STERIC EFFECTS IN THE SYNERGIC EXTRACTION OF THE LANTHANIDES, YTTRIUM, AND SCANDIUM

Abstract

From a study of the partitioning of the carrier-free radioisotopes Tm170, Ce144, Eu152/154, Tb160, Lu177, and Y91 between nitric acid and organic solutions containing various proportions of thenoyltrifluoroacetone (HTTA) and dialkyl alkyl phosphonates (S) in odorless kerosene, concentration equilibrium constants (k2) have been computed for the reaction[Formula: see text]where M represents a metal ion, and "w" and "o" are aqueous and organic species respectively.When used in conjunction with the data of Bronaugh and Suttle, the equilibrium constants determined in this study yielded comparative equilibrium constants (k3) for the solvation process [Formula: see text]for the rare-earth metals listed.In the extraction of Sc46, however, the species extracted is dependent on the alkyl groups of the phosphonates, the butyl and 2-ethylhexyl derivatives giving mono- and di-solvates respectively.It is concluded that steric effects are dominant in these synergic systems.