Density, Refractive Index and Volumetric Properties of Water–Ionic Liquid Binary Systems with Imidazolium-Based Cations and Tetrafluoroborate, Triflate and Octylsulfate Anions at T = 293 to 343 K and p = 0.1 MPa

Abstract

The density and refractive index of ionic liquids (ILs) + water binary mixtures were determined as a function of temperature (from 293.15 to 343.15 K) at atmospheric pressure over the whole composition range in which the mixtures were miscible. To carry out a systematic study, all of the ILs selected are imidazolium-based ILs with a different number of carbons in the alkyl chain of the cation and also different anions (tetrafluoroborate, triflate, and octylsulfate). Specifically, the studied ILs were 1-ethyl-3-methylimidazolium tetrafluoroborate [emim]­[BF4], 1-butyl-3-methylimidazolium tetrafluoroborate [bmim]­[BF4], 1-hexyl-3-methylimidazolium tetrafluoroborate [hmim]­[BF4], 1-methyl-3-octylimidazolium tetrafluoroborate [omim]­[BF4], 1-ethyl-3-methylimidazolium triflate [emim]­[TfO], 1-butyl-3-methylimidazolium triflate [bmim]­[TfO], and 1-butyl-3-methylimidazolium octylsulfate [bmim]­[OcSO4]. The excess molar volumes and the deviation in the molar refraction of the binary mixtures were calculated for a better understanding of the interactions that take place between the components and were successfully correlated by the Redlich–Kister empirical correlations. The Bahe–Varela model, which has a more physical meaning, was also used to successfully correlate the excess molar volume values. Volumetric properties, such as apparent molar volumes, partial molar volumes, isobaric thermal expansion coefficients, partial molar volumes at infinite dilution and excess partial molar volumes at infinite dilution were also calculated in order to obtain information about the influence of composition and temperature on the thermodynamic behavior of the selected ILs and water in the mixture. The results are discussed in order to understand the formation of hydrogen bonds between components of the mixture and the possible packing effects that take place in the mixing process. The density and refractive index experimental data were correlated by the Lorentz–Lorenz, Wiener, Dale–Gladstone, and Eykman equations to determine the relationship between both parameters, and good agreement between the experimental and calculated refractive index values was obtained.

Antitumor Activity of Rosmarinic Acid-Loaded Silk Fibroin Nanoparticles on HeLa and MCF-7 Cells

“…In a previous work, our research group developed a novel procedure to produce SFNs from ionic liquid-SF solutions obtained by high-power ultrasounds [ 27 ]. This procedure represented a notable improvement over traditional methods of SF dissolution [ 33 , 34 ] mainly as a result of: (i) the negligible vapor pressure and easy recyclability of ionic liquids, which make them a “greener” alternative to organic solvents [ 35 ], (ii) the possibility of obtaining high concentrations of a stable SF solution (up to 25 w/w% [ 27 ]) and (iii) the general ease with which SF can be dissolved.…”

Density, refractive index, and derived properties of binary mixtures of water + ionic liquid 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate

“…However, some values reported for the pure compounds are used for purposes of comparison. Figure 1 shows the deviations between the experimental density values obtained and those reported in the literature for water [4,23,24,37,38] and for ionic liquid [EtOHmim][BF4] [19,[39][40][41][42]. Figure 1 a) shows the small deviations between the density values obtained and those reported in the literature for water.…”

“…Such basic properties as density and refractive index need to be determined and understood so that equipment for commercial applications that use aqueous IL mixtures can be designed, scaled up and sized [23]. Of all the thermophysical properties of aqueous mixtures of ILs, density is probably the most widely studied because of its importance and experimental accessibility [24]. Also, several volumetric properties can be obtained from density measurements.…”

“…Correlations such as Lorentz-Lorenz, Gladstone-Dale or Newton have been extensively tested and validated in the literature [24,28,31]. However, despite the close relationship between the two properties, few studies address the determination of density and refractive index in aqueous mixtures of ILs [4,23,24,27,32,33]. And most of the ones that do provide experimental data of the density and refractive index at only one temperature.…”

“…For 𝑥 2 ≥ 0.08, the magnitude of 𝑉 𝑚 𝐸 gets smaller as the concentration of water decreases in the mixture. This is probably due to the increased intermolecular interaction between the anionic and cationic species of [EtOHmim][BF4], which is favored over the interaction between water molecules and IL ions [24,25]. It is also observed that the magnitude of 𝑉 𝑚 𝐸 decreases with temperature from 293.15 K to 323.15 K at a given IL mole fraction.…”