Reversed micellar solubilization extraction and separation of thorium(IV) from rare earth(III) by primary amine N1923 in ionic liquid

The extraction behavior of thorium(IV) sulfate by primary amine N1923 in imidazolium-based ionic liquid (IL) namely 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim]PF6) was systematically studied in this paper. Results showed that the extraction behavior was quite different from that using conventional solvent as diluent. A reversed micellar solubilization extraction mechanism was proposed for the extraction of thorium(IV) by N1923/[C8mim]PF6 via slope analysis method and polarized optical microscopy (POM)/transmission electron microscopy (TEM) observation. The salt-out agent, Na2SO4, was demonstrated to prompt this extraction mechanism. The extraction of several rare earths(III) (La, Ce, Nd, Gd, Er) by N1923/[C8mim]PF6 was investigated to evaluate the separation coefficients between Th(IV) and rare earth(III) (RE(III)). On this basis, we made a preliminary assessment for the possibility of using ionic liquid as diluent for the separation of Th(IV) from RE(III) in clean process.