Solvent Extraction and Separation of Tervalent Lanthanides and Yttrium Using Cyanex 923

Abstract

The paper embodies extraction behavior of some tervalent lanthanides [La, Ce, Nd, Eu, Gd, Ho, Yb] along with Y(III) from HNO3, HCl, H2SO4, and H3PO4 media in a toluene solution of Cyanex 923. The effect of some important variables like equilibration time, nature of diluent and the concentration of acid, extractant and metal ion on the extraction is investigated. Based on the partition data the stoichiometry of the extracting species is formulated as Ln(NO3)3·2Cyanex 923. The reagents like 5.0 mol L−1 HNO3, 0.5 mol L−1 H2SO4/HCl and 1.0 mol L−1 H3PO4 have been found effective for stripping of the metal ions. Cyanex 923 is stable even after prolonged acid contact and the extraction efficiency remains unaffected even after 20 recycling steps. Based on the partition data the lanthanides can be divided into four distinct groups namely light (La, Ce, Nd), middle (Eu, Gd), holmium (Ho), and heavy (Yb). The separation factors indicate that the separation of light and heavy fractions can be conveniently achieved from all the four investigated acid media. However, the separation of lanthanides into the said four fractions is more apparent from nitric acid medium. The data have been successfully employed for the separation of lanthanides and yttrium in different fractions from a synthetic mixture.