The Use of Weakly Basic Ion Exchange Resin Amberlite IRA-68 for the Chromatographic Separation of Rare Earth Elements

The possibility of applying the system: weakly basic Amberlite IRA-68 resin-nitrilotriacetic acid (NTA) solutions for the separation of rare earth elements (REE) by ion exchange chromatography was investigated. Preliminary research results revealed that the affinity of REE towards the ion exchanger is closely correlated with the stability of their negative complexes that they form with NTA. Three separate groups of lanthanides could be distinguished, i.e. light (La, Ce, Pr, Nd), medium (Y, Sm, Eu, Gd, Tb, Dy, Ho, Er) and heavy (Tm, Yb, Lu, Sc). Moreover, it seemed that within the first and third groups it was possible to individually separate elements from each other. Based on the experimentally obtained relationships, the theoretically assumed course of the ion exchange reaction of anionic REE complexes with NTA on the Amberlite IRA-68 resin was confirmed. The influence of the ion exchanger particle size, column size and composition of the mobile phase, i.e. pH, NTA and neutral salt (NaNO₃) concentration, on the chromatographic separation of REE was investigated. It has been shown that the proper selection of these parameters makes it possible not only to divide REE into the three groups mentioned above, but also to individually separate some elements, i.e. La, Ce, Pr, Nd, Tm, Yb, Lu and Sc.