Recent Advances In Modeling Thermodynamic Properties of Aqueous Strong Electrolyte Systems (original) (raw)
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Iranian Journal of Oil and Gas Science and Technology, 2017
In this work, the performance of four electrolyte models for prediction the osmotic and activity coefficients of different aqueous salt solutions at 298 K, atmospheric pressure and in a wide range of concentrations are evaluated. In two of these models, (electrolyte Non-Random Two-Liquid e-NRTL and Mean Spherical Approximation-Non-Random Two-Liquid MSA-NRTL), association between ions of opposite charges for simplification purposes is ignored and in the other two ones, (Associative Mean Spherical Approximation-Non-Random Two-Liquid AMSA-NRTL and Binding Mean Spherical Approximation BiMSA) association and solvation effects are considered. The predictions of these four models for the osmotic and activity coefficients of electrolyte solutions at 298 K and atmospheric pressure are compared with the experimental data reported in the literature. This comparison includes, 28 different aqueous salt solutions including thio-cyanates, perchlorates, nitrates, hydroxides, quaternary ammonium sal...
Chemical Engineering Science, 1992
The concept of ionic hydration has been used earlier to get a new representation of the excess free energy of aqueous, single-electrolyte solutions, which leads to the prediction of y* and # values using only two parameters for each electrolyte at 25°C. Here this concept is extended to cover higher temperatures (up to 300°C) using temperature-dependent parameters. The resulting equations arc tested with experimental data for several electrolytes of different charge types, covering temperatures up to 300°C and concentrations up to an ionic strength of 15 mol kg-l. It is found that six or seven parameters are enough to get excellent predictive accuracy for y* and # over these concentration and temperature ranges. A detailed comparison with equations of earlier works clearly brings out the predictive superiority of the present method. In recent years, one of the earlier approaches, based on a virial equation for excess free energy, has been shown to give comparable predictive accuracy. However, it has been demqnstrated only for a few electrolytes, and involves 15 or more parameters. The genera1 applicability of the present method is therefore obvious. It has also been shown to be useful in the accurate calculation of the thermal properties, such as enthalpy and heat capacity, which involve successive differentiation of the excess free energy with temperature.
A New Gibbs Energy Model for Obtaining Thermophysical Properties of Aqueous Electrolyte Solutions
Journal of Solution Chemistry, 2008
In this paper, a new Gibbs energy model is proposed to study the thermophysical properties of aqueous electrolyte solutions at various temperatures. The proposed model assumes that the electrolytes completely dissociate in solution. The model also has two temperature-independent adjustable parameters that were regressed using experimental values of the mean ionic activity coefficients (MIAC) for 87 electrolyte solutions at 298.15 K. Results from the proposed model for the MIAC were compared with those obtained from the E-Wilson, E-NRTL, Pitzer and the E-UNIQUAC models, and the adjustable model parameters were used directly to predict the osmotic coefficients at this temperature. The results showed that the proposed model can accurately correlate the MIAC and predict the osmotic coefficients of the aqueous electrolyte solutions better on the average than the other models studied in this work at 298.15 K. Also, the proposed model was examined to study the osmotic coefficient and vapor pressure for a number of aqueous electrolyte solutions at high temperatures. It should be stated that in order to calculate the osmotic coefficients for the electrolyte solutions, the regressed values of parameters obtained for the vapor pressure at high temperatures were used directly. The results obtained for the osmotic coefficients and vapor pressures of electrolyte solutions indicate that good agreement is attained between the experimental data and the results of the proposed model. In order to unequivocally compare the results, the same experimental data and same minimization procedure were used for all of the studied models.
A thermodynamic model has been developed for calculating phase equilibria and other properties of multicomponent electrolyte systems. The model has been designed to reproduce the properties of both aqueous and mixed-solvent electrolyte systems ranging from infinite dilution to solid saturation or pure solute limit. The model incorporates formulations for the excess Gibbs energy and standard-state properties coupled with an algorithm for detailed speciation calculations. The excess Gibbs energy model consists of a long-range interaction contribution represented by the Pitzer-Debye-Hückel expression, a second virial coefficient-type term for specific ionic interactions and a short-range interaction term expressed by the UNIQUAC equation. The accuracy of the model has been demonstrated for common acids and bases and for multicomponent systems containing aluminium species in various environments.
Fluid Phase Equilibria, 2002
Recent advances in modeling thermodynamic and transport properties of electrolyte solutions are reviewed. In particular, attention is focused on mixed-solvent electrolyte models, equations of state for high-temperature and supercritical electrolyte systems and transport property models for multicomponent, concentrated solutions. The models are analyzed with respect to their capability of computing thermodynamic and transport properties in wide ranges of conditions and composition (i.e. for aqueous or mixed-solvent, dilute or concentrated solutions). Various frameworks for the development of electrolyte models are discussed, i.e. models that treat electrolytes on a completely dissociated or undissociated basis and those that take into account the speciation of solutions. A new mixed-solvent electrolyte model is developed for the simultaneous calculation of speciation and phase equilibria. The role of speciation is discussed with respect to the representation of the thermodynamic properties of mixed-solvent electrolyte solutions and diffusion coefficients in aqueous systems.
AIChE Journal, 1986
The overall nonideality of an aqueous mixed electrolyte solution is characterized in terms of a newly defined parameterr*, called the overall reduced ionic activity coefficient. It is shown that I ' * for the mixed solution is simply related to the properties of single-electrolyte solutions. r* is related to the vapor pressure of a mixed-electrolyte solution through well-known thermodynamic equations. This leads to a predictive equation for the vapor pressure of a mixed-electrolyte solution in terms of the vapor pressures of single-electrolyte solutions of the components. This equation is valid over the entire concentration range encountered in practice, without any empirical constants, and has a predictive accuracy of 2%. A predictive equation for the latent heat of vaporization is also developed and tested against experimental data.