SEPARATION OF LIGHT LANTHANOIDS BY CENTRIFUGAL PARTITION CHROMATOGRAPHY IN 30-PERCENT TBP EXTRACTION SYSTEM

Separation of light lanthanoids (III) with centrifugal partition chrom atography (CPC) in 30% tri.n.butyl phosphate (TBP) extraction system w ith the aid of salting-out agent lithium nitrate (LiNO3) was investiga ted. Carbon tetrachloride (CCl4) and n-dodecane were used as diluents to control the density difference between mobile and stationary phases . By a batch method, it was proved that distribution ratios (D) and se paration factors (alpha) of several light lanthanoids increased with t he LiNO3 concentration in 1 M (mol.dm-3 ) nitric acid in the aqueous p hase. Addition of CCl4 to 30% TBP-n.dodecane organic phase resulted in a decrease of the D values, holding the alpha values constant. On the basis of these data, separations of Ce, Pr and Eu with a CPC apparatu s were successfully performed by decreasing the density difference. Al though the chromatogram data differed considerably from the batch data owing to the concentration effect of the lanthanoids, satisfactory se paration was obtained in 30% TBP-35% n.dodecane-35% CCl4 and 5 M LiNO3 -1 M HNO3 (alpha(Pr/Eu): 5.8, resolution(Pr/Eu): 2.0).