Mining, Metallurgy & Exploration (2019) 36:571–578, https://doi.org/10.1007/s42461-019-0048-8
Rare earth elements (REEs) and their compounds are essential in a multitude of mundane and sophisticated applications, such as renewable-energy technologies, catalysts, medicine and defense. Cost-effective and environmentally benign opportunities are being explored for the production of REEs from nonconventional mineral sources, including coal and coal byproducts, to stabilize the supply chain. The objective of this study was to concentrate the REEs contained in the coal samples from the Healy coal mine and Wishbone Hill deposits in Alaska by froth flotation. A Box-Behnken design of experiments was carried out to maximize REE recovery and REE concentration by modeling and optimizing three operating variables: frother dosage, pulp density (percent solids) and collector dosage. Based on the results, the optimum flotation conditions for maximum recovery at an elevated concentration of REEs in the froth fraction was obtained at 4.2 percent solids and 32.7 ppm of frother dosage for the Healy sample, and 10 percent solids and 37.9 ppm of frother dosage for the Wishbone Hill coal sample.