The Need
Rare earth elements (REEs) are important in the transition to net-zero emissions economies because they are used in key technologies such as turbines and electric motors. They are included as a group on lists of minerals that many countries consider ‘critical’, including Canada, China, the EU and the US. REEs are among the top six priority minerals and metals identified by the federal government as having the most significant potential for Canadian economic growth.
REEs are a group of 17 metals that are often found as trace elements and mined together. Traditional REE deposits are becoming depleted, while demand is anticipated to increase substantially over the next fifteen to twenty years.
Coal deposits are known to be a potential source of REEs, and work is underway in the US and elsewhere to separate and concentrate REEs during coal processing.
Though scientific literature indicates the presence of REEs in some Canadian coal deposits, especially in BC coalfields, there has been little research to quantify and characterize these coal deposits as an REE source. The purpose of this project was to characterize and quantify the REEs and their mode of occurrence in different processing products of coal from the East Kootenay coal deposits, as well as to study the possible extraction of REEs.
Project Goals
This project fits under Geoscience BC’s Strategic Objective of ‘Identifying New Natural Resource Opportunities’.
The main objectives of this study were to characterize and quantify the REEs and their mode of occurrence in the East Kootenay coal deposits and to study the possible extraction of these elements using bench scale testing methods.
Project Benefits
The new geoscience information generated by this project offers insight into the REE concentrations in East Kootenay coal to evaluate a potential Canadian source of REEs, which are critical to renewable energy development. The project helps the BC metallurgical coal industry, researchers and government agencies make decisions about developing sources of REEs within BC.
Survey Area
Coal samples were collected from coal mines and operating plants in the East Kootenays in BC’s Southeast Region. The information primarily relates to the traditional territory of the Ktunaxa Nation.
What was found
Over 100 samples (low-to-medium volatile bituminous, metallurgical coal) were collected from across the mines and operating plants and tested at the Coal and Mineral Processing laboratory at the University of British Columbia. All samples were analyzed for REE content using inductively coupled plasma mass spectrometry (ICP-MS). Samples were also characterized through coal proximate analysis, a four-step sequential extraction process to characterize REEs’ association with the coal. A range of separation techniques (density, magnetic, gravity, and flotation) were performed to understand the separation potential of REEs. REE extraction experiments were conducted through direct acid leaching, acid baking and water leaching. Mineralogical analyses were performed to identify and quantify the REEs’ host mineralogy. It was found that monzonite, xenotime and zircon (generally locked in a clay matrix) are the dominant REE-bearing minerals in the samples. The study could not establish the original source of these sedimentary grains.
Total REE values calculated on an ash basis generally exceeded the crustal average of 190 ppm, with most between 190 ppm and 400 ppm, and the highest at 686 ppm. Using the US Department of Energy’s 2016 threshold of 300 ppm total REE as the coal seam content considered a potential cutoff grade for REE extraction, it suggests that some samples within these coalfields may indicate resource potential. A further ‘outlook coefficient’ factor analysis that examples the ratio of critical REEs to excessive REEs also suggests that these coalfields may be a viable source of REEs if extraction practices are refined.
Owing to the inorganic nature of the REE-bearing minerals, waste streams from coal processing offer the possible potential for REE sources. Of the separation techniques tested, gravity based separation showed the most promise and is recommended for further study. Flotation was also shown to be a potential concentrating technique; however, further tests would be required to optimize it. Hydrometallurgical leaching should be explored further in order to improve REE recovery, as the highest REE recovery by leaching was only around 70%.