The Separation of Cerium(IV) from Nitric Acid Solutions Containing Thorium(IV) and Lanthanides(III) Using Pure C8mimPF6 as Extracting Phase

The extraction behavior of Ce(IV) along with Th(IV) and Ln(III) (Ln = Ce, Gd, Yb) nitrate by pure ionic liquid, C8mimPF6, was investigated. C8mimPF6 alone showed good extraction ability for Ce(IV), while it was slight for Th(IV) and negligible for Ln(III). The extraction behavior of Ce(IV) by C8mimPF6 was particularly studied, and the most probable extraction mechanism proposed was the anion exchange mechanism. Moreover, the stripping of Ce(IV) from IL phase was also investigated. The Ce(IV) in IL phase can be quantitatively recovered by water. Recycle test indicated that IL loss could be avoided via adding C8mim+ to the initial Ce(NO3)4 solutions before extraction and/or using PF6- solutions for stripping. Inspired by the proposed extraction mechanism, a new kind of Ce(IV)-doped IL was prepared to give further elucidation for the anion exchange mechanism. The result indicated that pure C8mimPF6 may act as extracting phase for separating Ce(IV) from nitric acid solutions containing Th(IV) and other trivalent lanthanides.