Separation of rare earths by non-aqueous solvent extraction

Solvent extraction is widely used for the separation of mixtures of rare earths on an industrial scale. However, these separation processes are not very efficient so that many extraction stages are required to produce pure rare earths. In this project, we develop a new approach to separation of rare earths: non-aqueous solvent extraction with two immiscible organic phases. Non-aqueous solvent extraction offers some advantages compared to conventional solvent extraction with an aqueous feed phase. The speciation of rare-earth ions in non-aqueous solutions often differs greatly, hence influencing the extraction. Making use of these differences, novel and very selective separation processes can be developed. Research efforts were directed towards the development of a continuous non-aqueous solvent extraction process for separation of a rare-earth concentrate by means of mixer-settler cascades.