Extracted species of rare earth elements using bis(1,1,3,3-tetramethylbutyl)phosphinic acid as an extractant and their effective mutual separation by high-performance extraction chromatography

The possible extracted species of rare earth elements (REE) in bis(1,1,3,3-tetramethylbutyl)phosphinic acid (Hmbp)/cyclohexane-HNO3 system was proposed by a log-log plot analysis and a saturated extraction method as being [M(mbp)(3)(Hmbp)(3)] (M = REE). It was also verified by IR, H-1 NMR spectra and element analysis of lutetium-Hmbp extracted species. The effective mutual separation of REEs was achieved on the Hmbp modified C-18 column by a pH gradient elution. Moreover, the degree of the mutual separation of europium(III) from gadolinium(III) was remarkably improved by adding glycollic acid in the mobile phase. A fine concentrate of Sm2O3, Eu2O3, and Gd2O3 from a rare earths smeltery was analyzed by the present method with the spectrophotometric detection after postcolumn derivatization with Arsenazo III.