Rc. Gatrone et al., THE EFFECT OF STERIC HINDRANCE OF THE AMIDIC SUBSTITUENTS OF THE CARBAMOYLMETHYLPHOSPHINE OXIDES ON 3RD PHASE FORMATION, Solvent extraction and ion exchange, 11(3), 1993, pp. 411-422
Increasing the steric hindrance of the substituents on the amidic nitr
ogen of the carbamoylmethylphosphine oxide class of extractants leads
to a significant decrease in the tendency of these compounds to form a
third phase during the extraction of nitric acid. An increase in ster
ic hindrance leads to a reduction in the accessibility of the nitrogen
and in the dipole-dipole and dipole-induced-dipole attractions betwee
n extractant molecules, thereby reducing the tendency to form a third
phase. A corresponding increase in the amount of uranium that could be
extracted without third phase formation was not observed due to a red
uction in the interaction of the extractant with the diluent because o
f coordination with the metal ion by both polar groups.