Extraction of rare earths and scandium by 2-phosphorylphenoxyacetic acid amides in the presence of ionic liquids

The distribution of Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc between aqueous solutions of their salts and solutions of 2-phosphorylphenoxy acid amides in dichloroethane containing an ionic liquid (1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide) have been studied. Metal ion extraction has been found to increase considerably in the presence of this ionic liquid in the organic phase. The stoichiometries of extractable complexes have been determined. The influence of aqueous HNO₃ concentration and of the nature of extractant and ionic liquid on the efficiency of REE(III) and scandium(III) recovery to the organic phase has been considered.     

Effect of anionic structure on the phase formation and hydrophobicity of amino acid ionic liquids aqueous two-phase systems

Compared with the conventional ionic liquids, amino acid ionic liquids are more biodegradable and biocompatible, and can enhance stability of biomaterials. In this work, amino acid ionic liquids 1-butyl-3-methylimidazolium L-serine ([C(4)mim][Ser]), 1-butyl-3-methylimidazolium glycine ([C(4)mim][Gly]), 1-butyl-3-methylimidazolium L-alanine ([C(4)mim][Ala]) and 1-butyl-3-methylimidazolium L-leucine ([C(4)mim][Leu]) have been synthesized. These ionic liquids are found to form aqueous two-phase systems (ATPSs) by the salted-out of K(3)PO(4) in aqueous solutions. Phase diagram of the ATPSs and the Gibbs energies of transfer of methylene group from the bottom salt-rich phase to the top ionic liquid-rich phase have been determined at 298.15K and pH 14, and the effect of anionic structure of the ionic liquids on phase formation of the ATPSs and the relative hydrophobicity between the top and the bottom phases are then examined. In order to understand the effect of relative hydrophobicity of the phases in equilibrium in the ATPSs on the extraction/separation capability of biomolecules, the partition coefficients of cytochrome-c (as a model biomolecule) in the ATPSs are measured by spectrophotometry. It is suggested that hydrophobic interactions are mainly responsible for the higher partition coefficients of cytochrome-c in aqueous two-phase systems at pH 14, and the extraction and separation capacity of biomolecules can be improved by the modulation of the relative hydrophobicity of the phases and/or the pH of the system.     

Effect of ionic liquids on the extraction of rare-earth elements by bidentate neutral organophosphorus compounds from chloride solutions

The partition of microamounts of lanthanide chlorides (Ln = La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y) between aqueous HCl and organic solutions of tetraphenylmethylenediphosphine dioxide, diphenyl(diethylcarbamoylmethyl)phosphine oxide, and dibutyl(diethylcarbamoylmethyl)phosphine oxide was studied in the presence of ionic liquids (ILs): 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The stoichiometry of extracted complexes was determined. The effect of the aqueous HCl concentration, the nature of the extractant, and the organic diluent on the efficiency of lanthanide extraction was studied.     

Efficient precipitation of dyes from dilute aqueous solutions of ionic liquids.

The addition of only approximately 1.7 wt% (approximately 0.06 M) ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate to aqueous solutions of six popular cationic dyes resulted in the precipitation of almost all of the dye from the solution.     

Solvation of 1-butyl-3-methylimidazolium hexafluorophosphate in aqueous ethanol--a green solution for dissolving 'hydrophobic' ionic liquids

The relatively hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate has been found to be totally miscible with aqueous ethanol between 0.5 and 0.9 mol fraction ethanol, whereas the ionic liquid is only partially miscible with either pure water or absolute ethanol; the ability to dissolve 1-butyl-3-methylimidazolium hexafluorophosphate in a 'green' aqueous solvent system has important implications for cleaning, purification, and separations using ionic liquids.     

Extraction of Cu<Superscript>2+</Superscript> from aqueous solutions using microcapsules containing ionic liquid [BMIM]PF<Subscript>6</Subscript>

Polysulfone (PSF) microcapsules filled with ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] were successfully prepared via solvent evaporation method. The encapsulation capacity of 38.0% was achieved. Microcapsules showed a spherical, porous honeycomb structure. The size of microcapsules was approximately 110 μm and the thickness was approximately 10 μm. Microcapsules have excellent thermal stability, with a higher thermal degradation onset temperature of 360°C compared to traditional extractant-loaded microcapsules. Microcapsules were used to extract Cu²⁺ from aqueous solutions. The effect of chelator, pH, PSF, and ionic liquid on the extraction rate were studied. When chelator was added in aqueous solutions, and the pH of aqueous solutions was 4.5, the extraction rate of microcapsules reached the maximum value, which was 99.0%. These PSF microcapsules containing [BMIM][PF₆] showed potential ability in the treatment of wastewater.     

Experiments and model for the surface tension of (MDEA + [Bmim][BF4]) and (MDEA + [Bmim][Br]) aqueous solutions

The surface tension (γ) of 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF₄]), 1-butyl-3-methylimidazolium bromide ([Bmim][Br]), (N-methyldiethanolamine(MDEA) + [Bmim][BF₄]) and (MDEA + [Bmim][Br]) aqueous solutions were measured by using the BZY-1 surface tension meter. The temperature ranged from (293.2 to 323.2) K. The mass fraction of MDEA ranged from 0.35 to 0.45. A thermodynamic equation was proposed to model the surface tension of (MDEA + ionic liquids) (ILS) aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fractions of MDEA and ILS on the surface tension were demonstrated on the basis of experiments and calculations.     

Quantitative High Performance Liquid Chromatography Determination of Alkanolamines in Ionic Liquid Absorbents

The development of modern absorption media suitable for CO₂ scrubbing, such as ionic liquids and their mixtures, requires appropriate analytical protocols. In this paper, the application of high-performance liquid chromatography to the determination of alkanolamine at various concentrations in ionic liquid solutions was investigated. Both hydrophilic and hydrophobic commercial ionic liquids, such as 1-butyl-3-methylimidazolium acetate [bmim][OAc], 1-ethyl-3-methylimidazolium octylsulfate [emim][OcSO₄], and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [bmim][NTf₂], were studied in this paper and different sample preparation procedures were used for each class of solvent. A simple extraction step was necessary prior to HPLC analysis for hydrophobic ionic liquids. This step was performed using five times more 0.05 M KH₂PO₄ than needed for the ionic liquid sample. Hydrophilic ionic liquid solutions could be analyzed after diluting the sample with water. The general procedure involved separation at room temperature using a cation-exchange HPLC with 0.05 M KH₂PO₄ as the mobile phase and refractometric detection without derivatizing the amines. The influence of the temperature and mobile phase composition on alkanolamine retention was investigated. The relationship between the peak area and alkanolamine concentration was linear over 3 orders of magnitude (2–200 nmol). The detection limit (LOD) for monoethanolamine (MEA) and diethanolamine (DEA) was 1.5 and 2 nmol, respectively. For hydrophobic ionic liquids, which require extraction, it was possible to analyze a 0.004% MEA solution. The quantity of the sample required for analysis was 0.1 g, and the analysis time did not exceed 20 minutes.     

(Vapor + liquid) equilibria of binary mixtures containing light alcohols and ionic liquids

This work presents (vapor + liquid) equilibrium (VLE) of binary mixtures containing methanol or ethanol and three imidazolium based ionic liquids: 1-butyl-3-methylimidazolium tetrafluoroborate, 1-butyl-3-methylimidazolium acetate, and 1-butyl-3-methylimidazolium hydrogen sulfate. VLE measurements were carried out over the whole range of composition between (283.15 and 298.15) K using a static apparatus. Activity coefficients γ_i of these solvents in the ionic liquids have been determined from the VLE data and correlated using the NRTL model. The results show that the NRTL model can be applied successfully with systems containing ionic liquids.     

The thermochemistry of solvation of imidazolium-based ionic liquids in benzene

ABSTRACT

The present work is devoted to the thermochemical study of solvation of ionic liquids (IL) in benzene. The solution enthalpies of 1-ethyl-3-methylimidazolium tricyanomethanide [EMIM][C(CN)₃], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF₆], 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF₄], 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf₂] and 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO] in benzene were measured. The solvation enthalpies of imidazolium-based IL were calculated. Molar refractions of imidazolium-based IL form literature data on density and refractive indexes of IL were also calculated. The linear correlation between solvation enthalpy and molar refraction of IL was observed. This correlation can be used to calculate the vaporization enthalpy of imidazolium-based IL from solution calorimetry data.     

A new diastereoselective intramolecular electroreductive coupling of unsaturated β-ketoesters and β-ketoamides in ionic liquids at a tin cathode

The diastereoselective intramolecular electroreductive coupling of several β-ketoesters and β-ketoamides has been accomplished at a tin cathode in ionic liquids and isopropanol (9:1). The ionic liquids used are 1-butyl-3-methylimidazolium bromide [BMIM]Br, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM]BF₄, 1-methoxyethyl-3-methylimidazolium trifluoroacetate [MOEMIM]CF₃COO and 1-methoxyethyl-3-methylimidazolium mesylate [MOEMIM]Ms. This methodology offers a clean and green process for the synthesis of functionalized carbocycles in good yields with excellent stereochemical control at three stereogenic centres.     

[Bmim]PF6 and BF4 ionic liquids as novel and recyclable reaction media for aromatic amination

Activated aryl halides undergo smooth nucleophilic substitution reactions with secondary amines in 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) or 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄) ionic liquids (ILs) at room temperature to afford the corresponding arylamines in excellent yields under mild and neutral conditions.     

Imidazolium salt assisted hydrolysis of 1-chloro-2,2,2-trifluoroethane

The use of imidazolium-based ionic liquids as promoters was found to be highly effective for the hydrolysis reaction of CF₃CH₂Cl with aqueous potassium acetate to produce 2,2,2-trifluoroethanol (TFE). Among ionic liquids tested, 1-butyl-3-methylimidazolium chloride ([bmim]Cl) showed the highest yield of TFE, over 90%, which is almost two times higher than that obtained in the absence of an ionic liquid. The integrity of imidazolium salt was maintained during the reaction, which was confirmed from the recycling studies and ¹H NMR spectroscopy.     

Electrochemical behavior of nickel in electrolytes based on 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid for capacitor applications

Electrochemical studies were performed using Ni electrodes in solutions of a mixture of ethylene glycol or of γ-butyrolactone with 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid. The aim of the study was to evaluate the use of these systems in electrochemical double-layer capacitor. Cyclic voltammetry experiments showed a potential range at which the Ni electrode behaved as a polarizable electrode. Ni oxidizes at high anodic potentials. Inside the potential range without electrochemical activity, the capacitance and the solution resistance, which were evaluated by impedance electrochemical spectroscopy, were compared for the two solutions tested. Conductivity measurements of the electrolytes with different compositions were also acquired. The results of cyclic voltammetry indicated that the Ni has a wide electrochemical window and low current peak densities of oxidation in the γ-butyrolactone medium than in ethylene glycol medium. The γ-butyrolactone and 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions had the highest conductivity values. Decreased 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid content in different solvent mixtures resulted in an increase in the capacitance value at the Ni/electrolyte interface. The highest capacitance values were obtained for Ni in ethylene glycol and 1-n-butyl-3-methylimidazolium tetrafluoroborate medium.     

Ionic liquids as modulators of the critical micelle concentration of sodium dodecyl sulfate

Critical micelle concentration (CMC) of sodium dodecyl sulfate (SDS), an anionic surfactant, has been investigated in aqueous solutions of a variety of room temperature ionic liquids (RTILs): 1,3-dimethylimidazolium iodide (Me2IM-I, 2), 1-butyl-3-methylimidazolium chloride (BMIM-Cl, 3), 1-hexyl-3-methylimidazolium chloride (HxMIM-Cl, 4), 1-methyl-3-octylimidazolium chloride (MOIM-Cl), 5, and 1-methyl-3-octylimidazolium tetrafluoroborate (MOIM-BF4, 6). The CMC of SDS is shown to correlate with the nature of the alkyl groups in the RTILs; SDS showed appreciably higher CMCs in presence of ionic liquids 2 and 3, whereas in the presence of ionic liquids 4, 5, and 6 much smaller CMCs were observed. The nature of the gigenions, Cl- or BF4-, has no noticeable effect on the observed CMC values.     

[Bmim]BF4 ionic liquid: a novel reaction medium for the synthesis of β-amino alcohols

Epoxides undergo smooth ring-opening with aryl amines in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild and neutral conditions to afford the corresponding β-amino alcohols in excellent yields with high regioselectivity.     

The salting-out effect and phase separation in aqueous solutions of tri-sodium citrate and 1-butyl-3-methylimidazolium bromide

The aim of this work is to obtain further evidence about the salting-out effect produced by the addition of tri-sodium citrate to aqueous solutions of water miscible ionic liquid 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]) by evaluating the effect of tri-sodium citrate on the thermodynamic properties of aqueous solutions of this ionic liquid. Experimental measurements of density and sound velocity at different temperatures ranging from (288.15 to 308.15) K, the refractive index at 308.15 K and the liquid–liquid phase diagram at different temperatures ranging from (288.15 to 338.15) K for aqueous solutions containing 1-butyl-3-methylimidazolium bromide ([C₄mim][Br]) and tri-sodium citrate (Na₃Cit) are taken. The apparent molar volume of transfer of [C₄mim][Br] from water to aqueous solutions of Na₃Cit have positive values and it increases by increasing salt molality. Although at high IL molality, the apparent molar isentropic compressibility shows similar behaviour with that of the apparent molar volume. However at low concentrations of IL, the apparent molar isentropic compressibility of transfer of [C₄mim][Br] from water to aqueous solutions of Na₃Cit have negative values. The effects of temperature and the addition of Na₃Cit and [C₄mim][Br] on the liquid–liquid phase diagram of the investigated system have been studied. It was found that an increase in temperature caused the expansion of the one-phase region. The presence of Na₃Cit triggers a salting-out effect, leading to significant upward shifts of the liquid–liquid de-mixing temperatures of the system. The effect of temperature on the phase-forming ability in the system investigated has been studied based on a salting-out coefficient obtained from fitting the binodal values to a Setschenow-type equation for each temperature. Based on cloud point values, the energetics of the clouding process have been estimated and it was found that both of entropy and enthalpy are the driving forces for biphasic formation.     

Glycolysis of poly(ethylene terephthalate) (PET) using basic ionic liquids as catalysts

The glycolysis of poly(ethylene terephthalate) (PET) was studied using several ionic liquids and basic ionic liquids as catalysts. The basic ionic liquid, 1-butyl-3-methylimidazolium hydroxyl ([Bmim]OH), exhibits higher catalytic activity for the glycolysis of PET, compared with 1-butyl-3-methylimidazolium bicarbonate ([Bmim]HCO₃), 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) and 1-butyl-3-methylimidazolium bromide ([Bmim]Br). FT-IR, ¹H NMR and DSC were used to confirm the main product of glycolysis was bis(2-hydroxyethyl) terephthalate (BHET) monomer. The influences of experimental parameters, such as the amount of catalyst, glycolysis time, reaction temperature, and dosages of ethylene glycol on the conversion of PET, yield of BHET were investigated. The results showed a strong influence of the mixture evolution of temperature and reaction time on depolymerization of PET. Under the optimum conditions of m(PET):m(EG): 1:10, dosage of [Bmim]OH at 0.1 g (5 wt%), reaction temperature 190 °C and time 2 h, the conversion of PET and the yield of BHET were 100% and 71.2% respectively. Balance between the polymerization of BHET and depolymerization of PET could be changed when the reaction time was more than 2 h and contents of catalyst and EG were changed.     

Surface Property of Nonionic Surfactant Triton X-100 in an Ionic Liquid

A common nonionic surfactant Triton X-100 was dissolved in a commercial ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄). The surface tension of the bmimBF₄ solution was decreased with increasing the content of surfactant Triton X-100, a similar phenomenon with aqueous solution systems. Dynamic surface properties of Triton X-100 in bmimBF₄ were measured. It was found that pure IL solvents need rearrangement at the air-bmimBF₄ interface during the beginning stage of absorption. Moreover, the adsorption model was found to be in accord with the diffusion-controlled adsorption mechanism, and further, the dilute bmimBF₄ solutions are close to the diffusion-controlled adsorption.     

Measurement and modeling of osmotic coefficients of aqueous solution of ionic liquids using vapor pressure osmometry method

Osmotic coefficients of binary mixtures containing an ionic liquid, (1-butyl-3-methylimidazolium tetrafluoroborate, [BMIm]BF₄, 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIm]ES, and 1-butyl-3-methylimidazolium methyl sulfate, [BMIm]MS) with water were measured until about 3 molal concentrations using vapor pressure osmometry method (VPO) at temperature ranges 298.15–328.15 K and modeled using different electrolyte excess Gibbs free energy models including electrolyte non-random two liquids (NRTL), modified NRTL (MNRTL), mean spherical approximation NRTL (MSA-NRTL), non random factor (NRF), and extended Wilson models. The results show that osmotic coefficient data increase with increasing temperature. The calculated standard deviations of the studied systems show that the applicability of these models for the correlation of VLE properties of ionic liquid solutions. The average standard deviations for the models have the order σ(?) MNRTL < σ(?) Wilson < σ(?) NRTL < σ(?) MSA-NRTL < σ(?)NRF. The results show MNRTL model is able to reproduce experimental osmotic coefficients of aqueous solution of studied ionic liquids with good precision.