MULTITRACER STUDY ON PERMEATION OF RARE-EARTH ELEMENTS THROUGH A SUPPORTED LIQUID MEMBRANE

Separation by means of supported liquid membranes is a useful method f or the preparation and preconcentration of radioactive nuclides. The p ermeation of rare earth elements through a bis(2-ethylhexyl) hydrogen phosphate-decalin membrane supported on a microporous polytetrafluoroe thylene sheet was studied using a multitracer containing radioactive n uclides of Sc, Zr, Nb, Hf, Ce, Pm, Gd, Yb, and Lu. Permeation rates of these elements from feed solutions of Various acidity to receiving so lutions of 0.5 mol.dm(-3) HCl were determined simultaneously. The feed solution at pH 1.4 gave the highest permeation rate for Ce, Pm, and G d, amounting to about 95% of permeation for Ce and Pm, 80% for Gd, and 10% for Yb in 21 h. Scandium, Zr, Nb, Hf, and Lu were not transported at all from the feed solution. Permeation rates of Yb and Lu from the feed solution at pH 1.4 to receiving solutions of 0.75, 1.0, 2.3, and 4.0 mol.dm(-3) HCl increased with the concentration. The results obta ined indicate that the light rare earth elements can be separated from the heavy ones by this method.