POLYMERIZATION AND ADDUCT FORMATION OF SOME LANTHANIDE(III) DECANOATES IN THE EXTRACTION OF LANTHANIDES(III) WITH DECANOIC ACID USING 1-OCTANOL AND BENZENE AS A SOLVENT

The solvent extraction of lanthanum(III), cerium(III), neodymium(III), samarium(III), gadolinium(III), dysprosium(III), erbium(III) and ytte rbium(III) with decanoic acid in 1-octanol and benzene was carried out at 25 degrees C and at an aqueous ionic strength of 0.1 mol dm(-3) (N aNO3). In extraction systems using 1-octanol as a solvent, all of the lanthanides were found to be extracted as two kinds of monomeric decan oates; in those using benzene, the monomeric, dimeric and tetrameric l anthanide(III) decanoates were proven to be responsible for the extrac tion. except for gadolinium(III), whose extracted species were the mon omeric and dimeric species. The dimerization, tetramerization and addu ct formation constants of lanthanide(III) decanoates in the organic ph ase were estimated. A so-called ''gadolinium break'' was observed for the polymerization constants of lanthanide(III) decanoates.