Measurement Of Activity Coefficients Research Articles

Fluoride Ion in Alcohols: Isopropanol vs Hexafluoroisopropanol.

The utility of alcohol as a hydrogen bonding donor is considered a providential avenue for moderating the high basicity and reactivity of the fluoride ion, typically used with large cations. However, the practicality of alcohol-fluoride systems in reactions is hampered by the limited understanding of the pertinent interactions between the OH group and F-. Therefore, this study comparatively investigates the thermal, structural, and physical properties of the CsF-2-propanol and CsF-1,1,1,3,3,3-hexafluoro-2-propanol systems to explicate the effects of the fluoroalkyl group on the interaction of alcohols and F-. The two systems exhibit vastly different phase diagrams despite the similar saturated concentrations. A combination of spectroscopic analyses, alcohol activity coefficient measurements, and theoretical calculations reveal the fluorinated alcohol system harbors the stronger OH···F- interactions between the two systems. The diffusion coefficient and ionic conductivity measurements attribute the present results to disparate states of ion association in the two systems.

Unveiling the Borohydride Ion through Force-Field Development.

The borohydride ion, BH4-, is an essential reducing agent in many technological processes, yet its full understanding has been elusive, because of at least two significant challenges. One challenge arises from its marginal stability in aqueous solutions outside of basic pH conditions, which considerably limits the experimental thermodynamic data. The other challenge comes from its unique and atypical hydration shell, stemming from the negative excess charge on its hydrogen atoms, which complicates the accurate modeling in classical atomistic simulations. In this study, we combine experimental and computer simulation techniques to devise a classical force field for NaBH4 and deepen our understanding of its characteristics. We report the first measurement of the ion's activity coefficient and extrapolate it to neutral pH conditions. Given the difficulties in directly measuring its solvation free energies, owing to its instability, we resort to quantum chemistry calculations. This combined strategy allows us to derive a set of nonpolarizable force-field parameters for the borohydride ion for classical molecular dynamics simulations. The derived force field simultaneously captures the solvation free energy, the hydration structure, as well as the activity coefficient of NaBH4 salt across a broad concentration range. The obtained insights into the hydration shell of the BH4- ion are crucial for accurately modeling and understanding its interactions with other molecules, ions, materials, and interfaces.

Measurement of SnO Activity Coefficient in CaO–SiO2–FetO–Al2O3 Slag Saturated with Fe

It is important to clarify the behavior of elements in the reaction between molten CaO–SiO2–FetO–Al2O3 slag and liquid metal during the remelting of Cu scrap. To estimate the desirable slag composition for retaining Sn in metal, the effects of the slag basicity and the concentrations of FetO and Al2O3 on the SnO activity coefficient were investigated. Molten CaO–SiO2–FetO slag (with optional Al2O3 addition) was reacted with liquid Pb–Sn alloy in a pure Fe crucible at 1573 K for 5 h while blowing the CO–CO2 mixture. From the activity coefficients of Sn, Pb, and Fe oxides in the slag, which were calculated using the PCO/PCO2 ratio during heating and the chemically analyzed compositions of slag and metal, their behaviors in slag/metal reaction were discussed. The order of reducibility was PbO > SnO >> FetO. Finally, it was suggested from the thermodynamic and industrial smelting perspectives that the slag condition favorable to SnO reduction is high basicity, around 50 mass% FetO, and low Al2O3 content.Graphical

Measurement of Activity Coefficients at Infinite Dilution for Various Organic Solutes in Deep Eutectic Solvent (1-Butyl-2,3-dimethylimidazolium Chloride + Ethylene Glycol) at Different Temperatures

Activity coefficients at infinite dilution (γ13∞) for organic solutes in deep eutectic solvent (DES) prepared by {1-butyl-2,3-dimethylimidazolium chloride (BDMIM Cl) + ethylene glycol (EG)} at a molar ratio of 1:3 have been measured using the gas–liquid chromatographic method (GLC). The thermal stability of the entrainer was determined by the thermogravimetric analyzer. The measurements were carried out in the temperature range of T = (313.15 to 343.15) K and at atmospheric pressure. The values of the partial molar excess enthalpies at infinite dilution (H1E,∞) were derived from the temperature dependence of the γ13∞∞ values. The entropies (Tref ΔS1E,∞) and Gibbs energies (ΔG1E,∞) of organic solutes at a reference temperature Tref = 323.15 K were also calculated from the γ13∞ values. These excess thermodynamic functions were calculated to further explain the intermolecular interactions occurring between the volatile organic solvents and the prepared deep eutectic solvent. Important separation parameters such as selectivities (Sij∞) and capacities (Kj∞) at infinite dilution were computed from the activity coefficients at infinite dilution data at T = 313.15 K. Selectivity and capacity data were calculated for the industrial mixtures such as cyclohexane/benzene, hexane/thiophene, cyclohexane/ethanol. There results were compared to the literature data comprising deep eutectic solvents and ILs with the cation of 1-butyl-3-methylimidazolium. The investigated solvent was found suitable to separate azeotropes formed by alkanes/alcohols.

Determination of mean activity coefficients and prediction of phase equilibria of the NaCl‐SrCl2‐H2O solution at 318.15 K

AbstractIn this work, the cell potential method is used to measure activity coefficients of NaCl‐SrCl2‐H2O mixed solution at 318.15 K. The potential values of NaCl in NaCl‐H2O single salt solution were measured, and the standard cell potential E0 and electrode response slope k were fitted with linear regression. Subsequently, the results show that the ion‐selective electrode has a good Nernst response. The mean activity coefficients NaCl in NaCl‐SrCl2‐H2O solution are also determined with Nernst equation, and the total ionic strength in the mixed solution range is from 0.1000 ~ 0.8000 mol·kg−1, the ionic strength fraction of SrCl2 with yb = (0.0, 0.2, 0.4, 0.6, 0.8). Using the mean activity coefficients data and Pitzer model, the Pitzer ion interaction parameters and of Pitzer equations at 318.15 K are fitted. Furthermore, the mean activity coefficients of SrCl2, permeability coefficient Φ, water activity aw, and excess Gibbs free energy GE were also calculated by Pitzer's equations. The phase equilibria of the NaCl‐SrCl2‐H2O solution at 318.15 K are predicted, and corresponding phase diagram of the ternary solution is plotted according to the calculated solubilities in this work, and comparison of phase equilibria at different temperatures is also presented. The results show that the ion interaction parameters of Pitzer equations obtained in this work can be used for calculation of thermodynamic parameters and prediction of phase equilibria of salt‐water solutions containing strontium.

Measurements of mean activity coefficients and solubility prediction in ternary system KBr-K2SO4-H2O at 308.15 K and 288.15 K

In this work, the mean activity coefficients of KBr in KBr-H2O binary system and KBr-K2SO4-H2O ternary system were determined at 308.15 K and 288.15 K by the cell potential method. The potassium ion selective electrode and bromide ion selective electrode are used to measure the cell potential value of single salt electrolyte solution,and the standard potential value E0 and electrode response slope k of the binary system are obtained. The experimental results showed that ion selective electrodes of used in this work had a good Nernst response. The mean activity coefficients KBr in KBr-K2SO4-H2O system are also determined, the total ionic strength in the mixed solution ranging from (0.0100 to 1.0000) mol·kg−1, and ionic strength fractions yb of K2SO4 with yb=(0.8, 0.6, 0.4, 0.2 and 0.0). Using mean activity coefficients obtained in this work and Pitzer model, the Pitzer mixed ion interaction parameters θBr,SO4 and ψK,Br,SO4are fitted respectively. Furthermore, those osmotic coefficient Φ, water activity aw, excess Gibbs free energy GE were also calculated by Pitzer’s equations. The solubilities of salts in the KBr-K2SO4-H2O system at 308.15 K and 288.15 K are predicted by using Pitzer equations and ion interaction parameters fitted in this work, and phase diagrams of the ternary system are also plotted according to the calculated solubilities. The results show that the ion interaction parameters of Pitzer equations by fitting the activity coefficients can be used for calculation thermodynamic parameters and prediction of phase equilibria.

(Digital Presentation) Uncertainty Analysis on Activity Coefficients Determination Using Vapor Pressure Osmometry on Electrolyte Solutions

Vapor Pressure Osmometry (VPO) is a reliable technique for experimental measurement of both activity coefficient of solvents and molar weight of solutes. In this work were analyzed the uncertainty sources that affect the measurements on VPO, establishing a general model for uncertainty, and applying this model to the particular case of a VPO prototype designed and constructed in this work as well. In the analysis was included the effect of strong electrolyte solutes of different ratios on the uncertainty of the measurements.In order to obtain a reliable mathematical model, a simplified thermodynamic model for the activity coefficient was used. Two types of electrolytes (1:1 and 1:2) were used for experimental runs in the diluted and non-diluted concentrations.The osmometer was designed using thermistors, so, four commercial thermistors of two different types were calibrated in the range of 0-40°C according to ASTM E879 Standard, obtaining an expanded uncertainty of 0.014°C with a confidence level of 95%.For the uncertainty budget, the relevant sources were identified and quantified. The expected uncertainty of the measurements ranged from 1.03x10-6 to 1.81x10-4 for the estimation of the activity coefficient with a confidence level of 95%.

Measurements of infinite dilution activity coefficient for aromatic and aliphatic hydrocarbons in Deep Eutectic Solvent, 1-ethyl-1-methylpyrrolidinium bromide + ethylene glycol at different temperatures and a stated molar ratio

It is reported data concerning the thermodynamic properties of organic mixtures in pyrrolidinium based DES with ethylene glycol at different temperatures ranging from T = 313.15 to 343.15 K. The infinite dilution activity coefficients (IDACs) for 32 various organic solutes (e.g., alkanes, alkenes, alkynes, aromatics, cycloalkanes, cycloalkenes, alcohols, and ketones) as part of the limiting thermodynamic properties were studied using Gas Liquid Chromatography (GLC). The excess thermodynamic properties (enthalpies, entropies, and Gibbs free energies) were subsequently calculated from the experimental infinite dilution activity coefficients. Moreover, the values of the selectivities and capacities at infinite dilution were determined from the experimental infinite dilution activity coefficients achieved at the fixed experimental temperature, T = 313.15 K. The obtained selectivity and capacity values were compared to those found in the literature. Lastly, the results of the investigated [[EMPYR]Br + EG] DES in a molar ratio of 1:4 proved that this investigated system could be utilized for all the selected separation problems: benzene/toluene, cyclohexane/benzene, acetone/ethanol, and n-butanol/MEK.

Infinite Dilution Activity Coefficient Measurements for 1-Methyl-4-(1-methylethenyl)-cyclohexene as a Green Solvent for Separation

Infinite dilution activity coefficients for various solutes, which include alkanes, alkenes, alkynes, cycloalkanes, heterocycles, alcohols, aromatics, ketones, ethers, nitrile, and water, in a 1-methyl-4-(1-methylethenyl)-cyclohexene solvent were measured using gas–liquid chromatography at 303.15, 313.15, and 323.15 K. The focus of this study was to assess 1-methyl-4-(1-methylethenyl)-cyclohexene as a green solvent for separation processes. 1-Methyl-4-(1-methylethenyl)-cyclohexene, a nonpolar monoterpene solvent extracted from essential oils of citrus peels, was investigated as an alternative solvent to currently employed conventional organic solvents in separation processes. Through experimental infinite dilution activity coefficients, γ13∞, the values of partial molar excess enthalpy at infinite (ΔHiE,∞) were obtained using the Gibbs–Helmholtz equation. The infinite dilution selectivity (Sij∞) and capacity (Δkj∞) values were calculated from the experimental limiting activity coefficients and were compared with deep eutectic solvents, ionic liquids, and industrial solvents. From this study, it was observed that 1-methyl-4-(1-methylethenyl)-cyclohexene is not suitable to be used as an alternative for separation processes. In addition, activity coefficients at infinite dilution of different organic solutes in hexadecane were measured at various temperatures to validate the reliability and accuracy of gas–liquid chromatography. Finally, the experimental data were modeled using Aspen Plus, compared with experimental data, and found to be in good agreement.

Abraham model correlations for describing solute transfer into anisole based on measured activity coefficients and molar solubilities

ABSTRACT Mole fraction solubilities are reported for anthracene, pyrene, salicylamide, benzoin, benzil, thioxanthen-9-one, 1-chloroanthraquinone, and 4-methyl-3-nitrobenzoic acid dissolved in neat anisole at 298.15 K based on spectrophotometric measurements. Results of the experimental measurements, combined with published infinite dilution activity coefficient and solubility data gathered from the published chemical literature, are used to derive Abraham model expressions for describing solute transfer into anisole from both water and the gas phase. The derived mathematical equations describe the observed solute transfer coefficients to within the overall standard deviations of 0.14 log units (or less).

Aqueous ion partitioning in Nafion: Applicability of Manning's counter-ion condensation theory

Nafion is a well-studied polymer of significant interest as a fuel cell membrane due to rapid transport of protons, which is often ascribed, at least in part, to its phase-separated morphology. The literature detailing ion sorption and transport in Nafion diverges considerably from that of water purification membranes, with contrasting analyses and models. To help bridge these gaps and facilitate comparisons of membranes with various structures, this study presents measurements of ion activity coefficients and sorption in Nafion 117 equilibrated with aqueous solutions of NaCl, MgCl2, and Na2SO4, which are relevant to water purification. The experimental data are compared to a theoretical framework based on Manning's counter-ion condensation theory and Donnan theory. Good agreement between the model and data is observed for NaCl and MgCl2, using no adjustable parameters. However, the model significantly underpredicts Na2SO4 solubility, which is attributed to ion pairing effects. The results highlight the general applicability of counter-ion condensation theory to highly charged polymers, including those exhibiting nanoscale ordering, while revealing fundamental limitations related to ion pairing.

Measurement and modeling of mean activity coefficients in ternary electrolyte system (Nicl2/Triton X-100/H2O) at T=298.15 ± 0.1 K

In this work, the results relating to the thermodynamic properties for the ternary electrolyte system of (NiCl2 + Triton X-100 + water) using the potentiometric method were reported at T = 298.15 K. The electromotive force measurements were carried out on the galvanic cell without liquid junction of the type: Ni2+-ISE | NiCl2 (m), Triton X-100 (%wt.), H2O (100-%wt.) | AgCl|Ag over total ionic strengths from 0.0010 to 6.0000 mol.kg-1 for different percentage mass fraction of Triton X-100 (%wt. = 0.0, 1.0, 2.5, 5.0, 7.5 and 10.0). The mean activity coefficients of NiCl2 were determined by using potentiometric data. Then, the mean activity coefficients of NiCl2 were correlated with Pitzer ion interaction model and TCPC model. The Pitzer ion-interaction parameters (βo, β1 and C^∅) and the adjustable parameters (b and S) of TCPC model were determined by correlating of data for the series under investigated system. The Pitzer ion interaction parameters were used to calculating of thermodynamic properties such as the osmotic coefficients and the excess Gibbs energy of solution. The result showed that the Pitzer ion interaction model could be used to investigation of the system, successfully.

The investigation of the infinite dilution activity coefficients for molecular compounds in 1-(3-hydroxypropyl)-3-methyl-imidazolium thiocyanate

Measurements of infinite dilution activity coefficients of 46 organic solutes including alkanes, alkenes, alkynes, aromatic hydrocarbons, alcohols, ethers, ketones, pyridine, thiophene, acetonitrile, and 1-nitropropane in ionic liquids (IL), 1-(3-hydroxypropyl)-3-methyl-imidazolium thiocyanate (abbreviated as [C1C3OHIM][SCN]) are reported in the temperature range from T = (318.15 to 358.15) K. Based on the experimental data, the infinite dilution capacity and selectivity of the studied IL are presented to evaluate the effectiveness of using it as an extractant in the separation of aliphatic from aromatic hydrocarbons and sulfur compounds from alkanes. Obtained selectivity and capacity values for different separation processes are compared with the literature data for other ionic liquids. From the temperature – dependence of the infinite dilution activity coefficient, the partial molar excess Gibbs energy, ΔG1E,∞, enthalpyΔH1E,∞ and entropy term TrefΔS1E,∞ at infinite dilution were calculated and discussed.

Electrochemical measurements of LiF-CaF2-ThF4 melt and activity coefficient of ThF4 in LiF-CaF2 eutectic melt

Thermodynamic and electrochemical properties of actinides in molten fluoride salts are one of the key data required for design and safety assessment of any molten salt reactor concept using liquid fluoride based fuel. In the case of the Molten Salt Fast Reactor (MSFR), special attention has to be paid to thorium fluoride, which is a direct fuel carrier salt constituent. This work presents experimental measurement of ThF4 activity coefficient in eutectic LiF-CaF2 melt by electrochemical techniques. The proposed approach is overcoming problems related to the lack of a thermodynamic reference electrode for high-temperature molten fluoride media. The method can be used to compare stability of fissile material and fission products in a given molten fluoride solvent by estimating their activity coefficients using the described electrochemical measurements. In addition, electrochemical methods were successfully used to evaluate and confirm purity of the used materials, with a special regard to oxygen content in the ThF4 input material synthesised during the previous work from ThO2.

Thermodynamic properties and activity coefficients at infinite dilution for different solutes in deep eutectic solvent: 1-butyl-3-methylimidazolium chloride + glycerol

Activity coefficients for 33 solutes at infinite dilution were determined in deep eutectic solvent (1-butyl-3-methylimidazolium chloride + glycerol) prepared by a molar ratio of 2 [BMIM] [Cl]: 1 glycerol. The retention data of solutes in prepared deep eutectic solvent (DES) as an extracting solvent were obtained with the aid of gas liquid chromatography (g.l.c) operated at different temperatures, T = (313.15–343.15) K and at ambient pressure. The separation capacity and molecular interactions of solutes in DES were determined from the activity coefficient measurements. The intermolecular interactions were further expressed by calculating thermodynamic functions including partial molar enthalpies (∆H1E, ∞), Gibbs free energy (∆G1E, ∞), and entropy term (Tref∆S1E, ∞), at infinite dilution. These were calculated from the activity coefficients at infinite dilution data. The activity coefficient data was also used to compute the separation parameters (selectivity and capacity) for selected industrial extraction problems (hexane/benzene; cyclohexane/benzene; acetone/ethanol and cyclohexane/ethanol). Activity coefficients data are important as they can be used for pre-screening of separation solvents for industrial extraction processes.

Activity Coefficients of NaClO4 in (PEG 4000 + H2O) Mixtures at (288.15, 298.15 and 308.15) K

The cell potential of the cell containing two ion-selective electrodes (ISE), Na-ISE | NaClO4 (m), PEG 4000 (Y), H2O (100-Y) | ClO4-ISE has been measured at temperatures of (288.15, 298.15, and 308.15) K as a function of the weight percentage Y of PEG 4000 in a mixed solvent at a 1 Mpa and the standard state for measured activity coefficients will be a solution of the salt in pure water. Y was varied between (0 and 25) wt.% in five-unit steps and the molality of the electrolyte (m) was between 0.05 mol kg-1 and almost saturation. The values of the standard cell potential were calculated using routine methods of extrapolation together with extended Debye-Huckel and Pitzer equations. The results obtained produced good internal consistency for all the temperatures studied. Once the standard electromotive force was determined, the mean ionic activity coefficients for NaClO4, the Gibbs energy of transfer from the water to the PEG 4000-water mixture, and the primary NaCl hydration number were calculated.

Measurements of Activity Coefficients at Infinite Dilution for Organic Solutes in the Ionic Liquids N-Ethyl- and N-Octyl-N-methylmorpholinium Bis(trifluoromethanesulfonyl)imide. A Useful Tool for Solvent Selection.

In recent years, many papers describing ionic liquids (IL) as promising solvents in separation techniques have been published. The conscious choice of appropriate ionic liquid as absorption media in effective extraction of selected types of analytes requires deeper understanding of the analyte−IL interactions. Therefore, intensive research is conducted to determine the values of activity coefficient at infinite dilution, which allows us to characterize the nature of these interactions. Based on the inverse gas chromatography retention data, activity coefficients at infinite dilution of 48 different organic compounds in the ionic liquids N-ethyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide [C2C1Mor][TFSI] and N-octyl-N-methylmorpholinium bis(trifluoromethanesulfonyl)imide [C8C1Mor][TFSI] were determined. The measurements covered a broad range of volatile organic compounds, including n-alkanes, n-alkenes, n-alkynes, alcohols, aldehydes, ketones, aromatic compounds and common polar solvents, representing different types of interactions. Activity coefficients at infinite dilution were measured in the temperature range from 313.15 to 363.15 K. The excess partial molar enthalpies and entropies at infinite dilution were determined. Selectivity at infinite dilution was also calculated for exemplary separation processes in the hexane/benzene system. The obtained results were analyzed and compared with literature data for ionic liquids containing the same anion [TFSI]¯ and different cations. The study results indicate that some potential applications of the investigated ionic liquids in separation problems exist.

Combined Thermogravimetric Determination of Activity Coefficients and Binary Diffusion Coefficients—A New Approach Applied to Ferrocene/n-Tetracosane Mixtures

The use of isothermal thermogravimetry is investigated for combined measurements of activity coefficients and diffusion coefficients in binary mixtures, where the vapor pressure is dominated by one...

Abraham model correlations for solute transfer into 2-methyl-2-butanol based on measured activity coefficient and solubility data at 298.15 K

Experimental infinite dilution activity coefficients, gas-to-liquid partition coefficients and mole fraction solubilities are reported for numerous liquid and solid organic compounds dissolved in 2-methyl-2-butanol at 298.15 K. Experimental values were determined using headspace chromatographic and spectroscopic methods of analysis. Abraham model correlations were developed by combining our measured values with solubility data gathered from the published chemical literature. The mathematical correlations that we have developed described the measured partition coefficient and solubility data to within 0.14 log units (or less).

Redox potential measurement of AgCl in molten LiCl-KCl salt using chronopotentiometry and potentiodynamic scan techniques

Here we report an innovative application of chronopotentiometry (CP) and potentiodynamic scan (PD) techniques to the measurement of redox potentials in a molten salt. Commonly, a stable Cl2/Cl− reference electrode is achieved by direct injection of chlorine gas to a graphite electrode, which requires rigorous design and operation for the high-temperature system to be studied. Instead, in situ techniques (CP and PD) were introduced to generate chlorine gas on the working graphite electrode, which then acts as the chlorine gas source. The measurements of formal potential and activity coefficient of AgCl/Ag at different AgCl mole fractions (X = 0.0039 and X = 0.0145) and temperatures (723–823 K) in molten LiCl-KCl salt were carried out using these two techniques. Moreover, these simple methods can be applied to measure the equilibrium potentials, formal potentials and activity coefficients of other metal chlorides in molten chloride salt as well as in other molten salt systems.