Aggregation of the neodymun complexes of HDEHP, Cyanex 272, Cyanex 302, andCyanex 301 in toluene

摘要

Visible absorption spectroscopy and small-angle neutron scattering have been usedto study the morphology and aggregation of a series of purified acidic organophosphorus extractants with oxygen and sulfur donor atoms and the Nd(III) complexes of these extractants in toluene solutions. The extractants bis(2-ethylhexyl)phosporic acid (HDEHP), bis(2,2,4-trimethyl pentyl)phosphinic acid (HC272), bis(2,4,4-trimethylpentyl) monothiophosphinic acid (HC302), and Bis(2,4,4-trimethylpentyl) dithiophosphinic acid (HC301) were studied. The phosphinic acid based extractants are the primary constituents of the commercial extractants Cyanex 272, Cyanex 302, and Cyanex 301 respectively. Small-angle neutron scattering experiments show that although 0.10 M solutions of the oxygen containing extractants HDEHP andHC302 are dimeric in toluene, HC301, which contains only sulfur donor atoms, is monomeric within the uncertainty of the experiment. When high concentrations of Nd (greater than 30% theoretical Nd capacity) are extracted into the organic phases, the oxygen containing extractants, HDEHP, HC272, and HC302 all form dinuclear complexes with a 2:6 metal:extractant ratio. The sulfur bearing extractant HC301, on the other hand, forms only 1:3 meal:extractant complexes when the Nd loadingis less than 50% of the theoretical capacity of the solution. However, at higher Nd loading, 86% of the theoretical capacity, 2:6 Nd:C301 complexes are formed.