Dissolution of the Rare-Earth Mineral Bastnaesite by Acidic Amide Ionic Liquid for Recovery of Critical Materials

Rare-earth elements provide the cornerstones to clean sustainable energy and modern technologies such as computers, communications, and transportation. As such, the recovery of rare earths (REs) from minerals such as bastnaesite remains important for modern times. As the light lanthanides (La-Nd) constitute the majority (typically >98.7 %) of the REs in bastnaesite with the heavy REs (Sm-Lu) contributing the remainder (approximately 1.3 %), an enrichment of heavier REs may serve as an effective means of assisting rare-earth recovery. Such an extractive metallurgy process involving ionic liquids (ILs) leads to an enrichment of heavy REs by nearly an order of magnitude. The acidic IL N,N-dimethylacetamidium bis(trifluoromethylsulfonyl)imide (DMAH⁺NTf₂^-) in the IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM⁺NTf₂^-) dissolves froth flotation bastnaesite, synthetic bastnaesite analogues (RECO₃F), RE₂O₃, and RE₂(CO₃)₃ minerals. An overall reaction for the dissolution of bastnaesite is proposed for this IL system. This IL system may provide the initial stages of a greater RE separation scheme for bastnaesite froth flotation concentrates.