Selective recovery of rare earths from bauxite residue by combination of sulfation, roasting and leaching
Continuous development of advanced technologies has created increasing demand for rare earths elements (REE), with global emphasis on identifying new alternate sources to ensure adequate supply. Clay deposits containing physically adsorbed lanthanides are substantially lower grade than other types of REE mineral resources; however, their abundance in sub‐ tropical regions, existence as surface layers requiring low mining cost, and their high cation exchange capacity make them economically‐important sources of rare earths. At the University of Toronto we have conducted a systematic study of clay minerals from various locations. It was found that REE are easily recovered via an ion‐exchange mechanism during leaching with monovalent salt solutions under ambient conditions, based on a 3:1 stoichiometric ratio between the trivalent lanthanides and the exchange monovalent cation. The present paper reports on the most important findings of this investigation.