Phase equilibrium for ozone-containing hydrates formed from an (ozone + oxygen) gas mixture coexisting with gaseous carbon dioxide and liquid water

The paper reports the three-phase (gas + aqueous liquid + hydrate) equilibrium pressure (p) versus temperature (T) data for a (O₃ + O₂ + CO₂ + H₂O) system and, for comparison, corresponding data for a (O₂ + CO₂ + H₂O) system for the first time. These data cover the temperature range from (272 to 279) K, corresponding to pressures up to 4 MPa, for each of the three different (O₃ + O₂)-to-CO₂ or O₂-to-CO₂ mole ratios in the gas phase, which are approximately 1:9, 2:8, and 3:7, respectively. The mole fraction of ozone in the gas phase of the (O₃ + O₂ + CO₂ + H₂O) system was from ∼0.004 to ∼0.02. The modified pressure-search method, developed in our previous study [S. Muromachi, T. Nakajima, R. Ohmura, Y.H. Mori, Fluid Phase Equilib. 305 (2011) 145–151] for p–T measurements in the presence of chemically unstable ozone, was applied, having been further modified for dealing with highly water-soluble CO₂, for the (O₃ + O₂ + CO₂ + H₂O) system, while the conventional temperature-search method was used for the (O₂ + CO₂ + H₂O) system. The measurement uncertainties (with 95% coverage) were ±0.11 K for T, ±6.0 kPa for p, and ±0.0015 for the mole fraction of each species in the gas phase. It was confirmed that, at a given CO₂ fraction in the gas phase, p for the (O₃ + O₂ + CO₂ + H₂O) system was consistently lower than that for the (O₂ + CO₂ + H₂O) system over the entire T range of the present measurements, indicating a preference of O₃ to O₂ in the uptake of guest-gas molecules into the cages of a structure I hydrate.     

(Liquid + liquid) equilibria of ternary and quaternary systems containing n-hexane,toluene, m-xylene,propanol, sulfolane,and water at T = 303.15 K

(Liquid + liquid) equilibrium data for ternary and quaternary systems containing n-hexane (C₆H₁₄), toluene (C₇H₈), m-xylene (C₈H₁₀), propanol (C₃H₈O), sulfolane (C₄H₈SO₂), and water (H₂O) were measured at T = 303.15 K. Phase diagrams of {w₁C₄H₈SO₂ + w₂C₇H₈ + (1 − w₁ − w₂)C₆H₁₄}, {w₁C₄H₈SO₂ + w₂C₈H₁₀ + (1 − w₁ − w₂)C₆H₁₄}, {w₁C₄H₈SO₂ + w₂C₃H₈O + w₃C₇H₈ + (1 − w₁ − w₂ − w₃)C₆H₁₄} and also systems containing water: {w₁C₄H₈SO₂ + w₂H₂O + w₃C₇H₈ + (1 − w₁ − w₂ − w₃)C₆H₁₄} and {w₁C₄H₈SO₂ + w₂H₂O + w₃C₈H₁₀ + (1 − w₁ − w₂ − w₃)C₆H₁₄} (w = mass fraction) were obtained at T = 303.15 K. The (liquid + liquid) equilibrium data of the systems were used to obtain interaction parameters in non-random two-liquid (NRTL) and universal quasi-chemical theory (UNIQUAC) activity coefficient models. These parameters can be used to predict equilibrium data of ternary and quaternary systems. The root mean square deviations (RMSDs) using these models were calculated and reported. The partition coefficients and the selectivity factors of solvents for extraction of toluene or m-xylene from n-hexane at T = 303.15 K are calculated and presented. The experimental selectivity factors of sulfolane for the system {w₁C₄H₈SO₂ + w₂C₇H₈ + (1 − w₁ − w₂)C₆H₁₄} at T = 298.15 K and T = 323.15 K were taken from the literature and the influence of temperature on the extraction of toluene was also investigated. The phase diagrams for the ternary and quaternary systems including both the experimental and correlated tie lines are presented. The tie-line data of the studied systems were also correlated using the Hand equation and the correlation parameters are calculated and reported.     

Excess thermodynamic properties of binary mixtures of N,N-dimethylacetamide with water or water-d2 at temperatures from 277.13 K to 318.15 K

Densities of binary mixtures of N,N-dimethylacetamide (DMA) with water (H₂O) or water-d₂ (D₂O) were measured at the temperatures from T=277.13 K to T=318.15 K by means of a vibrating-tube densimeter. The excess molar volumes V_m^E, calculated from the density data, are negative for the (H₂O + DMA) and (D₂O + DMA) mixtures over the entire range of composition and temperature. The V_m^E curves exhibit a minimum at x(DMA)≅0.4. At each temperature, this minimum is slightly deeper for the (D₂O + DMA) mixtures than for the corresponding (H₂O + DMA) mixtures. The difference between D₂O and H₂O systems becomes smaller when the temperature increases. The V_m^E results were correlated using a modified Redlich–Kister expansion. The partial molar volume of DMA plotted against x(DMA) goes through a sharp minimum in the water-rich region around x(DMA)≅0.08. This minimum is more pronounced the lower the temperature and is deeper in D₂O than in H₂O at each temperature. Again, the difference becomes smaller as the temperature increases. The excess expansion factor α^E plotted against x(DMA) exhibit a maximum in the water rich region of the mole fraction scale. At each temperature, this maximum is higher for the (D₂O + DMA) mixtures than for the corresponding (H₂O + DMA) mixtures, and the difference becomes smaller as the temperature increases. At its maximum, α^E can be even more than 25 per cent of total value of the cubic expansion coefficient α in the (H₂O + DMA) and (D₂O + DMA) mixtures.     

Isopiestic measurement and solubility evaluation of the ternary system (CaCl2 + SrCl2 + H2O) at T = 298.15 K

Water activities in the ternary system (CaCl₂ + SrCl₂ + H₂O) and its sub-binary system (CaCl₂ + H₂O) at T = 298.15 K have been elaborately measured by an isopiestic method. The data of the measured water activity were used to justify the reliability of solubility isotherms reported in the literature by correlating them with a thermodynamic Pitzer–Simonson–Clegg (PSC) model. The model parameters for representing the thermodynamic properties of the (CaCl₂ + H₂O) system from (0 to 11) mol ⋅ kg⁻¹ at T = 298.15 K were determined, and the experimental water activity data in the ternary system were compared with those predicted by the parameters determined in the binary systems. Their agreement indicates that the PSC model parameters can reliably represent the properties of the ternary system. Under the assumption that the equilibrium solid phases are the pure solid phases (SrCl₂ ⋅ 6H₂O and CaCl₂ ⋅ 6H₂O)_(s) or the ideal solid solution consisting of CaCl₂ ⋅ 6H₂O_(s) and SrCl₂ ⋅ 6H₂O_(s), the solubility isotherms were predicted and compared with experimental data from the literature. It was found that the predicted solubility isotherm agrees with experimental data over the entire concentration range at T = 298.15 K under the second assumption described above; however, it does not under the first assumption. The modeling results reveal that the solid phase in equilibrium with the aqueous solution in the ternary system is an ideal solid solution consisting of SrCl₂ ⋅ 6H₂O_(s) and CaCl₂ ⋅ 6H₂O_(s). Based on the theoretical calculation, the possibility of the co-saturated points between SrCl₂ ⋅ 6H₂O_(s) and the solid solution (CaCl₂ ⋅ 6H₂O + SrCl₂ ⋅ 6H₂O)_(s) and between CaCl₂ ⋅ 6H₂O_(s) and the solid solution (CaCl₂ ⋅ 6H₂O + SrCl₂ ⋅ 6H₂O)_(s), which were reported by experimental researchers, has been discussed, and the Lippann diagram of this system has been presented.     

Isopiestic studies on the saturated systems {H2O + BaCl2(sat) + NaCl + NH4Cl} and {H2O + BaCl2(sat) + mannitol(sat) + NaCl + NH4Cl} at the temperature 298.15 K: Comparison with the ideal-like solution model

Isopiestic measurements have been carried out at the temperature 298.15 K for two saturated aqueous solutions: {H₂O + BaCl₂(sat) + NaCl + NH₄Cl} saturated with barium chloride and {H₂O + BaCl₂(sat) + mannitol(sat) + NaCl + NH₄Cl} saturated with barium chloride and mannitol. Taking sodium chloride (aq) as reference solutions, osmotic coefficients of the aqueous solutions were determined. The experimental results are well represented by the ideal-like solution model.     

Thermodynamic properties of calcium titanates: CaTiO3, Ca4Ti3O10, and Ca3Ti2O7

The chemical potentials of CaO in two-phase fields (TiO₂ + CaTiO₃), (CaTiO₃ + Ca₄Ti₃O₁₀), and (Ca₄Ti₃O₁₀ + Ca₃Ti₂O₇) of the pseudo-binary system (CaO + TiO₂) have been measured in the temperature range (900 to 1250) K, relative to pure CaO as the reference state, using solid-state galvanic cells incorporating single crystal CaF₂ as the solid electrolyte. The cells were operated under pure oxygen at ambient pressure. The standard Gibbs free energies of formation of calcium titanates, CaTiO₃, Ca₄Ti₃O₁₀, and Ca₃Ti₂O₇, from their component binary oxides were derived from the reversible e.m.f.s. The results can be summarised by the following equations: CaO(solid) + TiO₂(solid) → CaTiO₃(solid), ΔG° ± 85/(J · mol^?1) = ?80,140 ? 6.302(T/K); 4CaO(solid) + 3TiO₂(solid) → Ca₄Ti₃O₁₀(solid), ΔG° ± 275/(J · mol^?1) = ?243,473 ? 25.758(T/K); 3CaO(solid) + 2TiO₂(solid) → Ca₃Ti₂O₇(solid), ΔG° ± 185/(J · mol^?1) = ?164,217 ? 16.838(T/K).The reference state for solid TiO₂ is the rutile form. The results of this study are in good agreement with thermodynamic data for CaTiO₃ reported in the literature. For Ca₄Ti₃O₁₀ Gibbs free energy of formation obtained in this study differs significantly from that reported by Taylor and Schmalzried at T = 873 K. For Ca₃Ti₂O₇ experimental measurements are not available in the literature for direct comparison with the results obtained in this study. Nevertheless, the standard entropy for Ca₃Ti₂O₇ at T = 298.15 K estimated from the results of this study using the Neumann–Koop rule is in fair agreement with the value obtained from low-temperature heat capacity measurements.     

(Liquid + solid) metastable equilibria in quinary system Li2CO3 + Na2CO3 + K2CO3 + Li2B4O7 + Na2B4O7 + K2B4O7 + H2O at T=288 K for Zhabuye salt lake

An experimental study on metastable equilibria at T=288 K in the quinary system Li₂CO₃ + Na₂CO₃ + K₂CO₃ + Li₂B₄O₇ + Na₂B₄O₇ + K₂B₄O₇ + H₂O was done by isothermal evaporation method. Metastable equilibrium solubilities and densities of the solution were determined experimentally. According to the experimental data, the metastable equilibrium phase diagram under the condition saturated with Li₂CO₃ was plotted, in which there are four invariant points; nine univariant curves; six fields of crystallization: K₂CO₃ · 3/2H₂O, K₂B₄O₇ · 5H₂O, Li₂B₂O₄ · 16H₂O, Na₂B₂O₄ · 8H₂O, Na₂CO₃ · 10H₂O, NaKCO₃ · 6H₂O. Some differences were found between the stable phase diagram at T=298 K and the metastable one at T=288 K.     

Measurement and correlation of the solubility of MnSO4·H2O with MgSO4·7H2O in MeOH + H2O solution

Data on the solubility of manganese sulphate monohydrate in water, and in aqueous alcohols is essential for salting-out crystallization studies. The solubilities for the quaternary system MnSO₄·H₂O + MgSO₄·7H₂O + H₂O + MeOH solution were determined in the temperature ranges 293.2–308.2 K over the mole fraction methanol ranges of 0.00–0.16. The solubility data were used for modelling with the modified extended electrolyte non-random two-liquid (NRTL) equation. The present extension uses ion-specific parameters instead of the electrolyte-specific NRTL binary interaction parameters. This approach has feasibility for many electrolytes and mixed aqueous solution systems principally. The model was found to correlate the solubility data satisfactory.     

About the OH yield in the radiolysis of an aqueous/H2O2 system. Its optimisation for water treatment

Unless the radiolytic reducing species are neutralised or converted into oxidising species, an EB remediation system cannot be considered a true Advanced Oxidation Processes (AOP). A water/H₂O₂ system irradiated by UVC mercury lamps constitutes a widely used OH production method. Employing H₂O₂ in radiolysis as well, an enhancement of the oxidative efficiency of an EB treatment can be obtained. Pulse radiolysis measurements of an aerated aqueous/H₂O₂/KSCN system have been systematically undertaken to assess the optimal H₂O₂ concentration. By linearly fitting a competition kinetics relationship, it is found that the scavengeable extra-yield of OH is ΔG(OH)=0.24 μmol J^?1 (R=0,9958), while the maximum experimental yield is measured G(OH)_max=(0.52±0.02) μmol J^?1 when [H₂O₂]=5–10 mM. Exceeding these concentrations the OH yield drops off.     

Excess molar enthalpies of the ternary mixtures: (tetrahydrofuran or 2-methyltetrahydrofuran + methyl tert-butyl ether + n-octane) at the temperature 298.15 K

Microcalorimetric measurements of excess enthalpies at the temperature T = 298.15 K are reported for the two ternary mixtures {x₁(C₄H₈O or C₅H₁₀O) + x₂C₅H₁₂O + x₃C₈H₁₈}. Smooth representations of the results are presented and used to construct constant excess molar enthalpy contours on Roozeboom diagrams. It is shown that good estimates of the ternary enthalpies can be obtained from the Liebermann and Fried model, using only the physical properties of the components and their binary mixtures.     

The P, V, T,x properties of binary aqueous chloride solutions up to T = 573 K and 100 MPa

A highly accurate P, V, T,x model is developed for aqueous chloride solutions of the binary systems, viz. (LiCl + H₂O), (NaCl + H₂O), (KCl + H₂O), (MgCl₂ + H₂O), (CaCl₂ + H₂O), (SrCl₂ + H₂O), and (BaCl₂ + H₂O). The applied ranges of temperature, pressure, and concentrations for the systems (LiCl + H₂O), (NaCl + H₂O), (KCl + H₂O), (MgCl₂ + H₂O), (CaCl₂ + H₂O), (SrCl₂ + H₂O), and (BaCl₂ + H₂O) are (273 K to 564 K, 0.1 MPa to 40 MPa, and 0 to 10 molal), (273 K to 573 K, 0.1 MPa to 100 MPa, and 0 to 6.0 molal), (273 K to 543 K, 0.1 MPa to 50 MPa, and 0 to 4.5 molal), (273 K to 543 K, 0.1 MPa to 40 MPa, and 0 to 3.0 molal), (273 K to 523 K, 0.1 MPa to 60 MPa, and 0 to 6.0 molal), (298 K to 473 K, 0.1 MPa to 2 MPa, and 0 to 2.0 molal) and (273 K to 473 K, 0.1 MPa to 20 MPa, and 0 to 1.6 molal), respectively. Comparison of the model with thousands of experimental data points concludes that the average deviation over the above T, P, m range is 0.020% to 0.066% in density (or volume) for these systems, which indicates high accuracy. From this model, various volumetric properties, such as the apparent molar volume at infinite dilution and isochores of fluid inclusions, can be calculated, thus having a wide range of geological applications, such as reservoir fluid flow simulation and fluid-inclusion study. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm and online calculations is made available on: www.geochem-model.org/models.htm     

Thermodynamic properties of chloropinnoite

The molar enthalpies of solution of 2MgO · 2B₂O₃ · MgCl₂ · 14H₂O in approximately 1 mol · dm⁻³ aqueous hydrochloric acid (HCl) and of MgCl₂ · 6H₂O(s) in aqueous (approximately 1 mol · dm⁻³ HCl + MgCl₂ + H₃BO₃) at T=298.15 K were determined. From a combination of these results with measured enthalpies of solution of boric acid (H₃BO₃) in HCl(aq) and of magnesium oxide (MgO) in aqueous (HCl + H₃BO₃) solution, together with the standard molar enthalpies of formation of MgO(s), H₃BO₃(s), MgCl₂ · 6H₂O(s) and H₂O(l), the standard molar enthalpy of formation of −(8812 ± 3) kJ · mol⁻¹ of 2MgO · 2B₂O₃ · MgCl₂ · 14H₂O was obtained. Thermodynamic properties of this compound were also calculated by group contribution method.     

Measurement and modelling of mean activity coefficients of aqueous mixed electrolyte solution containing glycine

Electrochemical measurements were made on (H₂O + NaBr + K₃PO₄ + glycine) mixtures at T = 298.15 K by using ion selective electrodes. The mean ionic activity coefficients of NaBr at molality 0.1 were determined at five K₃PO₄ molalities (0.01, 0.03, 0.05, 0.07, and 0.1) mol · kg⁻¹. The activity coefficients of glycine were evaluated from mean ionic activity coefficients of NaBr. The modified Pitzer equation was used to model the experimental data.     

Thermodynamic study of the system (LiCl + CaCl2 + H2O)

Solubility isotherms of the ternary system (LiCl + CaCl₂ + H₂O) were elaborately determined at T = (283.15 and 323.15) K. Several thermodynamic models were applied to represent the thermodynamic properties of this system. By comparing the predicted and experimental water activities in the ternary system, an empirical modified BET model was selected to represent the thermodynamic properties of this system. The solubility data determined in this work at T = (283.15 and 323.15) K, as well as those from the literature at other temperatures, were used for the model parameterization. A complete phase diagram of the ternary system was predicted over the temperature range from (273.15 to 323.15) K. Subsequently, the Gibbs free energy of formation of the solid phases CaCl₂ · 4 H₂O_(s), CaCl₂ · 2 H₂O_(s), LiCl · 2H₂O_(s), and LiCl · CaCl₂ · 5H₂O_(s) was estimated and compared with the literature data.     

X-ray and infrared spectrum on metal complexes with indolecarboxylic acids: Part V. Catena-poly[{aqua(η2-indole-3-propionato-O,O′)zinc}-η2-:-μ-indole-3-propionato-O,O′:-O]

The catena-poly[{aqua(η²-indole-3-propionato-O,O′)zinc}-η²-:-μ-indole-3-propionato-O,O′:-O], [Zn(I3PA)₂(H₂O)]_n was prepared and characterized by infrared spectroscopy and X-ray structure determination. The crystals are monoclinic, space group Pc, with a = 21.380(2), b = 5.9076(7), c = 8.1215(9) Å, V = 1020.2(2) Å³ and Z = 2. The central zinc atom shows the coordination distorted from ideal octahedral. Each zinc centre is coordinated by two oxygen atoms of the bidentate chelating indole-3-propionato (I3PA), two oxygen atoms tridentate chelating-bridging I3PA, water molecule and one oxygen atom tridentate chelating-bridging I3PA from an adjacent [Zn(I3PA)₂(H₂O)] unit. The infrared spectrum of [Zn(I3PA)₂(H₂O)]_n in the solid state is supported by X-ray analysis. The theoretical wavenumbers and infrared intensities have been calculated by the density functional methods (B3LYP and mPW1PW) with the 6-311++G(d,p)/LanL2DZ basis sets. The theoretical wavenumbers, infrared intensities show a good agreement with experimental data. Detailed band assignment has been made on the basis of the calculated potential energy distribution (PED).     

New α,ω-dicarboxylate coordination polymers with 4,4′-bipyridine: Cu(bpy)(C5H6O4), Zn(bpy)(C5H6O4), Zn(bpy)(C6H8O4) and Mn(bpy)(C8H12O4) · H2O

Four 4,4′-bipyridine α,ω-dicarboxylate coordination polymers Cu(bpy)(C₅H₆O₄) (1), Zn(bpy)(C₅H₆O₄) (2), Zn(bpy)(C₆H₈O₄) (3) and Mn(bpy)(C₈H₁₂O₄) · H₂O (4) have been synthesized and structurally characterized by single crystal X-ray diffraction methods (bpy = 4,4-bipyridine, (C₅H₆O₄)²⁻ = glutarate anion, (C₆H₈O₄)²⁻ = adipate anion, (C₈H₁₂O₄)²⁻ = suberate anion). Their crystal structures are featured by dimeric metal units, which are co-bridged by 4,4′-bipyridine ligands and dicarboxylate anions such as glutarate, adipate and suberate anions to generate 2D layers with a (4,4) topology in 1, 2 and 4 as well as to form 3D frameworks in 3. Two 3D frameworks in 3 interpenetrate with each other to form a topology identical to the well-known Nb₆F₁₅ cluster compound. Over 5–300 K, the paramagnetic behavior of 4 follows the Curie–Weiss law χ_m(T − Θ) = 4.265(5) cm³ mol⁻¹ with the Weiss constant Θ = −6.3(2) K. Furthermore, the thermal behavior of 3 and 4 is also discussed.     

Study of bromide salts solubility in the (m1NaBr + m2MgBr2)(aq) system at T = 323.15 K. Thermodynamic model of solution behavior and (solid + liquid) equilibria in the (Na + K + Mg + Br + H2O) system to high concentration and temperature

The bromide minerals solubility in the mixed system (m₁NaBr + m₂MgBr₂)(aq) have been investigated at T = 323.15 K by the physico-chemical analysis method. The equilibrium crystallization of NaBr·2H₂O(cr), NaBr(cr), and MgBr₂·6H₂O(cr) has been established. The solubility-measurements results obtained have been combined with all other experimental equilibrium solubility data available in literature at T = (273.15 and 298.15) K to construct a chemical model that calculates (solid + liquid) equilibria in the mixed system (m₁NaBr + m₂MgBr₂)(aq). The solubility modeling approach based on fundamental Pitzer specific interaction equations is employed. The model gives a very good agreement with bromide salts equilibrium solubility data. Temperature extrapolation of the mixed system model provides reasonable mineral solubility at high temperature (up to 100 °C). This model expands the previously published temperature variable sodium–potassium–bromide and potassium–magnesium–bromide models by evaluating sodium–magnesium mixing parameters. The resulting model for quaternary system (Na + K + Mg + Br + H₂O) is validated by comparing solubility predictions with those given in literature, and not used in the parameterization process. Limitations of the mixed solution models due to data insufficiencies at high temperature are discussed.     

Thermodynamic studies for aqueous solutions involving 18-crown-6 and alkali bromides at 298.15 K

Osmotic vapor pressure measurements have been carried out for three ternary systems, H₂O + 0.2 m 18-crown-6 + NaBr, H₂O + 0.2 m 18-crown-6 + KBr and H₂O + 0.2 m 18-crown-6 + CsBr at 298.15 K using vapor pressure osmometry. The concentration of salts was varied between 0.04 and 0.6 m. The measured water activities were used to calculate the activity coefficient of water, 18-crown-6 and mean molal activity coefficients of ions. The lowering of activity coefficients of one component in presence of other is attributed to the existence of host–guest type complex equilibria in solution phase. The Gibbs transfer free energies, which have been calculated using the activity data, were used to estimate the McMillan–Mayer pair and triplet interaction parameters and are compared with that of alkali chlorides reported recently by us using similar studies. The pair interaction parameters, g_NE (non-electrolyte–electrolyte interaction coefficient), are used to obtain the thermodynamic equilibrium constant values for 18-crown-6:M⁺ complexes, which on comparison with alkali chlorides indicate that the counter anions plays a definite role in stabilizing such complexes in solution phase. Sign and the magnitude of triplet interaction parameters (g_NNE or g_NEE) show that along with electrostatic interactions hydrophobic effects also play an important role in stabilizing the host–guest type complexes.     

Thermodynamic study of the system (LiCl + LiNO3 + H2O)

The solubility of the binary system (LiNO₃ + H₂O) from T = 273.15 K to T = 333.15 K and solubility isotherms of the ternary system (LiCl + LiNO₃ + H₂O) were elaborately measured at T = 273.15 K and T = 323.15 K. These solubility data, as well as water activities in the binary systems from the literature, were treated by an empirically modified BET model. The isotherms of the ternary system (LiCl + LiNO₃ + H₂O) were reproduced and a complete phase diagram of the ternary system in the temperature range from 273.15 K to 323.15 K predicted. It is shown that the solubility data for the binary system (LiNO₃ + H₂O) measured in this work are slightly different from the literature data. Simulated results showed that the saturated salt solution of (2.8LiCl + LiNO₃) is in equilibrium with the stable solid phase LiNO₃(s) over the temperature range from 283.15 K to 323.15 K, other than the solid phases LiNO₃ · 3H₂O(s) and LiClH₂O(s) as reported by Iyoki et al. [S. Iwasaki, Y. Kuriyama. T. Uemura, J. Chem. Eng. Data 38 (1993) 396–398].     

(Liquid + liquid) equilibrium of (imidazolium ionic liquids + organic salts) aqueous two-phase systems at T = 298.15 K and the influence of salts and ionic liquids on the phase separation

(Liquid + liquid) equilibrium for the {1-ethyl-3-methylimidazolium tetrafluoroborate ([C₂mim]BF₄)/1-propyl-3-methylimidazolium tetrafluoroborate ([C₃mim]BF₄) + organic salt + H₂O} aqueous two-phase systems (ATPSs) have been experimentally ascertained at T = 298.15 K. Three empirical equations were used to correlate the binodal data. On the basis of the empirical equation of the binodal curve with the highest accuracy and lever rule, the (liquid + liquid) equilibrium data were calculated by MATLAB. The reliability of the tie line compositions was proved by the empirical correlation equations given by the Othmer–Tobias and Bancroft equations. The effective excluded volume (EEV) values obtained from the binodal model for these systems were determined. The EEV and the binodal curves plotted in molality both indicate that the salting-out abilities of the four salts follow the order: Na₃C₆H₅O₇ > (NH₄)₃C₆H₅O₇ > Na₂C₄H₄O₄ ≈ Na₂C₄H₄O₆, while the phase-separation abilities of the investigated ILs are in the order of [C₃mim]BF₄ > [C₂mim]BF₄. In the systems investigated, the effect of salts on the phase-forming capability was also evaluated in the shape of the salting-out coefficient obtained from fitting the tie-line data to a Setschenow-type equation. The phase-forming ability increases with the increase of salting-out coefficient.