Extraction of Selected Tervalent Lanthanides Using Dicyclohexylphosphinic Acid

The extraction behavior of lanthanum(III), praseodymium(III), europium(III), holmium(III), and ytterbium(III) into chloroform solutions containing dicyclohexylphosphinic acid (DCHPA) was investigated. The lanthanides were found to extract as self-adducts of the form LnL3 3HL, where L and HL denote the ligand anion and neutral ligand, respectively. The extraction selectivity of DCHPA was found to be inferior to that exhibited by other phosphinic acids. It is possible that the cyclohexyl sub-stituents.in DCHPA lead to steric hindrance in chelate formation, decreasing the ligand selectivity.