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

Abstract

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 μ = 0.1 was investigated. The composition of the extracted species was established as LnQ3 with HQ alone and as LnQ3·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.

Keywords

• synergistic extraction
• 8-hydroxyquinoline
• dibenzo-24-crown-8
• dibenzo-18-crown-6
• lanthanides separation factors