Extraction and separation of rare earths using mixtures of sec-nonylphenoxy acetic acid and alkylated phosphine oxides

Abstract

The increasing demand for high-purity rare earths and their compounds promoted the separation technology of rare earths. In this work, the mixtures of sec-nonylphenoxy acetic acid (CA100) and alkylated phosphine oxides (Cyanex923 and Cyanex925) were used as extractants instead of single CA100 for high-efficiency extraction of rare earths from chloride medium. Compared with single CA100 , the mixture of CA100 and Cyanex923/Cyanex925 could improve the selectivity of yttrium (Y) extraction from the lanthanoids based on their separation factors. The synergistic effects of CA100 and Cyanex923 on lanthanum (III) extraction were investigated by using the methods of slope analysis and constant mole to determine the extraction reaction. The reaction product, equilibrium constants, formation constants, and the thermodynamic functions were determined. The synergistic extraction of lanthanum (III) with CA100 and Cyanex923 was proved to be endothermically driven.