Y. Nagaosa et Y. Binghua, SOLVENT-EXTRACTION OF RARE-EARTH-METALS WITH BIS(2-ETHYLHEXYL)PHOSPHINIC ACID, Fresenius' journal of analytical chemistry, 357(6), 1997, pp. 635-641
The extraction behavior of tervalent rare-earth metals (Ln) using a he
ptane solution containing bis(2-ethylhexyl)phosphinic acid (PIA-8, HR)
from 0.1 mol/dm(3) sodium perchlorate media was studied. The pH(0.5)
values and separation factors obtained were compared among the metals.
The stoichiometry of the extracted species and the extraction constan
ts for the present aqueous/heptane system were determined by slope ana
lysis. It is demonstrated that the rare-earth metals were extracted as
monomers LnR(3).mHR (m = 3, 4, 5 or 6), and the extracted species cou
ld be stripped into a relatively low concentrated hydrochloric acid. P
IA-8 was found to be the most selective extractant for the mutual sepa
ration of rare-earth metals among the other phosphinic acids reported.