R. Luxmi Varma

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(NO3)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), trio...

Synergistic Solvent Extraction of Trivalent Lanthanoids with Mixtures of 1‐Phenyl‐3‐methyl‐4‐pivaloyl‐5‐pyrazolone and Crown Ethers

Abstract This paper embodies the results of the investigations carried out on the extraction behavior of lanthanoids such as Nd(III), Eu(III), and Tm(III) from perchlorate solutions into chloroform with 1‐phenyl‐3‐methyl‐4‐pivaloyl‐5‐pyrazolone (HPMPP) in the presence and absence of various crown ethers (CE), 18‐crown‐6 (18C6), dicyclohexano‐18‐crown‐6 (DC18C6), and dibenzo‐18‐crown‐6 (DB18C6). The results demonstrate that these trivalent metal ions are extracted into chloroform as Ln(PMPP)3, with HPMPP alone, and in the presence of CE as Ln(PMPP)3·CE. The equilibrium constants of the extracted complexes have been determined by nonlinear regression analysis and are found to increase monotonically with decreasing ionic radii of these metal ions. The addition of a CE to the metal chelate system not only enhances the extraction efficiency but also improves the selectivities among these trivalent lanthanoids, especially in the presence of DB18C6.

Mixed-ligand chelate extraction of trivalent lanthanides with 4,4,4-trifluoro-1-phenyl-1,3-butanedione and neutral oxo-donors

Mixed-ligand chelate extraction of trivalent lanthanides such as Nd(III), Eu(III) and Lu(III) into benzene with mixtures of 4,4,4-trifluoro-1-phenyl-1,3-butanedione (HBFA) and bis-2-ethylhexyl sulphoxide (B2EHSO) or triphenylphosphine oxide (TPhPO) from thiocyanate solutions was investigated. The results demonstrate that these metal ions are extracted as Ln(BFA)(3) with HBFA alone and in the presence of a neutral oxo-donor, B2EHSO or TPhPO(S), as Ln(BFA)(3).S and Ln(BFA)(3).2S. The equilibrium constants of the above species increase monotonically with decreasing ionic radii of these metals ions. The addition of a neutral donor to the metal chelate system not only enhances the extraction efficiency but also improves the selectivity among these trivalent lanthanides. Hence this mixed-ligand system may be useful for the extraction and separation of individual lanthanides and also for the separation of lanthanides as a group from other metal ions.