EXTRACTION OF TERVALENT LANTHANIDES AS HYDROXIDE COMPLEXES WITH TRI-NORMAL-OCTYLPHOSPHINE OXIDE

The extraction behavior of lanthamim(III), prase odymium-(III), europlum(III), terblum(III), holmlum(III), and yt-terblum(III) from dilute chloride solutions Into chloroform solutions containing tri-n-octylphosphlne oxide (TOPO) was examined. The lanthanldes were found to extract as hydroxide complexes of the form Ln(OH)3-nTOPO. The extraction selectivity for this system increases with increasing TOPO concentration, rivaling those for common acidic organophosphorus extractants in the TOPO concentration range 0.025-0.100 M and surpassing them at higher concentrations. When TOPO concentrations of 0.25 M or greater are employed, the extraction system Is, overall, the most selective for lanthanlde separations to date. This is the first report of the lanthanldes extracting as hydroxide complexes. © 1990, American Chemical Society. All rights reserved.