Liquid–liquid extraction of certain trivalent lanthanides from nitrate solutions with N,N,N',N'-tetrabutylsuccinamide as new extractant

Abstract

The extraction of Nd(III), Eu(III), Sm(III), Gd(III), and Dy(III) from nitrate solutions with N,N,N',N'-tetrabutylsuccinamide (TBSA) in toluene was studied. The distribution ratios of the investigated metal ions were determined in relation to the nitric acid concentration, kind of diluent, concentrations of the extractant and salting-out agents, and temperature. The stoichiometry of the TBSA–HNO3 adducts that prevail under the experimental conditions is 1: 1 (HNO3·TBSA). The investigated Ln(III) are poorly extracted with TBSA in the entire range of nitric acid concentration (0.1–7 M). Good separation of U(VI) or Th(IV) from the investigated lanthanides can be achieved at high nitric acid concentrations (7 M). The distribution ratios of the investigated metal ions sharply decrease with increasing nitric acid concentration in the presence of 5 M LiNO3. The extractable species of Nd(III), Eu(III), Sm(III), Gd(III), and Dy(III) with TBSA were found to be trisolvates. The extractable species were also studied by IR spectroscopy. The thermodynamics functions for the extraction of the investigated Ln(III) were calculated.