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

点击翻译按钮获取中文摘要

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.