Showing papers on "Activity coefficient published in 2014"
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TL;DR: In this article, a new approach for applying ePC-SAFT is suggested that accounts explicitly for dispersion interactions between anions and cations, and it is also possible to directly model weak electrolyte solutions without using an additional approach that accounts for ionpair formation.
Abstract: So far, the electrolyte PC-SAFT equation of state developed in Cameretti et al. (2005) has been applied to model solution densities, vapor–liquid equilibria (VLE), liquid–liquid equilibria (LLE), and solid–liquid equilibria (SLE) of solutions containing electrolytes. For that purpose, two ion-specific parameters were used to characterize any ion: the diameter of the solvated ion and the dispersion-energy parameter between ion and solvent. Dispersion was only considered between ions and solvents. Considering the small number of adjustable parameters, this approach yielded acceptable results especially for low and moderate electrolyte concentrations. However, for high salt concentrations, a distinct deviation between modeled and experimental data was observed. In this work a new modeling approach is suggested that accounts explicitly also for dispersion interactions between anions and cations. This yields a much more precise description of electrolyte solutions at higher concentrations compared to original ePC-SAFT. With this new approach it is also possible to directly model weak electrolyte solutions without using an additional approach that accounts for ion-pair formation. The new approach for applying ePC-SAFT is now able to model phase equilibria (VLE, LLE, SLE) of ternary electrolyte solutions containing water, organic solvents, salts, and amino acids even at high salt concentrations in good agreement with experimental data.
192 citations
TL;DR: The results of the pure experimental data showed that, the heat of adsorption for methane is approximately independent of loading (about 20kJ/mol), and for carbon dioxide decreases by increasing loading when q
177 citations
TL;DR: It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.
Abstract: The influence of the cation's central atom in the behavior of pairs of ammonium- and phosphonium-based ionic liquids was investigated through the measurement of densities, viscosities, melting temperatures, activity coefficients at infinite dilution, refractive indices, and toxicity against Vibrio fischeri. All the properties investigated are affected by the cation's central atom nature, with ammonium-based ionic liquids presenting higher densities, viscosities, melting temperatures, and enthalpies. Activity coefficients at infinite dilution show the ammonium-based ionic liquids to present slightly higher infinite dilution activity coefficients for non-polar solvents, becoming slightly lower for polar solvents, suggesting that the ammonium-based ionic liquids present somewhat higher polarities. In good agreement these compounds present lower toxicities than the phosphonium congeners. To explain this behavior quantum chemical gas phase DFT calculations were performed on isolated ion pairs at the BP-TZVP level of theory. Electronic density results were used to derive electrostatic potentials of the identified minimum conformers. Electrostatic potential-derived CHelpG and Natural Population Analysis charges show the P atom of the tetraalkylphosphonium-based ionic liquids cation to be more positively charged than the N atom in the tetraalkylammonium-based analogous IL cation, and a noticeable charge delocalization occurring in the tetraalkylammonium cation, when compared with the respective phosphonium congener. It is argued that this charge delocalization is responsible for the enhanced polarity observed on the ammonium based ionic liquids explaining the changes in the thermophysical properties observed.
144 citations
TL;DR: F fluorination and aromatization of anions are shown to reduce their interaction with water, and the nature of hydrogen bonding between water and anion as well as the possibility of anion-water complex formation is provided.
Abstract: For an adequate choice or design of ionic liquids, the knowledge of their interaction with other solutes and solvents is an essential feature for predicting the reactivity and selectivity of systems involving these compounds. In this work, the activity coefficient of water in several imidazolium-based ionic liquids with the common cation 1-butyl-3-methylimidazolium was measured at 298.2 K. To contribute to a deeper insight into the interaction between ionic liquids and water, COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies. The results showed good agreement between experimental and predicted activity coefficient of water in ionic liquids and that the interaction of water and ionic liquids was strongly influenced by the hydrogen bonding of the anion with water. Accordingly, the intensity of interaction of the anions with water can be ranked as the following: [CF3SO3](-) < [SCN](-) < [TFA](-) < Br(-) < [TOS](-) < Cl(-) < [CH3SO3](-) [DMP](-) < [Ac](-). In addition, fluorination and aromatization of anions are shown to reduce their interaction with water. The effect of temperature on the activity coefficient of water at infinite dilution was measured by inverse gas chromatography and predicted by COSMO-RS. Further analysis based on COSMO-RS provided information on the nature of hydrogen bonding between water and anion as well as the possibility of anion-water complex formation.
123 citations
TL;DR: In this article, an improved formulation of the extension of the statistical associating fluid theory for potentials of variable range to electrolytes (SAFT-VRE) is presented, incorporating a representation for the dielectric constant of the solution that takes into account the temperature, density and composition of the solvent.
Abstract: An improved formulation of the extension of the statistical associating fluid theory for potentials of variable range to electrolytes (SAFT-VRE) is presented, incorporating a representation for the dielectric constant of the solution that takes into account the temperature, density and composition of the solvent. The proposed approach provides an excellent correlation of the dielectric-constant data available for a number of solvents including water, representative alcohols and carbon dioxide, and it is shown that the methodology can be used to treat mixed-solvent electrolyte solutions. Models for strong electrolytes of the metal-halide family are considered here. The salts are treated as fully dissociated and ion-specific interaction parameters are presented. Vapour pressure, density, and mean ionic activity coefficient data are used to determine the ion–ion and solvent–ion parameters, and mixed-salt electrolyte solutions (brines) are then treated predictively. We find that the resulting intermolecular p...
86 citations
TL;DR: In this article, it was shown that the activity coefficients of water in a series of cholinium-based ionic liquids can be reliably and quickly estimated at 298.15 K using a humidity meter instrument.
81 citations
TL;DR: The activity coefficients at infinite dilution, γ 13 ∞, for 63 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane and 6 diols in the ionic liquid (IL) choline bis(trifluoromethylsulfonyl)imide, [N1112OH][
79 citations
TL;DR: In this paper, the solubilities of sulfadiazine (SD), sulfamerazine (SMR) and sulfamethazine(SMT) in some 1-propanol+water co-solvent mixtures were measured at five temperatures from 293.15 to 313.15 K over the polarity range provided by the aqueous solvent mixtures.
Abstract: The solubilities of sulfadiazine (SD), sulfamerazine (SMR) and sulfamethazine (SMT) in some 1-propanol + water co-solvent mixtures were measured at five temperatures from 293.15 to 313.15 K over the polarity range provided by the aqueous solvent mixtures. The mole fraction solubility of all these sulfonamides was maximal in the 0.80 mass fraction of 1-propanol solvent mixture (δ
solv = 28.3 MPa1/2) and minimal in water (δ = 47.8 MPa1/2) at all temperatures studied. The apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution were obtained from these solubility data by using the van’t Hoff and Gibbs equations. Apparent thermodynamic quantities of mixing were also calculated by using the ideal solubilities reported in the literature. Nonlinear enthalpy–entropy relationships were observed for these drugs in the plots of enthalpy versus Gibbs energy of mixing. The plot of ∆mix
H° versus ∆mix
G° shows different trends according to the slopes obtained when the mixture compositions change. Accordingly, the mechanism for the solution process of SD and SMT in water-rich mixtures is enthalpy driven, whereas it is entropy driven for SMR. In a different way, in 1-propanol-rich mixtures the mechanism is enthalpy driven for SD and SMR and entropy driven for SMT. Ultimately, in almost all of the intermediate compositions, the mechanism is enthalpy driven. Nevertheless, the molecular events involved in the solution processes remain unclear.
70 citations
TL;DR: On the basis of quantum-chemical calculations, it is found that cation-anion interaction plays an important role upon the ability of the IL anion to interact with water.
Abstract: A systematic study of the interactions between water and alkyl methyl imidazolium chloride ionic liquids at 298.2 K, based on activity coefficients estimated from water activity measurements in the entire solubility range, is presented. The results show that the activity coefficients of water in the studied ILs are controlled by the hydrophilicity of the cation and the cation–anion interaction. To achieve a deeper understanding on the interactions between water and the ILs, COSMO-RS and FTIR spectroscopy were also applied. COSMO-RS was used to predict the activity coefficient of water in the studied ionic liquids along with the excess enthalpies, suggesting the formation of complexes between three molecules of water and one IL molecule. On the basis of quantum-chemical calculations, it is found that cation–anion interaction plays an important role upon the ability of the IL anion to interact with water. The changes in the peak positions/band areas of OH vibrational modes of water as a function of IL conce...
66 citations
TL;DR: In this article, the extraction efficiency of ionic liquids (IL) was estimated based on COSMO-RS predictions of infinite dilution activity coefficients of benzene and cyclohexane in different ILs.
55 citations
TL;DR: In this article, two ionic liquids (ILs), namely 1-butyl-1-methylpyrrolidinium dicyanamide [BMPYR][DCA] and 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN], were studied as agents for the separation of the methyl acetate+methanol azeotropic mixture by extractive distillation.
TL;DR: The ternary mixtures were prepared by mixing ethanol and pure water with three concentrations (10, 30, and 50)wt% of 1,3-propanediol in the overall liquid mixtures in order to study the effect of 1 3-propnaediol on the VLE of (ethanol+water).
TL;DR: In this article, the activity coefficients at infinite dilution, γ 13 ∞, for 61 solutes, including alkanes, cycloalkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, water, thiophene, ethers, ketones, esters, aldehyde, acetonitrile, pyridine and 1-nitropropane, [BMMOR][TCM] were determined by gas-liquid chromatography at six temperatures within the range of (318.15 to 368.15)
TL;DR: In this paper, the micellization behavior of PMT with 1-decyl-3methylimidazolium hydrochloride, at different temperatures was investigated by using electrical conductivity.
TL;DR: In this paper, the authors investigated the possibility of using ionic liquid as a solvent for the separation processes, especially for extraction of azeotropic mixtures i.e. aliphatic from aromatic hydrocarbons.
TL;DR: In this article, the interaction between volatile organic compounds and the ionic liquid (IL) 1-ethyl-3-methylimidazolium 2-(2-methoxyethoxy) ethylsulfate [EMIM]+[MDEGSO4]− were investigated using gas+ liquid chromatography measurements.
TL;DR: In this article, a surface component activity (SCA) model was proposed for solvent extraction from oily sludge generated from the petroleum industry, in which the activity coefficient of solid surface sites (fS) was proposed as a function of solid concentration (CS) rather than unity.
TL;DR: In this paper, the Gibbs energy, enthalpy and entropy of fusion of 1-methylethyl 2-[4-(4-chlorobenzoyl)-phenoxy]-2-methylpropanoate (fenofibrate) and the heat capacity of the solid and the melt have been determined.
TL;DR: Experiments carried out allowed the relative sensitivity of the activity coefficients of key risk drivers such as benzene, toluene, ethylbenzene and xylene compounds to be quantified with respect to the presence of other types of compounds and where the source LNAPL had undergone different types of weathering.
TL;DR: In this article, infinite dilution activity coefficients (γ 1,2∞) were reported for 31 and 40 diverse organic solutes dissolved in trihexyl(tetradecyl)phosphonium l-lactate and (1S)-(+)-10-camphorsulfonate, as determined by inverse gas chromatography at temperatures from 323 K to 373 K.
Abstract: Infinite dilution activity coefficients (γ1,2∞) are reported for 31 and 40 diverse organic solutes dissolved in trihexyl(tetradecyl)phosphonium l-lactate and trihexyl(tetradecyl)phosphonium (1S)-(+)-10-camphorsulfonate, as determined by inverse gas chromatography at temperatures from 323 K to 373 K. The measured retention data were further transformed to gas-to-ionic liquid and water-to-ionic liquid partition coefficients using standard thermodynamic expressions based upon measured values for corresponding gas-to-water partition coefficients of the test solutes. Both sets of partition coefficients were interpreted using an ion-specific equation coefficient form of the basic Abraham general solvation parameter model. Finally, ion-specific equation coefficients were calculated for the chiral l-lactate and (1S)-(+)-10-camphorsulfonate anions.
25 Feb 2014
TL;DR: In this article, the authors present an updated Abraham Model Equation Coefficients for Solute Activity Coefficient and Partition Coefficient Predictions for Ionic Liquid Solvents.
Abstract: This document includes supplemental material to an article titled "Thermochemical Investigations of Solute Transfer into Ionic Liquid Solvents: Updated Abraham Model Equation Coefficients for Solute Activity Coefficient and Partition Coefficient Predictions," published in Physics and Chemistry of Liquids.
TL;DR: In this article, a brief review on the structures and thermodynamic properties of ionic liquids is given, including density, phase behavior, enthalpy of vaporization, and heat capacity.
Abstract: This chapter gives a brief review on the structures and thermodynamic properties of ionic liquids. It is organized as follows. The introduction gives the definition and application fields of ionic liquids. Following that is the main part where we present a review on the density, phase behavior, enthalpy of vaporization, and heat capacity of ionic liquids. The properties of both pure ionic liquids and mixtures with ionic liquids are discussed. Some experimental pieces of apparatus for working with these properties are introduced briefly. We then review the correlations with the experimental data and prediction methods based on MD or ab initio methods. In the discussion of phase behavior, the vapor–liquid equilibria, liquid–liquid equilibria, and the activity coefficients at infinite dilution are presented separately. In the last part, a summary and outlook on this topic are given.
TL;DR: In this article, experimental data of 34 different systems were used for parameter estimation and to evaluate four of the main activity coefficient models (ASOG, UNIFAC,UNIFAC-LLE, and UNIFAAC-Dortmund) that could be used with biodiesel systems.
TL;DR: In this article, the (gas+ liquid) chromatographic method was used to measure the activity coefficients at infinite dilution (γ i ∞ ) and (gas + liquid) partition coefficients (KL) for organic solutes: alkanes, alkenes, alkyl benzenes, acetonitrile, acetone, tetrahydrofuran, ethyl acetate, and chloromethanes.
TL;DR: In this work, Δ(R)g(+) values for the enzymatic G6P isomerization were determined as a function of the G 6P equilibrium molality between 25 °C and 37 °C, and the influence of the buffer and of potassium glutamate as an additive on the reaction equilibrium was measured and predicted with ePC-SAFT in good agreement.
TL;DR: In this paper, a revised formulation of the Extended Universal QUAsiChemical (EUNIQUAC) activity model has been developed, which fits excess thermodynamic properties of binary and selected aqueous ternary electrolyte solutions in the system Na-K-Ca-Mg-H-Cl-SO4-H2O over temperatures from 298 to 573 K and concentrations to 5 molal for saturated water vapor conditions.
1 Jan 2014
TL;DR: In this article, the distribution of indium between FeOx-CaO-SiO2 slags and copper was examined at an oxygen partial pressure of 1028 MPa (1027 atm) and at 1300uC.
Abstract: Electronic waste (WEEE) is being generated at a rapidly increasing rate and leading to the removal of scarce and valuable metals from the materials cycle. The search for efficient WEEE reprocessing methods requires reliable data on the distribution of these valuable metals during smelting. In this work the distribution ratio of indium between FeOx-CaO-SiO2 slags and copper was examined at an oxygen partial pressure of 1028 MPa (1027 atm) and at 1300uC. The indium distribution ratio was strongly dependant on the CaO content, decreasing as the CaO content increased, but relatively unaffected by the Fe/SiO2 ratio of the slag over the range examined. Indium was inferred to be present in slag as InO1?5. The activity coefficient of InO1?5 was calculated and presented as iso-activity coefficient curves on the copper-saturated FeOx-CaO- SiO2 phase diagram. Volatilisation of indium under the oxidising conditions used in this work was insignificant, and it was shown that this is consistent with theoretical expectations. Only in much lower oxygen partial pressure environments can indium volatilisation be expected.
TL;DR: In this paper, a static analytical method was used to determine the solubility of valnemulin hydrogen tartrate in five pure solvents in temperature range of 278.15 to 333.15 K.
TL;DR: In this article, the authors used the Chen-Guo model for the hydrate phase and the UNIQUAC activity coefficient is applied for nonideality of the liquid phase.
TL;DR: In this paper, the thermodynamically stable form I of the drug risperidone has been determined by a gravimetric method in nine pure organic solvents in the temperature range 278.15-323.15 K.