Mutual separation of rare earth elements by extraction chromatography using bis(1,1,3,3-tetramethylbutyl)phosphinic acid as a stationary phase

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+1/z) and explained by thermodynamic function-the relative free energy change of adjacent rare earth elements(III) Delta(Delta G degrees)(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.