Lanthanum(III) and gadolinium(III) separation by cloud point extraction

In the present study, cloud point extraction (CPE) is used with lipophilic chelating agents, 8-hydroxyquinoline (HQ) and Kelex 100 (K100), to extract and separate lanthanum(III) and gadolinium(III) from aqueous solutions. The methodology used is based on the formation of lanthanide(III) organic complexes that are soluble in a micellar phase of a non-ionic surfactant, Triton X-114. The lanthanide(III) complexes are then extracted into the surfactant-rich phase at a temperature above the cloud-point temperature. Influence of pH of the solution, structure of the chelating agent, chelating agent/lanthanides(III) molar ratio, on extraction efficiency and selectivity is studied. High extraction efficiency and selectivity for Gd(III) is observed using HQ whereas K100 is a poor extractant. By pH switching, yields of Gd(III) recovery higher than 95% were obtained with selectivity factors up to 37 against La(III), indicating the feasibility of separating Gd(III) from La(III) using CPE.