Extension of Valderrama–Patel–Teja equation of state to modelling single and mixed electrolyte solutions (original) (raw)
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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, 1997
The aqueous electrolyte equation of state (EOS) developed by FiJrst and Renon [W. Fiirst, H. Renon, AIChE J. 39 (1993) 335-343] has been extended to nonaqueous electrolyte solutions. Binary interaction parameters for ion-solvent and ion-ion pairs are estimated from ionic Stokes and Pauling diameters. The temperature dependence of the interaction parameters involving ions has been neglected since the temperature range in question is from 278.15 to 348.25 K. The extended electrolyte EOS has been used to calculate vapor pressures and mean ionic activity coefficients of nonaqueous solutions of single electrolytes without any adjustable parameters. The predicted results are quite satisfactory, the overall average absolute deviation (AAD) for predicted vapor pressure being approximately 1%. In addition, the extended electrolyte EOS has been compared with the electrolyte NRTL model of Mock et al. [B.
Journal of Molecular Liquids, 2012
The Electrolyte-UNIQUAC-NRF model proposed by Haghtalab and Peyvandi, Fluid Phase Equilib., 281, 2009 is modified and extended to represent the excess Gibbs energy function of multicomponent electrolyte solutions. Using the experimental mean activity coefficient of aqueous binary electrolyte systems in the extensive domain of temperature and molality, the adjustable temperature dependent parameters are obtained for the several binary electrolyte systems. Furthermore, the osmotic coefficient and vapor pressure of some binary systems are predicted at the wide range of temperature and molality using the adjustable parameters. Having the binary interaction parameters, the solubility of electrolytes in ternary aqueous electrolyte solutions are predicted at 298 K and the higher temperatures so that the phase diagram of the salt solubility are obtained for the several ternary aqueous-salt systems. The results of the solubility, osmotic coefficient and vapor pressure for the electrolyte systems demonstrate that the generalized Electrolyte-UNIQUAC-NRF model can be successfully applied for prediction of the thermodynamic properties of multicomponent electrolyte systems with very good accuracy.
Chemical Engineering Science, 2000
The Extended UNIQUAC model for electrolyte solutions is an excess Gibbs energy function consisting of a Debye-H uckel term and a term corresponding to the UNIQUAC equation. For vapor-liquid equilibrium calculations, the fugacities of gas-phase components are calculated with the Soave-Redlich-Kwong equation of state. The model only requires binary, temperature-dependent interaction parameters. It has previously been used to describe the excess Gibbs energy for aqueous electrolyte mixtures and aqueous electrolyte systems containing methanol. It has been found to be an adequate model for representing solid-liquid-vapor equilibrium and thermal property data for strongly non-ideal systems. In this work, the model is extended to aqueous salt systems containing higher alcohols. The calculations are based on an extensive database consisting of salt solubility data, vapor liquid equilibrium data, and liquid-liquid equilibrium data for solvent mixtures and for mixed solvent-electrolyte systems.
Modeling of vapor–liquid–solid equilibrium in gas–aqueous electrolyte systems
Chemical Engineering Science, 1999
A thermodynamic model for the description of vapor-liquid-solid equilibria is introduced. This model is a combination of the extended UNIQUAC model for electrolytes and the Soave-Redlich-Kwong cubic equation of state. The model has been applied to aqueous systems containing ammonia and/or carbon dioxide along with various salts. Model parameters valid in the temperature range 0-110°C, the pressure range from 0-100 bar, and the concentration range up to approximately 80 molal ammonia are given. The model parameters were evaluated on the basis of more than 7000 experimental data points. Edwards et al. (1975) used an extended form of the Debye-Hu¨ckel law for the liquid-phase activity coefficients, and the virial equation of state for the pure component fugacity of each component in the vapor phase. Vega and Vera (1976) calculated liquid-phase activity coefficients with a semi-empirical equation. Henry's law constants at reference concentrations were used to calculate the vapor pressures. Similarly to the model of van Krevelen et al. and the SWEQ model, Vega and Vera's model only apply to the low-pressure region where the vapor phase can be considered ideal.
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...
Fluid Phase Equilibria, 2004
A new equation of state (EoS) for describing the thermodynamic properties of aqueous non-electrolytes at infinite dilution is proposed. It is based on the accurate EoS for the solvent (H 2 O) given by Hill [21], it requires only three empirical parameters to be fitted to experimental data, and these are independent of temperature and pressure. Knowledge of the thermodynamic properties of the pure gas, together with these three parameters, enables prediction of the whole set of thermodynamic properties of the solute at infinite dilution (chemical potential, entropy, molar volume, and apparent molar heat capacity) over a wide range of temperatures (0-500 • C) and pressures (1-2000 bar), including the near-critical region. In the cases where experimental thermodynamic data are lacking, the empirical parameters can be estimated solely from the known standard-state properties of the solute. The proposed approach has been tested for non-polar (Ar, Ne, H 2 , N 2 , O 2 , CO 2 , H 3 BO 3 ), polar (H 2 S, NH 3 ) dissolved molecules, ion pairs (HCl, HF), and aqueous hydrocarbons (CH 4 , C 2 H 4 , C 2 H 6 , C 3 H 8 , C 4 H 10 , C 6 H 6 ). Some preliminary calculations show that the approach also has promise for the description of electrolytes.
Industrial & Engineering Chemistry Research, 2008
MgCl 2 ) have been measured by a reliable differential temperature technique. The available experimental literature data on the freezing point depression in addition to the vapor pressure data of aqueous electrolyte solutions for NaCl, KCl, KOH, CaCl 2 , MgCl 2 , CaBr 2 , ZnCl 2 and ZnBr 2 have been used to optimize binary interaction parameters between salts and water. The fugacity of water in salt-free aqueous phase has been modeled by the Cubic-Plus-Association (CPA) equation of state. The Debye-Hückel electrostatic term has been used for taking into account the effect of salt on the fugacity of water when electrolytes are present. Model predictions are validated against independent experimental data generated in this work for both single and mixed electrolyte solutions and a good agreement between predictions and experimental data is observed, supporting the reliability of the developed model.