Separation of rare earths using solvent extraction consisting of three phases

Abstract A new approach for grouping separation of multi- rare earths coexisting complex systems by liquid-liquid-liquid three phase system consisting of Cyanex272/PEG/(NH 4 ) 2 SO 4 -H 2 O was investigated. It was found that, the 15 rare-earth elements, including lanthanides and yttrium, could be separated into three groups and respectively partitioned into the top, middle and bottom layers of the three liquid phases coexisting system. The formation of three-layered coexisting liquid phases played an important role in inducing the grouping separation of multi- rare earths mixed systems. Various influences from the initial aqueous pH, the added amount of water-soluble complexing agent DTPA, the concentration of phase-forming polymer PEG in aqueous solutions and its average molecular weights, the concentration of electrolyte salt (NH 4 ) 2 SO 4 , and the concentration of organic extractant Cyanex272 on the performance of grouping separation of rare earths were evaluated. Experimental results confirmed that the grouping separation of multi- rare earths had a close relationship with the change in phase-forming conditions in three-liquid-phase systems. The occurrence positions of yttrium in separation of different rare-earth groups moved with the change in aqueous pH and the extractant concentration. The present work highlights a new strategy for controllable grouping separation of multi- rare earths based upon the phase-forming behaviors of three-liquid-phase systems and discrepancy in interaction of different rare-earth groups respectively with three coexisting liquid layers.