Solvent Activity Coefficients Research Articles

Derivation and consistency of the partial functions of a ternary system involving interaction coefficients

Abstract Margules equations are used to express the thermodynamics of a ternary system containing one solvent and two solutes in the vicinity of solvent, in terms of first order interaction coefficients of binary and ternary systems. Considering just the first order Margules coefficients, the resultant excess Gibbs energy function was convergent and the derived logarithmic activity coefficients of solvent and solutes were thermodynamically consistent. In the present study Margules equations are modified to get consistent equations. Partial functions of a ternary system are deduced using these modified equations via the excess Gibbs energy function. Derived partial functions are thermodynamically consistent and also deduced results are the same as those obtained using Maclaurin infinite series. Using the activity coefficient expressions of solvent and solutes, the activity coefficients of solvent and solute are calculated in Ni– Cr–Fe and Fe–Ti –C ternary systems, which are in excellent agreement with the experimental data.

Extremely Low Vapor-Pressure Data as Access to PC-SAFT Parameter Estimation for Ionic Liquids and Modeling of Precursor Solubility in Ionic Liquids.

Precursor solubility is a crucial factor in industrial applications, dominating the outcome of reactions and purification steps. The outcome and success of thermodynamic modelling of this industrially important property with equations of states, such as Perturbed‐Chain Statistical Associating Fluid Theory (PC‐SAFT), vastly depends on the quality of the pure‐component parameters. The pure‐component parameters for low‐volatile compounds such as ionic liquids (ILs) have been commonly estimated using mixture properties, e. g. the osmotic pressure of aqueous solutions. This leads to parameters that depend on the solvent, and transferability to other mixtures often causes poor modeling results. Mixture‐independent experimental properties would be a more suitable basis for the parameter estimation offering a way to universal parameter sets. Model parameters for ILs are available in the literature [10.1016/j.fluid.2012.05.029], but they were estimated using pure‐IL density data. The present work focuses on a step towards a more universal estimation strategy that includes new experimental vapor‐pressure data of the pure IL. ILs exhibit an almost negligible vapor pressure in magnitude of usually 10−5 Pa even at elevated temperatures. In this work, such vapor‐pressure data of a series of 1‐ethyl‐3‐methyl‐imidazolium‐based [C2mim]‐ILs with various IL‐anions (e. g. tetrafluoroborate [BF4]−, hexafluorophosphate [PF6]−, bis(trifluoromethylsulfonyl)imide [NTf2]−) were experimentally determined and subsequently used for PC‐SAFT parameter estimation. The so‐determined parameters were used to predict experimental molecular precursor solubility in ILs and infinitely diluted activity coefficients of various solvents in ILs. The parameters were further compared to modeling results using classical parametrization methods (use of liquid‐density data only for the molecular PC‐SAFT and the ion‐based electrolyte PC‐SAFT). As a result, the modeled precursor solubilities using the new approach are much more precise than using the classical parametrization methods, and required binary parameters were found to be much smaller (if needed). In sum, including the pure‐component vapor‐pressure data of ILs opens the door towards parameter estimation that is not biased by mixture data. This procedure might be suitable also for polymers and for all kind of ionic species but needs extension to ion‐specific parametrization in the long term.

Studies of osmotic and activity coefficient properties of aqueous solutions of triethylammonium formate and triethylammonium glycolate protic ionic liquids at 298.15 K

The triethylammonium-based carboxylate protic ionic liquids (PILs) are called as truly bio-ionic liquids. They can be used as green solvent, additives (biphasic catalysis) and for other considerable effects involving nano-material specially related to biomolecules. In this work, osmotic coefficient (φ) measurements using vapor pressure osmometry technique for aqueous solutions of two PILs, namely, triethylammonium formate [TEAF] (0.01290–0.55988 mol·kg−1) and triethylammonium glycolate [TEAG] (0.00989–0.53176 mol·kg−1) have been reported at 298.15 K. The water activity (aw) and solvent activity coefficient (γ1), mean molal activity coefficient (γ±) of PILs and osmotic pressure (π) of solutions properties in a binary mixture, were determined using experimentally measured φ data. The analysis of osmotic pressure data revealed that the studied PILs are electrolytes in the limit of infinite dilution and yield correct molecular weights as well as show negative values for virial coefficients. The variations of osmotic coefficient and mean molal activity coefficient of studied PILs with concentration indicate positive deviations from Debye-Hückel limiting law similar to that of ammonium ions. Further, Gibbs free energy changes due to mixing (ΔGm) and excess Gibbs free energy changes (ΔGE) for the studied binary systems are estimated. The solute-solute virial coefficient (NB22∗0) for the studied PILs in aqueous solutions were estimated by an application of the McMillan−Mayer theory of solutions. The results indicate that the hydration effect is dominant in PILs through the cooperative H–bonding with water-structure making effect suggesting the significance of hydrophobic hydration as observed in tetraalkylammonium salts and aprotic ionic liquids. A need to study the water molecule splitting at nitrogen charge centre and possible attenuation of water structural effects due to hydrophobic moieties present in the molecule is emphasized.

Thermodynamically Consistent Equations for the Accurate Description of the Logarithm of the Solvent Activity and Related Properties of Electrolyte Solutions with a Unique Set of Parameters: Critical Analysis of the Mean Activity Coefficient Evaluation

Thermodynamically consistent equations for the accurate description of the dependence on concentration of the properties of electrolyte solutions are proposed, based on a polynomial of order i/4 and a unique set of adjustable coefficients. The equation for the logarithm of the solvent activity ln a1(m) was derived first, followed by analogous expressions for the osmotic coefficient ϕ(m), the solvent activity a1(m) and activity coefficient γ1(m) and finally for the mean ionic activity coefficient $$\gamma_{ \pm }^{o} (m)$$. The descriptive capability of these equations was verified and favorably compares with the extended Pitzer equation. Finally, it was demonstrated that the evaluation of $$\ln \gamma_{ \pm }^{o} (m)$$ is strongly influenced by the fitting capability of the expression used in the correlation of ϕ(m) in the low molality region.

Speciation Analysis and Thermodynamic Criteria of Solvated Ionic Liquids: Ionic Liquids or Superconcentrated Solutions?

Lithium-glyme solvated ionic liquids (Li-G SILs) and superconcentrated electrolyte solutions (SCESs) are expected to be promising electrolytes for next-generation lithium secondary batteries. The former consists of only the oligoether glyme solvated lithium ion and its counteranion, and the latter contains no full solvated Li+ ion by the solvents due to the extremely high Li salt concentration. Although both of them are similar to each other, it is still unclear that both should be room-temperature ionic liquids. To distinctly define them, speciation analyses were performed with the Li-G SIL and the aqueous SCES to evaluate the free solvent concentration in these solutions with a new Raman/infrared spectral analysis technique called complementary least-squares analysis. Furthermore, from a thermodynamic point of view, we investigated the solvent activity and activity coefficient in the gas phase equilibrated with sample solutions and found they can be good criteria for SILs.

РАВНОВЕСНЫЕ ПОТЕНЦИАЛЫ ОКСИДА СВИНЦА (II) В ЭКВИМОЛЬНОМ РАСПЛАВЕ KCl-PbCl2

The electromotive forces (EMF) of the electrochemical system (GC)Pb|(1-N)·KCl-PbCl2+N·PbO|ZrO2(Y2O3)|O2(Pt) in the concentration range of PbO 0.16-7.32 % mol. were measured at temperatures 776, 821 and 874 K. From the experimental values of EMF activities, coefficients of the activity and basic thermodynamic functions of lead oxide for dilute solutions were calculated. It is shown that PbO activities in the KCl-PbCl2 melt have moderate negative deviations from Raoul's law for ideal solutions. The activity coefficients of PbO at each temperature within the calculation errors are constant, that is, the diluted solutions of PbO in KCl-PbCl2 obey Henry's law. In the studied area of dilute solutions of PbO solvent activity coefficients are constant within the error, and their value is close to 1, as a consequence of the solvent activity within the calculation error will be equal to its molar fraction. This confirms the rule of Kubashevskii-Alcock about the obedience behavior of the solvent KCl-PbCl2 to Raoult's law for ideal solutions. Partial thermodynamic functions of the solvent - melt KCl-PbCl2 and integral thermodynamic functions of the KCl-PbCl2-PbO system are calculated using the standard equations. The interaction of lead oxide with chloride melts is caused by the formation of oxychloride compounds. According to the literature, there is a compound {[Pb2OCl]++Cl-} in the ion melt. The results of x-ray phase analysis show the presence of Pb2OCl2 compound in the frozen electrolyte melt. Using the device LECO ONH836 the concentration of oxygen in the metal lead was determined. It is shown that the oxygen concentration was 0.031 wt. % after the long-term exposure, which also exceeds the values in the Pb-O diagram almost twice.

Molecular design of mass-separating agents for separation of cyclic ethers and acetonitrile from water

The conductor-like screening model for realistic solvation (COSMO-RS) and molecular dynamics simulation were used to evaluate the salting-out capacity of piperazine-containing Good's buffers (GBs) on the removal of 1,4-dioxane, 1,3-dioxolane, and acetonitrile from water. The general formula of piperazine-based GBs is 2-[4-(2-hydroxyethyl)piperazin-1-yl]alkanesulfonic acid, HO − (CH2)2 − N<CH2CH2CH2CH2 > NH+ − (CH2)n − SO3−, (n = 1–10). The buffers with n = 1 to 4 are commercially available, while the buffers with n = 5 to 10 are molecular designed in order to predict their salting-out effects on the organic solvent + water systems. The isobaric vapor-liquid equilibria of the ternary piperazine-based GB + organic solvent + water systems were predicted. The studied organic solvents are miscible with water at any composition under ambient condition and form a minimum boiling azeotropes. It was observed that the piperazine-based GBs are able to shift the azeotropic composition. The activity coefficients of water and organic solvents in presence of piperazine-based GBs were predicted using the COSMO-RS model. The influence of alkyl chain length between the zwitterion end groups on the phase behavior of the ternary systems was evaluated. Piperazine-based GBs have displayed potent mass-separating agents in the recovery of 1,4-dioxane, 1,3-dioxolane, or acetonitrile from water. The hydrogen bonds formation in MSA + organic solvent + water mixture was analyzed using molecular dynamics simulation.

New Modeling of Nitric Acid Dissociation Function of Acidity and Temperature.

Nitric acid is widely used for many applications. However, because of the large number of nitrogen species and the fact that for concentrations greater than 10–2 mol·L–1, its dissociation is incomplete in an aqueous medium, nitric media are very complex to describe especially in temperature. Using data from the literature and some nitrous acid analyses, it was possible to determine the balance sheet of all different aqueous nitrogen species for a total nitric acidity ranging from 1.5 to 8.5 mol·L–1 and for temperature ranging from 50 to 95 °C with the assumption that the use of a refrigerant column makes gaseous species negligible. For this, it was necessary to determine the ionic, molecular, and solvent activity coefficients and then solve an eight equation system with nine unknowns by determining one unknown experimentally.

Prediction of solubility of active pharmaceutical ingredients by semi- predictive Flory Huggins/Hansen model

In this work, solubility of four Active Pharmaceutical Ingredients (APIs) including Butyl Paraben, Fenoxycarb, Fenofibrate and Risperidone were predicted using Hansen Flory Huggins model using two different scenarios. In the first method, activity coefficient of APIs were obtained through fitting the experimental activity coefficients of solvents at particular temperature of 293K, then components solubility in entire temperature range of study was predicted. In the second scenario, the model parameters were adjusted using experimental data of two selected solvents, then components solubility were predicted in other solvents. In order to check the physical meanings of obtained values, Molecular Dynamic (MD) simulations was utilized and the results were compared. Finally the predictive capabilities of two Hansen Flory Huggins models were compared to temperature-dependent NRTL-SAC model.

Modeling the Thermodynamic Properties of Solutions Containing Polymer and Electrolyte with New Local Composition Model

A new theory model based on the local composition concept (TNRF-modified NRTL (TNRF-mNRTL) model) was developed to express the short-range contribution of the excess Gibbs energy for the solutions containing polymer and electrolyte. An equation represented the activity coefficient of solvent was derived from the proposed excess Gibbs energy equation. The short-range contribution of interaction along with the long-range contribution of interaction and configurational entropy of mixing were used to correlate the activity coefficient of ternary polymer + electrolyte + water systems and also binary polymer + water and electrolyte + water systems. The long-range interaction and configurational entropy have been given by the Pitzer-Debye-Huckel equation and the Flory-Huggins relation, respectively. The performance of the proposed model in fitting the solvent activity of ternary polymer + electrolyte + water solutions has been compared with that obtained from the ternary NRTL, ternary Wilson, ternary modified NRTL and ternary modified Wilson models. Results comparison was demonstrated the validity of the proposed model for solvent activity of polymer + electrolyte + water solutions.

Inverse gas chromatography study of polyvinylacetate-solvent and polyethylene-solvent systems

In this article, the thermodynamic behavior of polyvinylacetate (PVAc)–solvent, and polyethylene (PE)–solvent mixtures have been studied by determining the thermodynamic sorption parameters (enthalpy, entropy, and free energy), the mass-based solvent activity coefficients (Ω) and the Flory Huggins parameters (χ), by means of inverse gas chromatography (IGC) measurements. According to the Flory Huggins parameters of the PE–solvent mixtures, determined between 40 and 60°C the compatibility (the ability to interact with each other) of this polymer with the different types of solvents follows this order: dispersion solvents > polar solvents > association solvents. In the case of PVAc mixtures, the thermodynamic parameters were determined between 60 and 80°C, only for polar-type and association-type solvents due to, in the studied temperature range, the retention diagrams of dispersion solvents show that there are not bulk interactions. The Hildebrand solubility parameters of both polymers were also determined, according to Guillet procedure. The higher values of PVAc material (14.1 MPa0.5 for PE and 19.8 MPa0.5 for PVAc, at 60°C) are related to the strong interactions of vinyl acetate monomer. POLYM. ENG. SCI., 56:36–43, 2016. © 2015 Society of Plastics Engineers

A Priori Prediction of Dissociation Phenomena and Phase Behaviors of Ionic Liquids

Many unique properties of ionic liquids (ILs) are closely related to the extent of dissociation (α) in solution. However, most of the existing models for ILs assume either full dissociation or full nondissociation regardless of mixture compositions. In this work, the dissociation of ILs (CA = C+ + A–) is described as a chemical reaction. Together with the predictive COSMO-SAC model, the dissociation constant can be determined based on the value of α in the pure state. Our results show that the predicted composition dependence of α is in good agreement with experiment over the entire concentration range. We further examine the prediction of a variety of thermodynamic properties and phase behaviors of IL solutions, covering high (infinite dilution activity coefficient of solvent), medium (vapor–liquid and liquid–liquid), and low (osmotic coefficient and mean ionic activity coefficient) IL concentrations (a total of 9857 data points). Our results show that the composition dependence of IL dissociation has a ...

Thermodynamic Studies of Ionic Interactions for the Drug Ranitidine Hydrochloride in Aqueous Solutions at 298.15 K

In the present communication, we report the activities and activity coefficients of a model drug, ranitidine hydrochloride (RT·HCl) in aqueous solutions at 298.15 K. These calculations are based on the experimental measurements of densities and osmotic coefficients of RT·HCl in aqueous solutions as a function of concentration of the drug at 298.15 K. The density data have been used to obtain apparent and partial molar volumes at finite concentrations as well at infinite dilution and the experimental osmotic coefficient data are used to determine the activity and mean ionic activity coefficients of solute and solvent, respectively. The activity data have been processed to obtain the mixing and excess Gibbs energy changes as well as to obtain the osmotic pressure and osmotic virial coefficient of the drug. The variation of osmotic coefficient (ϕ) and ln γ ± as functions of concentration are studied; we observed a negative deviation from the limiting law in solution. The values of critical micelle concentration (cmc) and aggregation number (n) are estimated by applying the pseudo-phase separation model to the ϕ data. The data have been examined by applying the McMillan–Mayer theory of solutions and Pitzer approach for aqueous ionic solutions. The results are interpreted in terms of hydrophobic stacking interactions, structure making/breaking effects (kosmotropic/chaotropic effects) and cation–cation, cation–anion-cation attractions in aqueous solutions.

Measurement, correlation, and prediction of vapor pressure for binary and ternary systems containing an ionic liquid 1,3-dimethylimidazolium methylsulfate

Vapor pressure data for water, ethanol, 1-propanol, and 2-propanol, as well as the mixtures of {water+1-propanol} and {water+2-propanol}, were experimentally measured in the presence of an ionic liquid (IL) 1,3-dimethylimidazolium methylsulfate ([MMIM][MS]) at varying IL-contents and temperatures using a quasi-static ebulliometric method. The experimental vapor pressure data for binary systems containing IL were correlated using NRTL model with an overall relative root mean square deviation (rRMSD) of 0.0055, and the obtained binary NRTL parameters were employed to predict the vapor pressure for two ternary systems with an overall rRMSD less than 0.0234. Moreover, the inter-molecular interaction between [MMIM][MS] and volatile solvent was assessed theoretically in terms of the predicted activity coefficients of solvents for binary systems and quantum chemical calculations with polarizable continuum model. Finally, isobaric VLE data were predicted for three ternary systems containing [MMIM][MS] with IL mole fraction of 0.05, 0.15, and 0.25 at 101.325kPa, respectively. The results indicate that [MMIM][MS] might be applied as a promising entrainer to separate the azeotropic mixtures of {water+ethanol}, {water+1-propanol}, and {water+2-propanol} by extractive distillation.

Prediction of CO&lt;sub&gt;2&lt;/sub&gt; Solubility in Aqueous DEA and MDEA Binary Solutions Using O'Connell's Expression

In this work, the CO2solubility predicted for amines of DEA and MDEA by using the OConnell (1964) expression as a base model. This expression fits between the solvent compositions and the thermodynamic properties beside the gas solubility. The solvent activity coefficient, Gibbs energy and Henrys law constants have been generated using Aspen plus data analysis tools. The self-interaction binary parameters (Margules parameters) have been calculated based on Henry constants values. The data input for this work depends on the amine system process conditions (temperature range between 298.15 K and 393.15 K), materials composition (concentrations of 10 wt%, 20 w% and 30 wt %). For both of the DEA and MDAE and the pressure fixed to be 101.3 KPa. The solubility values of this work give satisfactory results compared to the literature data.

Thermodynamic Studies of Aqueous Solutions of 2,2,2-Cryptand at 298.15 K: Enthalpy–Entropy Compensation, Partial Entropies, and Complexation with K+ Ions

The osmotic coefficient measurements for binary aqueous solutions of 2,2,2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8] hexacosane) in the concentration range of ~0.009 to ~0.24 mol·kg(-1) and in ternary aqueous solutions containing a fixed concentration of 2,2,2-cryptand of ~0.1 mol·kg(-1) with varying concentration of KBr (~0.06 to ~0.16 mol·kg(-1)) have been reported at 298.15 K. The diamine gets hydrolyzed in aqueous solutions and needs proper approach to obtain meaningful thermodynamic properties. The measured osmotic coefficient values are corrected for hydrolysis and are used to determine the solvent activity and mean ionic activity coefficients of solute as a function of concentration. Strong ion-pair formation is observed, and the ion-pair dissociation constant for the species [CrptH](+)[OH(-)] is reported. The excess and mixing thermodynamic properties (Gibbs free energy, enthalpy, and entropy changes) have been obtained using the activity data from this study and the heat data reported in the literature. Further, the data are utilized to compute the partial molal entropies of solvent and solute at finite as well as infinite dilution of 2,2,2-cryptand in water. The concentration dependent non-linear enthalpy-entropy compensation effect has been observed for the studied system, and the compensation temperature along with entropic parameter are reported. Using solute activity coefficient data in ternary solutions, the transfer Gibbs free energies for transfer of the cryptand from water to aqueous KBr as well as transfer of KBr from water to aqueous cryptand were obtained and utilized to obtain the salting constant (ks) and thermodynamic equilibrium constant (log K) values for the complex (2,2,2-cryptand:K(+)) at 298.15 K. The value of log K = 5.8 ± 0.1 obtained in this work is found to be in good agreement with that reported by Lehn and Sauvage. The standard molar entropy for complexation is also estimated for the 2,2,2-cryptand-KBr complex in aqueous medium.

Thermodynamic studies of ionic interactions in aqueous solutions of N-butyl-pyridinium bromide at 298.15 K

Density and osmotic coefficient measurements for aqueous solutions of N-butyl-pyridinium bromide [Bpy][Br] in concentration range ~0.019 to ~0.39mol·kg−1 at 298.15K are reported. The density data are used to obtain apparent molar volume (ϕV), partial molar volume of solute and solvent V¯2andV¯1 respectively as well the limiting partial molar volume ϕ¯V0=V¯20 of the solute [Bpy][Br] (by appropriate extrapolation). The experimental osmotic coefficient (ϕ) data are used to determine the activity and mean ionic activity coefficients of solute and solvent respectively. Experimental activity coefficient data are compared with those obtained from Debye–Hückel and Pitzer models. The activity data have been further processed to obtain the Gibbs free energy change due to mixing (ΔGm) and excess Gibbs free energy change (ΔGE). The aggregation number (n) and critical micelle concentration (cmc) are obtained for ionic salt in solution phase by applying pseudo-phase separation model to ϕ and ϕV data respectively. Application of McMillan–Mayer theory of solutions to the data is made. The results have been interpreted on the basis of structural characteristic of salt, ion–solvent and ion–ion interactions.

Sibutramine characterization and solubility, a theoretical study

Solubility data from sibutramine (SBA) in a family of alcohols were obtained at different temperatures. Sibutramine was characterized by using thermal analysis and X-ray diffraction technique. Solubility data were obtained by the saturation method. The van’t Hoff equation was used to obtain the theoretical solubility values and the ideal solvent activity coefficient. No polymorphic phenomena were found from the X-ray diffraction analysis, even though this compound is a racemic mixture of (+) and (−) enantiomers. Theoretical calculations showed that the polarisable continuum model was able to reproduce the solubility and stability of sibutramine molecule in gas phase, water and a family of alcohols at B3LYP/6-311++G (d,p) level of theory. Dielectric constant, dipolar moment and solubility in water values as physical parameters were used in those theoretical calculations for explaining that behavior. Experimental and theoretical results were compared and good agreement was obtained. Sibutramine solubility increased from methanol to 1-octanol in theoretical and experimental results.

Autoprotolysis in water/methanol/NaCl ternary systems

A potentiometric method was used to determine the autoprotolysis constant for aqueous solutions containing 0, 20 and 40 mass % of methanol over a wide range of NaCl concentrations at 25 °C. The ionic strength ranged between 0.25 and 2.00 mol L -1 at intervals of 0.25 units. The osmotic and activity coefficients of the mixed solvents were calculated as a function of ionic strength. The dependence on ionic strength was analyzed using the ori.- ginal specific ion interaction theory. The specific ion interaction parameters associated with the thermodynamic autoprotolysis constant were extracted. Results indicate that interaction between ions increases with increasing metha- nol content in the mixture.

Activity and Activity Coefficient Studies of Aqueous Binary Solutions of Procaine, Lidocaine, and Tetracaine Hydrochloride at 298.15 K

Osmotic coefficient and density measurements are reported for the aqueous solutions of three hydrochloride salts of local anesthetical drug compounds, procaine (PC·HCl), lidocaine (LC·HCl), and tetracaine (TC·HCl) at 298.15 K and at ambient pressure. The experimental osmotic coefficient data are used to determine the activity and mean ionic activity coefficients of solute and solvent, respectively. The activity data have been processed to obtain the mixing and excess thermodynamic properties, such as Gibbs free energy (which has been studied as a function of drug concentration), as well as to obtain the osmotic pressure and osmotic virial coefficients of the drug compounds. The mean ionic activity coefficients of the ions decrease with the increase in drug concentration. The results of mixing and excess free energy changes do not show abrupt changes. These results are examined from the point of view of premiceller (associative) equilibria and the occurrence of critical micelle concentration (cmc). A discussion is presented on the basis of aggregation of cations, and the aggregation numbers of 2, 1.56, and 6 are obtained for PC·HCl, LC·HCl, and TC·HCl, respectively, in the solution phase, applying the pseudophase separation model. An application of the McMillan–Mayer theory of solutions to the data is made. It is noted that overall second virial coefficients are small and negative for the drug molecular salt, whereas it is positive for nonelectrolyte contribution. All of these are examined on the basis of structural characteristic of molecules and electrostatic and hydrophobic interactions.