Recovery of Rare Earth Elements from coal tailings from British Columbia coalfields by nano-flotation

稀土元素（RE）是周期表中的17种元素，包括15种镧系元素和两种过渡金属：Sc和Y。这些元素用于各种现代电子产品和绿色能源应用。随着新的清洁能源和国防相关技术的出现，稀土元素的消费量迅速增加，它们已被美国，欧盟和加拿大列为关键元素（CREEN，2015）。考虑到供应不足以满足需求的无数风险，目前正在评估未来开采的非常规稀土资源。稀土富集的煤矿床已被世界各地确定为潜在的稀土资源。从美国煤及其副产品中提取稀土元素的研究使用了不同的方法，如磁性，密度和重力方法，浮选，离子交换和浸出，但分离技术仍处于开发的初始阶段，尚未开发出商业提取工艺。煤中的稀土元素与非常细的矿物（通常小于10 µm）有关;因此，由于这些常见的分离方法（包括泡沫浮选）对这些细颗粒的分离效率有限，因此煤中稀土元素的常见物理浓缩方法是可行的。 在泡沫浮选中使用纳米气泡的纳米浮选被证明在矿物加工应用中有效地捕获非常细的颗粒，并且它是从这些非常规资源中分离稀土矿物的有前途的方法。然而，它从来没有被研究过的背景下，从煤中回收稀土。我的小组以前对来自不列颠哥伦比亚省（BC）的煤进行的研究表明，大多数稀土煤在加工时报告为废物流。因此，有机会发展纳米浮选作为从这些废弃物中回收稀土的方法。我的发现补助金研究计划将研究纳米浮选作为一种从不列颠哥伦比亚省活跃煤田的煤尾矿中回收稀土元素的方法。目前，该省生产近3000万吨优质冶金煤，虽然这些煤的加工捕获了大部分粉煤，但仍有大量（约1-2百万/年）作为尾矿处理。从煤尾矿中回收稀土元素有许多优点;不需要采矿，如果洁净煤也可以作为二次产品回收，则可能消除煤尾矿。煤尾矿的再利用并将其转化为宝贵的资源为加拿大提供了巨大的经济效益，特别是如果稀土元素可以从这种非常规资源中回收，以及减少甚至消除煤尾矿废物将产生明显的环境效益。目前在加拿大还没有进行这类研究。

Rare Earth Elements (REEs) are a group of 17 elements in the periodic table including 15 lanthanides and two transition metals: Sc and Y. These elements are used in a wide variety of modern electronic products and green energy applications. With the emergence of new clean-energy and defense-related technologies, consumption of REEs has increased rapidly, and they have been classified as critical elements by the United States, the European Union and Canada (CREEN, 2015). Considering the myriad risks of insufficient supply to meet demand, unconventional sources of REEs are currently being assessed for future exploitation. Coal deposits with enriched concentrations of REEs have been identified across the world as potential REE resources. The extraction of REEs from US coal and its by-products has been studied using different processes such as magnetic, density and gravity-based methods, flotation, ion-exchange and leaching, but the separation technology is still in the initial stages of development, and a commercial extraction process has not yet been developed. REEs in the coal are associated with minerals that are very fine (usually less than 10 µm in size); as a result, common physical concentration methods of REE from coal are feasible due to limitations of separation efficiency by these common separation processes, including froth flotation, for such fine particles. Nano-flotation which uses nano-bubbles in froth flotation was shown to be efficient in capturing very fine particles in mineral processing applications and it is a promising method for separating REE minerals from these unconventional resources. However, it has never been studied before in the context of REE recovery from coal. Previous studies carried out in my group on the coals from British Columbia (BC) showed that most of the REEs coal report to waste streams when processed. Hence, there is an opportunity for the development of nano-flotation as a process for recovery of REEs from these rejects. My Discovery Grant research program will study the nano-flotation as a process for REE recovery from coal tailings from active coalfields in BC. Currently, close to 30mln tonnes of high-quality metallurgical coal is produced in the province, and while the processing of these coals captures most of the fine coal, a significant amount (~1-2 mln/year) is still disposed as tailings. There are number of advantages of recovering REE from coal tailings; there is no mining required, possible elimination of coal tailings if clean coal can be also recovered as a secondary product. Reutilization of coal tailings and turning them into valuable resources provides Canada with significant economic benefits, especially if the REEs could be recovered from this unconventional resource as well as there will be clear environmental benefits of reducing or even eliminating coal tailings waste. There has been no study currently undertaking this type of research in Canada.