Maria Atanassova

Effect of the diluents on the synergistic solvent extraction of some lanthanides with thenoyltrifluoroacetone and quaternary ammonium salt

Abstract The solvent extraction of La, Nd, Eu, Ho and Lu with thenoyltrifluoroacetone (HTTA) and the quaternary ammonium salt Aliquat 336 in chloride (QCl) or perchlorate (QClO 4 ) form in CHCl 3 , C 6 H 6 , CCl 4 and C 6 H 12 has been studied. On the basis of the slope analysis data, the composition of the extracted species was determined as Q + [Ln(TTA) 4 ] − (Q + is the quaternary ammonium salt cation). The values of the equilibrium constant and the separation factors were calculated. The effect of the diluents on the metal extraction and separation has been discussed.

Synergism as a phenomenon in solvent extraction of 4f-elements with calixarenes

The main objective of the present review is to provide an overview on the synergistic solvent extraction of lanthanoids, in particularly on the use of β-diketone/calixarene i.e. acidic/neutral mixture, as well as the analysis of data hitherto reported in this scientific topic. Based on the previously presented results, the extraction efficiency has been careful examined and discussed mainly in terms of the corresponding equilibrium constants among other outlined extraction parameters. Furthermore, the evaluation of the chelating ligand structures and pKa values are emphasized. Major conclusions on the role of calixarenes ligating groups towards the mechanism, the improved extraction enhancement and selectivity are additionally provided. Consequently, it is very important that the obtained remarkable architecture of the formed complexes with very high coordination numbers (10/12) including a few cyclic molecules is in accordance with the well-established principles of coordination 4f-ion chemistry. Finally, a critical analysis of the lanthanoid intra-group selectivity (light/middle, heavy/middle and light/heavy 4f-ion pairs) versus the extraction performance of the acidic/neutral combinations and, on the other hand, the nature of the water-immiscible molecular or ionic diluent used have also been carried out and are here presented and critically addressed.

Are fancy acidic or neutral ligands really needed for synergism in ionic liquids? A comparative study of lanthanoid extraction in CHCl3 and an ionic liquid

The study of trivalent lanthanoid (La, Nd, Eu, Ho and Lu) extraction by two individual ligands, one acidic such as a pyrazolone derivative, 3-methyl-1-phenyl-4-(4-phenylbenzoyl)-pyrazol-5-one (HL), and one neutral such as 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis-(dimethylphosphinoylmethoxy)calix[4]arene (SIV), was performed in CHCl3 and in one ionic liquid, IL 1-methyl-1,3-butylimidazolium-bis(trifluoromethanesulfonyl)imide ([C1C4im][Tf2N]), in order to establish and examine the impact of the diluent on individual and synergistic extraction processes. Chloride aqueous medium and constant ionic strength μ = 0.1 M were set in both cases. The parameters of the extraction processes were determined. Comparison between the two diluents was made on the basis of (i) composition of the extracted species: LnL3·HL in CHCl3vs. LnL3 in IL with HL as a single extractant (L− represents the HL anion), and LnL3·SIV in the presence of the phosphorus-containing calix[4]arene in both diluents; and (ii) values of the equilibrium constants and the synergistic enhancements; the separation factors between metals were evaluated as well. The IL medium appears far superior to the molecular solvent in terms of individual and overall synergistic extraction efficiencies. However, the huge differences in extraction efficiencies observed in CHCl3 for chemically different ligands are erased in the IL medium, thus modifying the lever arms on which chemists should rely in order to obtain even better extracting systems in ionic liquid media.

Solvent extraction and separation of light lanthanoids with mixtures of two chelating extractants: Benzene vs. ionic liquid

ABSTRACT Solvent extraction of lanthanoids (La-Gd) with mixtures of a chelating extractants (HL), either 4-(4-fluorobenzoyl)-3-methyl-1-phenyl-pyrazol-5-one(HPMFBP) or 3-methyl-4-(4-methylbenzoyl)-1-phenyl-pyrazol-5-one (HPMMBP) and 1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedione (thenoyltrifluoroacetone, HTTA) has been studied in benzene. The composition of the extracted species was established as LnL3·HL with the two para-substituted 4-aroyl-3-methyl-1-phenyl-pyrazol-5-ones. It was found that, in the presence of a thenoyltrifluoroacetone, the lanthanoids were extracted as LnL3·HTTA. The separation factors between adjacent metals were evaluated. The extraction of Eu(III) ions was investigated by use of ionic liquid, 1-methyl-1,3-butylimidazolium-bis(trifluoromethanesulfonyl)imide instead of benzene in order to make comparison without looking at the mechanism aspects.

Coordination chemistry of a para-tert-octylcalix[4]arene fitted with phosphinoyl pendant arms towards 4f-elements: Extraction, synergism, separation

Abstract The solvent extraction of trivalent lanthanoids (Ln3+) by 5,11,17,23-tetra(para-tert-octyl)-25,26,27,28-tetrakis(dimethylphosphinoylmethoxy)calix[4]arene (S), bearing four phosphine oxide donor groups at the lower rim as synergistic agent in combination with a 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP) in CHCl3 from chloride medium at µ = 0.1 was quantitatively described in the form of LnP3·S complexes. The role of the synergistic agent on the extraction process was discussed. The values of the separation factors have been evaluated. On the basis of the IR and NMR spectra the stoichiometry and the structure of the solid mixed complex of Eu(III) with HP and S were proposed.