Mutual Separation of Rare Earth Elements by Extraction Chromatography Using Bis(1, 1, 3, 3-tetramethylbutyl)phosphinic Acid as a Stationary Phase

Abstract

The extraction behavior of rare earth elements was systematically investigated by using bis(1, 1, 3, 3- tetramethylbutyl)phosphinic acid (HMBP) in HNO₃ medium. The extraction mechanism was evaluated through a log-log plot analysis, and the overall extraction equilibrium constant K was calculated for each rare earth element(III). The degree of mutual separation of adjacent pair of rare earth elements was discussed from the value of separation factor S.F. _z+I/z and explained by thermodynamic function- the relative free energy change of adjacent rare earth elements(III) Δ(ΔG°)_z+1/z. The separation of scandium from lanthanoids and yttrium was achieved by a single HMBP extraction and the mutual separation of lanthanum. cerium and praseodymium was achieved by HMBP-extraction chromatography.