Multitracer studies on the permeation of rare earth elements through a supported liquid membrane containing 2-ethylhexyl phosphonic acid-2-ethylhexyl ester (EHEHPA)

The simultaneous permeation of Sc, Y, Ce, Pm, Eu, Gd, Yb and Lu through a 2-ethylhexyl phosphonic acid-2-ethylhexyl ester (EHEHPA)-decalin membrane supported on a microporous polytetralluoroethylene sheet was studied using a multitracer. The permeation rates of the elements from feed solutions of various acidity into receiving solutions of 2 mol dm(-3) HCl were determined. The feed solution at pH 1.5 gave the highest percentage of permeation for Ce, Pm, Eu, Gd and Yb. amounting to about 90% after 25-h permeation. The percentage of permeation of Y and Lu was the highest at pH 1, amounting to about 90% after 25-h permeation. The permeation of Sc from all the feed solutions was less than 4% due to its adsorption on the vessel. The permeation from the feed solution at pH 1.5 into the receiving solutions of 1, 2, 3, 4 and 5 mol dm(-3) HCl showed that the maximum percentage of transport for Y and Yb was obtained in 2 mol dm(-3) HCl receiving solution and that for Lu in 2-4 mol dm(-3) HCl receiving solutions. The other elements gave a percentage of transport more than 90% in 1-5 mol dm(-3) HCl receiving solutions, showing no obvious HCl concentration effect. The permeability coefficients of these elements were determined. Solvent extraction of the elements by EHEHPA-decalin was also carried out for comparison.