Osmotic Coefficients Of Aqueous Solutions Research Articles

Modeling Osmotic Coefficients in Aqueous Solutions of 1-Alkyl-3-methylimidazolim Halides: A Theory That Reflects the Electrical Structure of Ions and ePC-SAFT

Modeling Osmotic Coefficients in Aqueous Solutions of 1-Alkyl-3-methylimidazolim Halides: A Theory That Reflects the Electrical Structure of Ions and ePC-SAFT

Modelling of Mean Ionic Activity and Osmotic Coefficients in Aqueous Solutions of Symmetrical Tetra alkyl Ammonium Halides

Modelling of Mean Ionic Activity and Osmotic Coefficients in Aqueous Solutions of Symmetrical Tetra alkyl Ammonium Halides

Molecular simulation of osmometry in aqueous solutions of the BMIMCl ionic liquid: a potential route to force field parameterization of liquid mixtures.

Despite widespread development and use of ionic liquids (ILs) in both academic and industrial research, computational force fields (FFs) for most of those are not available for a precise description of inter-species interactions in aqueous environments. In the scope of this study, by means of molecular simulations, the osmotic coefficient of an aqueous solution of an IL is calculated and used as a basis to reparameterize popular IL-FFs existing in the literature. We first calculate the osmotic coefficients (at 298.15 K and 1 atm pressure) of aqueous solutions of 1-butyl-3-methylimidazolium chloride (BMIMCl), a generic IL, popularly used in biomass processing and the subsequent conversion to value-added intermediates. The performance of two popular atomic, nonpolarizable FFs developed for BMIMCl, one by Lopes, Pádua, and coworkers (FF-LP) and the other by Sambasivarao, Acevedo, and coworkers (FF-SA), when mixed with the SPC/E water model, is tested with respect to their ability to reproduce the experimental osmotic coefficient data. Interestingly, the osmotic coefficient is found to be increasing with a gradual increase in IL molality within the concentration range of our investigation, which is contrary to the experimental trend reported in the literature for the same IL-water mixture. Henceforth, necessary corrections to the nonbonded ion-ion and ion-water interactions are made to match the experimental osmotic coefficient. To further assess the reliability of the new FF, we extensively explore the thermodynamic (density, isothermal compressibility, and thermal expansion coefficient), dynamic (diffusivity and viscosity), and association/dissociation properties (rationalized with the help of radial distribution functions) with both the original and reparameterized FF for a wider range of concentrations up to a molality of 18.50 mol kg-1. The calculated quantities are compared against experimental data wherever available. The modified FF parameters exhibit significant improvements in terms of its ability to match experimental solution properties, such as density, viscosity, association/dissociation, etc. We report that excessive dissociation of BMIMCl in water is responsible for the shortcomings observed in the original FFs and improved prediction of physicochemical properties could be achieved using the modified FFs.

Thermodynamic studies of phosphonium and imidazolium based ionic liquids in water at 298.15 K: Application of McMillan-Mayer theory and Pitzer model

Experimental results of the osmotic coefficients of aqueous solutions of 1-ethyl-3-methylimidazolium ethylsulfate [EMIM][EtSO4], 1-ethyl-3-methylimidazolium methylsulfate [EMIM][MeSO4], 1-ethyl-3-methylimidazolium tosylate [EMIM][Tos], 1,3-dimethylimidazolium methylsulfate [MMIM][MeSO4], tributylmethylphosphonium methylsulfate [TBMP][MeSO4] and triisobutylmethylphosphonium tosylate [(iBu)3MP][Tos] obtained by vapor pressure osmometry (VPO) at 298.15 K and at atmospheric pressure are reported in this work. From this data water activity (aw), vapor pressure (p), mean molal activity coefficients (γ±), Gibbs free energy due to mixing (ΔGmix) and excess Gibbs free energy change (ΔGE) are calculated. The activity coefficient data obtained are correlated with McMillan-Mayer theory and Pitzer model. The results obtained are elucidated in terms of ion association and structural characteristics of ILs.

Aqueous solutions of ionic liquids. Description of osmotic coefficients within the Binding Mean Spherical Approximation

The Binding Mean Spherical Approximation (BiMSA) is used to describe osmotic coefficients of aqueous solutions of salts containing imidazolium cations and bulky anions over the whole concentration range at temperature in the range (25 to 60)°C. A total of 13 salts have been considered altogether. The ion diameters, the permittivity of solution and the association constant were taken as adjustable parameters. Ionic liquids are described as being weakly associated in water, and association constants values obtained within the BiMSA model are in good agreement with those from the literature. Diameter values were assigned to 1-alkyl-3-methylimidazolium cations. The adjusted values obtained for the cation diameters increased with the number of carbons on the alkyl chain. For all systems studied, average relative deviations were found to be satisfactory.

Nonlinear Contribution of Hydrophobic Hydration in Osmotic Coefficients of Electrolyte Solutions

The osmotic coefficients of aqueous electrolyte solutions containing hydrophobic and hydrophilic ions is known since 1942, exhibit a nonlinear dependences on concentration. On the basis of the cluster representations proposed model solution which takes into account the hydration of the cation and anion of the electrolyte separately. Empirical parameters of the model equations are the hydration numbers and the dispersion of their distribution over the stoichiometric coefficients. The model is used to describe data on the osmotic coefficients of aqueous solutions of sodium carboxylates and tetrabutylammonium chloride and to calculate the mean ionic activity coefficients of salts. The numbers hydrophobic hydration of ions, as shown, nonlinearly dependent on electrolyte concentration. Concluded that extreme osmotic coefficients depending on the concentration due to differences of behavior hydration numbers of hydrophilic and hydrophobic ions.

Calculating the thermodynamic properties of aqueous solutions of alkali metal carboxylates

A modified Robinson-Stokes equation with terms that consider the formation of ionic hydrates and associates is used to describe thermodynamic properties of aqueous solutions of electrolytes. The model is used to describe data on the osmotic coefficients of aqueous solutions of alkali metal carboxylates, and to calculate the mean ionic activity coefficients of salts and excess Gibbs energies. The key contributions from ionic hydration and association to the nonideality of solutions is determined by analyzing the contributions of various factors. Relations that connect the hydration numbers of electrolytes with the parameters of the Pitzer-Mayorga equation and a modified Huckel equation are developed.

Osmotic and activity coefficients of α,ω-amino acids in aqueous solutions at 298.15 K

The osmotic coefficients of aqueous solutions of the α,ω-amino acids: 3-aminopropanoic acid, 4-aminobutanoic acid, 5-aminopentanoic acid and 6-aminohexanoic acid were measured using the isopiestic method at 298.15K. The activity coefficients of these solutes were calculated from the experimental osmotic coefficients and the pairwise free energy coefficients for solute–solute interactions were obtained using the Mc-Millan-Mayer theory. The results are compared with the activity coefficients of α-amino acids and are discussed in terms of solute–solute interactions.

Mean Activity Coefficients and Osmotic Coefficients in Aqueous Solutions of Salts of Ammonium Ions with Univalent Anions at 25 °C

The Hückel equation used in this study to describe the thermodynamic properties of dilute solutions of the ammonium salts of NH4Cl, NH4Br, NH4I, NH4NO3, NH4SCN, and NH4H2PO4 up to 1.5 mol·kg–1 is consisted of two electrolyte-dependent parameters B and b1. Parameter B is linearly related to the ion-size parameter a* in the Debye–Hückel equation, and parameter b1 is the coefficient of the linear correction term with respect to the molality. This coefficient is associated with the hydration numbers of the ions forming the electrolyte. For NH4ClO4 solutions, the estimated Hückel equation applies up to 2.1 mol·kg–1, and the equation was obtained from the isopiestic data measured by Esval and Tyree (J. Phys. Chem.1962, 66, 940–942) against KCl solutions. For molalities above 1.5 mol·kg–1 (in the best case up to 10 mol·kg–1), an extended Hückel equation was used. For this equation, the Hückel equation is supplemented with a quadratic term in molality, and the coefficient of this term is parameter b2. All of the parameters for the Hückel equations of NH4Cl and NH4NO3 solutions were estimated from isopiestic data of Wishaw and Stokes (Trans. Faraday Soc.1953, 49, 27–31). The former data were measured against KCl solutions and the latter against NaCl solutions. The Hückel parameters for NH4Br, NH4I, NH4SCN, and NH4H2PO4 solutions were estimated from the data measured by Covington and Irish (J. Chem. Eng. Data1972, 17, 175–176), Bonner (J. Chem. Eng. Data1976, 21, 498–499), Covington and Matheson (J. Solution Chem.1977, 6, 263–267), and Filippov et al. (J. Appl. Chem., U.S.S.R., 1985, 58, 1807–1811), respectively, using the same experimental technique against NaCl solutions. In all of these estimations, the Hückel parameters of a recent KCl and NaCl study (J. Chem. Eng. Data2009, 54, 208–219) were used for the solutions of the reference electrolyte. In the tests of the new parameter values, the cell potential difference, vapor pressure, and isopiestic data available in the literature were used. These data support well the tested Hückel parameters in most cases at least up to 3.5 mol·kg–1. Reliable thermodynamic activity quantities for ammonium salt solutions are, therefore, obtained using the new Hückel parameters. The activity coefficients, osmotic coefficients, and the vapor pressures obtained using these equations are tabulated here at rounded molalities. These values were compared to those suggested by Robinson and Stokes (Electrolyte Solutions, 2nd ed.; Butterworths Scientific Publications: London, 1959), to those obtained using Pitzer equations (Activity Coefficients in Electrolyte Solutions, 2nd ed.; CRC Press: Boca Raton, 1991; pp 100–101), and to those obtained using the extended Hückel equations presented by Hamer and Wu (J. Phys. Chem. Ref. Data1972, 1, 1047–1099).

The use of a thermoelectric osmometer to measure the osmotic coefficients of aqueous solutions of sodium salicylate at 25 degrees.

Abstract The use of a thermoelectric osmometer to measure osmotic coefficients for the binary system water-sodium salicylate at low concentrations (0·0 to 0·3 molal) is described. The accuracy and reproducibility of the instrument have been enhanced by employing a microscope to measure sample and reference drop sizes. Activity coefficients, calculated from the osmotic coefficients obtained in these experiments, have been combined with density and diffusional measurements to calculate frictional coefficients for the system.

Osmotic and Activity Coefficients of Trimethyloctylammonium Bromide and Decyltrimethylammonium Bromide in Aqueous Solutions as a Function of Temperature

Osmotic coefficients of aqueous solutions of trimethyloctylammonium bromide and decyltrimethylammonium bromide were measured by the isopiestic method at the following temperatures: 298.15, 293.15, 288.15 and 283.15 K. Activity coefficients of the solutes were calculated from the osmotic coefficients. The results were compared with the Debye-Huckel limiting law and analyzed according to their variation with the alkyl chain length of the cation and with the change in temperature.

Measuring and Modeling Activity Coefficients in Aqueous Amino-Acid Solutions

The perturbed-chain statistical association theory (PC-SAFT) is applied to simultaneously describe various thermodynamic properties (density, vapor-pressure depression, activity coefficient, solubility) of aqueous solutions containing an amino acid or an oligopeptide. The 28 organic compounds considered within this work are glycine, alanine, serine, proline, hydroxyproline, valine, leucine, arginine, lysine, threonine, asparagine, tyrosine, histidine, cysteine, methionine, aspartic acid, glutamic acid, α-ABA, α-isoABA, β-ABA, γ-ABA, α-AVA, γ-AVA, diglycine, triglycine, dialanine, Gly-Ala, and Ala-Gly. If not yet available in literature, amino-acid solubility data and activity coefficients were determined experimentally. To prove the predictivity of PC-SAFT, osmotic coefficients in aqueous solutions containing two amino acids (glycine/valine and alanine/valine) were measured and predicted without applying any additional model parameters.

Using Monte Carlo simulation to compute osmotic coefficients of aqueous solutions of ionic liquids

We perform, for the first time to our knowledge, Monte Carlo simulation to compute osmotic coefficient of ionic liquid aqueous solutions. The ionic liquids chosen are 1-ethyl-3-methylimidazolium bromide [Emim][Br], 1-methyl-3-methylimidazolium chloride [Mmim][Cl], 1-methyl-3-methylimidazolium bromide [Mmim][Br], 1-methyl-3-methylimidazolium iodide [Mmim][I] and 1-methyl-3-methylimidazolium hexafluorophosphate [Mmim][PF 6]. Simulations are carried out in the NVT ensemble at 298.15 K. The Unrestricted Primitive Model (UPM) of electrolyte is used as microscopic model in simulation process. Accuracy of simulation to predict osmotic coefficients is verified by a direct comparison of simulation results with experimental data. Computed osmotic coefficients are in good agreement with available experimental values.

Osmotic coefficients of aqueous solutions of potassium acesulfame, sodium saccharin, and ammonium and tetramethylammonium cyclohexylsulfamates at the freezing point of solutions

The osmotic coefficients of aqueous solutions of potassium acesulfame (0.67 mol kg−1), sodium saccharin (0.75 mol kg−1), and tetramethylammonium (0.55 mol kg−1) and ammonium (0.35 mol kg−1) cyclohexylsulfamates were determined up to the molality indicated in parentheses. The osmotic coefficients were fitted to the Pitzer equation, and the ion interaction parameters α 1, β (0), and β (1) were evaluated. The mean ionic activity coefficients of the solutes were calculated, and the non-ideal behaviour of the systems investigated were characterized by calculation of the excess Gibbs energy of the solution and the respective partial molar functions of solute and solvent. The partial molar excess Gibbs energies of the solutes are negative, as also are the corresponding excess Gibbs energies of their solutions, and the partial molar excess Gibbs energies of the solvent are positive and increase slightly with increasing concentrations of the solutes. The solvation ability of water was calculated from differences between the Gibbs energy of solution of water in the aqueous solutions and that of pure water, and are positive and small for all the solutes investigated, throughout the concentration ranges studied.

Isopiestic Determination of the Osmotic and Activity Coefficients of Aqueous Solutions of Symmetrical and Unsymmetrical Quaternary Ammonium Bromides at T = (283.15 and 288.15) K

Osmotic coefficients of aqueous solutions of Bu4NBr, sec-Bu4NBr, iso-Bu4NBr, Bu2Et2NBr, and Bu3EtNBr are measured at T = (283.15 and 288.15) K by the isopiestic method. A branched isopiestic apparatus was used. The osmotic data of the solutions were compared at T = (283.15 and 298.15) K. Osmotic coefficient data are correlated using the Pitzer model. The parameters obtained with the Pitzer model are used to calculate the mean molal activity coefficients. Vapor pressures of the solutions are evaluated from osmotic coefficients, and their depression was used for qualitative deduction of solute−solvent interactions occurring in these solutions.

Osmotic coefficients of aqueous solutions of four ionic liquids at T=(313.15 and 333.15) K

Measurements of osmotic coefficients of BmimCl (1-butyl-3-methylimidazolium chloride), HmimCl (1-hexyl-3-methylimidazolium chloride), MmimMeSO 4 (1,3-dimethylimidazolium methylsulfate), and BmimMeSO 4 (1-butyl-3-methylimidazolium methylsulfate) with water at T = (313.15 and 333.15) K are reported in this work. Vapour pressure and activity data of all the studied binary systems are obtained from experimental data. The osmotic coefficients data are correlated using the extended Pitzer model of Archer and the modified NRTL (MNRTL) model and standard deviations obtained with both models are given too. The parameters obtained with the extended Pitzer model of Archer are used to calculate the mean molal activity coefficients.

Lanthanide Salts Solutions: Representation of Osmotic Coefficients within the Binding Mean Spherical Approximation

Osmotic coefficients of aqueous solutions of lanthanide salts are described using the binding mean spherical approximation (BIMSA) model based on the Wertheim formalism for association. The lanthanide(III) cation and the co-ion are allowed to form a 1-1 ion pair. Hydration is taken into account by introducing concentration-dependent cation size and solution permittivity. An expression for the osmotic coefficient, derived within the BIMSA, is used to fit data for a wide variety of lanthanide pure salt aqueous solutions at 25 degrees C. A total of 38 lanthanide salts have been treated, including perchlorates, nitrates, and chlorides. For most solutions, good fits could be obtained up to high ionic strengths. The relevance of the fitted parameters has been discussed, and a comparison with literature values has been made (especially the association constants) when available.

Osmotic Coefficients of Aqueous Solutions of Some Poly(oxyethylene) Glycols at the Freezing Point of Solution

Summary. The freezing temperatures of dilute aqueous solutions of some poly(oxyethylene) glycols (PEG, HO–(CH2CH2O)n–H, n varying from 4 to 117) were measured over a solute to solvent mass ratio from 0.0100 to 0.3900. The second and third osmotic virial coefficient (A22 and A222 )o f poly(oxyethylene) glycols in aqueous solution were determined. The molecular weight dependence of the second virial coefficient can be described by a simple relation A22 ¼ 2 � 10 � 5 M 1:86 n , and the third virial coefficient is A222 ¼ 0:038A 2 . The activity coefficients of the solute were calculated using the Gibbs-Duhem equation as applied by Bjerrum. From the osmotic and activity coefficients the excess Gibbs energies of solution, as well as the respective partial molar functions of solute and solvent and the virial pair interaction coefficients for the excess Gibbs energies were estimated. The second and the third osmotic virial coefficients are correlated with the Mc-Millan-Mayer virial coefficients.

Vapor Pressures and Osmotic Coefficients of Aqueous Solutions of SDS, C6TAB, and C8TAB at 25 °C

A comparison is given between the osmotic coefficients inferred from direct vapor pressure lowering and from indirect vapor pressure osmometry, for three aqueous surfactant solutions at 25 °C. The results show that vapor pressure osmometry is a rapid but very reliable technique even at room temperature, in contrast to the indications of the manufacturer. Furthermore, the comparison of both techniques reveals that dissolved gas has no noticeable influence on the osmotic coefficients.

Activity Coefficients of Potassium Dihydrogen Phosphate in Aqueous Solutions at 25°C and in Aqueous Mixtures of Urea and this Electrolyte in the Temperature Range 20–35°C

Abstract Simple two-parameter Hückel and Pitzer equations were determined for the calculation of the activity and osmotic coefficients of aqueous solutions of potassium dihydrogen phosphate at 25°C up to a molality of the saturated solution (= 1.83 mol kg−1). The isopiestic data measured by Stokes (1945) were used in the parameter estimations. The resulting parameter values were tested with all thermodynamic data found in the literature for this electrolyte at this temperature. In these tests it was observed, that the Hückel equation applies to the data within experimental error up to a molality of 1.0 mol kg−1, and the Pitzer equation applies well to the data in the molality range 1.0–1.83 mol kg−1 but not very well in dilute solutions. Therefore, also a three-parameter Pitzer equation was determined that applies to all data. The activity and osmotic coefficients calculated by these three models were compared to the values suggested by Robinson and Stokes (1959) and to those calculated by the equations of Hamer and Wu (1972) and of Pitzer and Mayorga (1973) for this electrolyte. Solubility measurements of KH2PO4 at 20, 25, 30 and 35°C were made in aqueous urea solutions, and the molality of urea varied in these measurements from 0 to 2.5 mol kg−1. The thermodynamics of these studies were analyzed by using the Pitzer formalism. It was observed that only one interaction parameter between urea molecules and ions (this parameter is linearly dependent on the temperature) was needed to describe almost completely the new solubility data.