Synergistic extraction equilibrium of lanthanoids(III) with 2-thenoyltrifluoroacetone and nitrogen-containing bidentate ligands, ethylenediamine derivatives

The synergistic extraction of lanthanoids(III), Ln(III), i.e., La, Sm, Tb, Tm and Lu, using 2-thenoyltrifluoroacetone (Htta) sind nitrogen-containing neutral bidentate ligands (S), i.e., three ethylenedi-amine derivatives, su ch as N,N'-dimethylethylenediamine (dmen), N,N'-diethylethylenediamine (dee n) and cis-1,2-cyclohexanediamine (chda), was studied in the benzene and aq ueous system. The synergistic enhancement in these extraction systems was m ainly attributed to the formation of an adduct, Ln(tta)(3)S, in the benzene phase. The variation of the adduct formation constants ((beta(S,1)) was di scussed with the basicity of ligands and structure hindrance around the met al ion.