Selectivity enhancement in the permeation of rare earth metals through supported liquid membranes by addition of diethylenetriaminepentaacetic acid to the aqueous phase

Abstract

Separation of erbium and yttrium was carried out by using the supported liquid membrane system containing diethylenetriaminepentaacetic acid (DTPA) in the aqueous feed phase. The effects of the concentrations of DTPA, H + and the carrier on the permeation rates and selectivities were investigated. As the concentration of DTPA approached the total concentration of the rare earth metals, the selectivity increased to a maximum of about 4.5, which was much larger than that by conventional solvent extraction. Further, the selectivity increased as the carrier concentration increased. This separation method has the feature that the highest selectivity can be obtained when the mass transfer accompanying the dissociation reaction of DTPA complexes in the aqueous stagnant layer is rate determining. The obtained permeation rates and selectivities were satisfactorily simulated by taking account of the dissociation reaction of DTPA complexes in the aqueous stagnant layer.