Synergic solvent extraction studies of gadolinium using a combination of the di(2-ethylhexyl)phosphoric acid and three adductants into kerosine/chloroform

Abstract

The equilibrium extraction behaviour of Gd(III) using a chloroform/kerosine solution containing di(2-ethylhexyl)phosphoric acid (HDEHP), either alone or combined with one of three adductants, 1,10-phenanthroline monohydrate (phen), α,α′-dipyridyl(2,2′-bipyridine) (bipy) or trioctylphosphine oxide (TOPO) is described. The enhancement of the extraction by addition of such neutral adductants is explained in terms of adduct formation of the metal chelate in the organic phase. Among the three synergistic mixtures, 1,10-phenanthroline is the most promising for the extraction of the last member of light lanthanoids, gadolinium. Gadolinium ions are found to be extracted in the absence of phen, bipy or TOPO; the species was M(HA 2) 3 but M(HA 2) 3)(phen) 2 was found when phen was added and M(HA 2) 3(bipy), M(HA 2) 3(bipy) 2 was found when bipy was added and M(HA 2) 3(TOPO) was found when TOPO was added. The compositions of the extracted species are obtained from the slope analysis method. pH 1 2 values were also obtained. The stoichiometry, extraction constants and stability constants of these systems were determined. Synergistic extraction can be carried out at lower pH.