Clotilde Gaillard
University of Lyon
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Publication
Featured researches published by Clotilde Gaillard.
Analytical and Bioanalytical Chemistry | 2011
Isabelle Billard; Ali Ouadi; Clotilde Gaillard
Liquid–liquid extraction of actinides and lanthanides by use of ionic liquids is reviewed, considering, first, phenomenological aspects, then looking more deeply at the various mechanisms. Future trends in this developing field are presented.
Green Chemistry | 2007
Ali Ouadi; Olga Klimchuk; Clotilde Gaillard; Isabelle Billard
A novel class of hydrophobic ionic liquids based on quaternary ammonium cation and bearing phosphoryl groups was synthesized. The preliminary results of U(VI) extraction from aqueous solution into the ionic liquid are presented.
Solvent Extraction and Ion Exchange | 2011
Isabelle Billard; Ali Ouadi; Emilie Jobin; Julie Champion; Clotilde Gaillard; Sylvia Georg
Abstract The extraction of U(VI) by tributylphosphate in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), C4-mimTf2N, has been studied as a function of TBP and HNO3 initial concentrations. Extraction measurements have been completed by UV-vis spectroscopy in order to get insights into the extraction mechanism. The proposed chemical model describes the data through a fit of uranyl distribution ratios, while some other suggestions are unable to do so. In this model, uranyl extraction is proposed to proceed via cation exchange at low initial acidities ([UO2(TBP)n]2+ versus C4-mim+ and H+) and via anion exchange at high HNO3 concentrations ([(UO2(NO3)3(TBP)m]− versus Tf2N−). By contrast to the usual TBP/dodecane organic phase, the IL system does not favor the neutral species UO2(NO3)2(TBP)2, and TBP does not extract nitric acid.
Journal of Physical Chemistry B | 2010
Sylvia Georg; Isabelle Billard; Ali Ouadi; Clotilde Gaillard; Laetitia Petitjean; Michel Picquet; Vitaly Solov’ev
The complexation of UO(2)(2+) with NO(3)(-) has been investigated in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide by UV-vis spectroscopy at T = 18.5 degrees C. The complexation is evidenced through the appearance of four peaks at 425, 438, 453, and 467 nm. EXAFS data indicate that the trinitrato complex, UO(2)(NO(3))(3)(-), is dominating the speciation for a reagent ratio of [NO(3)(-)]/[UO(2)(2+)] > 3. Assuming three successive complexation steps, the conditional stability constants are calculated, the individual absorption spectra are derived, and a speciation plot is presented.
Inorganic Chemistry | 2010
Clotilde Gaillard; Alain Chaumont; Isabelle Billard; Christoph Hennig; Ali Ouadi; Sylvia Georg; Georges Wipff
By coupling EXAFS, UV-vis spectroscopy, and molecular dynamics and quantum mechanical calculations, we studied the competitive complexation of uranyl cations with nitrate and chloride ions in a water immiscible ionic liquid (IL), C(4)mimTf(2)N (C(4)mim(+): 1-butyl-3-methyl-imidazolium; Tf(2)N(-) = (CF(3)SO(2))(2)N)(-): bis(trifluoromethylsulfonyl)imide). Both nitrate and chloride are stronger ligands for uranyl than the IL Tf(2)N(-) or triflate anions and when those anions are simultaneously present, neither the limiting complex UO(2)(NO(3))(3)(-) nor UO(2)Cl(4)(2-) alone could be observed. At a U/NO(3)/Cl ratio of 1/2/2, the dominant species is likely UO(2)Cl(NO(3))(2)(-). When chloride is in excess over uranyl with different nitrate concentrations (U/NO(3)/Cl ratio of 1/2/6, 1/4/4, and 1/12/4) the solution contains a mixture of UO(2)Cl(4)(2-) and UO(2)Cl(3)(NO(3))(2-) species. Furthermore, it is shown that the experimental protocol for introducing these anions to the solution (either as uranyl counterion, as added salt, or as IL component) influences the UV-vis spectra, pointing to the formation of different kinetically equilibrated complexes in the IL.
Green Chemistry | 2005
Soufiane Mekki; Chien M. Wai; Isabelle Billard; Gilles Moutiers; Clive H. Yen; Joanna S. Wang; Ali Ouadi; Clotilde Gaillard; Peter Hesemann
Copper(II) can be extracted in supercritical CO2 from a room temperature ionic liquid using CO2-philic fluorinated β-diketonate ligands; thanks to the 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIMTf2N) ionic liquid properties, there is no need to add modifiers to the neat supercritical CO2 to reach high extraction efficiencies.
RSC Advances | 2013
Michal Sypula; Ali Ouadi; Clotilde Gaillard; Isabelle Billard
The kinetics of metal transfer in the system Eu3+/HNO3//TODGA/[C1C4im][Tf2N], where TODGA is N,N,N′,N′-tetraoctyl diglycolamide, is shown to depend on the chemical conditions (nitric acid and TODGA concentrations) and the time needed to reach equilibrium which may vary from less than 10 min to more than 4 h. At [HNO3] = 4 M, a detailed kinetic study is performed for two different concentrations of TODGA. It is shown that the time required for water and acid solubilisation in the IL phase is very short, as is the time for IL solubilisation in the aqueous phase. By contrast, the extraction of Eu(III) takes more than 100 min to be completed and depends on the TODGA concentration. On the basis of these experimental facts, a simple kinetic model is proposed which is able to account for the data.
ChemPhysChem | 2015
Clotilde Gaillard; Maria Boltoeva; Isabelle Billard; Sylvia Georg; Valérie Mazan; Ali Ouadi; Dariia Ternova; Christoph Hennig
We present new results on the liquid-liquid extraction of uranium (VI) from a nitric acid aqueous phase into a tri-n-butyl phosphate/1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (TBP/[C4 mim][Tf2 N]) phase. The individual solubilities of the ionic-liquid ions in the upper part of the biphasic system are measured over the whole acidic range and as a function of the TBP concentration. New insights into the extraction mechanism are obtained through the in situ characterization of the extracted uranyl complexes by coupling UV/Vis and extended X-ray absorption fine structure (EXAFS) spectroscopy. We propose a chemical model to explain uranium (VI) extraction that describes the data through a fit of the uranyl distribution ratio DU . In this model, at low acid concentrations uranium (VI) is extracted as the cationic complex [UO2 (TBP)2 ](2+) , by an exchange with one proton and one C4 mim(+) . At high acid concentrations, the extraction proceeds through a cationic exchange between [UO2 (NO3 )(HNO3 )(TBP)2 ](+) and one C4 mim(+) . As a consequence of this mechanism, the variation of DU as a function of TBP concentration depends on the C4 mim(+) concentration in the aqueous phase. This explains why noninteger values are often derived by analysis of DU versus [TBP] plots to determine the number of TBP molecules involved in the extraction of uranyl in an ionic-liquid phase.
Journal of Physical Chemistry B | 2012
Alain Chaumont; Olga Klimchuk; Clotilde Gaillard; Isabelle Billard; Ali Ouadi; Christoph Hennig; Georges Wipff
The complexation of perrhenate (ReO(4)(-)) anions by the uranyl (UO(2)(2+)) cation has been investigated by joint molecular dynamics simulations and spectroscopic (UV-vis, TRLFS, and EXAFS) studies in aqueous solution, acetonitrile, and three ionic liquids (ILs), namely, [Bmi][Tf(2)N], [Me(3)BuN][Tf(2)N], and [Bu(3)MeN][Tf(2)N] that are based on the same Tf(2)N(-) anion (bis(trifluoromethylsulfonyl)imide) and either Bmi(+) (1-butyl,3-methylimidazolium), Me(3)BuN(+), or Bu(3)MeN(+) cations. They show that ReO(4)(-) behaves as a weak ligand in aqueous solution and as a strong ligand in acetonitrile and in the ILs. According to MD simulations in aqueous solution, the UO(2)(ReO(4))(2) complex quickly dissociates to form UO(2)(H(2)O)(5)(2+), while in acetonitrile, a stable UO(2)(ReO(4))(5)(3-) species forms from dissociated ions. In the ILs, the UO(2)(ReO(4))(n)(2-n) complexes (n = 1 to 5) remained stable along the dynamics, and to assess their relative stabilities, we computed the free energy profiles for stepwise ReO(4)(-) complexation to uranyl. In the two studied ILs, complexation is favored, leading to the UO(2)(ReO(4))(5)(3-) species in [Bmi][Tf(2)N] and to UO(2)(ReO(4))(4)(2-) in [Bu(3)MeN][Tf(2)N]. Furthermore, in both acetonitrile and [Bmi][Tf(2)N] solutions, MD and PMF simulations support the formation of dimeric uranyl complexes [UO(2)(ReO(4))(4)](2)(4-) with two bridging ReO(4)(-) ligands. The simulation results are qualitatively consistent with spectroscopic observations in the different solvents, without firmly concluding, however, on the precise composition and structure of the complexes in the solutions.
Inorganic Chemistry | 2016
Andrea Melchior; Clotilde Gaillard; Sara Gràcia Lanas; Marilena Tolazzi; Isabelle Billard; Sylvia Georg; Lola Sarrasin; Maria Boltoeva
The complex formation of nitrate ions with nickel(II) in dry [C4mim][Tf2N] ionic liquid (IL) was investigated by means of UV-visible spectrophotometry, isothermal titration calorimetry (ITC), extended X-ray absorption fine structure spectroscopy (EXAFS), and molecular dynamics (MD) simulations. EXAFS spectroscopy and MD simulations show that the solvated Ni(II) cation is initially coordinated by the oxygens of the [Tf2N](-) anion of IL, which can behave either as mono- or bidentate. Spectroscopic and thermodynamic data show that Ni(II) is able to form up to three stable mononuclear complexes with nitrate in this solvent. The stability constants for Ni(NO3)j complexes (j = 1-3) calculated from spectrophotometry and ITC experiments decrease in the order log K1 > log K2 > log K3. The formation of the first two species is enthalpy-driven, while the third species is entropy-stabilized. The UV-vis spectra of solutions containing different nitrate/Ni(II) ratios show that the metal ion retains the six-coordinate geometry. Furthermore, the EXAFS evidences that nitrate is always bidentate. Molecular dynamics simulations show that the [Tf2N](-) anions bind Ni(II) through the sulfonyl oxygen atoms and can coordinate either as monodentate or chelate. The analysis of the MD data shows that introduction of nitrates in the first coordination sphere of the metal ion results in remarkable structural rearrangement of the ionic liquid.