Peiming Wang - Academia.edu (original) (raw)
Papers by Peiming Wang
To address the need to predict the properties of fluids in severe environments in the oil and gas... more To address the need to predict the properties of fluids in severe environments in the oil and gas industry, a comprehensive thermodynamic model has been developed for mixtures containing H2S, CO2, H2O, and selected salts. The model is based on the previously developed Mixed-Solvent Electrolyte (MSE) framework, which combines an equation of state for standard-state properties of individual species, an excess Gibbs energy model, and an algorithm for solving phase and chemical equilibria in multiphase systems. The standard-state properties are calculated from the Helgeson-Kirkham-Flowers equation whereas the excess Gibbs energy is expressed as a sum of a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. The model has been parameterized using critically evaluated phase equilibrium data for various binary and ternary subsystems of the H2S – CO2 – H2O – Na – Ca – Cl system and has been validated for temperatures ranging from 0°C to 300°C, pressures up to ~3500 atm and salt concentrations up to solid saturation. Furthermore, it reproduces chemical speciation in acid gas – brine systems as exemplified by the accurate prediction of pH. Because of its capability of predicting pH and activities of solution species, the model can serve as a foundation for studying metal – environment interactions in severe oil and gas environments.
International Journal of Thermophysics, Oct 21, 2014
A previously developed model for calculating the thermal conductivity of electrolyte solutions ha... more A previously developed model for calculating the thermal conductivity of electrolyte solutions has been revised. The model represents the effect of electrolytes by introducing two terms in addition to the thermal conductivity of the solvent, i.e., a contribution of individual species expressed using modified Riedel coefficients and an ionic strength-dependent term that accounts for interactions between species. The revision improves and simplifies the ionic strength dependence of the species interaction term. The model has been parameterized based on extensive data for binary, ternary, and quaternary aqueous solutions containing the \hbox {Na}^{+}, \hbox {K}^{+}, \hbox {Mg}^{2+}, \hbox {Ca}^{2+}, \hbox {Cl}^{-}, \hbox {SO}_{4}^{2-}, \hbox {HCO}_{3}^{-}$$Na+,K+,Mg2+,Ca2+,Cl-,SO42-,HCO3-, and \hbox {Br}^{-}$$Br- ions at temperatures ranging from 273 K to 573 K and pressures up to at least 1000 bar. Good agreement between the calculations and experimental data has been obtained with an overall average deviation of 0.44 %. Further, the model has been used to predict the thermal conductivity of seawater and to evaluate the consistency and accuracy of experimental seawater data in view of those for its key components. While older seawater data suffer from significant discrepancies and are not in satisfactory agreement with the model, the predictions are in an excellent agreement with the recent data of Sharqawy. Finally, a much simplified yet accurate model has been formulated specifically for seawater by recasting the complete model in terms of salinity (rather than concentrations of individual components), temperature, and pressure.
Industrial & Engineering Chemistry Research, Nov 5, 2004
A comprehensive model has been developed for calculating electrical conductivities of aqueous or ... more A comprehensive model has been developed for calculating electrical conductivities of aqueous or mixed-solvent electrolyte systems ranging from dilute solutions to fused salts. The model consists of a correlation for calculating ionic conductivities at infinite dilution as a function of solvent composition and a method for predicting the effect of finite electrolyte concentration. The effect of electrolyte concentration is calculated using an extended form of the mean-sphericalapproximation (MSA) theory coupled with a mixing rule for predicting the conductivities of multicomponent systems on the basis of the conductivities of constituent binary cation-anion subsystems. The MSA theory has been extended to very concentrated and mixed-solvent systems by introducing effective ionic radii that take into account various interactions between ions, solvent molecules, and ion pairs. The model has been coupled with thermodynamic equilibrium computations to provide the necessary concentrations of individual ions in complex, multicomponent systems. The model accurately reproduces experimental conductivity data over wide ranges of composition with respect to both solvents and electrolytes. In particular, the model is shown to be accurate for aqueous acids (e.g., H 2 SO 4 , HNO 3 , and H 3 PO 4) up to the pure acid limit, various nitrates ranging from dilute solutions to fused salts, salts in water + alcohol mixtures, and LiPF 6 solutions in propylene and diethyl carbonate.
Journal of Geochemical Exploration, Jul 1, 2010
A comprehensive thermodynamic model has been applied to calculating phase equilibria, speciation,... more A comprehensive thermodynamic model has been applied to calculating phase equilibria, speciation, and other thermodynamic properties of systems that are of geochemical importance. The analyzed systems are relevant to the mineralization of Pb, Ni, Cu, Zn, and Fe. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300°C and for concentrations ranging from infinite dilution to the fused salt limit. The accuracy of the model has been demonstrated by calculating solubilities in multicomponent solutions and predicting the effects of chemical speciation, pH, temperature, CO 2 partial pressure, and concentrations of acids, bases, and selected salts on the formation of various solid phases.
Industrial & Engineering Chemistry Research, Oct 30, 2013
A comprehensive thermodynamic model has been developed for calculating thermodynamic and transpor... more A comprehensive thermodynamic model has been developed for calculating thermodynamic and transport properties of mixtures containing monoethylene glycol (MEG), water, and inorganic salts and gases. The model is based on the previously developed mixed-solvent electrolyte (MSE) framework, which has been designed for the simultaneous calculation of phase equilibria and speciation of electrolytes in aqueous, nonaqueous, and mixed solvents up to the saturation or pure solute limit. In the MSE framework, the standard-state properties of species are calculated from the Helgeson−Kirkham−Flowers equation of state, whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a Pitzer− Debye−Huckel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. Model parameters have been established to reproduce the vapor pressures, solubilities of solids and gases, heat capacities, and densities for MEG + H 2 O + solute systems, where the solute is one or more of the following components:
Fluid Phase Equilibria, Dec 1, 2004
A comprehensive model has been developed for calculating the viscosity of aqueous or mixed-solven... more A comprehensive model has been developed for calculating the viscosity of aqueous or mixed-solvent electrolyte systems ranging from dilute solutions to fused salts. The model incorporates a mixing rule for calculating the viscosity of solvent mixtures and a method for predicting the effect of finite electrolyte concentrations. The mixing rule represents the viscosity of multi-component solvent mixtures using molar volumes and viscosities of pure components together with binary parameters. With this mixing rule, the viscosity of ternary systems can be accurately predicted using parameters determined from only binary data. The effect of electrolyte concentration on viscosity is modeled by combining a long-range electrostatic term obtained from the Onsager-Fuoss theory, a contribution of individual ions, which is quantified by the Jones-Dole B coefficients, and a contribution of specific interactions between ions or neutral species. Formulations have been developed for the contributions of individual ions and species-species interactions to account for the effect of multiple solvents. In addition to solvent composition, the species-species interaction term is also a function of ionic strength. The model accurately reproduces the viscosity of systems such as salts in water, organic or mixed water-organic solvents and aqueous acids or bases up to the pure solute limit. The model has been coupled with thermodynamic equilibrium calculations to reproduce the effects of complexation or other ionic reactions on viscosity.
Fluid Phase Equilibria, Dec 1, 2002
A comprehensive model has been developed for the calculation of speciation, phase equilibria, ent... more A comprehensive model has been developed for the calculation of speciation, phase equilibria, enthalpies, heat capacities and densities in mixed-solvent electrolyte systems. The model incorporates chemical equilibria to account for chemical speciation in multiphase, multicomponent systems. For this purpose, the model combines standard-state thermochemical properties of solution species with an expression for the excess Gibbs energy. The excess Gibbs energy model incorporates a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a short-range interaction term expressed by the UNIQUAC model and a middle-range, second virial coefficient-type term for the remaining ionic interactions. The standard-state properties are calculated by using the Helgeson-Kirkham-Flowers equation of state for species at infinite dilution in water and by constraining the model to reproduce the Gibbs energy of transfer between various solvents. The model is capable of accurately reproducing various types of experimental data for systems including aqueous electrolyte solutions ranging from infinite dilution to fused salts, electrolytes in organic or mixed, water + organic, solvents up to the solubility limit and acid-water mixtures in the full concentration range.
Corrosion Science, May 1, 2010
To investigate the behavior of molybdenum dissolution products in systems that approximate locali... more To investigate the behavior of molybdenum dissolution products in systems that approximate localized corrosion environments, solubility of Mo(III) in equilibrium with solid MoO 2 has been determined at 80°C as a function of solution acidity, chloride concentration and partial pressure of hydrogen. The measurements indicate a strong increase in solubility with acidity and chloride concentration and a weak effect of hydrogen partial pressure. The obtained results have been combined with literature data for systems containing Mo(III), Mo(IV), and Mo(VI) in solutions to develop a comprehensive thermodynamic model of aqueous molybdenum chemistry. The model is based on a previously developed framework for simulating the properties of electrolyte systems ranging from infinite dilution to solid saturation or fused salt limit. To reproduce the measurements, the model assumes the presence of a chloride complex of Mo(III) (i.e., MoCl 2+) and hydrolyzed species (MoOH 2+ , Mo(OH) 2 + , and Mo(OH) 3 0) in addition to the Mo 3+ ion. The model generally reproduces the experimental data within experimental scattering and provides a tool for predicting the phase behavior and speciation in complex, concentrated aqueous solutions. Thus, it provides a foundation for simulating the behavior of molybdenum species in localized corrosion environments.
Fluid Phase Equilibria, Mar 1, 2011
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Journal of Geochemical Exploration, Apr 1, 2009
Industrial & Engineering Chemistry Research, Jun 10, 2003
A comprehensive model has been developed for calculating self-diffusion coefficients in mixedsolv... more A comprehensive model has been developed for calculating self-diffusion coefficients in mixedsolvent electrolyte solutions. The model includes methods for calculating the self-diffusion coefficients of ions and neutral species at infinite dilution and for predicting the effect of finite concentrations of electrolytes. For limiting diffusivities, a mixing rule has been developed for predicting the diffusivity in multicomponent mixed solvents using the limiting diffusivities or ion conductivities in pure solvents. The effect of finite concentrations of electrolytes is modeled by combining the contributions of long-range (Coulombic) and short-range interactions. The longrange interaction contribution is obtained from the mean spherical approximation theory of the relaxation effect, while the short-range interactions are represented using the hard-sphere model of diffusion. Aqueous species are characterized by effective species diameters, which are defined to reflect the interactions between the components of the solution. The model has been integrated with a thermodynamic speciation model, which makes it possible to take into account the effects of complexation or other reactions in the solution. The model accurately reproduces experimental self-diffusion coefficients of ions and neutral molecules in mixed solvents over wide ranges of concentrations.
Industrial & Engineering Chemistry Research, Jun 28, 2008
A comprehensive model has been developed for calculating the thermal conductivity of aqueous, non... more A comprehensive model has been developed for calculating the thermal conductivity of aqueous, nonaqueous, and mixed-solvent electrolyte systems ranging from dilute solutions to fused salts or pure solutes. The model consists of a correlation for calculating the thermal conductivity of solvent mixtures and a method for predicting the effect of electrolyte components. The thermal conductivity of multicomponent solvent mixtures can be represented using surface area parameters and thermal conductivities of pure solvents in conjunction with a single binary parameter per solvent pair. The effect of electrolytes is modeled by accounting for a contribution of individual ions, which is quantified by the Riedel coefficients, and a contribution of specific interactions between ions or neutral species. Formulations have been developed for the contributions of individual ions and species-species interactions to represent the effect of multiple solvents. In addition to solvent composition, the species-species interaction term is also a function of ionic strength. The model accurately reproduces experimental thermal conductivity data over a wide range of electrolyte concentrations in aqueous and nonaqueous systems. In particular, the model has been shown to be accurate for aqueous acids and bases (e.g., H 2 SO 4 , HNO 3 , H 3 PO 4 , NaOH, and KOH) up to the limit of a pure acid or base, various nitrates ranging from dilute solutions to fused salts, and other salts in water and various organic solvents. The model has been coupled with thermodynamic equilibrium calculations to reproduce the effects of complexation or other ionic reactions on thermal conductivity.
Fluid Phase Equilibria, Aug 1, 2001
A general model has been developed for calculating the static dielectric constant of mixed-solven... more A general model has been developed for calculating the static dielectric constant of mixed-solvent electrolyte solutions. For mixtures of solvents without electrolyte components, the model is based on an empirical modification of the Kirkwood theory for multicomponent systems. For systems containing electrolytes, the model takes into account the effects of ions and ion pairs and, therefore, it is capable of reproducing the dependence of the dielectric constant on electrolyte concentration. For most solvent mixtures, dielectric constants can be reasonably predicted using only pure solvent properties. In the case of strongly nonideal solvent mixtures, the results can be significantly improved by adjusting a single binary parameter. The model has also been verified for a number of electrolyte solutions in various solvents over wide composition and temperature ranges. In particular, the increase in the dielectric constant due to ion pairing and its decrease due to the presence of ions and their solvation can be accurately represented.
Fluid Phase Equilibria, Jun 1, 2016
A comprehensive thermodynamic model has been developed for calculating phase equilibria and speci... more A comprehensive thermodynamic model has been developed for calculating phase equilibria and speciation in aqueous mixtures containing neutralizing amines and corresponding amine hydrochlorides. The model has been designed to simulate the behavior of refinery overhead environments, in which the presence of amines in combination with hydrogen chloride may lead to the formation of potentially corrosive solid or concentrated aqueous amine hydrochloride phases. For this purpose, the previously developed Mixed-Solvent Electrolyte (MSE) model has been extended to calculate simultaneously solidegas, solideliquid, and vaporeliquid equilibria, liquid-phase chemical equilibria, and caloric properties. In the model, standard-state properties of individual species are calculated from the HelgesoneKirkhameFlowers equation of state whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a PitzereDebyeeHückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. This framework accurately represents the properties of systems that range from weak electrolytes, such as amine e water mixtures, to strong electrolytes such as amine hydrochloride e water solutions. For amine hydrochlorides, the model is applicable up to the limit of solid or fused liquid hydrochloride phases. Model parameters have been developed for methylamine, morpholine, N-methylmorpholine, Nethylmorpholine and their hydrochlorides. The model offers the possibility of understanding the formation of amine hydrochlorides in multicomponent mixtures containing amines, water, hydrogen chloride, and carbon dioxide.
Industrial & Engineering Chemistry Research, May 13, 2013
A comprehensive model has been developed for calculating the interfacial tension (σ) in liquid−li... more A comprehensive model has been developed for calculating the interfacial tension (σ) in liquid−liquid systems with or without electrolyte components. The model consists of an equation for computing the interfacial tension of two-liquidphase nonelectrolyte systems and an expression for the effect of the electrolyte concentration. The dependence of the interfacial tension on the electrolyte concentration was derived by combining the Gibbs equation with a modified Langmuir adsorption isotherm that represents the interfacial excess of the solute species. The Langmuir adsorption formalism was extended by introducing the effects of binary interactions between solute species (ions or molecules) on the interface. The equation for the interfacial tension of nonelectrolyte liquid−liquid systems was derived using a general thermodynamic framework that was empirically extended by introducing an effective interfacial area that is defined for each component and takes into account the effects of other components at the interface. The model was found to reproduce experimental data for a variety of liquid−liquid systems. In particular, the interfacial tension of ternary systems can be accurately predicted using parameters determined from only binary data. Furthermore, the interfacial tension model was coupled with a previously developed thermodynamic model to provide activity coefficients and equilibrium concentrations in coexisting liquid phases. This makes it possible to reproduce the effects of speciation and salting out or salting in. Because of the coupling of the thermodynamic model with interfacial tension calculations, the variation of σ with electrolyte concentration can be reasonably predicted even without introducing electrolytespecific parameters in the interfacial tension model. Thus, the model can be used to estimate the electrolyte effect on σ in the absence of experimental data. With regressed model parameters, the average deviations between the calculated results and experimental data were 0.50 mN•m −1 for 30 binary nonelectrolyte systems, 0.88 mN•m −1 for 23 ternary nonelectrolyte systems, and 0.16 mN•m −1 for 26 systems with ionic components.
Industrial & Engineering Chemistry Research, Mar 1, 2011
A comprehensive model has been developed for calculating the surface tension of aqueous, nonaqueo... more A comprehensive model has been developed for calculating the surface tension of aqueous, nonaqueous, and mixedsolvent electrolyte systems ranging from dilute solutions to fused salts. The model consists of a correlation for computing the surface tension of solvent mixtures and an expression for the effect of electrolyte concentration. The dependence of surface tension on electrolyte concentration has been derived from the Gibbs equation combined with a modified Langmuir adsorption isotherm for modeling the surface excess of species. The model extends the Langmuir adsorption formalism by introducing the effects of binary interactions between solute species (ions or molecules) on the surface. This extension is especially important for high electrolyte concentrations and in strongly speciated systems. The surface tension of mixed solvents is calculated by utilizing the surface tensions of the constituent pure components together with an effective surface concentration, which is defined for each component and takes into account interactions between solvent molecules. This procedure has been shown to reproduce experimental data for a variety of mixtures. In particular, it accurately predicts the surface tension of ternary solvent mixtures using parameters determined from only binary data. The surface tension model has been coupled with a previously developed thermodynamic equilibrium model to provide speciation and activity coefficients, which are necessary for electrolyte systems. This makes it possible to reproduce the effects of complexation or other reactions in solution. In all cases for which experimental data are available and have been tested, the new model has been shown to be accurate in reproducing surface tension over wide ranges of temperature and concentration. The average deviations between the calculated results and experimental data are 0.68% for binary solvent mixtures, 1.89% for ternary solvent mixtures, and 0.71% for salt solutions up to the solid saturation or pure solute limit.
Fluid Phase Equilibria, Aug 1, 2007
A comprehensive thermodynamic framework for mixed-solvent electrolyte systems has been applied to... more A comprehensive thermodynamic framework for mixed-solvent electrolyte systems has been applied to the simultaneous computation of phase behavior and acid-base equilibria. The computational approach combines an excess Gibbs energy model with a formulation for standard-state properties of individual species and an algorithm for speciation calculations. Using this framework, a consistent methodology has been established to calculate the pH of mixed-solvent solutions using a single, aqueous reference state. It has been shown that solid solubilities, vapor-liquid equilibria, solution pH and other properties can be reproduced for mixed solvents ranging from pure water to pure non-aqueous components and for solutes ranging from infinite dilution to the fused salt limit. In particular, the model has been shown to be accurate for mixtures containing hydrogen peroxide and ethylene glycol as solvents and various salts, acids and bases as solutes.
The Journal of Chemical Thermodynamics, 2019
Rare earth sulfates in aqueous systems: Thermodynamic modeling of binary and multicomponent syste... more Rare earth sulfates in aqueous systems: Thermodynamic modeling of binary and multicomponent systems over wide concentration and temperature ranges,
Journal of Solution Chemistry, Feb 17, 2017
A comprehensive thermodynamic model, referred to as the Mixed-Solvent Electrolyte model, has been... more A comprehensive thermodynamic model, referred to as the Mixed-Solvent Electrolyte model, has been applied to calculate phase equilibria and chemical speciation in selected aqueous actinide systems. The solution chemistry of U(IV, VI), Np(IV, V, VI), Pu(III, IV, V, VI), Am(III), and Cm(III) has been analyzed to develop the parameters of the model. These parameters include the standard-state thermochemical properties of aqueous and solid actinide species as well as the ion interaction parameters that reflect the solution's nonideality. The model reproduces the solubility behavior and accurately predicts the formation of competing solid phases as a function of pH (from 0 to 14 and higher), temperature (up to 573 K), partial pressure of CO 2 (up to p CO 2 = 1 bar), and concentrations of acids (to 127 molÁkg-1), bases (to 18 molÁkg-1), carbonates (to 6 molÁkg-1) and other ionic components (i.e., Na ? , Ca 2? , Mg 2? , OH-, Cl-, ClO À 4 , and NO À 3). Redox effects on solubility and speciation have been incorporated into the model, as exemplified by the reductive and oxidative dissolution of Np(VI) and Pu(IV) solids, respectively. Thus, the model can be used to elucidate the phase and chemical equilibria for radionuclides in natural aquatic systems or in nuclear waste repository environments as a function of environmental conditions. Additionally, the model has been applied to systems relevant to nuclear fuel processing, in which nitric acid and nitrate salts of plutonium and uranium are present at high concentrations. The model reproduces speciation and solubility in the U(VI) ? HNO 3 ? H 2 O and Pu(IV, VI) ? HNO 3 ? H 2 O systems up to very high nitric acid concentrations (x HNO3 % 0:70). Furthermore, the similarities and differences in the solubility behavior of the actinides have been analyzed in terms of aqueous speciation.
To address the need to predict the properties of fluids in severe environments in the oil and gas... more To address the need to predict the properties of fluids in severe environments in the oil and gas industry, a comprehensive thermodynamic model has been developed for mixtures containing H2S, CO2, H2O, and selected salts. The model is based on the previously developed Mixed-Solvent Electrolyte (MSE) framework, which combines an equation of state for standard-state properties of individual species, an excess Gibbs energy model, and an algorithm for solving phase and chemical equilibria in multiphase systems. The standard-state properties are calculated from the Helgeson-Kirkham-Flowers equation whereas the excess Gibbs energy is expressed as a sum of a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. The model has been parameterized using critically evaluated phase equilibrium data for various binary and ternary subsystems of the H2S – CO2 – H2O – Na – Ca – Cl system and has been validated for temperatures ranging from 0°C to 300°C, pressures up to ~3500 atm and salt concentrations up to solid saturation. Furthermore, it reproduces chemical speciation in acid gas – brine systems as exemplified by the accurate prediction of pH. Because of its capability of predicting pH and activities of solution species, the model can serve as a foundation for studying metal – environment interactions in severe oil and gas environments.
International Journal of Thermophysics, Oct 21, 2014
A previously developed model for calculating the thermal conductivity of electrolyte solutions ha... more A previously developed model for calculating the thermal conductivity of electrolyte solutions has been revised. The model represents the effect of electrolytes by introducing two terms in addition to the thermal conductivity of the solvent, i.e., a contribution of individual species expressed using modified Riedel coefficients and an ionic strength-dependent term that accounts for interactions between species. The revision improves and simplifies the ionic strength dependence of the species interaction term. The model has been parameterized based on extensive data for binary, ternary, and quaternary aqueous solutions containing the \hbox {Na}^{+}, \hbox {K}^{+}, \hbox {Mg}^{2+}, \hbox {Ca}^{2+}, \hbox {Cl}^{-}, \hbox {SO}_{4}^{2-}, \hbox {HCO}_{3}^{-}$$Na+,K+,Mg2+,Ca2+,Cl-,SO42-,HCO3-, and \hbox {Br}^{-}$$Br- ions at temperatures ranging from 273 K to 573 K and pressures up to at least 1000 bar. Good agreement between the calculations and experimental data has been obtained with an overall average deviation of 0.44 %. Further, the model has been used to predict the thermal conductivity of seawater and to evaluate the consistency and accuracy of experimental seawater data in view of those for its key components. While older seawater data suffer from significant discrepancies and are not in satisfactory agreement with the model, the predictions are in an excellent agreement with the recent data of Sharqawy. Finally, a much simplified yet accurate model has been formulated specifically for seawater by recasting the complete model in terms of salinity (rather than concentrations of individual components), temperature, and pressure.
Industrial & Engineering Chemistry Research, Nov 5, 2004
A comprehensive model has been developed for calculating electrical conductivities of aqueous or ... more A comprehensive model has been developed for calculating electrical conductivities of aqueous or mixed-solvent electrolyte systems ranging from dilute solutions to fused salts. The model consists of a correlation for calculating ionic conductivities at infinite dilution as a function of solvent composition and a method for predicting the effect of finite electrolyte concentration. The effect of electrolyte concentration is calculated using an extended form of the mean-sphericalapproximation (MSA) theory coupled with a mixing rule for predicting the conductivities of multicomponent systems on the basis of the conductivities of constituent binary cation-anion subsystems. The MSA theory has been extended to very concentrated and mixed-solvent systems by introducing effective ionic radii that take into account various interactions between ions, solvent molecules, and ion pairs. The model has been coupled with thermodynamic equilibrium computations to provide the necessary concentrations of individual ions in complex, multicomponent systems. The model accurately reproduces experimental conductivity data over wide ranges of composition with respect to both solvents and electrolytes. In particular, the model is shown to be accurate for aqueous acids (e.g., H 2 SO 4 , HNO 3 , and H 3 PO 4) up to the pure acid limit, various nitrates ranging from dilute solutions to fused salts, salts in water + alcohol mixtures, and LiPF 6 solutions in propylene and diethyl carbonate.
Journal of Geochemical Exploration, Jul 1, 2010
A comprehensive thermodynamic model has been applied to calculating phase equilibria, speciation,... more A comprehensive thermodynamic model has been applied to calculating phase equilibria, speciation, and other thermodynamic properties of systems that are of geochemical importance. The analyzed systems are relevant to the mineralization of Pb, Ni, Cu, Zn, and Fe. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300°C and for concentrations ranging from infinite dilution to the fused salt limit. The accuracy of the model has been demonstrated by calculating solubilities in multicomponent solutions and predicting the effects of chemical speciation, pH, temperature, CO 2 partial pressure, and concentrations of acids, bases, and selected salts on the formation of various solid phases.
Industrial & Engineering Chemistry Research, Oct 30, 2013
A comprehensive thermodynamic model has been developed for calculating thermodynamic and transpor... more A comprehensive thermodynamic model has been developed for calculating thermodynamic and transport properties of mixtures containing monoethylene glycol (MEG), water, and inorganic salts and gases. The model is based on the previously developed mixed-solvent electrolyte (MSE) framework, which has been designed for the simultaneous calculation of phase equilibria and speciation of electrolytes in aqueous, nonaqueous, and mixed solvents up to the saturation or pure solute limit. In the MSE framework, the standard-state properties of species are calculated from the Helgeson−Kirkham−Flowers equation of state, whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a Pitzer− Debye−Huckel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. Model parameters have been established to reproduce the vapor pressures, solubilities of solids and gases, heat capacities, and densities for MEG + H 2 O + solute systems, where the solute is one or more of the following components:
Fluid Phase Equilibria, Dec 1, 2004
A comprehensive model has been developed for calculating the viscosity of aqueous or mixed-solven... more A comprehensive model has been developed for calculating the viscosity of aqueous or mixed-solvent electrolyte systems ranging from dilute solutions to fused salts. The model incorporates a mixing rule for calculating the viscosity of solvent mixtures and a method for predicting the effect of finite electrolyte concentrations. The mixing rule represents the viscosity of multi-component solvent mixtures using molar volumes and viscosities of pure components together with binary parameters. With this mixing rule, the viscosity of ternary systems can be accurately predicted using parameters determined from only binary data. The effect of electrolyte concentration on viscosity is modeled by combining a long-range electrostatic term obtained from the Onsager-Fuoss theory, a contribution of individual ions, which is quantified by the Jones-Dole B coefficients, and a contribution of specific interactions between ions or neutral species. Formulations have been developed for the contributions of individual ions and species-species interactions to account for the effect of multiple solvents. In addition to solvent composition, the species-species interaction term is also a function of ionic strength. The model accurately reproduces the viscosity of systems such as salts in water, organic or mixed water-organic solvents and aqueous acids or bases up to the pure solute limit. The model has been coupled with thermodynamic equilibrium calculations to reproduce the effects of complexation or other ionic reactions on viscosity.
Fluid Phase Equilibria, Dec 1, 2002
A comprehensive model has been developed for the calculation of speciation, phase equilibria, ent... more A comprehensive model has been developed for the calculation of speciation, phase equilibria, enthalpies, heat capacities and densities in mixed-solvent electrolyte systems. The model incorporates chemical equilibria to account for chemical speciation in multiphase, multicomponent systems. For this purpose, the model combines standard-state thermochemical properties of solution species with an expression for the excess Gibbs energy. The excess Gibbs energy model incorporates a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a short-range interaction term expressed by the UNIQUAC model and a middle-range, second virial coefficient-type term for the remaining ionic interactions. The standard-state properties are calculated by using the Helgeson-Kirkham-Flowers equation of state for species at infinite dilution in water and by constraining the model to reproduce the Gibbs energy of transfer between various solvents. The model is capable of accurately reproducing various types of experimental data for systems including aqueous electrolyte solutions ranging from infinite dilution to fused salts, electrolytes in organic or mixed, water + organic, solvents up to the solubility limit and acid-water mixtures in the full concentration range.
Corrosion Science, May 1, 2010
To investigate the behavior of molybdenum dissolution products in systems that approximate locali... more To investigate the behavior of molybdenum dissolution products in systems that approximate localized corrosion environments, solubility of Mo(III) in equilibrium with solid MoO 2 has been determined at 80°C as a function of solution acidity, chloride concentration and partial pressure of hydrogen. The measurements indicate a strong increase in solubility with acidity and chloride concentration and a weak effect of hydrogen partial pressure. The obtained results have been combined with literature data for systems containing Mo(III), Mo(IV), and Mo(VI) in solutions to develop a comprehensive thermodynamic model of aqueous molybdenum chemistry. The model is based on a previously developed framework for simulating the properties of electrolyte systems ranging from infinite dilution to solid saturation or fused salt limit. To reproduce the measurements, the model assumes the presence of a chloride complex of Mo(III) (i.e., MoCl 2+) and hydrolyzed species (MoOH 2+ , Mo(OH) 2 + , and Mo(OH) 3 0) in addition to the Mo 3+ ion. The model generally reproduces the experimental data within experimental scattering and provides a tool for predicting the phase behavior and speciation in complex, concentrated aqueous solutions. Thus, it provides a foundation for simulating the behavior of molybdenum species in localized corrosion environments.
Fluid Phase Equilibria, Mar 1, 2011
This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright
Journal of Geochemical Exploration, Apr 1, 2009
Industrial & Engineering Chemistry Research, Jun 10, 2003
A comprehensive model has been developed for calculating self-diffusion coefficients in mixedsolv... more A comprehensive model has been developed for calculating self-diffusion coefficients in mixedsolvent electrolyte solutions. The model includes methods for calculating the self-diffusion coefficients of ions and neutral species at infinite dilution and for predicting the effect of finite concentrations of electrolytes. For limiting diffusivities, a mixing rule has been developed for predicting the diffusivity in multicomponent mixed solvents using the limiting diffusivities or ion conductivities in pure solvents. The effect of finite concentrations of electrolytes is modeled by combining the contributions of long-range (Coulombic) and short-range interactions. The longrange interaction contribution is obtained from the mean spherical approximation theory of the relaxation effect, while the short-range interactions are represented using the hard-sphere model of diffusion. Aqueous species are characterized by effective species diameters, which are defined to reflect the interactions between the components of the solution. The model has been integrated with a thermodynamic speciation model, which makes it possible to take into account the effects of complexation or other reactions in the solution. The model accurately reproduces experimental self-diffusion coefficients of ions and neutral molecules in mixed solvents over wide ranges of concentrations.
Industrial & Engineering Chemistry Research, Jun 28, 2008
A comprehensive model has been developed for calculating the thermal conductivity of aqueous, non... more A comprehensive model has been developed for calculating the thermal conductivity of aqueous, nonaqueous, and mixed-solvent electrolyte systems ranging from dilute solutions to fused salts or pure solutes. The model consists of a correlation for calculating the thermal conductivity of solvent mixtures and a method for predicting the effect of electrolyte components. The thermal conductivity of multicomponent solvent mixtures can be represented using surface area parameters and thermal conductivities of pure solvents in conjunction with a single binary parameter per solvent pair. The effect of electrolytes is modeled by accounting for a contribution of individual ions, which is quantified by the Riedel coefficients, and a contribution of specific interactions between ions or neutral species. Formulations have been developed for the contributions of individual ions and species-species interactions to represent the effect of multiple solvents. In addition to solvent composition, the species-species interaction term is also a function of ionic strength. The model accurately reproduces experimental thermal conductivity data over a wide range of electrolyte concentrations in aqueous and nonaqueous systems. In particular, the model has been shown to be accurate for aqueous acids and bases (e.g., H 2 SO 4 , HNO 3 , H 3 PO 4 , NaOH, and KOH) up to the limit of a pure acid or base, various nitrates ranging from dilute solutions to fused salts, and other salts in water and various organic solvents. The model has been coupled with thermodynamic equilibrium calculations to reproduce the effects of complexation or other ionic reactions on thermal conductivity.
Fluid Phase Equilibria, Aug 1, 2001
A general model has been developed for calculating the static dielectric constant of mixed-solven... more A general model has been developed for calculating the static dielectric constant of mixed-solvent electrolyte solutions. For mixtures of solvents without electrolyte components, the model is based on an empirical modification of the Kirkwood theory for multicomponent systems. For systems containing electrolytes, the model takes into account the effects of ions and ion pairs and, therefore, it is capable of reproducing the dependence of the dielectric constant on electrolyte concentration. For most solvent mixtures, dielectric constants can be reasonably predicted using only pure solvent properties. In the case of strongly nonideal solvent mixtures, the results can be significantly improved by adjusting a single binary parameter. The model has also been verified for a number of electrolyte solutions in various solvents over wide composition and temperature ranges. In particular, the increase in the dielectric constant due to ion pairing and its decrease due to the presence of ions and their solvation can be accurately represented.
Fluid Phase Equilibria, Jun 1, 2016
A comprehensive thermodynamic model has been developed for calculating phase equilibria and speci... more A comprehensive thermodynamic model has been developed for calculating phase equilibria and speciation in aqueous mixtures containing neutralizing amines and corresponding amine hydrochlorides. The model has been designed to simulate the behavior of refinery overhead environments, in which the presence of amines in combination with hydrogen chloride may lead to the formation of potentially corrosive solid or concentrated aqueous amine hydrochloride phases. For this purpose, the previously developed Mixed-Solvent Electrolyte (MSE) model has been extended to calculate simultaneously solidegas, solideliquid, and vaporeliquid equilibria, liquid-phase chemical equilibria, and caloric properties. In the model, standard-state properties of individual species are calculated from the HelgesoneKirkhameFlowers equation of state whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a PitzereDebyeeHückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. This framework accurately represents the properties of systems that range from weak electrolytes, such as amine e water mixtures, to strong electrolytes such as amine hydrochloride e water solutions. For amine hydrochlorides, the model is applicable up to the limit of solid or fused liquid hydrochloride phases. Model parameters have been developed for methylamine, morpholine, N-methylmorpholine, Nethylmorpholine and their hydrochlorides. The model offers the possibility of understanding the formation of amine hydrochlorides in multicomponent mixtures containing amines, water, hydrogen chloride, and carbon dioxide.
Industrial & Engineering Chemistry Research, May 13, 2013
A comprehensive model has been developed for calculating the interfacial tension (σ) in liquid−li... more A comprehensive model has been developed for calculating the interfacial tension (σ) in liquid−liquid systems with or without electrolyte components. The model consists of an equation for computing the interfacial tension of two-liquidphase nonelectrolyte systems and an expression for the effect of the electrolyte concentration. The dependence of the interfacial tension on the electrolyte concentration was derived by combining the Gibbs equation with a modified Langmuir adsorption isotherm that represents the interfacial excess of the solute species. The Langmuir adsorption formalism was extended by introducing the effects of binary interactions between solute species (ions or molecules) on the interface. The equation for the interfacial tension of nonelectrolyte liquid−liquid systems was derived using a general thermodynamic framework that was empirically extended by introducing an effective interfacial area that is defined for each component and takes into account the effects of other components at the interface. The model was found to reproduce experimental data for a variety of liquid−liquid systems. In particular, the interfacial tension of ternary systems can be accurately predicted using parameters determined from only binary data. Furthermore, the interfacial tension model was coupled with a previously developed thermodynamic model to provide activity coefficients and equilibrium concentrations in coexisting liquid phases. This makes it possible to reproduce the effects of speciation and salting out or salting in. Because of the coupling of the thermodynamic model with interfacial tension calculations, the variation of σ with electrolyte concentration can be reasonably predicted even without introducing electrolytespecific parameters in the interfacial tension model. Thus, the model can be used to estimate the electrolyte effect on σ in the absence of experimental data. With regressed model parameters, the average deviations between the calculated results and experimental data were 0.50 mN•m −1 for 30 binary nonelectrolyte systems, 0.88 mN•m −1 for 23 ternary nonelectrolyte systems, and 0.16 mN•m −1 for 26 systems with ionic components.
Industrial & Engineering Chemistry Research, Mar 1, 2011
A comprehensive model has been developed for calculating the surface tension of aqueous, nonaqueo... more A comprehensive model has been developed for calculating the surface tension of aqueous, nonaqueous, and mixedsolvent electrolyte systems ranging from dilute solutions to fused salts. The model consists of a correlation for computing the surface tension of solvent mixtures and an expression for the effect of electrolyte concentration. The dependence of surface tension on electrolyte concentration has been derived from the Gibbs equation combined with a modified Langmuir adsorption isotherm for modeling the surface excess of species. The model extends the Langmuir adsorption formalism by introducing the effects of binary interactions between solute species (ions or molecules) on the surface. This extension is especially important for high electrolyte concentrations and in strongly speciated systems. The surface tension of mixed solvents is calculated by utilizing the surface tensions of the constituent pure components together with an effective surface concentration, which is defined for each component and takes into account interactions between solvent molecules. This procedure has been shown to reproduce experimental data for a variety of mixtures. In particular, it accurately predicts the surface tension of ternary solvent mixtures using parameters determined from only binary data. The surface tension model has been coupled with a previously developed thermodynamic equilibrium model to provide speciation and activity coefficients, which are necessary for electrolyte systems. This makes it possible to reproduce the effects of complexation or other reactions in solution. In all cases for which experimental data are available and have been tested, the new model has been shown to be accurate in reproducing surface tension over wide ranges of temperature and concentration. The average deviations between the calculated results and experimental data are 0.68% for binary solvent mixtures, 1.89% for ternary solvent mixtures, and 0.71% for salt solutions up to the solid saturation or pure solute limit.
Fluid Phase Equilibria, Aug 1, 2007
A comprehensive thermodynamic framework for mixed-solvent electrolyte systems has been applied to... more A comprehensive thermodynamic framework for mixed-solvent electrolyte systems has been applied to the simultaneous computation of phase behavior and acid-base equilibria. The computational approach combines an excess Gibbs energy model with a formulation for standard-state properties of individual species and an algorithm for speciation calculations. Using this framework, a consistent methodology has been established to calculate the pH of mixed-solvent solutions using a single, aqueous reference state. It has been shown that solid solubilities, vapor-liquid equilibria, solution pH and other properties can be reproduced for mixed solvents ranging from pure water to pure non-aqueous components and for solutes ranging from infinite dilution to the fused salt limit. In particular, the model has been shown to be accurate for mixtures containing hydrogen peroxide and ethylene glycol as solvents and various salts, acids and bases as solutes.
The Journal of Chemical Thermodynamics, 2019
Rare earth sulfates in aqueous systems: Thermodynamic modeling of binary and multicomponent syste... more Rare earth sulfates in aqueous systems: Thermodynamic modeling of binary and multicomponent systems over wide concentration and temperature ranges,
Journal of Solution Chemistry, Feb 17, 2017
A comprehensive thermodynamic model, referred to as the Mixed-Solvent Electrolyte model, has been... more A comprehensive thermodynamic model, referred to as the Mixed-Solvent Electrolyte model, has been applied to calculate phase equilibria and chemical speciation in selected aqueous actinide systems. The solution chemistry of U(IV, VI), Np(IV, V, VI), Pu(III, IV, V, VI), Am(III), and Cm(III) has been analyzed to develop the parameters of the model. These parameters include the standard-state thermochemical properties of aqueous and solid actinide species as well as the ion interaction parameters that reflect the solution's nonideality. The model reproduces the solubility behavior and accurately predicts the formation of competing solid phases as a function of pH (from 0 to 14 and higher), temperature (up to 573 K), partial pressure of CO 2 (up to p CO 2 = 1 bar), and concentrations of acids (to 127 molÁkg-1), bases (to 18 molÁkg-1), carbonates (to 6 molÁkg-1) and other ionic components (i.e., Na ? , Ca 2? , Mg 2? , OH-, Cl-, ClO À 4 , and NO À 3). Redox effects on solubility and speciation have been incorporated into the model, as exemplified by the reductive and oxidative dissolution of Np(VI) and Pu(IV) solids, respectively. Thus, the model can be used to elucidate the phase and chemical equilibria for radionuclides in natural aquatic systems or in nuclear waste repository environments as a function of environmental conditions. Additionally, the model has been applied to systems relevant to nuclear fuel processing, in which nitric acid and nitrate salts of plutonium and uranium are present at high concentrations. The model reproduces speciation and solubility in the U(VI) ? HNO 3 ? H 2 O and Pu(IV, VI) ? HNO 3 ? H 2 O systems up to very high nitric acid concentrations (x HNO3 % 0:70). Furthermore, the similarities and differences in the solubility behavior of the actinides have been analyzed in terms of aqueous speciation.