Extraction of rare earth metals from low-grade ores using organic acids

Rare earth elements (REE), including lanthanides, scandium, and yttrium, are vital for advanced technologies but are primarily sourced from China, creating strategic dependency. With Canada holding 40%–50% of global REE reserves, there is significant potential for domestic production. Traditional extraction methods use harsh inorganic acids, which are mainly suited for high-grade ores. This research explores indirect bioleaching with organic acids as an alternative for extracting REE from low-grade ores and industrial wastes. Thermodynamic modelling was first conducted to assess the feasibility of organic acid leaching for various REE-bearing minerals. Experimental work was then carried out to evaluate the extraction of both light (Ce, Nd) and heavy (Y, Dy) REE under varying experimental conditions, including organic acid type (tartaric, lactic, oxalic, and citric acids), temperature (25-85°C), particle size (−38 to +75 μm), and organic acid concentration (0.05–0.4 M). Under optimal leaching conditions, which were 0.2 M citric acid, 85°C, and −38 μm, the extraction efficiencies reached 78% for Ce, 74% for Nd, 47% for Y, and 49% for Dy. Further tests using citric acid in combination with H2SO4 or HCl demonstrated enhanced selectivity and lower inorganic acid requirements, indicating potential for synergistic organic–inorganic leaching systems.