Solvent extraction of rare earth elements using a bifunctional ionic liquid. Part 2: Separation of rare earth elements.

The results suggest that the reaction mechanism is one of cation exchange, with antagonism compared with EHEHPA. This is thought to be caused by the decrease in free EHEHPA dimer concentration due to ion pairing between the quaternary ammonium and phosphonate ions. The extractant is not recommended for light rare earth circuits due to the low loading capacity at high pH, while the antagonistic effect would be beneficial in heavy rare earth separations due to reduction in the stripping acidity.