The Separation of Cerium(IV) from Nitric Acid Solutions Containing Thorium(IV) and Lanthanides(III) Using Pure [C₈mim]PF₆ as Extracting Phase

Abstract

The extraction behavior of Ce(IV) along with Th(IV) and Ln(III) (Ln = Ce, Gd, Yb) nitrate by pure ionic liquid, [C8mim]PF6, was investigated. [C8mim]PF6 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 [C8mim]PF6 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 [C8mim]PF6 may act as extracting phase for separating Ce(IV) from nitric acid solutions containing Th(IV) and other trivalent lanthanides.