EXTRACTION OF SCANDIUM, RARE-EARTH ELEMENTS, ANDYTTRIUM FROM NITRIC ACID SOLUTIONS BY SELECTED DIPHOSPHINE DIOXIDES

The extraction of microquantities of Sc, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y from HN03 solutions by selected diphosphine dioxides of various structures in dichlorethane has been studied. It has been found that the met in a 22-stage bank of 25-cm centrifugal contactors at 25°C with conservative assumptions regarding hydrodynamics and stage efficiency. Exploiting the temperature dependence of extraction and stripping could reduce the number of stages to 18. extraction of these elements decreases with an increase in the number of methylene units (n) in the molecule of dioxide Ph2P(0)(CH2)nP(O)Ph2. Extractability of rare-earth elements decreases from La to Lu when methylene dioxide is used. With ethylene dioxides, it changes in the reverse order. The effect of HNO3 concentration in the aqueous phase and that of the extractants in the organic phase on the extraction of Sc, rare earth elements, and Y are considered. The stoichiometry of the extracted complexes has been determined and the extraction constants calculated. met in a 22-stage bank of 25-cm centrifugal contactors at 25°C with conservative assumptions regarding hydrodynamics and stage efficiency. Exploiting the temperature dependence of extraction and stripping could reduce the number of stages to 18.