Browsing by Author "Billard I."
Now showing 1 - 6 of 6
Results Per Page
Sort Options
Item 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(2015-07-27) Atanassova M.; Kurteva V.; Lubenov L.; Varbanov S.; Billard I.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.Item Comparing extraction, synergism and separation of lanthanoids using acidic and neutral compounds in chloroform and one ionic liquid: Is the latter always ``better``?(2014-01-01) Atanassova M.; Kurteva V.; Lubenov L.; Billard I.The complexation properties of a pyrazolone derivative, 3-methyl-1-phenyl-4-(4-trifluoromethylbenzoyl)-pyrazol-5-one (HL), in chloroform were examined and it was found that it possesses improved complexation ability in comparison with 4-benzoyl, 4-(4-methylbenzoyl) and 4-(4-fluorobenzoyl) derivatives. Mixed ligand chelate extractions of trivalent lanthanoids (La, Nd, Eu, Ho and Lu) with HL and 5,11,17,23-tetra-tert-butyl-25,26,27- tris(dimethylphosphinoylpropoxy)-28-hydroxy-calix[4]arene (S1) or 5,11,17,23-tetra-tert-butyl-25,27-bis(dimethylphosphinoylpropoxy)-26, 28-dihydroxy-calix[4]arene (S2) as synergistic agents were also carried out in chloride medium at constant ionic strength μ = 0.1 and CHCl3 as organic phase. The interactions between the extractants in deuterochloroform were studied by 1H, 13C, and 31P NMR. The composition of the extracted species was established as LnL3· HL (L- represents HL anion) with HL as a single extractant, and as LnL3·S in the presence of the phosphorus-containing calix[4]arene. On the basis of the experimental data, the values of the equilibrium constants were calculated. The influence of the number of PO groups of tert-butyl-calix[4]arene on the extraction process was discussed. The synergistic enhancement and separation factors between metals were evaluated. Finally, the extraction of La(iii) and Eu(iii) ions was performed by using an ionic liquid, 1-butyl-3-methylimidazolium-bis(trifluoromethanesulfonyl)imide, as a solvent and varying the type of ligands. By comparison to CHCl3, the ionic liquid offers increased distribution ratios, at the expense of a levelling off of the separation factors. Reasons for such a phenomenon are discussed. © the Partner Organisations 2014.Item Coordination chemistry of europium(III) ion towards acylpyrazolone ligands(2015-01-01) Atanassova M.; Kurteva V.; Billard I.Two Eu(III) complexes were synthesized using 4-acylpyrazolone ligands: 3-methyl-4-(4-methylbenzoyl)-1-phenylpyrazol-5-one (HPMMBP) and 3-methyl-1-phenyl-4-(4-phenylbenzoyl)-pyrazol-5-one (HPPMBP). The composition of the obtained solid complexes was determined as Eu(PMMBP) 3 .C 2 H 5 OH and Eu(PPMBP) 3 .3H 2 O based on elemental analysis and was further studied by IR, NMR and TG-TSC data. The lanthanoid complexation in solid state and in solution during liquid-liquid extraction (molecular diluent and ionic liquid) is discussed. 2015Item Determination of pK aIL values of three chelating extractants in ILs: Consequences for the extraction of 4f elements(2015-04-01) Atanassova M.; Billard I.Abstract Aqueous-ionic liquid biphasic systems have been examined in terms of water and acid solubilities in the IL-rich phase at ambient temperature. The biphasic mixtures were comprised of acids of various concentrations (H+; Cl-, H+; NO3-, H+; ClO4-, mainly from 1 × 10-2 to 1 × 10-4 mol·dm-3) and four ionic liquids of the imidazolium family [C1C n im][Tf2N] (n = 4, 6, 8 and 10). The effects of ionic medium (μ = 0.1 mol·dm-3, by use of Na+; Cl-, Na+; NO3- or Na+; ClO4-, according to the acid investigated), the nature of the IL cation as well as the nature of the acid on the mutual solubilities of (H2O, H+, [C1C n im]+ and [Tf2N]-) entities were determined. Then, three chelating compounds (HL), which belong to the β-diketone family (thenoyltrifluoroacetone (HTTA), 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one (HP) and 4-benzoyl-3-phenyl-5-isoxazolone (HPBI)), were added to [C1C4im][Tf2N] and subsequent determination of the H+ distribution between the two phases allowed the determination of their dissociation constants (pK aIL) in the water-saturated ionic liquid phase. A very strong effect of the IL cation on the HTTA pK aIL value was observed from n = 4 to n = 10. The influence of this phenomenon on the lanthanide extraction process is discussed.Item Modulating the solubilities of ionic liquid components in aqueous-ionic liquid biphasic systems: A Q-NMR investigation(2015-06-01) Atanassova M.; Mazan V.; Billard I.Abstract Aqueous-ionic liquid (A-IL) biphasic systems have been examined in terms of deuterated water, acid, and IL cation and anion mutual solubilities in the upper (water-rich, in mole fraction) and lower phase of aqueous/IL biphasic systems at ambient temperature. The biphasic mixtures were composed of deuterated acids of various concentrations (mainly DCl, DNO3, and DClO4 from 10-2 to 10-4 M) and five ionic liquids of the imidazolium family with a hydrophobic anion (CF3SO2)2N-, that is, [C1Cnim][Tf2N], (n=2, 4, 6, 8 and 10). The analytical techniques applied were 1H NMR, 19F NMR, Karl-Fischer titration, pH potentiometry for IL cations and anions, and water and acid determination. The effects of the ionic strength (μ=0.1 M NaCl and NaNO3 as well as μ=0.1 M, 0.2 M and 0.4 M NaClO4, according to the investigated acid), the nature of the IL cation, and the nature of the mineral acid on the solubilities of the (D2O, D+, Tf2N-, C1Cnim+) entities in the lower or upper phases were determined. The addition of sodium perchlorate was found to enhance the Tf2N- solubility while inhibiting the solubility of the ionic liquid cation. Differences in IL cation and anion solubilities of up to 42 mM were evidenced. The consequences for the characterization of the aqueous biphasic system, the solvent extraction process of the metal ions, and the ecological impact of the ILs are discussed. The addition of sodium perchlorate enhances the solubility of ionic liquid (IL) anions while decreasing the solubility of the cations in a slightly acidic aqueous phase.Item NMR Study on the Possible Interactions between Imidazolium Based Ionic Liquids and Extractants Widely Applied in Solvent Extraction and Separation of f-Ions(2015-12-01) Kurteva V.; Atanassova M.; Billard I.A detailed NMR study on the possible interactions between a series of imidazolium based ionic liquids (1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) amide, RmimTf2N, n = 4, 6, 8, 10), and compounds commonly applied in the solvent extraction and separation of 4f and 5f-ions as acidic chelating agents and neutral extractants is presented. The analytical techniques applied are 1H, 13C, 19F and 31P NMR spectra and NOESY experiments. Investigation of the types and strengths of the solvent-solute interactions is necessary for a better understanding of the chemical solubility, reactivity and selectivity, as ILs have a strong influence on the solvent extraction mechanism of metal ions. The goal of the scientific research is to gain insight on the role of ILs as a perspective efficient ``green`` medium in the solvent extraction processes. The experimental results show that no IL-ligand interactions occurred in chloroform solution independently on the length of the imidazolium alkyl chain or on the structure and acidity of the ligand.