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UBC Theses and Dissertations

Characterization and extraction of rare earth elements from metallurgical coal-based source Kuppusamy, Vinoth Kumar


As global society moves towards a low-carbon economy, secure access to raw materials becomes the key bottleneck in achieving a green transition. Alternative resources such as coal-based materials have been evaluated for rare earth production in recent years to reduce import dependence and diversify production geographically. This study explores the possibility of using metallurgical coal-based materials from the East Kootenay coalfields in British Columbia as a source for rare earth elements (REEs). First, a characterization study was carried out to understand the target REEs and gangue mineralogy. The results showed that the concentration of REEs in the feed material varied between 230 to 314 mg/kg on an ash basis. When subjected to flotation, most of the REEs (by wt.%) were deported to waste streams such as middlings and tailings due to the inorganic (mineral matter) association of REEs. A mineralogical examination found that one of the rare earth-bearing minerals was monazite and indicated the presence of fine-sized multiple rare earth minerals in the sample. Feedstock materials were studied using different leaching techniques. Results demonstrated that acid baking followed by water leaching (ABWL) was the suitable method for extracting REEs for the samples studied. Acid dosages and bake temperature were found to be the most important process variables affecting REE extraction. The kinetic analysis showed that the process was controlled by interfacial transfer and diffusion through product layer, with an apparent activation energy of approximately 15 kJ/mol. The ability to recover REE ions from the leach solution was examined with a modified fruit peel. Results indicated that the new adsorbent was effective in adsorbing REE ions from the solution following the Langmuir isotherm model, with estimated equilibrium maximum adsorption capacities for Y³⁺, La³⁺, Dy³⁺, Er³⁺ of 34.99, 60.51, 65.08, and 66.79 mg/g, respectively. Further, an economic assessment of two process flowsheets examined for REE extraction showed that plant capacity, REE concentration in the feedstock, and price were key parameters affecting project economics. In addition to REEs, the co-production of other valuable elements from the feedstock has the potential to significantly improve the project’s viability on an industrial scale.

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