Leaching of rare earth elements from 'Rödberg' ore of Fen carbonatite complex deposit, using the ionic liquid HbetTf2N

In this study, the ionic liquid betainium bis(trifluoromethylsulfonyl)imide (HBetTf2N), has been applied directly as a leaching agent on a low-grade rare earth element (REE) ore called Rödberg, from the Fen carbonatite complex ore deposit located in Norway. REE in Rödberg are mainly present in the form of fluoro-carbonates of bastnäsite group minerals. Factors studied during leaching were water ratio into ionic liquid, leaching temperature, pulp density (%w/v) and retention time. Leaching of Rödberg ore with HbetTf2N resulted to 65-100% recovery of light REE and 40-60% recovery of heavy REE. Additionally > 80-90% of Ca and Mg content dissolves, whereas the HbetTf2N is selective against iron and silicon resulting in a Fe/Si rich residue. The metals dissolved into HbetTf2N after leaching are stripped with an aqueous acidic solution, regenerating the ionic liquid for reuse. Through acid stripping, REE concentration is doubled in the aqueous acidic solution, for further purification. The carboxylic acid functional group attached to the cation side of HbetTf2N is capable of dissolving bastnäsite thus enabling the development of new alternative methods for treating low-grade REE primary resources.