Values Of Activity Coefficients Research Articles

Azepanium based protic ionic liquids: Synthesis, thermophysical properties and COSMO-RS study

Protic ionic liquids (ILs) with seven-membered azepanium cation were synthesized and characterized. The molecular structure of the synthesized ILs was confirmed using 1H NMR and 13C NMR spectroscopy. In one hand, sulfonic acid (SO3H) group was tethered to the azepanium moiety combined with HSPO4 or H2PO4−anion and on the other hand azepanium based alkyl sulfate ILs were synthesized by reacting azepane with corresponding dialkyl sulfates. Thermo-physical properties (density, viscosity, glass transition temperature, thermal decomposition temperature) of the synthesized ILs were measured. All the studied ILs showed good thermal stability. From the viscosity and density data of alkyl sulfate ILs, the volumetric properties such as molar volume, lattice energy and standard molar entropy were calculated. COSMO-RS was used to predict hydrogen bonding energy, interaction energy, Van der Waals energy and H-bond accepting and H-bond donating nature of these pure ILs. Activity coefficient values have also predicted for these ILs with cellulose.

Conductometric study of the dissociation behavior of humic and fulvic acids

The dissociation behavior of humic and fulvic acids was characterized on the basis of conductometric measurements. It was confirmed that dissociation is strongly affected by the content of humic or fulvic acids in aqueous solution. In the case of fulvic acids, the dilution effect connected with the increase of dissociation degree and the values of activity coefficients was the main factor influencing their dissociation ability. In the case of humic acids, their aqueous leachates were used and characterized as the main fractions functioning actively in natural systems. These fractions can be rich in acidic functional groups and the chemical compositions of these fractions change with their contents in the leachates. The amount of the dissolved humic fraction, its chemical character and its dissociation ability can be considered to result from equilibrium between dissolved and undissolved humic substances.A maximum was observed for the dependence of the dissociation degree on the concentration of humic leachates. In less concentrated leachates, less soluble humic particles with weaker functional groups were able to be dissolved. The increase of humic contents in leachates caused smaller amounts of soluble fractions with the weakest functional groups to remain in an undissolved form, which led to an increase in the degree of dissociation up to a maximum. In the case of fulvic acids, the dissociation degree increases with decreasing concentration as a result of the dilution. Two different values of pKa were determined for each humic and fulvic sample. The first was determined for higher concentrations, where pKa values are practically constant. The second was the value extrapolated to infinite dilution.

Solubility and crystallisability of the ternary system: Hexadecane and octadecane representative in fuel solvents

The solubility and crystallisability of a range of binary mixtures of n-hexadecane (C16H34) and n-octadecane (C18H38), as the predominant alkanes present in hydrotreated vegetable oil (HVO), from three representative fuel solutions (dodecane, toluene and kerosene) is presented. The dissolution (saturation) and crystallisation (supersaturation) points of the solutions are measured using poly-thermal methods utilising turbidometric detection over four concentrations from (192 g/l to 400 g/l). The data reveals the existence of more soluble, less stable crystal structures that form from the alkane mixtures, when compared to the stable triclinic crystal structures formed from the single solute component solutions. An increased carbon chain length results in lower solubility for all three solvents and the solvent type is not found to have any significant effect on the solid forms produced from the mixtures. van’t Hoff analysis reveals the solvent type to influence the solute solubility with the closest to ideal behaviour being dodecane followed by kerosene and toluene, respectively. This finding is further supported by the calculated dissolution enthalpies and activity coefficients, which are the lowest in dodecane followed by kerosene and toluene. Larger values of activity coefficients are observed for compositions with molar fraction (y) = 0.1, 0.5–0.7 C18H38 which reflect the complex multi-phase formation in the solutions when compared with the more simple binary melt crystallisation system.

Effective synthesis of n-butyl salicylate over wash coated cordierite honeycomb by zirconia and its mixed oxides: a kinetic study

Cordierite honeycombs were coated with solid acid catalysts such as ZrO2 (Z), Mo(VI)/ZrO2 (MZ) and Pt-SO4 2-/ZrO2 (PSZ) were prepared and characterized for their physico-chemical properties. These catalytic materials were characterized for their total surface acidity, crystallinity, functionality, elemental analysis and morphology by using techniques such as NH3 -TPD, PXRD, FTIR, ICP-OES, SEM and TEM respectively. These honeycomb catalysts were used for the liquid phase transesterification reaction of methyl salicylate (MS) with n-butanol (n-BA). Optimization of reaction conditions such as reaction temperature, reaction time, amount of catalysts and molar ratio of the reactants were carried out to obtain maximum yield of transester (n-butyl salicylate). n-butyl salicylate is obtained as major product and di-butyl ether is obtained as minor product. Highest total transester 70 % obtained by MZ and 80 % n-butyl salicylate and 10 % selectivity of di-butyl ether obtained in the presence of 0.4 g of honeycomb coated catalysts at a molar ratio of MS: n-BA 2:1, reaction temperature 403 K and reaction time 4 h. The energy of activation (16.81 and 14.92 kJ mol-1) and temperature coefficient (1.36 and 1.12) values of the MZ and PSZ were obtained from the kinetic studies. Pre-adsorption studies showed that the transesterification reaction methyl salicylate with n-butyl alcohol over honeycomb catalysts follows Langmuir-Hinshelwood mechanism. A reaction mechanism for transesterification is proposed based on the kinetic data. Reactivation and reusability studies of the honeycomb coated as well as powder form of catalysts up to 6 reaction cycles were also studied.Bangladesh J. Sci. Ind. Res.53(1), 63-76, 2018

A new activity coefficient model: Simultaneous correlation of liquid-liquid equilibria for ternary systems and vapor-liquid equilibria for constitutive binary systems

A new activity coefficient model is proposed base on the regular solution theory and composition-dependent surface area parameters. Surface area parameters, which account for the number of interactions between molecules, may vary depending on partner molecules and the concentration of mixtures. Conventional models such as NRTL and UNIQUAC uses fixed number and they normally fail to describe vapor-liquid equilibria and liquid-liquid equilibria simultaneously. Composition-dependent surface area parameters were combined with interaction parameters to give four parameters for a binary mixture. The proposed model can successfully describe an exceptionally high value or convex behavior of activity coefficient in the dilute region. The proposed model also shows improved performances in correlating the liquid-liquid equilibria for ternary systems and the vapor-liquid equilibria for constituent binary systems with the same parameter sets.

Solubility determination and thermodynamic data of apigenin in binary {Transcutol® + water} mixtures

Solubility and thermodynamic data of apigenin (APG) in binary {2-(2-ethoxyethoxy)ethanol (Transcutol®) + water} mixtures were obtained in this work. The mole fraction solubilities (xe) of APG in binary {Transcutol® + water} mixtures were measured at temperature T = 298.15 K to318.15 K and atmospheric pressure p = 0.1 MPa. Solubility values of APG determined in this study were fitted well with four different computational models namely “van’t Hoff, Apelblat, Yalkowsky and Jouyban-Acree” models with root mean square deviations of <4.0%. The maximum xe value of APG was recorded in neat Transcutol® (0.382 at T = 318.15 K). However, the minimum xe value of APG was recorded in neat water (1.01 × 10−6 at T = 298.15 K). The values of activity coefficients were also determined for the evaluation of solute-solvent molecular interactions and results suggested higher solute-solvent molecular interaction in APG-Transcutol in comparison with other combinations studied. Apparent thermodynamic analysis suggested endothermic and entropy-driven dissolution of APG in all binary {Transcutol® + water} mixtures studied. Enthalpy-entropy compensation analysis suggested enthalpy-driven mechanism as the main mechanism for solvation behavior of APG.

Thermodynamic Properties Determination and Modeling of the (CaCl2 + Ca(NO3)2 + l-Glutamine + H2O) System Using Potentiometric Measurements at T = (293.2, 303.2, and 313.2) K

The thermodynamic properties of the quaternary (CaCl2 + Ca(NO3)2 + l-glutamine + H2O) system, determined using the potentiometric method, were reported. The potentiometric measurements were performed in aqueous solution containing 2.5% mass fraction of l-glutamine, over total ionic strengths from 0.0100 mol·kg–1 to 4.0000 mol·kg–1 at T = (293.2, 303.2 and 313.2) K and P = 0.1 MPa. Different series of the salt molal ratios r (r = mCaCl2/mCa(NO3)2= 1, 2.5, 5.0, 7.5, 10.0) and single salt CaCl2 and Ca(NO3)2 solution in aqueous solution containing 2.5% mass fraction of l-glutamine were used for the potentiometric measurements. The Ca-ISE was prepared in our laboratory using the ionophore treated by carbon nanotubes. The Pitzer ion interaction model was used to correlate the experimental data. The mixed ionic interaction parameters (θClNO3 and ψCaClNO3) were evaluated according to Pitzer graphical method. The mixing parameters obtained were used to calculate the values of the mean activity coefficients of Ca(NO3)2, the osmotic coefficients, the solvent activity, the excess Gibbs free energies, the excess enthalpy, excess heat capacity, and the excess entropy for the whole series of the studied mixed electrolyte system. There is a good consistency between the experimental results and Pitzer model.

Solubility, thermodynamic properties and solute-solvent molecular interactions of luteolin in various pure solvents

The objective of this study was to evaluate solubility, thermodynamic properties and solute-solvent molecular interactions of poorly water-soluble bioactive compound luteolin (LUT) in various pure solvents namely water (H2O), ethylene glycol (EG), propylene glycol (PG), polyethylene glycol-400 (PEG-400), methanol (MeOH), ethanol (EtOH), isopropanol (IPA), 1-butanol (1-BuOH), 2-butanol (2-BuOH), ethyl acetate (EA), dimethyl sulfoxide (DMSO) and Transcutol® (THP) at temperatures “T = 298.2 K to 318.2 K” and pressure “p = 0.1 MPa”. The solubility values of LUT at equilibrium were determined using a shake flask technique with the help of ultra-performance liquid chromatography technique at 348 nm. The solid state of LUT in pure and equilibrated form was characterized using differential scanning calorimetry (DSC) and powder X-ray diffraction (PXRD) techniques. The solubilities of LUT measured by shake flask method were correlated with “van't Hoff and Apelblat models”. The DSC and PXRD spectra of pure and equilibrated LUT were similar, suggesting no transformation of LUT during equilibrium. Good correlation was recorded between experimental and calculated solubilities of LUT. The solubility values of LUT (mole fraction) were obtained maximum in PEG-400 (1.27 × 10−1) followed by DMSO (7.15 × 10−2), THP (4.01 × 10−2), 2-BuOH (5.53 × 10−3), 1-BuOH (5.36 × 10−3), EA (5.11 × 10−3), IPA (4.14 × 10−3), PG (3.89 × 10−3), EtOH (3.08 × 10−3), EG (2.38 × 10−3), MeOH (8.16 × 10−4) and H2O (4.17 × 10−6) at “T = 318.2 K” and similar trend was obtained at each temperature studied. The physical values of activity coefficients were determined with the help of ideal solubilities of LUT. Based on the physical values of activity coefficients, maximum solute-solvent interactions were observed in LUT-PEG-400, LUT-DMSO and LUT-THP. Apparent thermodynamic analysis suggested endothermic and entropy-driven dissolution of LUT in each pure solvent studied.

Evaluation of Gas Chromatography Stationary Phases Based on Morpholinium Ionic Liquids by McReynolds Constants and Activity Coefficients at Infinite Dilution.

In this work, four ionic liquids (ILs) based on the N-alkyl-N-methylmorpholinium cation ([Mor1,R], in which R = 2, 4, 8, or 10) and bis(trifluoromethanesulfonyl)imide anion were synthesized. Using GLC, a number of parameters describing the sorption properties of the investigated ILs were determined. The values of Kovats indices, McReynolds constants, and activity coefficients at infinite dilution were the basis for the evaluation of intermolecular interactions. The effect of the chain length of the alkyl substituent in the cation, which was used to modify their polarity, has been discussed. Comparison of the characteristics of the investigated IL-based stationary phases with commercially available ones allowed for the statement that the investigated ILs were more polar. The tested ILs had a relatively high polarity. Increasing the length of the alkyl chain in the morpholinium ring reduced polarity. ILs based on the morpholinium cation were tunable in a wide range of their polarity.

Thermodynamics and vacuum distillation studies of liquid Al–Ga and In–Sn alloys

ABSTRACTActivities of components in liquid Al–Ga and In–Sn alloys, the separation coefficients and vapour–liquid phase equilibrium in vacuum distillation were predicted using the molecular interaction volume model as a function of the activity coefficients. The results indicated that both Al and In are preferentially volatilised into vapour phase while Ga and Sn remain in residue. Similarly, we found that both the mass fraction and the content of Al and In in vapour phase increase as distillation temperature increases such that when the content of Al is 0.005985 wt% and In is 0.004141 wt% in vapour phase, respectively, in liquid phase, it was 70 wt% at T = 1073 K for both. The calculated values of activity and activity coefficients at various temperatures are presented. Comparison of the predicted values with experimental data indicates good agreement, thus verifying from statistical thermodynamics viewpoint that the model is stable and reliable.

The correlation and prediction of infinite dilution activity coefficients of compounds in water at 298.15 K

We have assembled infinite dilution activity coefficients in water at 298 K for 661 varied compounds. For 655 of these compounds we were able to construct a multiple linear regression equation using Abraham descriptors with a standard deviation of 0.29 log units in log γ∞. Unlike methods such as ASOG or UNIFAC, our equation does not rely on functional groups, and so we can predict further values of activity coefficients for compounds with functional groups not included in the 655 data base. These include ferrocene, terpenes such as α-pinene, and compounds containing phosphorous atoms such as trimethylphosphate and dibutylphosphinic acid.

Electrochemical measurements of diffusion coefficients and activity coefficients for MnCl2 in molten eutectic LiCl-KCl

An electrochemical study of manganese chloride in molten salt mixtures of eutectic LiCl-KCl was carried out using a variety of electrochemical methods in a high temperature cell including cyclic voltammetry (CV), chronopotentiometry (CP), chronoamperometry (CA), and open circuit potentiometry. Single step reduction from Mn2+ to Mn(0) was observed on both W and Mo working electrodes. Using a combination of these methods, measurements were made of activity coefficient and diffusion coefficient for MnCl2 in LiCl-KCl as a function of concentration (3.54 × 10−4 to 3.60 × 10−3 mol fraction of MnCl2) at 773K. From OCP measurements, values for activity coefficient varied from 0.014 to 0.0071. Diffusion coefficients varied with concentration and differed based on measurement method (CV, CA, or CP). Based on cyclic Mn(II) ranged from 1.1 to 2.8 × 10−5 cm2/s depending on concentration.

Solubility modelling and mixing properties of biologically active 5-amino-3-methyl-1-phenylpyrazole in ten neat solvents from 283.15 K to 318.15 K

With the isothermal dissolution equilibrium method, the solid-liquid phase equilibrium for 5-amino-3-methyl-1-phenylpyrazole in ten organic solvents including methanol, ethanol, n-propanol, isopropanol, 2-butanone, acetonitrile, n-butanol, toluene, 1,4-dioxane and isobutanol was established over a temperature range from (283.15 to 318.15)K at atmospheric pressure (101.1kPa), and the solubility of 5-amino-3-methyl-1-phenylpyrazole in these solvents were determined by a high-performance liquid chromatography (HPLC). The mole fraction solubility of 5-amino-3-methyl-1-phenylpyrazole in the solvents increased with increasing temperature within the temperature range studied, and obeyed the following sequence from high to low in different solvents: 1,4-dioxane>acetonitrile>methanol>isobutanol>ethanol>n-propanol>isopropanol>2-butanone>toluene>cyclohexane. The obtained solubility values of 5-amino-3-methyl-1-phenylpyrazole were correlated with the modified Apelblat equation, λh equation, Wilson model and NRTL model. The maximum values of root-mean-square deviation (RMSD) and relative average deviation (RAD) were 4.95×10−4 and 0.62%, respectively. In total, the four thermodynamic models were all acceptable for describing the solubility behavior of 5-amino-3-methyl-1-phenylpyrazole in these solvents. Furthermore, the mixing Gibbs energy, mixing enthalpy, mixing entropy, activity coefficient at infinitesimal concentration and reduced excess enthalpy were obtained with Wilson model. The results demonstrated that the dissolution process of 5-amino-3-methyl-1-phenylpyrazole was spontaneous and favorable in the ten organic solvents. Moreover, the solute–solvent intermolecular interaction was roughly estimated based on the values of activity coefficients. The determined solubility data and thermodynamic models in this work would be helpful to optimize the purification procedure of 5-amino-3-methyl-1-phenylpyrazole.

Thermodynamic study of (sodium bromide + monosodium aspartate + water) system based on potentiometric measurements at T = (298.2 and 310.2) K

In this study, the results relating to the thermodynamic properties of (NaBr + monosodium aspartate + water) system were studied using the potentiometric method at T = (298.2 and 310.2)K and P = 0.1 MP. The electromotive force (emf) measurements were performed on the galvanic cell of the type: Br-ISE |NaBr (m1), monosodium aspartate (m2), H2O |Na-ISE, over total ionic strengths from 0.01 to 3.0073 mol.kg−1 for different series of salt molal ratios r (r = mNaBr/mNaAsp = 1.0,2.5, 5.0,7.5,10.0) and single salt NaBr in aqueous system at T = (298.2 and 310.2)K. The mean activity coefficients of NaBr in the NaBr + monosodium aspartate + water system were determined from emf measurements based on Nernst equation by using a galvanic cell containing a solvent polymeric (PVC) Na+ and Br− ion selective electrodes which were prepared in our laboratory. The study of ternary system was made based on the Pitzer interaction model and Harned rule. The resulting values of the mean activity coefficients, the osmotic coefficients and the excess Gibbs free energy together with Pitzer mixing interaction parameters (θBrAsp and ψNaBrAsp) for the series under investigated system were reported.

Determination of gas–liquid partition coefficients of several organic solutes in trihexyl(tetradecyl)phosphonium bromide using capillary gas chromatography columns

In this paper, we report gas-liquid partition constants for thirty-five volatile organic solutes in the room temperature ionic liquid trihexyl(tetradecyl)phosphonium bromide measured by gas-liquid chromatography using capillary columns. The relative contribution of gas-liquid partition and interfacial adsorption to retention was evaluated through the use of columns with different the phase ratio. Four capillary columns with exactly known phase ratios were constructed and employed to measure the solute retention factors at four temperatures between 313.15 and 343.15K. The partition coefficients were calculated from the slopes of the linear regression between solute retention factors and the reciprocal of phase ratio at a given temperature according to the gas-liquid chromatographic theory. Gas-liquid interfacial adsorption was detected for a few solutes and it has been considered for the calculations of partition coefficient. Reliable solute's infinite dilution activity coefficients can be obtained when retention data are determined by a unique partitioning mechanism. The partial molar excess enthalpies at infinite dilution have been estimated from the dependence of experimental values of solute activity coefficients with the column temperature. A thorough discussion of the uncertainties of the experimental measurements and the main advantages of the use of capillary columns to acquire the aforementioned relevant thermodynamic information was performed.

The effect of ionic liquid 1-ethyl-3-methylimidazolium hydrogen sulfate on thermodynamic properties of aqueous lithium nitrate solutions at different temperatures and ambient pressure

Some thermodynamic quantities are evaluated for the ternary ([Emim][HSO4]+LiNO3+water) mixture and their corresponding binary mixtures. For this purpose, the vapor – liquid equilibrium at T=298.15K and volumetric properties at T=293.15K – 313.15K for this mixture are considered. We evaluated these properties by using the measured osmotic coefficients, activity and density data. Then the quality of some thermodynamic models such as: Pitzer and modified - TCPC models to correlate the activity and osmotic coefficients values for studied binary systems and Scatchard model for the ternary systems have been examined. Also the polynomial equation which proposed by Redlich and Meyer is applied to correlate the apparent molar volume values. Also with helping the results which obtained from the vapor – liquid equilibrium and volumetric measurements, we described the possible interactions which are existed in the studied systems.

CALCULATION METHOD OF REAL ACTIVITY COEFFICIENTS OF IONS BY EXAMPLE OF HYDROGEN AND CHLORINE IONS IN AQUEOUS HCl SOLUTIONS

In this paper, we proposed a calculating method of the real individual activity coefficients. To calculate the energy of the ion, transfer through the interface we offered to use the value of the electrolyte solution surface potential, and to use electronegativity elements values for accounting contribution of the charge transfer energy between the surface and the bulk solution. To verify the proposed equation, the activity coefficients of hydrogen and chlorine ions in an aqueous HCl solutions were calculated over a wide range of electrolyte concentrations. The Debye-Hückel equation within 2nd approximation describes satisfactorily the dependence of the activity coefficient on the electrolyte concentration for anions, but not reproduce the minimum on the curve for cations. This dependence for the cation H⁺ is most extremal, and namely it is the reason of the choice of HCl for the model calculation. The calculated values were compared with the data obtained from the results of determining the activity coefficients by experimental method of "vertical jet" [1]. The comparison showed that our proposed equation reproduces the character of the concentration dependence of real activity coefficients not for anion only but for cation as well. Previously we found, that at low concentrations of solutes up to 0.1 mol/kg the values of some thermodynamic characteristics are strongly determined by not the volume concentration of the electrolyte, but the restructuring of the solvent structure in the surface layer of the solution, and therefore, the changing the energy state of the molecules at the interphase surface. Hence, the number of cations and anions at the surface in the areas of high and low bulk concentrations of electrolyte also differ greatly. Obviously, the small variation between calculated and experimental values of the real activity coefficients may be connected with necessity of using at calculation the bulk and surface concentration of ions. For citation:Fedorovа A.A., Sharonov N.Yu., Filippov D.V. Calculation method of real activity coefficients of ions by example of hydrogen and chlorine ions in aqueous HCl solutions. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 3. P. 29-35.

Dilute Vapor Absorption: A New Accurate Technique for Measurement of the Limiting Activity Coefficient of Water in Hydrophobic Solvents of Lower Volatility

An accurate experimental method for the determination of the limiting activity coefficient of water in hydrophobic solvents was described theoretically; the pertinent apparatus was built and its performance was duly verified. The method is based on continuously saturating the solvent by a gas stream of a constant and known humidity up to the attainment of the steady state and subsequent determination of the water content in the solvent by Karl Fischer titration. Using this new method, accurate values of the limiting activity coefficient of water were determined in eight selected solvents. The measurements were carried out at several temperatures and from these data the infinite dilution dissolution enthalpy and entropy of water in the solvents were evaluated. They both exhibit highly positive values reflecting the breakage of the hydrogen bonding network of water upon its dissolution in the solvents. Prediction of the water limiting activity coefficients was further attempted using the Modified UNIFAC met...

Thermodynamic Properties and Solubility of Sodium and Potassium Chloride in Ethane-1,2-diol/Water Mixed Solvent Systems to High Temperatures

Solid sodium chloride solubility is measured at temperatures from 297 to 467 K at pressure of 6.45 MPa in ethane-1,2-diol/water mixed solvent systems and at a concentration of cosolvent up to 75% w/w. The corresponding solubility is also predicted from an extension of the unified theory of electrolytes to mixed solvents (J. Phys. Chem. B 2012, 116, 9033−9042) for sodium and potassium chloride up to 473.15 K and over the whole composition range of the cosolvent. A comparison of the predicted solubility with the corresponding experimental values from this study and the available literature data indicates good agreement in all cases to well within the uncertainties of the experimental data. Also, for the saturated solution of sodium and potassium chloride in ethane-1,2-diol/water mixed solvent systems, the stoichiometric activity coefficient values are estimated up to 473.15 K. These stoichiometric activity coefficients, over the complete range of mole fraction of the cosolvent, are then extended to all conc...

Thermodynamic Study of the NaNO3–Cd(NO3)2–H2O Ternary System at 298.15 K by the Potential Difference Method

In this work, we have made some thermodynamic investigations about the NaNO3–Cd(NO3)2–H2O ternary system. The potential difference method of the battery cell, Na–ISE|NaNO3 (m1), Cd(NO3)2 (m2)|NO3–ISE, was used to study the activity coefficients in this mixed system at 298.15 K in the total ionic strengths range 0.0100–1.0000 mol·kg–1 with different ionic strength fractions yb of Cd(NO3)2 with yb = (0, 0.2, 0.4, 0.6, and 0.8). There was a good Nernst response between Na–ISE and NO3–ISE in this work, and the mean activity coefficients of NaNO3 can be interpreted well by the Pitzer models. Furthermore, the mixing Pitzer ion interaction parameters of θNa,Cd and ψNa,Cd,NO3 were fitted from Pitzer’s equation, and the two parameters were applied to compute the values of the mean activity coefficients of Cd(NO3)2, the osmotic coefficients, the solvent activity, and the excess Gibbs free energy in this mixed system.