The Ethylbenzene/Styrene Preferential Separation with Ionic Liquids in Liquid–Liquid Extraction

The objective of this work was to explore the feasibility of using ionic liquids (ILs), namely N-ethyl-N-methylmorpholinium dicyanamide, [EMMor][DCA], (3-hydroxypropyl)-1-methylmorpholinium dicyanamide, [N-C₃OHMMor][DCA], 1-(3-hydroxypropyl)-3-methylimidazolium dicyanamide, [N-C₃OHMIM][DCA], 1-(3-hydroxypropyl)pyridinium dicyanamide, [N-C₃OHPy][DCA], (3-cyanopropyl)pyridinium dicyanamide, [N-C₃CNPy][DCA], and (3-cyanopropyl)methylpyrrolidinium dicyanamide, [N-C₃CNMPyr][DCA] for the separation of ethylbenzene and styrene. The liquid–liquid equilibrium (LLE) data in ternary systems of {IL (1)?+?styrene (2)?+?ethylbenzene (3)} at T?=?298.15 K and ambient pressure is presented for the six ILs synthesized by us. The final chromatography analysis of the composition of tie-lines has shown that the studied ILs are not found in the raffinate phase and they show interesting results on the selectivity and solute distribution ratio for styrene extraction. A comparison of different ILs is presented for the studied separation problem. It was observed that the best separation selectivities were found for [N-C₃CNPy][DCA] (S_Av?=?2.38) and [N-C₃OHMMor][DCA] (S_Av?=?2.42) in comparison with other studied ILs in this work and those presented in the literature. While the data presented here are useful from a theoretical standpoint, the possibility of applications for these ILs in technological processes is questionable because of low solute distribution ratios, especially those calculated from the masses [N-C₃CNPy][DCA] (β_MAv?=?0.08) and [N-C₃OHMMor][DCA] (β_MAv?=?0.07). The experimental tie-lines were correlated with the non-random two liquid NRTL model.     

Selective extraction of Cs(I) using 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene in ionic liquid solvents and its application to the treatment of high-level liquid waste

To separate heat-generating Cs from high-level liquid waste (HLLW), the extraction of Cs(I) using 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-calix[4]arene (calix[4]arene-R14) in combination with 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) ionic liquids ([C _n mim][NTf₂], where n?=?2, 4, and 6) was investigated. Under moderately acidic conditions, the calix[4]arene-R14/[C _n mim][NTf₂] system showed a higher extraction efficiency (E_Cs) than that exhibited by the conventional calix[4]arene-R14/dichloromethane system. All extraction processes reached equilibrium within 5 min. Slope analysis revealed that the Cs:calix[4]arene-R14 inclusion complex has a 1:1 stoichiometry. The extraction was found to be exothermic and influenced by the presence of Na(I). These extraction systems exhibited high efficiency and selectivity for Cs(I) in simulated HLLW.     

The Temperature Effect on the Transport Properties of 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids

The temperature dependences of specific and equivalent conductivities, viscosity, density, and crystallization temperature are determined for three 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C _n MeIm] [Tf₂N], n = 2, 3, 4) ionic liquids saturated with water vapor at room temperature. It is established that in the area of positive temperatures, the relationship between viscosity and conductivity obeys the fractional Walden rule with exponents of 0.97, 0.92, and 0.92 for ionic liquids with ethyl-, propyl-, butylradicals, respectively. The temperature dependences of conductivity and viscosity are approximated using the Vogel–Fulcher–Tammann equation (R² > 0.999), and ideal glass transition temperatures T₀ are calculated for the investigated liquids. The obtained values of T₀ depend largely on the chosen range of temperatures. It is shown that [C₂MeIm][Tf₂N] occupies a separate position with regard to [C₃MeIm][Tf₂N] and [C₄MeIm][Tf₂N].     

Dual effects of dimethylsulfoxide on cellulose solvating ability of 1-allyl-3-methylimidazolium chloride

Polar aprotic solvents are considered to act as cosolvents with ionic liquids (ILs) for cellulose, strengthening the solvating ability of ILs by improving their cellulose solvating kinetics without influencing the solubility of cellulose in ILs. In this work, it was found that dimethylsulfoxide (DMSO) at low concentration improves the cellulose solvating ability of [AMIM][Cl], but weakens it at high concentration. To clarify the mechanism of these dual effects of DMSO on the cellulose solvating ability of [AMIM][Cl], the [AMIM][Cl]/DMSO system was investigated using excess infrared spectroscopy, nuclear magnetic resonance (NMR) T ₂ relaxometry, ¹H NMR, ³⁵Cl NMR, and dynamic light scattering. The results indicate that the tight association between the cation and anion in the [AMIM][Cl] network is loosened at low DMSO concentration. As a result, mass transport is accelerated due to the enhanced dynamics of [AMIM][Cl], promoting the cellulose solvating kinetics of [AMIM][Cl]. However, ion clusters of [AMIM][Cl] start to form when the molar fraction of DMSO (x _DMSO) exceeds 0.5. The hydrogen bonds between cations and anions in the ion clusters become much stronger than in pure [AMIM][Cl], leading to decreased ability of [AMIM][Cl] to form hydrogen bonds with cellulose and thus decreased cellulose solubility in the [AMIM][Cl]/DMSO mixture.     

Interactions Between Surface Active Ionic Liquid and Procaine Hydrochloride Drug in Aqueous Solution

Complex formation between the anesthetic drug, procaine hydrochloride and a surface active ionic liquid (SAIL), 1-tetradecyl-3-methylimidazolium chloride, [C₁₄mim][Cl], in aqueous medium has been investigated using surface tension, fluorescence and DLS measurements at 298.15 K and conductance at 288.15, 298.15 and 308.15 K. Critical aggregation concentration (CAC), degree of ionization (α), and various thermodynamic parameters were determined using the conductivity measurements. The interfacial behavior of SAIL at different concentrations of the drug was evaluated from surface tension measurements by calculating a series of surface parameters and CAC values. Fluorescence spectroscopy was used to evaluate the binding constant (K) and the standard state Gibbs energy change (ΔG°) for the formation of drug–SAIL complexes, which confirms the existence of cation–π interactions between the drug molecules and imidazolium ring of the SAIL molecules. The CAC values were found to decrease with increase in the concentration of the drug, which is due to the balancing between hydrophobic and electrostatic interactions. Dynamic light scattering provides sufficient information about the size of the aggregates and the variation in the hydrodynamic diameters pertaining to the changes in the drug concentration. The results from above methods show that the aggregation process of SAIL is favored by increases in the concentration of the drug. It is demonstrated that with the better understanding of the interactions, [C₁₄mim][Cl] can be judiciously utilized in making use of procaine hydrochloride.     

Extraction of $$ {\text{Np}}^{4+} $$ and $$ {\text{NpO}}_{2}^{2+} $$NpO22+ from Nitric Acid Medium Using TODGA in Room Temperature Ionic Liquids

Extraction of Np⁴⁺ and \( {\text{NpO}}_{2}^{2 + } \) was carried out from nitric acid feeds using solutions of N,N,N′,N′-tetra-n-octyldiglycolamide (TODGA) in two imidazolium-based room temperature ionic liquids, viz., 1-butyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide ([C₄mim][NTf₂]) and 1-octyl-3-methylimidazolium bis(trifluoromethanesulphonyl) imide ([C₈mim][NTf₂]). The extraction equilibrium was attained within 2 h for both the metal ions in both the ionic liquids. While a cation exchange mechanism is proposed for the extraction of \( {\text{NpO}}_{2}^{2 + } , \) an ion-pair mechanism of extraction is proposed for the Np⁴⁺ ion. The nature of the extracted species was determined by carrying out experiments at varying concentrations of TODGA, and species of the type Np(L)₂(NO₃)₄ and NpO₂(L)²⁺ were found to be extracted in 3 mol·dm^?3 HNO₃. The identification of these extracted species was also supported from the variable nitrate and C₄mim⁺ ion concentration experiments.     

The synthesis of Fe-containing ionic liquid and its catalytic performance for the dehydration of fructose

Four Fe-containing ionic liquids (ILs) were synthesized by coupling of conventional imidazole ionic liquids [C_xmim]Cl (x = 4, 8, 12, 16) with FeCl₃ and were characterized by FT-IR, Raman, ESI–MS and TG. All of the Fe-containing ILs were applied to the conversion of fructose into 5-hydroxymethylfurfural (HMF) in 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) subsequently and the result showed that [C₁₆mim]FeCl₄ exhibited excellent catalytic performance. Then the different reaction parameters with [C₁₆mim]FeCl₄ as catalyst were studied in detail. A 92.8% yield of HMF was obtained with 0.03 g [C₁₆mim]FeCl₄ and 0.1 g fructose in 1.0050 g [Bmim]Cl at 80 °C for 40 min in fructose/[Bmim]Cl solution.     

Property Comparison of Cellulose Acetate Prepared Homogenously in Different Ionic Liquids

Cellulose acetates were synthesized homogeneously in four types of ionic liquids without any catalyst using cotton linter as the raw material and acetic anhydride as the esterification agent. FTIR, XRD and DSC were used to characterize the obtained products. It was shown that the homogeneously prepared cellulose acetates became completely amorphous. Degree of substitution of cellulose acetate synthesized in [C₄C₁Im][OAc] was found the highest; whereas T_g of this ester was the lowest. It was also found that the film made of cellulose acetate prepared in [C₄C₁Im][OAc] had lower toughness.     

Physicochemical and excess properties of binary mixtures of (1-alkyl-3-methylimidazoliumchloride/bromide + ethylene glycol) at <Emphasis Type="Italic">T</Emphasis> = (288.15 to 333.15) K

In the present work, the density, ρ, refractive index, n_D, and dynamic viscosity, η, for four binary solutions containing ionic liquids [C_nmim]X (C_nmim = 1-alkyl-3-methylimidazolium; n = 6, 8; X = Cl, Br) and ethylene glycol (EG) were investigated at temperatures of 288.15–333.15 K and at ambient pressure. In addition, the excess molar volume, V_m^E, was calculated and correlated using the Redlich-Kister polynomial equation. The temperature effect on the density of the binary systems studied was expressed by a linear two-parameter equation. The variation in density, refractive index, and viscosity with the composition was described by polynomial equations. The influence of carbon chain-length and the anion of the ionic liquids, and the influence of the temperature on the physicochemical properties of the binary systems can be explained by comparison of the experimental results.     

Study of the Alkyl Chain Length on Laccase Stability and Enzymatic Kinetic with Imidazolium Ionic Liquids

The activity and stability of laccase and their kinetic mechanisms in water soluble ionic liquids (ILs): 1-butyl-3-methyl imidazolium chloride [C₄mim][Cl], 1-octyl-3-methyl imidazolium chloride [C₈mim][Cl], and 1-decyl-3-methyl imidazolium chloride [C₁₀mim][Cl] were investigated. The results show that an IL concentration up to 10% is satisfactory for initial laccase activity at pH 9.0. The laccase stability was well maintained in [C₄mim][Cl] IL when compared to the control. The inactivation of laccase increases with the length of the alkyl chain in the IL: [C₁₀mim][Cl] > [C₈mim][Cl] > [C₄mim][Cl]. The kinetic studies in the presence of ABTS as substrate allowed calculating the Michaelis–Menten parameters. Among the ILs, [C₄mim][Cl] was the suitable choice attending to laccase activity and stability. Alkyl chains in the ions of ILs have a deactivating effect on laccase, which increases strongly with the length of the alkyl chain.     

Selective adsorption of luteolin and aloe-emodin on ionic liquids-bonded silica

Ionic liquids (ILs)-bonded silica adsorbents were prepared by chemical modification of the silica surface using N-alkylimidazolium-based ILs with Cl^?, BF₄ ^?, PF₆ ^? or NO₃ ^? anion, and applied to selective separation of the model mixture of luteolin and aloe-emodin. Among the investigated ILs-bonded silica materials, the silica grafted with N-octyllimidazolium hexafluorophosphate ([C₈mim]PF₆@SiO₂) exhibited higher adsorption capacity and selectivity of luteolin from the model mixed solution of luteolin and aloe-emodin. The isotherm data of luteolin on [C₈mim]PF₆@SiO₂ correlated better to the Freundlich model than the Langmuir model, and the calculated thermodynamic parameters indicated that the adsorption of luteolin was spontaneous and exothermic. The dynamic adsorption and elution experiments demonstrated that the high adsorption capacity and good desorption efficiency of luteolin on fixed bed packed with the [C₈mim]PF₆@SiO₂. Moreover, the results from batch adsorption and dynamic adsorption showed well selective separation towards the model mixture of luteolin and aloe-emodin.     

Theoretical study of interactions between 1-alkyl-3-methyimidazolium tetrafluoroborate and dibenzothiophene: DFT,NBO, and AIM analysis

Density functional theory is employed to study the interaction energies between dibenzothiophene (DBT) and 1-alkyl-3-methylimidazolium tetrafluoroborate ([C _n mim]⁺[BF₄]^?). The structures of DBT, 1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim]⁺[BF₄]^?), 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mim]+[BF₄]?), 1-hexyl-3-methylimidazolium tetrafluoroborate ([C₆mim]⁺[BF₄]^?), 1-octyl-3-methylimidazolium tetrafluoroborate ([C₈mim]⁺[BF₄]^?), [C₂mim]⁺[BF₄]^?–DBT, [C₄mim]⁺[BF₄]^?–DBT, [C₆mim]⁺[BF₄]^?–DBT and [C₈mim]⁺[BF₄]^?–DBT systems are optimized systematically at the B3LYP/6-31G(d,p) level, and the most stable geometries are obtained by NBO and AIM analyses. The results indicate that DBT and imidazolium rings of ionic liquids are parallel to each other. It is found that the [BF₄]^? anion prefers to be located close to a C1–H9 proton ring in the vicinity of the imidazolium ring and the most stable gas-phase structure of [C _n mim]⁺[BF₄]^? has four hydrogen bonds between [C _n mim]+ and [BF₄]?. There are hydrogen bonding interactions, π–π and C–H–π interactions between [C₈mim]⁺[BF₄]^? and DBT, which is confirmed by NBO and AIM analyses. The calculated interaction energies for the studied ionic liquids can be used to interpret a better extracting ability of [C₈mim]⁺[BF₄]^? to remove DBT, due to stronger interactions between [C₈mim]⁺[BF₄]^? and DBT, in agreement with the experimental results of dibenzothiophene extraction by [C _n mim]⁺[BF₄]^?.     

PVT properties of imidazolium-, phosphonium-, pyridinium- and pyrrolidinium-based ionic liquids using critical point constants

Song and Mason equation of state (EOS) with a simple modification has been extended to modelling PVT properties of ionic liquids (ILs). The considered ILs are [C₁mim][MeSO4], [C₁mim][CH₃OC₂H₅SO₄], [C₁mim][(CH₃)₂PO₄], [C₂mim][MeSO4], [C₂mim][BF₄], [C₂mim][SCN], [C₂eim][NTf₂], [C₄mim][C(CN)₃], [C₄mim][CF₃SO₃], [C₄mim][SCN], [C₅mim][NTf₂], [C₈mim][NTf₂], [(C₆H₁₃)₃P(C₁₄H₂₉)][Cl], [(C₆H₁₃)₃P(C₁₄H₂₉)][NTf₂], [(C₆H₁₃)₃P(C₁₄H₂₉)][Ac], [C₃mpyr][NTf₂], [C₄mpyr][NTf₂] and [Py][C₂H₅OC₂H₄SO₄]. Three temperature-dependent parameters in the proposed EOS have been scaled as functions of reduced temperature with the use of the law of corresponding states. It is shown that the knowledge of just critical temperature and critical density is sufficient to predict the PVT properties of these ILs. The overall average absolute deviation of calculated densities from literature values for 1347 data points of 18 ILs was found to be 0.58%. The predicted density of ILs from proposed EOS has been compared with those obtained by other literature work. Moreover, we indicate that the Zeno line regularity can well be predicted by proposed model for ILs.     

Thermodynamic and spectroscopic studies on binary mixtures of imidazolium ionic liquids in ethylene glycol

The thermodynamic behaviour of imidazolium based ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride [C₄mim][Cl]; 1-octyl-3-methylimidazolium chloride [C₈mim][Cl], and 1-butyl-3-methylimidazolium methylsulfate [C₄mim][C₁OSO₃] in ethylene glycol [HOCH₂CH₂OH] (EG) have been investigated over the whole composition range at T = (298.15 to 318.15) K to probe the interactions in bulk. For the purpose, volumetric properties such as excess molar volume, $V_m^E$, apparent molar volume, V_?,i, and its limiting values at infinite dilution, $V_{?\text{,}i}^{\infty }$, have been calculated from the experimental density measurements. The molecular scale interactions between ionic liquids and EG have been investigated through Fourier transform infrared (FTIR) and ¹H NMR spectroscopy. The shift in the vibrational frequency for C–H stretch of aromatic ring protons of ILs and O–H stretch of EG molecules has been analysed. The NMR chemical shifts for various protons of RTILS or EG molecules and their deviations show multiple hydrogen bonding interactions of varying strengths between RTILs and EG in their binary mixtures.     

Tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate–ionic liquid mixtures for Li<Superscript>+</Superscript> extraction from Mg<Superscript>2+</Superscript>-containing brines at 303–343 K

Extraction of Li⁺ ions from salt lake brine into an ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₂mim][NTf₂]) mixed with tri-n-butyl was investigated. The extraction mechanism was been studied using UV–Vis spectroscopy From the temperature dependence data, the thermodynamic functions values (ΔG°, ΔH°, and ΔS°) were calculated. Furthermore, stripping of metals from ionic liquid phase to an aqueous phase by hydrochloric acid was accomplished.     

Ionic liquids enhanced oil recovery from oily sludge-experiment and mechanism

The oily sludge would cause environment pollution, and would cause the heavy oil waste. Therefore, it was vital for us to find novel methods to obtain heavy oil from the oily sludges. In this study, the [C₁₂mim][PF₆] and [C₁₂mim][Br] ionic liquids(ILs) were used to enhance the oil recovery. The toluene could obtain the highest oil recovery, and both the two ILs could increase the oil recovery. Toluene could obtain the highest oil recovery (89.4 wt%), and n-octane could obtain the lowest oil recovery (76.8 wt%). [C₁₂mim] [PF₆] could efficiently increase the heavy oil recovery to 91.2 wt%(by toluene). The [C₁₂mim][Br] could increase the heavy oil recovery further. Both the [C₁₂mim] [PF₆] and the [C₁₂mim][Br] ionic liquids could increase the heavy ois C/H ratio, decrease heavy oil viscosity and increase the sands hydrophilicity. The [C₁₂mim][Br] ionic liquids showed better effect. In addition, the ionic liquids could increase the solvents recovery, and the ionic liquids recovery were high. Therefore, the ionic liquids enhanced oil recovery could be recycled to ten times. The two ionic liquids could effectively decrease the heavy oil interaction force, and when the ionic liquids increased to 200 ppm, the force remained stable. In the end, the ionic liquids enhancing solvent extraction mechanism was put forward.     

Mononuclear cobalt (III) complexes with <Emphasis Type="Italic">N</Emphasis>-salicylidene-2-hydroxy-5-bromobenzylamine and <Emphasis Type="Italic">N</Emphasis>-salicylidene-2-hydroxy-5-chlorobenzylamine

Cobalt (III) complexes with N-salicylidene-2-hydroxy-5-bromobenzylamine (H₂sbba) and N-salicylidene-2-hydroxy-5-chlorobenzylamine (H₂scba), [n-(C₄H₉)₄N][Co(sbba)₂] (I) and [n-(C₄H₉)₄N][Co(scba)₂] (II), were synthesized. The crystal structure of II was determined by the single-crystal X-ray diffraction method at 90 K confirming its crystallization in the monoclinic space group P2₁/n with a = 11.729(2) Å, b = 16.901(3) Å, c = 21.483(4) Å, β = 98.840(4)°, V = 4208.2(14) ų, D_x = 1.295 g cm^?3, and Z = 4. The R1 [I > 2σ(I)] and wR2 (all data) values of 0.0664 and 0.1920, respectively, for all 9521 independent reflections. The compound is composed of a tetra(n-butyl)ammonium cation and an octahedral cobalt(III) complex anion with two scba^2? ligands in a meridional fashion. The electronic spectral features of I and II are consistent with the octahedral cobalt(III) ion with an N₂O₄ donor set.     

Special Mixing Behavior of Chelate-based Ionic Liquid with Methanol

Compared to the general ionic liquids (ILs), a significant deviation of the binary mixtures of 1-decyl-3-methylimidazolium tri(hexafluoroacetylaceto)-copper(II) ([C₁₀mim][Cu(hfacac)₃]) with methanol was found, indicating the way methanol interacts with ILs might be governed by the special structure of the chelating anion. IR results showed that the (C2-H) of 1-decyl-3-methylimidazolium hexafluoroacetylacetonate ([C₁₀mim][hfacac]) blue-shifted more significantly than that of [C₁₀mim][Cu(hfacac)₃], meanwhile the (C=O) red-shifted in [C₁₀mim][Cu(hfacac)₃], which is contrast with that in [C₁₀mim][hfacac]. Two-dimensional correlation analysis of the FTIR spectra indicated that the chelating cavity has little effect on the sequence of the ILs sites that interact with methanol. Combined with small angle X-ray scattering (SAXS) results, the picture of mixing processes in these two systems were proposed. Methanol interacts directly with the anion followed by the cation in [C₁₀mim][hfacac], while methanol preferentially enters the chelating cavity and enhances the packing effect in the [C₁₀mim][Cu(hfacac)₃] system.     

Synthesis and crystal structure of (<Emphasis Type="Italic">o</Emphasis>-Diaminobenzene)<Subscript>2</Subscript> Zn(OAc)<Subscript>2</Subscript>

The treatment of o-diaminobenzene with Zn ( OAc )₂ · 2H₂O in alcohol results in the formation of mononuclear bis(o-diaminobenzene)diacetate Zinc, Zn[C₈H₁₁N₂O₂]₂. Its structure was determined by X-ray diffraction analysis. The complex is also characterized by elemental analysis, ¹H NMR and IR. The crystal is monoclinic space group C2, parameters: a = 16.297(5), b = 4.775(3), c = 11.664(5) Å, β = 97.646(5)°, λ = 1.54184 Å, V = 899.6(7) ų, Z = 2, ρ _c = 1.476 g/cm³, M _r = 399.75, F(000) = 416.0, R ₁ = 0.0594, wR ₂ = 0.1439 for 995 observed reflections with I > 2σ(I).     

Fluorescence Spectroscopic Analysis of the Interaction of Papain with Ionic Liquids

The interaction between papain and two typical ionic liquids (ILs), 1-octyl-3-methylimidazolium chloride ([C₈mim]Cl) and 1-butyl-3-methylimidazolium chloride ([C₄mim]Cl), was investigated by using fluorescence spectroscopy technique at a pH value of 7.4. The results suggested that ILs could quench the intrinsic fluorescence of papain probably via a static quenching mechanism. The binding constants were determined by employing the fluorescence quenching method. They were very small compared with that of volatile organic solvents, indicating that only very weak interaction between ILs and papain existed. The Gibbs free energy change (?G), enthalpy change (?H), and entropy change (?S) during the interaction of papain and ILs were estimated. Negative values of these parameters indicated that the interaction between ILs and papain was a spontaneous process, also implying that hydrogen bonding and van der Waals forces played important roles in the interaction processes.