Abstract: The free energy, enthalpy and entropy of solution, were evaluated from solubility data for a group of sulfonamides from 25 to 40°C in octanol, water, and the mutually saturated solvents. In aqueous media, the solubility was determined at the isoelectric point and ionic strength 0.15 mol-L−1. The excess free energy and the activity coefficients of the solutes also were determined. The results are discussed in terms of solute–solvent interactions.

Abstract: Prior to equilibrium experiments, a clinoptilolite-type Korean natural zeolite was pretreated with HCl, NaOH, and NaCl to improve the ion-exchange capacity for heavy metals. Singleand multi-species equilibrium data of heavy metals such as copper, cadmium, cesium, and lead on treated and untreated natural zeolites were measured experimentally. For single-species equilibrium data, one of the conventional adsorption isotherms, the Sips equation, was used to fit them and then multi-species equilibrium data were predicted by using the loading ratio correlation (LRC), the ideal adsorbed solution (IAS) theory, and the real adsorbed solution (RAS) theory based on the Sips equation. In applying the RAS theory, we used the Wilson equation for fitting activity coefficients of metal ions in the ion-exchanger phase. It was proven that basic adsorption models except the LRC model could describe multi-species ion-exchange equilibrium for heavy metals/natural zeolite systems well.

Abstract: Silicones are an important class of hydrophobic compounds in widespread use. To evaluate their fate in the environment, an accurate value of the air-water partition (Henry's law) constant is necessary, which, unfortunately, is lacking at present. A static head space and a newly developed dynamic vapor entry loop method were used to obtain the air-water partition constant for six volatile methyl siloxanes. Internally consistent data were obtained. The value of Henry's constant, as calculated from pure component vapor pressure and aqueous solubility, was 10- to 170-fold greater than the experimental values. A correction to the Henry's constant that involves the ratio of the thermodynamic activity coefficient for a methyl siloxane at infinite dilution to that at saturation solubility in the aqueous phase is proposed.

Abstract: The aqueous electrolyte nonrandom two-liquid (NRTL) model of Chen et al. is extended to represent the excess Gibbs energy of aqueous organic electrolytes. These organic electrolytes exhibit very different solution nonideality from typical aqueous electrolytes with elemental ions. The proposed extension is an integration of the electrolyte NRTL model for aqueous electrolytes and the polymer NRTL model (Chen, 1993) for oligomers and polymers. Organic ions are treated as oligomers that consist of hydrocarbon segments and ionic segments that each exhibit distinctive physical interactions with neighboring species. This integrated NRTL model captures the nonideal phase behavior of aqueous organic electrolytes, including micelle formation. The model further provides a versatile thermodynamic framework to correlate solution nonideality of electrolyte systems, organic or inorganic, and complex systems containing both electrolytes and polymers.

Abstract: The water activity, pH and density of some aqueous amino acid solutions were determined at 25 degrees C in three different types of solvents. Previous published experimental data on water activity and solubility of amino acids in aqueous solutions were used together with data from this work to test the applicability of a group contribution model. The activity coefficients were estimated by the UNIFAC-Larsen model combined with the Debye-Huckel equation, taking also into account the partial dissociation phenomena of species in solution. Interaction energies between the charged species Na(+) and Cl(-) and the specific groups of amino acids (COOH and NH(2)) were adjusted using experimental solubility data.

Abstract: Equilibrium ion-exchange isotherms of Na+/Cu2+, Na+/Cd2+, and Na+/Zn2+ on a strong acid resin, Amberlite IR-120, in aqueous medium at (283 and 303) K have been determined in order to assess the possibility of using ion exchange to eliminate heavy metal ions from industrial aqueous liquid streams. The experimental equilibrium data have been satisfactorily correlated using the homogeneous mass action law model (LAM). This model assumes nonideal behavior for both the solution and the solid phase. Wilson and Pitzer equations have been used to calculate activity coefficients in the solid and liquid phases, respectively. The values of the thermodynamic equilibrium constant demonstrate temperature dependence.

Abstract: A review of requirements for equations to calculate the conductivity of a mixture of ions in low dielectric constant solvents (i.e., water at high temperatures) shows that there are conceptual difficulties with all current equations. To explore whether these difficulties limit our ability to predict mixtures, four models for the activity coefficients, two models for the conductivity of a single strong electrolyte, and an equation for the change in equivalent conductivity on mixing single strong electrolytes were chosen. These equations were then tested on the theoretical equation of Turq et al. (J. Phys. Chem. 1995, 99, 822−827) for three ion mixtures. Next the equations were tested on a single 1−1 electrolyte, NaCl (aq) at 652.6 K and 22.75 MPa measured by Gruskiewicz and Wood (J. Phys. Chem. B 1997, 101, 61549−6559) and new measurements at 623.9 K and 19.79 MPa. Then it was tested with new measurements on Na2SO4 (aq) from 300 to 574 K because, in water at high temperatures, this salt produces a solution...

Abstract: SXFIT is the latest in a series of programs designed to model solvent extraction systems of increasing complexity. Unlike its predecessors, SXFIT permits the user complete freedom to define the constituents from which the composition of each phase is to be specified in the data and from which all species of a model for a system are to be formed. This paper describes the manner in which the physical chemistry of the nonaqueous and aqueous solutions involved has come to be treated in this modelling effort. Included are: (1) solute activity coefficients and solvent activity in the nonaqueous phase, estimated by the Scatchard-Hildebrand-Scott treatment; (2) the effect of ionization on these quantities; (3) solute activity coefficients and water activity in the aqueous phase, estimated by the Pitzer treatment; (4) the effect of non ideal behavior on the total concentration of nonaqueous solute species as rendered by a vapor pressure osmometer; (5) a similar treatment of heats of mixing of nonaqueous solutions;...

Abstract: Isobaric vapor−liquid equilibrium data for the binary system water + 1,3-propanediol and for the ternary system water + 1,3-propanediol + glycerol were determined at 30 kPa. All the experimental data reported were thermodynamically consistent. The activity coefficients were correlated with the Wilson, NRTL, and UNIQUAC equations. A distillation column was simulated to study the removal of water from a fermentation broth containing 1,3-propanediol and glycerol.

Abstract: Equilibrium temperatures for liquid–liquid and solid–liquid transitions of systems containing sulfolane and propan-1-ol, butan-1-ol, octan-1-ol or tetradecan-1-ol were measured by a dynamic method. From butan-1-ol, the mixtures show an upper critical solution temperature, which increases with the length of the alcohol. It may attributed to a decreasing of the effective dipole moment of the alkan-1-ol which markedly decreases the interactions between unlike molecules. The coexistence curves become shifted to the high molar fractions of sulfolane in solutions with longer alkan-1-ols, probably due to size effects. Binary systems of sulfolane with cycloalkanes, n-alkanes, benzene or toluene, CCl4 or alkan-1-ols were analyzed in terms of a purely physical model, DISQUAC. The corresponding interaction parameters are reported. DISQUAC represents fairly well, over a rather wide range of temperature, a complete set of thermodynamic properties: liquid–liquid equilibria, LLE, solid–liquid equilibria, SLE, vapor–liquid equilibria, VLE, molar excess Gibbs energies, GE, molar excess enthalpies, HE and natural logarithms of activity coefficients at infinite dilution, ln γi∞. Deviations observed for LLE are typical for mean field theories as calculations are developed assuming that thermodynamic properties close to the critical points are analytical. Experimental data show that sulfolane may play the role of an almost inert diluent, because of the steric hindrance of its globular nature.

Abstract: Isothermal vapor−liquid equilibrium data were measured for two binary systems, 3-methylpentane + 2-methyl-2-propanol at 331 K and 3-methylpentane + 2-butanol at 331 K. The measurements were made with a recirculation still. The results were correlated with the Soave−Redlich−Kwong equation of state and the Wilson activity coefficient model.

Abstract: Activity coefficients of NaCl were determined in water–ethanol solvents, in the range 5–20% (w/w) ethanol, from emf data. The molalities varied from 0.1 mol-kg−1 to near saturation and measurements were taken in the temperature range 25–50°C. The Pitzer model was used to describe the nonideal behavior of the electrolyte and the corresponding coefficients were determined for each solvent. The Pitzer–Simonson equations were also applied and a detailed study, involving the short- and long-range forces, was done in order to better understand the different results obtained with both models.

Abstract: The UNIFAC group-contribution model is used to predict the critical micelle concentration (cmc) of nonionic surfactants in aqueous and nonaqueous solvents. For predicting the cmc, the phase-separation thermodynamic framework approach is used, where the micellar phase is approximated as a second liquid phase resulting from the liquid−liquid equilibrium between the solvent and the surfactant. The necessary activity coefficients are predicted by UNIFAC. The most promising UNIFAC model for this purpose was found to be the UNIFAC-Lyngby (Ind. Eng. Chem. Res. 1987, 26, 2274). To improve the results for surfactants containing oxyethylene chains, a new set of parameters was evaluated for this group, leading to still better cmc predictions for both water and organic solvents, as well as binary solvent systems.

Abstract: The osmotic coefficients of lithium chloride, lithium bromide, and lithium nitrate in 2-propanol have been measured by the isopiestic method at 25°C. Sodium iodide was used as the isopiestic standard. The molality ranges covered were from 0.2 to 1.5 for LiCl and LiBr, and to 1.9 mol-kg−1 for LiNO3. The system of equations developed by Clegg–Pitzer and Pitzer were used to fit each set of osmotic coefficients. The experimental osmotic coefficient data are successfully correlated with these models. The parameters from the fit were used to calculate the mean molal activity coefficients.

Abstract: This work confirms that the activities of individual ions measured with ion-selective electrodes are physically meaningful. The individual activities of the Cl - , Na + and K + ions in single-electrolyte aqueous solutions of HCl, NaOH and KOH were measured at 298.2 K in the range from 0 to 2 molal. In the pH range from 1 to 13, the pH values calculated from the measured activities of the ions are in good agreement with the values obtained with a pH probe. In agreement with previous results for potassium ions, and opposite to the behavior of other cations in 1:1 electrolyte solutions, the K + and the H + ions were found to have smaller activities than their conjugate anions. The experimental activity coefficients of the ions were correlated with the Khoshkbarchi-Vera equation and with the New Hydration Theory, and compared with the predictions given by the Pitzer theory.

Abstract: A method based on continuous thermodynamics has been presented for calculating the vapor pressure of undefined composition mixtures. In order to verify the proposed method the experimental data of an Indonesian petroleum fluid as well as a detailed true boiling point data on the lube-oil cut SAE 10 of Tehran Refinery have been used. In this work by using the combination of the Trouton's rule and the Clausius–Clapeyron equation in the well-known equation of Antonie, the continuous version of the Raoult's law has been developed and the results of the modeling and calculations have been compared with the experimental data and good agreement was found. Moreover, for improving the results of the ideal continuous mixture, modeling of non-ideal behaviour of such mixtures has been carried out by introducing the continuous version of the UNIFAC activity coefficient in the formulation and a better result has been obtained.