Column Separation of Rare-earth Metal Ions by Flash Chromatography Using Octadecylsilylated Silica Gel Particles Loaded with Bis (2-ethylhexyl) hydrogenphosphate

Abstract

The adsorption behavior of octadecylsilylated silica gel (ODS) particles which were loaded with bis (2-ethylhexyl) hydrogenphosphate (B2EHP) was studied for a series of rare-earth metal ions (RE)except Pm³⁺ in the dilute HCl solution. Based on the resultant adsorption equations for each metal ion, each RE was separated by the flash column chromatography using ODS particles loaded with B2EHP as the solid phase in high efficiency. Pairs of neighboring ions in the atomic number such as La³⁺-Ce³⁺, Ce³⁺-Pr³⁺, Sm3³⁺-Eu³⁺, Eu³⁺-Gd³⁺ and Tb³⁺-Dy³⁺ were separated each other completely by developing with 0.20 M to 1.2 M HCl at the eluting rate of 100 cm³/h and 45° C. At the smaller eluting rate, Pr3+ was separated from Nd³⁺. The heavier ions than Ho³⁺ were separated from their neighboring ions in the value of distribution ratio by developing with 1.8-3.5 M of HCl at the eluting rate of 30 cm³/h and 45° C. On the other hand, the separation of Y³⁺-Er³⁺ pair was incomplete with the resolution =0.52, coinciding with its smallest separation factor, 1.10 calculated from the present data of distribution ratios, among all the pairs.