Solvent extraction of trivalent lanthanides with Cyanex 302 from acidic aqueous chloride solutions

The Solvent extraction of trivalent lanthanides (except Pm) with Cyanex 302 (bis(2,4,4- trimethylpentyl) monothiophosphinic acid, hereafter abbreviated as HL) in heptane from acidic aqueous chloride solutions has been studied systematically. The effects of the equilibrium aqueous pH and extractant concentration on the extraction were observed. The separation of the lanthanides by Cyanex 302 and Cyanex 272 (bis(2,4,4-trimethylpentyl)phosphinic acid) has been contrasted. The extraction stoichiometry was studied with the method of slope analysis. The extraction of the lanthanides proceeds by a cation exchange reaction, which can be expressed as follows: Ln(3+(a) + 2- 5 (HL)2(o) = LnL (HL2)2(o) + 3H+(a). Purified Cyanex 302 (H[BTMPTP]) exhibited significantly lower extracting power for the lanthanides than Cyanex 302 used as received, and the Yb( II ) extraction stoichiometry with purified Cyanex 302 was also studied, the extraction equilibrium constant was calculated. The IR and NMR spectra of the (Yb( II ) extracted complexes with purified Cyanex 302 were measured. The role of the different components of Cyanex 302 in the Sm( II ) extraction have been discussed