Cyanex 923 as an extractant for trivalent lanthanides and yttrium

Abstract

The extraction of yttrium and some trivalent lanthanides from thiocyanate and nitrate solutions using Cyanex 923 (TRPO) in xylene as an extractant has been investigated. It has been found that these trivalent metal ions are extracted from thiocyanate solution as M(SCN)3.n TRPO; n in general having the values of 4 and 3 for the lighter and the heavier lanthanides respectively. On the other hand, from nitrate solutions these trivalent metal ions are extracted as M(N03)3' 3 TRPO. The equilibrium constants of the extracted complexes have been obtained by non-linear regression analysis. In both the thiocyanate and nitrate systems, the distribution ratios of trivalent lanthanides are found to increase with decreasing ionic radii and the distribution ratio of yttrium lies along with those of the middle lanthanides. The separation factors between these trivalent metal ions were evaluated and compared with those obtained using commercially important extraction reagents like tributylphosphate(TBP), trioctylphosphine oxide (TOPO) and di-2-ethylhexylphosphoric acid(DEHPA). The separation possibilities between yttrium and the trivalent lanthanides have also been discussed