Crown ethers as synergistic agents in the solvent extraction of trivalent lanthanides with 8-hydroxyquinoline

The liquid extraction of the 13 lanthanides with mixtures of 8-hydroxyquinoline (HQ) and crown ethers (S) dibenzo-18-crown-6 (DB18C6) and dibenzo-24-crown-8 (DB24C8) in 1,2-dichloroethane as a diluent from chloride medium at constant ionic strength mu = 0.1 was investigated. The composition of the extracted species was established as LnQ(3) with HQ alone and as LnQ(3).S in the presence of a crown ether. The values of the equilibrium constants were calculated. The addition of DB18C6 to the metal chelate system improved the extraction efficiency, while a weak synergistic enhancement was found when the metals were extracted with mixtures of HQ-DB24C8. The parameters of the extraction process were determined and the separation factors between two adjacent lanthanides(III) were calculated.