行为的模拟，提出了如果铀氧化物固体与碳酸盐离子反应在孔隙水中生成可溶的铀酰-碳酸盐络合物，那么它们可能会溶解在尾矿中。然而，碳酸盐离子也能与硫酸钙(石膏)反应生成碳酸钙，在尾矿设施的条件下(近中性pH)会析出碳酸钙。确定尾矿中是否存在碳酸钙(方解石)是了解如何控制(和减少)孔隙水中可溶性铀酰存在的重要步骤。预计尾矿中将存在无定形和晶态含钙化合物，如果存在方解石，将会发现微量的方解石。在这项工作中，将使用X射线吸收光谱、X射线微探针和X射线衍射来鉴定尾矿中存在的含钙物种，并确定是否形成方解石。

The natural resource sector is an important area of Canada's economy. Of the many natural resources that are mined, uranium mining is centred in northern Saskatchewan. The uranium ore bodies contain many mineral phases beside uranium oxide that need to be disposed of in a responsible fashion. Solid mining waste can be placed in a tailings management facility, which is designed to contain the waste elements and limit interaction with the external environment. To understand how a tailings facility will behave throughout the lifetime of the mining operations that feed the tailings management facility, and after the site has been decommissioned, it is important to understand the chemistry of the tailings and how they change with time. The JEB tailings management facility located at the McClean Lake operation contains many metals from the separation of uranium oxide, including iron (Fe), arsenic (As), molybdenum (Mo), and uranium (U), among other elements. In this continued research collaboration, we will study samples from the tailings facility to develop a better understanding of the calcium (Ca)-bearing species found in the tailings. By comparing the concentration of dissolved species in pore water samples and analysis of the solids in the tailings, coupled with modelling of the behaviour of the tailings, it has been proposed that uranium oxide solids could become soluble in the tailings if they react with carbonate ions to produce soluble uranyl-carbonate complexes in the pore water. However, carbonate ions could also react with calcium sulphate (gypsum) and produce calcium carbonate, which would precipitate under the conditions of the tailings facility (near neutral pH). Determining if calcium carbonate (calcite) is present in the tailings is an important step to understanding how to control (and decrease) the presence of soluble uranyl species in the pore water. It is anticipated that both amorphous and crystalline calcium-containing compounds will be present in the tailings, and that calcite, if present, will be found in trace quantities. In this work, X-ray absorption spectroscopy, X-ray microprobe, and X-ray diffraction will be performed to identify the Ca-bearing species present in the tailings and determine if calcite forms.