Removal of transition metals from rare earths by solvent extraction with an undiluted phosphonium ionic liquid: separations relevant to rare-earth magnet recycling
Vander Hoogerstraete, S. Wellens, K. Verachtert, K. Binnemans
Green Chemistry 15, 919-927 (2013).
An environmentally friendly process for the separation of the transition metals copper, cobalt, iron, manganese and zinc from rare earths by solvent extraction with the ionic liquid trihexyl(tetradecyl) phosphonium chloride has been developed. The solvent extraction process is carried out without the use of organic diluents or extra extraction agents and it can be applied as a sustainable hydrometallurgical method for removing transition metals from neodymium-iron-boron or samarium-cobalt permanent magnets. Transition metals are efficiently extracted, while the rare earths remain in the raffinate. The method was tested for the removal of cobalt and iron from samarium and neodymium, respectively.