Binodal Research Articles

Liquid-liquid equilibrium data and thermophysical properties for ternary systems composed of water, acetic acid and different solvents

Liquid-liquid equilibrium (LLE) data for water + acetic acid + {1-butanol or isopentanol or methyl-terc-butyl ether (MTBE) or methyl isobutyl ketone (MIBK) or diisobutyl ketone (DIBK) or isoamyl propionate} systems at T = {293.2 and 313.2} K and P ≈ 95 kPa were determined. Immiscibility region (LLE envelope) were determined experimentally through binodal curves (cloud point data). Thermophysical properties, i.e., density, refractive index, speed of sound, isentropic compressibility and molar refractivity were obtained for each cloud point. Tie lines were attained using indirect method utilizing equations obtained through cloud point data fit and partition coefficients, selectivities and percent of extraction were calculated in order to evaluate the effects of solvent type and temperature on acetic acid removal from water. Besides, thermophysical properties for all systems were compared. LLE data were correlated with NRTL model, presenting root mean square deviation equal to 1.2366% for 66 tie lines. NRTL modelling also estimated plait points for all systems.

Crystal structure and thermal properties of the LixNa1–xKZnP2O7 solid solutions and its relation to the MM′ZnP2O7 diphosphate family

New solid solutions of LixNa1–xKZnP2O7, belonging to the MM’ZnP2O7 structural family (M = Li+, Na+, Zn2+; M’ = Na+, K+), were prepared and phase equilibria along the LiKZnP2O7–NaKZnP2O7 section were reported. These solid solutions were investigated single-crystal X-ray diffraction, high-temperature X-ray powder diffraction (HTXRD), differential scanning calorimetry, and impedance spectroscopy. A miscibility gap was found within the range of 0.8 < x < 1.0, and a binodal curve was constructed using HTXRD data. The similarity of the thermal and compositional deformation of LixNa1–xKZnP2O7 solid solutions is revealed: increasing the radius of the metal by 0.01 Å leads to the same deformations of the crystal structure as increasing the temperature by 31 °C. The Li/Na↔Zn cation exchange lead to an increase in conductivity above 300 °C. The alkali mixed effect in activation energy occurs for LixNa1–xKZnP2O7 solid solutions near x = 0.5. The phase with the 2a×2b×c superstructure ordering was observed as a result of the solid solution melting.

Methane Hydration‐Shell Structure and Fragility

AbstractThe influence of oily molecules on the structure of liquid water is a question of importance to biology and geology and many other fields. Previous experimental, theoretical, and simulation studies of methane in liquid water have reached widely conflicting conclusions regarding the structure of hydrophobic hydration‐shells. Herein we address this question by performing Raman hydration‐shell vibrational spectroscopic measurements of methane in liquid water from −10 °C to 300 °C (at 30 MPa, along a path that parallels the liquid‐vapor coexistence curve). We show that, near ambient temperatures, methane's hydration‐shell is slightly more tetrahedral than pure water. Moreover, the hydration‐shell undergoes a crossover to a more disordered structure above ca. 85 °C. Comparisons with the crossover temperature of aqueous methanol (and other alcohols) reveal the stabilizing influence of an alcohol OH head‐group on hydrophobic hydration‐shell fragility.

Methane Hydration-Shell Structure and Fragility.

The influence of oily molecules on the structure of liquid water is a question of importance to biology and geology and many other fields. Previous experimental, theoretical, and simulation studies of methane in liquid water have reached widely conflicting conclusions regarding the structure of hydrophobic hydration-shells. Herein we address this question by performing Raman hydration-shell vibrational spectroscopic measurements of methane in liquid water from -10 °C to 300 °C (at 30 MPa, along a path that parallels the liquid-vapor coexistence curve). We show that, near ambient temperatures, methane's hydration-shell is slightly more tetrahedral than pure water. Moreover, the hydration-shell undergoes a crossover to a more disordered structure above ca. 85 °C. Comparisons with the crossover temperature of aqueous methanol (and other alcohols) reveal the stabilizing influence of an alcohol OH head-group on hydrophobic hydration-shell fragility.

Solid – liquid and liquid – liquid equilibrium of the systems composed of [Cnmim]Cl/Br (n = 2, 4, 6, 8) + Rb2SO4/Cs2SO4 + H2O

In this paper, the phase behavior of the systems composed of [Cnmim]Cl/Br (n = 2, 4, 6, 8), Rb2SO4/Cs2SO4 and H2O was investigated at 298.2 K and 308.2 K. Some systems were solid – liquid equilibrium and some were liquid – liquid equilibrium because of the effect of the inorganic salts and the cation and anion of the ionic liquids. For solid – liquid equilibrium systems, the solubility, density and refractive index of the saturated solution were determined. For liquid – liquid equilibrium systems, the binodal curves were measured. The experimental solubility, density and refractive index were fitted using an empirical equation. The binodal curves data of liquid – liquid equilibrium systems were correlated using Merchuk equation. Moreover, the effect of inorganic salts, ionic liquids, and temperature on the phase behavior of the studied systems was discussed in detail.

Thermodynamic study of aqueous two-phase systems containing biocompatible cholinium aminoate ionic-liquids and polyethylene glycol di-methyl ether 250 and their performances for bovine serum albumin separation

Aqueous two-phase systems, ATPSs, are known as an interesting media for the separation and purification of vital biomolecules in biotechnology applications. From this viewpoint, the ambition of this work is investigating ability of cholinium aminoate ([Ch][AA]) as novel, low toxic and high biodegradable ionic liquids, including of cholinium glycinate ([Ch][Gly]), cholinium prolinate ([Ch][l-Pro]) and cholinium valinate ([Ch][l-Val]) for inducing ATPSs with polyethylene glycol di-methyl ether 250, PEGDME250, and then evaluating their performances for partitioning of bovine serum albumin, BSA, as a model protein. For achieving this purpose, binodal curves and tie-lines were experimentally measured at T = (298.15, 308.15 and 318.15) K under atmospheric pressure (≈85 kPa) for all of the aforementioned systems. The influences of ionic liquid anion and temperature were searched systematically on the binodal curve and tie-lines. The phase splitting ability in these systems was assessed by utilizing the effective exclude volume theory from which the locations of binodals may be predicted and the Setschenow-type equation which provides salting-out coefficients by fitting the experimental tie-lines to this equation. Two empirical equations including of Merchuk equation were applied in order to represent the binodal data. Moreover, the Othmer-Tobias and Bancraft, Osmotic virial equations and two versions of NRTL models (m- or e-NRTL) were selected to correlate the tie-lines. In addition, the partition behaviour of BSA was studied by measuring of partition coefficient and extraction efficiency in the mentioned systems. The measured partition coefficients for BSA were discussed on the basis of physiochemical properties of amino acids involved in ionic liquid structure.

Surprising thermodynamic properties of alcohols and water on their coexistence curves

The thermodynamic properties of water and alcohols of the methanol series on their coexistence curves (CCs) are analyzed. The main attention is focused on the behavior of their specific volumes per molecule and the evaporation heats. We show that the special normalization of these quantities and standard normalization of temperature leads to the similarity of their temperature dependencies on their CCs. And what is more, they are similar to the temperature dependencies for argon. It means that the behavior of the specific volume and the evaporation heat are determined by the averaged interparticle potentials which have the argon-like structure. Small deviations from argon-like dependence are carefully studied. We suppose that these small deviations are caused by the weak angular correlations created by H-bond interactions and should be connected with the main characteristics of H-bond network that is the averaged number of H-bonds per molecule. A method for determination of the last is developed.

Equilibrium phase behavior of aqueous two-phase system formed by triblock copolymer + sulfate salt + water at different temperatures

Equilibrium data for the ternary liquid-liquid system formed of a triblock copolymer (L64 or F68), sulfate salts (Cu(II) or Fe(III)) and water were investigated in this work. The effects of temperature (278.15, 288.15 and 298.15 K), the nature of the cation and the copolymer molar mass on the phase diagram of the aqueous two-phase system were investigated. An increase in temperature decreased the biphasic region for the entire system. Cu(II) and F68 were better able to induce phase separation compared to Fe(III) and L64. The nature of the cation and the copolymer molar mass effect are discussed as a function of the formation of aqua acids through the reaction between the cation and water (Brønsted acids) and in relation to Flory-Huggins theory for macromolecule solutions, respectively. The consistencies of the tie line and binodal curve experimental compositions were evaluated by applying the Othmer-Tobias and Merchuk correlations, respectively.

Flory-Huggins Based Model to Determine Thermodynamic Property of Polymeric Membrane Solution

Flory-Huggins (F-H) model has been widely used to analyze the thermodynamic behavior of polymeric membrane solution during the formation of membrane structure in a phase inversion process. The F-H model involves concentration and binary interaction parameter of components in membrane solution. Those parameters are used to calculate the composition of membrane solution at equilibrium which is then plotted on ternary diagram known as a binodal curve. The binodal curve is used to determine the type of demixing of the polymeric membrane solution and to predict the structure of resulted membrane. Several modifications of F-H model have been conducted in relation to composition (ternary or quaternary) and temperature of the membrane solution. In this paper, the development of F-H model used in designing polymeric membrane by phase inversion method, particularly immersion precipitation method, will be reviewed. The structure and performance of membranes that are governed by the thermodynamic property of the membrane solution based on F-H model will be discussed.

Determination of limit of stability profiles for liquefied natural gas: a thermodynamic approach

Efficient design, operation, handling, and transportation of natural gas as liquefied natural gas (LNG) are controlled by its phase behavior. A phase, in a non-reacting system, is known to be stable when it is at its lowest Gibbs energy; an alternative criterion to the minimization of the Gibbs energy is presented for phase stability status determination of pure systems and mixtures. On this premise, the stability limit determination method by the Helmholtz stability criterion was employed for the determination of stability limits which were used to successfully generate stability limit profiles for LNG and its constituents. To further investigate the metastable region, a new and robust model was developed and successfully used to produce vapor and liquid spinodals as well as binodal curves for the LNG constituents. The model accurately predicted the critical points and was shown to be in very close agreement with the available predicted and experimental results.

Asymmetric liquid-liquid criticality in the ideal volumetric mixing approximation

Abstract We address the question on the validity of the ideal volumetric mixing approximation, a customarily used approach to analyze liquid-liquid phase transitions. Thus, liquid-liquid coexistence curves for the binary mixture composed by nitromethane and 3-pentanol were obtained from direct single-phase mass density measurements as a function of temperature. A reasonable agreement with previously reported data obtained from refractive index measurements has been found, indicating that assuming ideal mixing is rather reasonable. Furthermore, the implications of the ideal volumetric mixing approximation on asymmetric liquid-liquid criticality are explored in the framework of complete scaling formulation, with emphasis on the coexistence curves in the mole fraction-temperature and volume fraction-temperature planes as well as on the behaviour of the isobaric heat capacity per particle and per unit volume and the associated Yang-Yang-type anomalies.

Calculation of the surface tension of water: 40 years of molecular simulations

ABSTRACTWe focus here on the calculation of the surface tension of water by molecular simulations of planar interfaces. We provide a chronological list of the key dates in the calculation of the surface tension of water by using atomistic empirical models, polarisable, many-body and coarse-grained (CG) models. We investigate how the SPC/E, TIP4P and TIP4P/2005 atomistic force fields perform in the reproduction of the surface tension along the coexistence curve. We also study the temperature dependence of the surface tension of water for CG models. We also discuss the ability of ab initio molecular dynamics simulations to reproduce the surface tension of water at room temperature.

Measurements of the liquid-liquid coexistence curves of {(1 − x) dimethyl carbonate + x pentadecane} and {(1 − x) dimethyl carbonate + x heptadecane} in the critical region

The liquid-liquid coexistence curves in a temperature range of about 10 K from the upper consolute critical temperature for binary solutions of {dimethyl carbonate + pentadecane} and {dimethyl carbonate + heptadecane} have been precisely measured. The upper consolute mole fraction xc of n-alkane and the upper consolute temperature Tc were determined to be xc = 0.210, Tc = 312.234 K for {dimethyl carbonate + pentadecane} and xc = 0.183, Tc = 320.496 K for {dimethyl carbonate + heptadecane}, respectively. From the data collected in the near critical point, the critical exponent β was deduced and shown to be consistent well with its theoretical value for the 3-D Ising universality class. The dependences of critical properties on the chain length of n-alkane for a series of {dimethyl carbonate + n-alkane} binary solutions were investigated. Furthermore, it was found that the asymmetric behaviors of the coexistence curve could be well described by the complete scaling theory. The contribution of the heat capacity related term to the asymmetric behaviors of the coexistence curves was discussed.

Effect of Salt Type and Alkyl Chain Length on the Binodal Curve of an Aqueous Two-Phase System Composed of Imidazolium Ionic Liquids

The binodal data for an aqueous two-phase system (ATPS) containing 1-alkyl-3-methylimidazolium tetrafluoroborate ([Cnmim]BF4, n = 2, 3, 4) or 1-alkyl-3-methylimidazolium chloride ([Cnmim]Cl], n = 2, 4, 6, 8, 10, 12) and inorganic salts (K2HPO4, NaH2PO4, (NH4)2SO4, and NaCl) or organic salts (sodium citrate, sodium tartrate, and sodium acetate) were widely determined at T = 298.15 K. The various binodal curves could be fitted and summarized as two kinds of empirical nonlinear equations with the lowest standard deviation (SD). The effects of the salt type and cation alkyl chain length of the ionic liquid (IL) on ATPS binodal curves were further discussed. It was displayed that the salting-out ability of different salts was a major factor in these ATPS formations. For [Cnmim]BF4-based ATPS, the salting-out ability of various salts decreased in the following order: (NH4)2SO4 > Na3C6H5O7 > Na2C4H4O6 > NaH2PO4 > NaC2H3O2 > NaCl. For the [Cnmim]Cl aqueous solution, only K2HPO4 or (NH4)2SO4 could cause the phase ...

The role of ionic liquid [C4 C1 im]Br as an adjuvant on the two-phase formation and the extraction of l-phenylalanine in ABS composed of PEG400 and potassium citrate at different temperatures.

The potential of {polyethylene glycol 400 + potassium citrate} aqueous biphasic system (ABS) with ionic liquid (IL) 1-butyl-3-methylimidazolium bromide ([C4 C1 im]Br) as an adjuvant is examined for the extraction of l-phenylalanine (Phe), as a model biomolecule, at different temperatures and system compositions. The binodal curves and liquid-liquid equilibrium data were determined by the addition of 5 wt% IL to investigate its effect on phase diagrams and Phe partition coefficients. The results indicate that binodal curves of systems with and without IL are more deviated from each other with decreasing temperature. Moreover, IL has a high tendency to partition into the PEG-rich phase. This tendency increases with increasing temperature and system compositions. For Phe, the partition coefficients obtained in this work (KPhe ≈ 5.5-81.2) are significantly higher than those observed in other conventional PEG-inorganic salt ABS (KPhe ≈ 0.5-2.5), water-immiscible ILs two-phase extraction systems (KPhe ≈ 0.02-1.2), or even, in the IL-based ABS with the same IL as the main phase-forming component (KPhe ≈ 3.2). The phase hydrophobicity, salting-out and π⋯π stacking seem to be the main driving forces to affect the extraction aptitude of the studied ABS for Phe. Furthermore, the performance of using [C4 C1 im]Br as adjuvant to improve the partition of Phe in the studied ABS at different temperatures seems to be ruled by the differences in the phases hydrophobicities. Finally, the experimental tie lines and partition coefficients are accurately correlated using the NRTL model. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1149-1166, 2018.

Study of liquid-liquid equilibria in aqueous two-phase systems formed by poly (ethylene glycol) (PEG) and sodium thiosulfate pentahydrate (Na2S2O3.5H2O) at different temperatures

This study aimed at providing experimental liquid-liquid equilibrium (LLE) data for aqueous two-phase systems (ATPSs) formed by poly (ethylene glycols) (PEG) of different molecular weights (1500 or 4000 or 6000) g.mol−1 and sodium thiosulfate pentahydrate at different temperatures (293.15–313.15) K and under atmospheric pressure. Correlations of experimental data of binodal curves were carried out using the Merchuk methodology. The effects of temperature, polymer molecular weight and of the nature of the anion of salts on binodal curves were discussed. In comparison with other anions previously investigated, the salting-out ability of the thiosulfate anion was between those of citrate and tartrate anions. Finally, the Othmer-Tobias and Bancroft equations and the NRTL activity coefficient model were used for correlating tie line compositions.

Thermal molecular potential among micromolecules in charged AdS black holes

Considering the unexpected similarity between the thermodynamic features of charged AdS black holes and that of the van der Waals fluid system, we calculate the number densities of black hole micromolecules and derive the thermodynamic scalar curvature for the small and large black holes on the co-existence curve based on the so-called Ruppeiner thermodynamic geometry. We reveal that the microscopic feature of the small black hole perfectly matches that of the ideal anyon gas, and that the microscopic feature of the large black hole matches that of the ideal Bose gas. More importantly, we investigate the issue of molecular potential among micromolecules of charged AdS black holes, and point out explicitly that the well-known experiential Lennard-Jones potential is a feasible candidate to describe interactions among black hole micromolecules completely from a thermodynamic point of view. The behavior of the interaction force induced by the Lennard-Jones potential coincides with that of the thermodynamic scalar curvature. Both the Lennard-Jones potential and the thermodynamic scalar curvature offer a clear and reliable picture of microscopic structures for the small and large black holes on the co-existence curve for charged AdS black holes.

LIQUID-LIQUID EQUILIBRIUM DATA FOR THE PSEUDO-TERNARY BIODIESEL OF CHICKEN FAT + METHANOL + GLYCEROL

Liquid-liquid equilibrium (LLE) data for the system biodiesel of chicken fat + methanol + glycerol was measured at 25 and 45 °C and atmospheric pressure. The zone of miscibility was found by means of the binodal curve, using the density of turbidity in each point for its construction. Tie lines were defined through the calibration curves of the biodiesel and glycerin phases. The distribution and selectivity coefficients for the system were determined. The validation of the equilibrium data was proved using the Othmer-Tobias and Hand correlations, with coefficients close to the unity. The LLE data were correlated with the UNIQUAC model for temperatures of 25 °C and 45 °C, with global mean deviation values of 0.78% and 0.89%, respectively.

Liquid-liquid demixing of Tergitol solutions by sodium salts

Abstract The salting out effect of different inorganic (Na2CO3, Na2SO3, Na2S2O3, Na2SO4, Na2HPO4) and organic (C2H3Na2O2, C4H4Na2O6, C6H5Na3O7) sodium-based salts has been demonstrated in aqueous solutions of the non-ionic surfactant Tergitol NP10. To do that, the solubility curves of the systems (Tergitol NP10 + salt + H2O) were determined by the cloud point method at T = 298.15 K and 0.1 MPa. Additionally, a polynomial and three different exponential equations, including the most frequently used Merchuk model, were employed to describe the binodal curves. These data, together with the tie-lines, the tie-line length and the slopes of the tie-lines, allowed full characterization of the phase behaviour of the systems. Finally, Bancroft, Othmer-Tobias, and Setschenow empirical equations were employed to shed light on the thermodynamic consistency of the experimental tie-line data.

Influence of the Temperature, Type of Salt, and Alcohol on Phase Diagrams of 2-Propanol + Inorganic Salt Aqueous Two-Phase Systems: Experimental Determination and Correlation

The liquid–liquid equilibriums (LLEs) for 2-propanol + tripotassium phosphate + water at 298.15, 308.15, and 318.15 K and 2-propanol + dipotassium hydrogen phosphate + water at 298.15 K were measured. The binodal curves of 2-propanol + potassium sulfate/potassium sulfite + water at 298.15 K were measured and compared. Accordingly, the experimental binodal data were correlated using Merchuk, Hu, and Pirdashti equations, and the tie-line compositions were correlated using Othmer–Tobias and Bancroft equations. The effect of temperature, anion type, and length of alcohol chain on the binodal curve, tie-line length (TLL), slope of tie-line (STL), and phases’ physical properties were studied. It was found that an increase in salt’s hydrophobicity and alcohol’s carbon number in low temperature led to the expanding biphasic region and approaching the binodal curve to the origin. The phase-forming ability of different anions was studied using effective excluded volume (EEV) model, and the relation between the EEV ...