SOLVENT-EXTRACTION OF NEODYMIUM(III) AND ERBIUM(III) FROM CHLORIDE MEDIA BY MIXTURES OF 3,5-DIISOPROPYLSALICYLIC ACID AND NEUTRAL ORGANOPHOSPHORUS COMPOUNDS

Neutral organophosphorus compounds containing a phosphoryl donor group were found to cause synergistic shifts in the extraction of neodymium (III) and erbium(III) from chloride media by solutions of 3,5-diisopro pylsalicylic acid in xylene. With the series of compounds containing n -butyl substituent groups (R), the extent of the synergistic effect fo r both metals follows the order of increasing basicity caused by the p rogressive replacement of alkoxy groups by alkyl groups through the se ries: (RO)(3)PO < (RO)(2)RPO < (RO)R(2)PO < R(3)PO. For the series of compounds with R = isobutyl, irregularities occur in this order, presu mably because of steric effects. Both steric and electro-inductive eff ects appear to play a role in determining the extent of the synergisti c shifts caused by the series of isomeric phosphonates, (n-C4K9O)(2)RP O, where R = n-butyl, isobutyl, sec-butyl and tert-butyl. Treatment of distribution data by slope analysis and by the method of continuous v ariation suggests that the extracted neodymium and erbium complexes ha ve the composition NdA(3)L(2) and ErA(3)L(2), where HA = 3,5-diisoprop ylsalicylic acid and L = neutral organophosphorus compound.