Electrochemical behavior of uranyl in ionic liquid 1-butyl-3-methylimidazolium chloride mixture with water

Electrochemical behaviors of U(VI) in 1-butyl-3-methylimidazolium chloride (C₄MimCl) with various water contents investigated by chronopotentiometry and cyclic voltammetry. The electrochemical reduction of U(VI) was identified to follow two processes: a lower valence intermediate U(V) was initially formed at the potential of ca. ?0.2 V(vs. Ag wire). Then, further deposition of UO₂ was followed at around ?0.8 V. Little amount of water (1–4 wt%) in C₄MimCl, however, has an effect on the U(VI) reduction by changing the current density of the redox reaction and the diffusion coefficient of U(VI) in C₄MimCl. The deposited product by potentiostatic electrolysis on the surface of stainless steel electrode was characterized by the scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and X-ray diffraction (XRD) methods. Although the electrodeposited black film was amorphous, the electrochemical reduced product of U(VI) can be still confirmed to be UO₂ by XRD after the crystallization of the amorphous deposits at 1,073 K in nitrogen atmosphere.     

Homogeneous tritylation of cellulose in 1-butyl-3-methylimidazolium chloride

1-Alkyl-3-methylimidazolium-based ionic liquids, having chloride as a counter ion, were studied for cellulose solubility; and the influence of different alkyl chain lengths was also investigated. The alkyl chain length was incrementally varied from ethyl to decyl to determine structure-dissolution properties; a distinct odd-even effect was observed for short chain lengths. In addition, the tritylation of cellulose was performed in 1-butyl-3-methylimidazolium chloride using pyridine as base. The influences of reaction time and the ratio of trityl chloride per cellulose monomer unit on the degree of substitution were investigated in detail by elemental analysis and 1H NMR spectroscopy. A DS of around 1 was obtained after 3 h reaction time using a six fold excess of trityl chloride.     

TX-100/water/1-butyl-3-methylimidazolium hexafluorophosphate microemulsions

Both ionic liquids and water are typical green solvents. In this work, the phase behavior of the ternary system consisting of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF6), TX-100, and water was determined at 25.0 degrees C. The water-in-bmimPF6, bicontinuous, and bmimPF6-in-water microregions of the microemulsions were identified by cyclic voltammetry method using potassium ferrocyanide K4Fe(CN)6 as the electroactive probe. Dynamic light scattering (DLS) and the UV-vis method were used to characterize the microemulsions. It was demonstrated that the hydrodynamic diameter (Dh) of the bmimPF6-in-water microemulsions is nearly independent of the water content but increases with increasing bmimPF6 content due to the swelling of the micelles by the ionic liquid. The UV-vis further confirmed the existence of water domains in the water-in-bmimPF6 microemulsions, and the salt potassium ferricyanide K3Fe(CN)6 could be dissolved in the water domains.     

Physicochemical properties of 1-butyl-3-methylimidazolium acetate

Characteristic IR and UV absorption bands, as well as oxidation half-wave potential on a platinum disc electrode in the cyclic mode were determined for the low-temperature hydrophilic ionic liquid 1-butyl-3-methylimidazolium acetate. Temperature dependences of the refractive index, density, and ansolute viscosity were determined in the temperature range 298–328 K. The activation energy of viscous flow was calculated.     

Thermochemical properties of 1-butyl-3-methylimidazolium nitrate

Heat capacity for 1-butyl-3-methylimidazolium nitrate [C₄mim][NO₃] in the temperature range (5–370) K has been measured by adiabatic calorimetry. Temperatures and enthalpies of its phase transitions have been determined. Thermodynamic functions have been calculated for the crystalline and the liquid states. Phase transition temperatures for set of nitrate salts have been compared. Enthalpy of combustion and enthalpy of formation for crystalline [C₄mim][NO₃] have been determined using a static-bomb isoperibol combustion calorimeter. A correlation scheme for the estimation of C_p of ionic liquids has been developed.     

Electrochemical properties of 1-butyl-3-methylimidazolium bromide melt containing water impurities

The effect of a water impurity (1.8–10 wt %) on the conductivity of the ionic liquid-H₂O binary system was studied in a wide temperature range. It was shown that the interaction between components is characteristic of this system, and the molar ratio of components 1: 1 is boundary between the structures of solution and melt. The basic kinetic features of electrochemical reduction of water of the BMImBr-H₂O binary system were determined by voltammetry with linear potential sweep. The transfer coefficient for the cathodic process (α = 0.46) and H₂O molecule diffusivities were determined depending on the water content ( $ D_{H_2 O} The effect of a water impurity (1.8–10 wt %) on the conductivity of the ionic liquid-H₂O binary system was studied in a wide temperature range. It was shown that the interaction between components is characteristic of this system, and the molar ratio of components 1: 1 is boundary between the structures of solution and melt. The basic kinetic features of electrochemical reduction of water of the BMImBr-H₂O binary system were determined by voltammetry with linear potential sweep. The transfer coefficient for the cathodic process (α = 0.46) and H₂O molecule diffusivities were determined depending on the water content ( = (0.2–1.3) × 10⁻¹⁰ cm²s⁻¹). Original Russian Text ? E.P. Grishina, A.M. Pimenova, L.M. Ramenskaya, O.V. Kraeva, 2008, published in Elektrokhimiya, 2008, Vol. 44, No. 11, pp. 1352–1358.     

Supported phospholipid membrane interactions with 1-butyl-3-methylimidazolium chloride

Quartz crystal microbalance with dissipation measurements were conducted for a 98/2 mole ratio of 1,2-dielaidoylphosphocholine (DEPC) and 1,2-dimyristoylphosphoglycerol (DMPG) on silica, gold, and a self-assembled monolayer of 11-mercapto-1-undecanol (11MU) and 11-mercaptoundecanoic acid (11MUA) at 50 mol % each. This study demonstrates that vesicles composed of DEPC and DMPG at 98 and 2 mol %, respectively, formed a supported bilayer with unruptured vesicles present when adsorbed onto the self-assembled monolayer. Also, the partially formed supported bilayer apparently deadsorbed in the presence of 1-butyl-3-methylimidazolium chloride, suggesting that surface-bilayer interactions are weaker on a hydrophilic modified gold surface composed of 50/50 11MU/11MUA than the surface-bilayer interactions on silica.     

Effects of crosslinking ratio and aging time on properties of physical and chemical cellulose gels via 1-butyl-3-methylimidazolium chloride solvent

Papers used in the field of electro-responsive applications are known as Electroactive-papers (EAPaps), consisting primarily of a cellulose. 1-Butyl-3-methylimidazolium chloride is an interesting ionic liquid that acts as an effective cellulose solvent for EAPaps due to its high solubility without chain derivatization, less chain degradation, and stability in electro-responsive applications. In our work, physical and chemical cellulose gels were fabricated and studied for the effects of various crosslinking ratios (CR) and aging time (t_ag), with glutaraldehyde acting as the crosslinking agent. The crosslinking reaction conversion could be increased by increasing the CR and t_ag; the reaction products were ketone linkages and by-product water molecules. A difference in optical properties could be observed and related to the differing amounts of ketone linkages, as confirmed by FTIR-ATR quantitative analysis. UV–visible spectra showed that the prepared samples had a maximum wavelength λ_max nm, a characteristic of ketone linkages. By-product water molecules exhibited plasticizing effects, as observed by the decrease in the storage moduli (G′) at 1 day aging time. The outward migration of by-product water molecules caused a slight increase in G′ at 15 days aging time due to a closer packing. The by-product water molecules induced the H⁺-hopping and more disordered domains resulting in an ease in ion migration. Our paper-gels showed potential characteristics towards electro-responsive applications: less preparation time (<14 h) and stable gel properties.     

Phase equilibria study of the binary systems (1-butyl-3-methylimidazolium tosylate ionic liquid + water,or organic solvent)

(Solid + liquid) phase equilibria (SLE) and (liquid + liquid) phase equilibria (LLE) for the binary systems: ionic liquid (IL) 1-butyl-3-methylimidazolim tosylate (p-toluenesulfonate) {[BMIM][TOS] + water, an alcohol (ethanol, or 1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol), or n-hexane, or an aromatic hydrocarbons (benzene, or toluene, or ethylbenzene, or propylbenzene, or thiophene)} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (230 to 340) K. For the binary systems containing water, or an alcohol, simple eutectic diagrams were observed with complete miscibility in the liquid phase. As usual, with increasing chain length of the alcohol the solubility decreases. In the case of mixtures {IL + n-hexane, or benzene, or alkylbenzene, or thiophene} the eutectic systems with mutual immiscibility in the liquid phase with an upper critical solution temperature (UCST) were detected. The basic thermal properties of the pure IL, i.e. melting and glass-transition temperatures, as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). Density at high temperatures was determined and extrapolated to 298.15 K. Well-known UNIQUAC, Wilson and NRTL equations have been used to correlate experimental SLE data sets for alcohols and water. For the systems containing immiscibility gaps {IL + n-hexane, or benzene, or alkylbenzene, or thiophene}, parameters of the LLE correlation equation have been derived using only the NRTL equation.     

Electrodeposition of Ni-Mg alloys from 1-butyl-3-methylimidazolium chloride/glycerin eutectic-based ionic liquid

Journal of Solid State Electrochemistry - The electrodeposition of Ni-Mg alloys in 1-butyl-3-methylimidazolium chloride/glycerin (BMIC/GL, 1:1&nbsp;M ratio) eutectic-based ionic liquid...     

Impact of 1-butyl-3-methylimidazolium chloride on the electrospinning of cellulose acetate nanofibers

Additives like ionic liquids (ILs) have proven to be excellent materials useful in improving the electrospinnability and conductivity of both synthetic and biopolymers. The aim of this study is to investigate the effect of 1-buthyl-3-methylimidazolium chloride [BMIM]Cl on the electrospinnability of cellulose acetate (CA). The results showed that [BMIM]Cl has the greater effect on viscosity and conductivity of the spinning solution while the morphology of the nanofibers significantly improved as the concentration of the IL increases from 0% to 12% (v/v) of [BMIM]Cl. To understand the interaction between CA and [BMIM]Cl, Fourier-transform infrared spectroscopy (FTIR) has been used. Observations by scanning electron microscopy (SEM) suggested that [BMIM]Cl significantly altered the morphology of the CA nanofibers and 12% (v/v) of [BMIM]Cl would be an ideal concentration producing uniform fibers with a mean diameter of 180nm. In addition, the membranes showed a significant increase in conductivity (from 0 to 2.21 × 10^?7S/cm) as the concentration of ionic liquid increases up to 12% (v/v) that indicates a successful loading of IL inside the nanofibers.     

Structural change of 1-butyl-3-methylimidazolium tetrafluoroborate + water mixtures studied by infrared vibrational spectroscopy

Mixtures of ionic liquid (IL, 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4]) and water with varying concentrations were studied by attenuated total reflection infrared absorption and Raman spectroscopy. Changes in the peak intensities and peak positions of CHx (x = 1, 2, 3) vibration modes of the cation of the IL and OH vibration modes of the water molecules were investigated. Peaks from normal-mode stretch vibrations of CH bonds belonging to the imidazolium ring of the cation did not change their positions, while those from the terminal methyl group of the butyl chain blueshifted by approximately 10 cm-1 with the addition of water. On the other hand, change in the spectral shape in the OH stretch vibration region shows hydrogen-bonding network of water molecules breaking down rapidly as the IL is added. Trends in the change of the peak positions and the peak intensities suggested qualitative change of the intermolecular structure in the [BMIM][BF4] + H2O mixture at 32 +/- 2 and 45 +/- 2 mol/L of water concentration.     

Viscosities and refractive indices of binary mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate and 1-butyl-2,3-dimethylimidazolium tetrafluoroborate with water at 298 K

Viscosities and refractive indices have been determined for (water + 1-butyl-3-methylimidazolium tetrafluoroborate) and (water + 1-butyl-2,3-dimethylimidazolium tetrafluoroborate) mixtures at 298.15 K, over the whole composition range. The refractive indices were compared with the predictions of the Lorentz–Lorenz, Wiener, and Gladstone–Dale equations. Viscosity deviations (Δη) and refractive index deviations (Δn_D) have been calculated and fitted to the Redlich–Kister polynomial equations. Δn_D are positive whereas Δη are negative over the entire mixture composition for the two salts. The influence of the structure of imidazolium cation on the above physicochemical properties was discussed.     

Osmotic and apparent molar properties of binary mixtures alcohol + 1-butyl-3-methylimidazolium trifluoromethanesulfonate ionic liquid

In this work, physical properties (densities and speeds of sound) for the binary systems {1-propanol, or 2-propanol, or 1-butanol, or 2-butanol, or 1-pentanol + 1-butyl-3-methylimidazolium trifluoromethanesulfonate} were experimentally measured from T = (293.15 to 323.15) K and at atmospheric pressure. These data were used to calculate the apparent molar volume and apparent molar isentropic compression which were fitted to a Redlich–Meyer type equation. This fit was used to obtain the corresponding apparent molar properties at infinite dilution. On the other hand, the osmotic and activity coefficients and vapor pressures of these binary mixtures were also determined at T = 323.15 K using the vapor pressure osmometry technique. The Extended Pitzer model of Archer was employed to correlate the experimental osmotic coefficients. From the parameters obtained in the correlation, the mean molal activity coefficients and the excess Gibbs free energy for the studied mixtures were calculated.     

Beyond a solvent: the roles of 1-butyl-3-methylimidazolium chloride in the acid-catalysis for cellulose depolymerisation

In this report, 1-butyl-3-methylimidazolium chloride ([C₄C₁im]Cl) is demonstrated to enhance the kinetics of acid-catalysed hydrolysis of 1,4-β-glucans in binary solvent mixtures. [C₄C₁im]Cl plays other roles in the reaction beyond acting as a solvent for cellulose, as currently accepted. In fact, the presence of the IL increases the Hammett acidity of the catalyst dissolved in the reaction medium. The kinetic data from cellobiose and cellulose hydrolysis directly correlate with the acid strength found for p-toluenesulfonic acid in the different reaction media studied here. The current report identifies neglected, but yet very important phenomena occurring in cellulose depolymerisation.     

Behaviour of a binary solvent mixture constituted by an amphiphilic ionic liquid, 1-decyl-3-methylimidazolium bromide and water Potentiometric and conductimetric studies

We investigated the properties of 1-decyl-3-methylimidazolium bromide (DMImBr), a molten salt at room temperature, and its mixtures with water in the whole proportions.At low concentrations, this salt behaved like a classical cationic amphiphile. Its critical micellar concentration (cmc) was determined by conductimetry and by measuring electromotive forces (EMF) with bromide or cationic surfactant-selective electrodes. Moreover, the association rate of the counter ion to micelle has been determined on a wide range of concentrations, allowing characterising the micellisation equilibrium by a solubility product.The conductivity of this liquid electrolyte in mixtures with water was maximal at high concentrations. We modelled this behaviour, taking into account the molar volume fraction of both phases.Our results show that these solutions, which are composed of dispersed aggregates, behave like mixtures of two phases that interpenetrate themselves.     

Structural characterization of the 1-butyl-3-methylimidazolium chloride ion pair using ab initio methods

Ab initio theoretical methods are used to investigate the gas-phase ion pairs of the ionic liquid 1-butyl-3-methylimidazolium chloride. Multiple stable conformers with the chloride anion positioned (in-plane) around the imidazolium ring or above the C2-H bond are determined. The relative energy ordering of the conformers is examined at the B3LYP, MP2, and CCSD(T) levels. Zero-point energies, BSSE, and basis set effects are examined. For accurate results, correlation (dispersion) effects must be included. The most stable conformers are essentially degenerate and have the chloride H-bonding to, or lying above, the C2-H bond. Other conformers are found to lie approximately 30 and approximately 60 kJ mol(-1) higher in energy. Results are compared with those from recent simulations and experimental studies. The effect of the chloride anion on rotation of the butyl chain is investigated and found to lower some rotational barriers while enhancing others. The origin of the rotational barriers is determined. The number and type of hydrogen bonds formed between the imidazolium cation and chloride anion is found to vary significantly among conformers. No evidence of a possible intra C(alkyl)-H...pi interaction is obtained; however, hints of a Cl...pi interaction are found. The vibrational spectrum of each conformer is examined, and the origin of multiple (H-bonding) features in the vibrational spectrum of the ionic liquid explained.