An empirical mixing rule for estimating mean ionic activity coefficients in multielectrolyte solutions from binary data only

An empirical mixing rule is proposed for mean ionic activity coefficient of electrolytes in multielectrolyte mixtures. The mean activity coefficients are calculated from data of the constituent binary single-salt water solutions only. Using the mixing rule, the trace mean activity coefficients and the Harned's coefficients of electrolytes in ternary mixtures with and without a common ion are predicted and compared with literature data. The agreement of the calculated values with the experimental data is very good, particularly for systems which follow Brönsted ion interaction theory. Calculations for sea water are presented as example for multielectrolyte systems. The predictions agree well with experimental data.     

Generalized LIQUAC model for the single‐ and mixed‐solvent strong electrolyte systems

A generalized strong electrolyte LIQUAC model is presented to describe the vapor–liquid equilibria, osmotic coefficients, mean ion activity coefficients, and solid–liquid equilibria for the single‐ and mixed‐solvent electrolyte systems over the entire concentration range from infinite dilution to saturated solutions. An appropriate reference state for the ions was first applied to test the capability of the model in simultaneously describing the mean ion activity coefficients and the solubility of a salt in a binary solvent mixture. The influence of salt on the vapor–liquid equilibrium behavior is predicted with the new correlated parameters. The generalized activity coefficient formulations are presented through the investigation of thermodynamic properties and phase phenomena in the single‐ and mixed‐solvent electrolyte systems. This work is a continuous study for the LIQUAC activity coefficient model. A reliable representation of the single‐ and mixed‐solvent salt solutions is obtained. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Modeling for mean ion activity coefficient of strong electrolyte system with new boundary conditions and ion-size parameters

A rigorous approach is proposed to model the mean ion activity coefficient for strong electrolyte systems using the Poisson–Boltzmann equation. An effective screening radius similar to the Debye decay length is introduced to define the local composition and new boundary conditions for the central ion. The crystallographic ion size is also considered in the activity coefficient expressions derived and non-electrostatic contributions are neglected. The model is presented for aqueous strong electrolytes and compared with the classical Debye–Hückel (DH) limiting law for dilute solutions. The radial distribution function is compared with the DH and Monte Carlo studies. The mean ion activity coefficients are calculated for 1:1 aqueous solutions containing strong electrolytes composed of alkali halides. The individual ion activity coefficients and mean ion activity coefficients in mixed sol-vents are predicted with the new equations.     

Effect of methylimidazolium-based ionic liquids on vapor–liquid equilibrium behavior of tert-butyl alcohol + water azeotropic mixture at 101.3 kPa

Three ionic liquids(ILs),1-ethyl-3-methylimidazolium bromine([EMIM]Br),1-butyl-3-methylimidazolium bromine([BMIM]Br),and 1-hexyl-3-methylimidazolium bromine([HMIM]Br),were used as the solvent for separation of {tert-butyl alcohol(TBA)+ water} azeotrope.Vapor–liquid equilibrium(VLE)data for {TBA + water + IL}ternary systems were measured at 101.3 k Pa.The results indicate that all the three ILs produce an obvious effect on the VLE behavior of {TBA + water} system and eliminate the azeotropy in the whole concentration range.[EMIM]Br is the best solvent for the separation of {TBA + water} system by extractive distillation among the three ILs.The experimental VLE data for the ternary systems are correlated with the NRTL model equation with good correlations.Explanations are given with activity coefficients of water and TBA,and the experimental VLE-temperature data for {TBA or water + IL} binary systems.     

An equation of state for systems containing electrolytes and nonelectrolytes

A general model is presented to obtain consistent calculations of phase equilibria for mixtures containing electrolytes. Consideration is given to mixed solvents and mixed electrolyte systems with both weak and strong electrolytes; applications are cited for several systems. The method is based on the formation of the mixture in a hypothetical state. Contributions from molecular interactions are added to the Helmholtz energy of formation. Differentiation of the Helmholtz energy gives the chemical potential of all species in the mixture. Minimization of the total Gibbs energy yields the desired physical and chemical equilibria.     

Nuclear magnetic resonance study of PEO-chitosan based polymer electrolytes

This work investigates lithium dynamics in a series of polymer electrolytes formed by poly(ethylene oxide) PEO, chitosan (QO), amino propil siloxane (pAPS) and lithium perchlorate by means of nuclear magnetic resonance techniques. Lithium (⁷Li) lineshapes and spin-lattice relaxation times were measured as a function of temperature. The results suggest that the chemical functionality of QO, particularly the amine group, participate in coordinating lithium ion in the composites. The competition between QO and PEO for lithium ions is evident in the binary system. In the ternary electrolyte containing PEO, QO and pAPS, it is observed that the lithium ions can competively interact with the two polymers. The heterogeneity, at a local microscopic scale, is revealed by a temperature-dependent equilibrium of lithium ion concentration between at least two different microphases; one dominated by the interactions with chitosan and the other one with polyether. The data of the ternary electrolyte was analysed by assuming two lithium dynamics, the first one associated to the motion of the lithium ion dissolved in PEO and the second one associated to those complexed by the chitosan.     

气体溶解度的分子热力学(Ⅲ)气体在1—1价电解质溶液中的Henry常数

本工作将胡英、徐英年、Prausnitz建立的气体溶解度的分子热力学模型推广到溶剂为电解质溶液的系统中.为计入离子电荷对流体混合物Helmholtz自由能的影响,作者考虑了位于中性分子的第一配位圈中离子的电荷与此分子的诱导偶极和偶极的相互作用.对于第一配位圈以外的离子的影响则由于正、负电荷关于中心分子的对称分布而略去.本模型给出了有效离子硬球直径与Pauling晶格直径的关联式σ=ησ~(cryatal)、其中,η=-6.645+747.2511/T+2.9539×10~(-2)T-5.05798×10~(-5)T~2+3.2431×10~(-8)T~3,T>453.15K时η=1.021.对78个1-1价电解质系统的计算结果表明,本模型只需要气体在水中的分子参数即可在很大的温度和电解质浓度范围内(273K相似文献   

Pathwardhan-Kumer密度规则及基于线性等压关系的密度规则可适性的研究

The applicability of the density rule of Pathwardhan and Kumer and the rule based on the linear isopiestic relation is studied by comparison with experimental density data in the literature. Predicted and measured values for 18 electrolyte mixtures are compared. The two rules are good for mixtures with and without common ions, including those containing associating ions. The deviations of the rule based on the linear isopiestic relation are slightly higher for the mixtures involving very strong ion complexes, but the predictions are still quite satisfactory.The density rule of Pathwardhan and Kumer is more accurate for these mixtures. However, it is not applicable for mixtures containing non-electrolytes. The rule based on the linear isopiestic relation is extended to mixtures involving non-electrolytes. The predictions for the mixtures containing both electrolytes and non-electrolytes and the non-electrolyte mixtures are accurate. All these results indicate that this rule is a widely avvlicable approach.     

The activity coefficients of glycine,DL‐Serine and DL‐Valine in aqueous solutions containing nitrates at 298.15 K

An electrochemical method was used to measure the mean activity coefficients of amino acids in water‐electrolyte‐amino acid systems. The amino acids were glycine, DL‐serine and DL‐valine and the electrolytes were KNO₃ and NaNO₃. The activity coefficients of the electrolytes were obtained from the e.m.f measurements in an electrochemical cell with an anion and a cation ion‐selective electrodes, each measured versus a double junction reference electrode at 298.15 K. The activity coefficients of the amino acids in the ternary systems were obtained from those of the electrolyte according to the cross differential relation. A simple semi‐empirical model based on a modification of a more complex form, derived from perturbation theory, was used to correlate the activity coefficients in binary aqueous solutions and in ternary systems.     

On the predictive capabilities of CPA for applications in the chemical industry: Multicomponent mixtures containing methyl-methacrylate,dimethyl-ether or acetic acid

The predictive performance of the CPA (Cubic-Plus-Association) equation of state for applications relevant to the chemical industry is illustrated in this work. Three such applications inspired by industrial requests/interest are illustrated here, all of which involve aqueous multicomponent mixtures exhibiting vapor–liquid (VLE) and/or liquid–liquid (LLE) equilibrium. The first two cases include mixtures of methyl-methacrylate with acetone or methanol and dimethyl-ether with ethanol, respectively. In these two cases, the classical form of CPA is used. The third case involves aqueous mixtures with acetic acid, esters, ethers and alcohols, and in this case for water–acetic acid the CPA-Huron Vidal (CPA-HV) version of the model is used. For the latter binary mixture, new CPA-HV binary parameter sets are estimated using, among others, data for activity coefficients at infinite dilutions. The modeling approach is similar in all three cases, i.e. the binary parameters are solely fitted to binary data and thus all multicomponent calculations are considered predictions.It is shown that CPA correlations for binary systems are excellent in all cases using temperature independent parameters except for the acetic acid–water system for which different parameter sets at different temperatures can be recommended. Even with the use of CPA-HV mixing rules, modeling of the acetic acid–water system with few interaction parameters remains a challenging task. Excellent simultaneous VLE and LLE correlation is obtained for complex systems such as aqueous mixtures with ethers and esters. The multicomponent results are, with a few exceptions, very satisfactory, especially for the vapor–liquid equilibrium cases. For the demanding aqueous acetic acid–water containing systems, one parameter set is recommended at the end for modeling ternary or multicomponent mixtures containing acetic acid and water.     

Activity coefficients in aqueous multicomponent electrolyte solutions from ambient to 200 C

A thermodynamic model for aqueous solutions of strong electrolytes has been developed in order to evaluate activity and osmotic coefficients of multicomponent solutions of strong electrolytes.The excess Gibbs energy is given by three contributions: the Debye-Huckel term, the Born term and the Wilson term, the latter taking into account the effect of short range intermolecular forces.The proposed model needs only binary parameters, which can be obtained by fitting experimental data of binary aqueous electrolyte solutions. This makes it valuable when experimental data of multicomponent solutions are lacking.The proposed model can be used in calculating boiling point elevation or solubility of strong electrolytes in multicomponent aqueous solutions in a wide range of temperature and concentration.     

Ternary and constituent binary excess molar enthalpies of {1,2-dichloropropane + 2-pentanol + 3-pentanol} at T=298.15K

Excess molar enthalpies for the ternary system of {1,2-dichloropropane (1,2-DCP)+2-pentanol+3-pentanol} and their constituent binary mixtures {1,2-DCP+2-pentanol}, {1,2-DCP+3-pentanol}, and {2-pentanol+3-pentanol} have been measured over the whole range of composition using an isothermal micro-calorimeter with flow-mixing cell at T=298.15 K and atmospheric pressure. The experimental excess molar enthalpies of all the binaries and ternary mixture, including three pseudo-binary mixtures, are positive (endothermic effect) throughout the mole fraction range, except for the binary mixture {2-pentanol+3-pentanol} in which shows a small negative values over the entire composition range. The experimental binary H _{m, ij} ^E data were fitted to Redlich-Kister equation, and the Cibulka and the Morris equations were employed to correlate the ternary H _{m, 123} ^E data. Several empirical equations for predicting ternary excess enthalpies from constituent binary mixing data have been also examined and compared. The experimental results have been qualitatively discussed in terms of molecular interactions.     

An electrolyte CPA equation of state for mixed solvent electrolytes

Despite great efforts over the past decades, thermodynamic modeling of electrolytes in mixed solvents is still a challenge today. The existing modeling frameworks based on activity coefficient models are data‐driven and require expert knowledge to be parameterized. It has been suggested that the predictive capabilities could be improved through the development of an electrolyte equation of state. In this work, the Cubic Plus Association (CPA) Equation of State is extended to handle mixtures containing electrolytes by including the electrostatic contributions from the Debye–Hückel and Born terms using a self‐consistent model for the static permittivity. A simple scheme for parameterization of salts with a limited number of parameters is proposed and model parameters for a range of salts are determined from experimental data of activity and osmotic coefficients as well as freezing point depression. Finally, the model is applied to predict VLE, LLE, and SLE in aqueous salt mixtures as well as in mixed solvents. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2933–2950, 2015     

ON THE POSSIBILITY OF PREDICTING PHASE EQUILIBRIA FROM MOLECULAR STRUCTURE

The abvent of the ASOG and UNIFAC group-contribution methods for the prediction of activity coefficients approximately 15 years ago was a significant boost to the ability of chemical engineers to model chemical processes. This paper reviews the status and recent progress in the group-contribution approach to predicting liquid-phase activity coefficients.Several different types of liquid mixtures arc considered: non electrolyte mixtures with normal-boiling components; mixtures with dissolved gases; mixtures with polymers; and mixtures including strong electrolytes. It is concluded that in recent years much progress has been made in the development of group-contribution models for the prediction of activity coefficients. It is in addition shown that combining activity coefficient models with equations of state renders the group-contribution approach applicable also to the highpressure region.Due to space limitation, this review emphasizes UNIFAC and related models.     

Correlation between mass transfer and operating parameters in zinc electrowinning

The effects of antimony additions, acid concentration, and current density on mass transfer and deposition morphology were examined. The mass transfer coefficients of zinc were calculated using a codeposition method with cadmium as a tracer. The experiments were carried out for vertical electrodes in a Hull cell. The results indicate that the mass transfer coefficients increase with increasing antimony additions, acid concentration, and current density. Zinc dissolution is more severe at low current density and higher antimony levels than at higher current densities and lower antimony levels. A mass transfer correlation for pure zinc electrolyte data is $$Sh = 12.47\left( {ReSc} \right)^{0.45} $$ whereSh, Re, andSc are the Sherwood, Reynolds, and Schmidt numbers, respectively. The correlation fits very well with the experimental data. A correlation for electrolytes containing antimony was also obtained and has an exponent of 0.42. The correlations cover a wide range of operating parameters and provide a fast quantitative estimation of the change in mass transfer in zinc electrowinning.     

双组分无机电解质溶液的纳滤膜分离性能

纳滤膜是20世纪90年代问世的新型分离膜,具有两个显著特点：一是其截留分子量介于反渗透膜和超滤膜之间,约为2002000;另一是纳滤膜的表面分离层由聚电解质构成,一般带有负电荷,因此对无机电解质有一定的截留率．     

Effect of gas sparging on mass transfer in zinc electrolytes

The effect of sparging on mass transfer is reported for zinc electrolytes containing antimony and antimony-free electrolytes. Comparative results with non-sparged electrolytes show, an enhancement in mass transfer. In the sparged electrolyte, the mass transfer coefficients,K _Zn, increase with increasing current density, antimony additions, and sulphuric acid concentration. The deposition morphology is consistent with the mass transfer results. A relationship between the mass transfer coefficients for sparged and non-sparged systems is obtained. The relationship correlates satisfactorily with the data and provides a quantitative method for determining the degree of enhancement in mass transfer coefficients due to sparging. The correlation which best represents the mass transfer data for sparged zinc electrolytes is $$Sh = 105(ReSc)^{0.23} $$ whereSh, Re, andSc are the Sherwood, Reynolds, and Schmidt numbers, respectively. The correlation represents the case where sparging is applied to a gas evolving electrode, hydrogen in this case.     

Water diffusion coefficients during copper electropolishing

Cu electropolishing was studied using a rotating disc electrode in a variety of phosphoric acid-based electrolytes, including several with ethanol and other species added as diluents. Diluents allow a wider range of water concentrations and electrolyte viscosities to be accessed and also reduce the removal rate during Cu electropolishing, simplifying possible application to damascene processing. Transient and steady state currents in the mass transfer limited regime are shown to depend on both the number of water acceptor molecules associated with each dissolving Cu ion and on the effective diffusion coefficient of water. Transient analysis samples the bulk transport properties, whereas steady state analysis integrates them through the diffusion layer. Assuming that the effective diffusion coefficients appropriate to transient and steady state behavior are the same, about one water molecule is associated with each dissolving Cu ion. This analysis yields effective diffusion coefficients for water on the order of 10^–9cm²s^–1. However, the data is also consistent with an assumption that six water molecules are associated with each dissolving Cu ion, but the effective diffusion coefficient appropriate for a Levich analysis is somewhat lower than that in the bulk electrolyte. This analysis yields effective diffusion coefficients for water on the order of 10^–8–10^–7cm²s^–1. The latter interpretation, that six water molecules are associated with each dissolving Cu ion, appears more likely since it provides almost exact agreement with the effective diffusion coefficient reported previously by Vidal and West. In combination with previously published impedance results ruling out a salt film mechanism, the good agreement between the transient and steady state analyses confirm that water is the acceptor species that complexes dissolving Cu ions in phosphoric acid-based electropolishing baths.     

Purification of glycerol/water solutions from biodiesel synthesis by ion exchange: sodium removal Part I

BACKGROUND: In this study, equilibrium and kinetic data of the ion exchange of sodium from glycerol–water mixtures on the strong acid resin Amberlite‐252 were obtained. Basic parameters for the design of ion exchange units for the purification of the crude glycerol phase from biodiesel production have been determined. RESULTS: Equilibrium uptake of sodium ions with the strong acid ion exchanger Amberlite‐252 was studied at three temperatures. The Langmuir equation and the mass action law model were used to fit the experimental equilibrium data. Equilibrium constants and thermodynamic parameters were obtained at each temperature. Kinetic experiments were carried out to evaluate the effective diffusion coefficients of sodium on the resin Amberlite‐252 in glycerine–water media. CONCLUSIONS: Equilibrium results indicate that this process is favourable and also that its selectivity decreases with temperature increase from 303 to 333 K. Both models were able to fit the experimental equilibrium data. Kinetic experiments showed that the rate of mass transfer in this binary system is high. An Arrhenius type equation allowed the correlation of effective diffusion coefficients and temperature. The results indicate that the macroporous resin Amberlite‐252 could be useful for removal of sodium ions from glycerine/water solutions with a high salt concentration. Copyright © 2008 Society of Chemical Industry