Aqueous Single Electrolyte Research Articles

Thermodynamic modeling of aqueous lithium salt solutions with association electrolyte nonrandom two-liquid activity coefficient model

The high charge density of lithium ion and the resulting strong association phenomena make thermodynamic modeling of aqueous lithium electrolyte solutions extremely challenging. In this study, the association electrolyte nonrandom two-liquid activity coefficient model of Lin et al. (AIChE J. 2022, 68(2), e17422) is utilized to correlate and predict thermodynamic properties and solubility behavior of aqueous single electrolyte solutions of LiCl, LiBr, LiI, and LiNO3, and their mixed electrolyte solutions. Capturing self-association of water, cross-association of ion and water for hydration, and cross-association of cation and anion for ion-pairing, the association model accurately represents the literature experimental data up to saturation concentrations and at the temperature ranging from 263 K to 523 K. This study further investigated the effect of anions of the lithium salts, and re-confirmed that the order of solution non-ideality as LiI > LiBr > LiCl > LiNO3 because the anions with stronger association strengths are more likely to form ion pairs and thus lower the mean ionic activity coefficients.

Modeling dynamic viscosities of multi-component aqueous electrolyte solutions containing Li+, Na+, K+, Mg2+, Ca2+, Cl−, SO42− and dissolved CO2 under conditions of CO2 sequestration

Two accurate models were developed by this study for dynamic viscosities of multi-component aqueous electrolyte solutions containing Li+, Na+, K+, Mg2+, Ca2+, Cl−, SO42− and dissolved CO2 under conditions of CO2 sequestration. The first model is constructed by extending the Mao–Duan model for viscosities of binary aqueous solutions (aqueous single electrolyte solutions) of alkali-chloride to binary solutions of alkaline-earth chlorides, common sulfate and CO2 and combining it with Hu's mixing rule to model viscosities of multi-component solutions. The second model is constructed by improving the Goldsack–Franchetto model based on the Eyring's absolute rate theory to account for the effect of temperature on viscosity. The forms of both models are simple.Comparisons of calculations of the two models with experimental viscosity data show that both models can well represent dynamic viscosities of aqueous single electrolyte solutions and aqueous CO2 solutions at temperatures from 273 K to temperatures higher than 473 K, and at pressures from 0.1 MPa to 100 MPa. Furthermore, the two models can predict viscosities of aqueous NaCl solutions with dissolved CO2, brine containing Li+, Na+, K+, Mg2+, Ca2+, Cl−, SO42− and seawater over a wide P-T range. The absolute average deviations of the two models from most of experimental data sets are less than 2%.

Effect of various aqueous electrolytes on the electrochemical performance of porous NiO nanocrystals as electrode material for supercapacitor applications

The electrochemical performance of porous Nickel oxide nanocrystals synthesised by the hydrothermal method is discussed here. In this porous Nickel oxide, crystal structure and morphology were investigated by XRD, FT-Raman, FE-SEM and HR-TEM. The electrochemical performance of porous Nickel oxide electrode examined by various aqueous electrolytes such as 1 M Na2SO4, 0.5 M KOH and 1 M Na2SO4 + 0.5 M KOH solution. The electrode material delivers high specific capacitance found as 200 F/g at 1 A/g using a single aqueous electrolyte 1 M Na2SO4. The porous Nickel oxide nanocrystals electrode performed the long-term good cyclic stability around 2000 cycles with 91% capacity retention. Here, 1 M Na2SO4 electrolyte achieves high capacity among various electrolytes can be considered as promising electrode material for supercapacitor applications.

Electrodeposition of textured Bi27Sb28Te45 nanowires with enhanced electrical conductivity

This work presents the template based pulsed potential electrodeposition technique of highly textured single crystalline bismuth antimony telluride (Bi1-xSbx)2Te3 nanowires from a single aqueous electrolyte. Cyclic voltammetry was used as an electroanalytical tool to assess the effect of the precursor concentrations on the composition of the deposits and to determine the deposition potential for each element. Pulsed potential electrodeposition was then applied on a gold-coated anodised alumina template to examine the effect of the pulse parameters on the composition and texture of Bi27Sb28Te45 nanowires. The nanowires are cylindrical in shape formed during the deposition inside the porous template and highly textured as they are decorated with sparse distribution of small crystal domains. The electrical conductivity (24.1 × 104 S m−1) of a single nanowire was measured using a four-point probe technique implemented on a custom fabricated test chip. In this work, we demonstrated that crystal orientation with respect to the transport direction controlled by tuning the pulsed electrodeposition parameters. This allowed us to realise electrical conductivities ∼2.5 times larger than Sb doped bismuth-tellurium based ternary material systems and similar to what is typically seen in binary systems.

Correlations for Densities of Aqueous Electrolyte Solutions

We present simple %-level accuracy universal correlations for densities of aqueous electrolyte solutions at 298.15 K and 0.1 MPa. The developed expressions and parameters are based on 1032 experimental density data points for 56 aqueous single electrolyte solutions including chlorides, bromides, iodides, bicarbonates, carbonates, sulfates, nitrates, nitrites, phosphates, hydrogen phosphates, and dihydrogen phosphates. The correlations relate the solution density with “excess” mass fraction of electrolytes in solution. With molar mass and concentrations of electrolytes as input, the correlation yields density results for all 56 electrolytes with the average error of 0.97% and the maximum error of 8.05%. When grouping the electrolytes as either structure making, structure breaking, or structure superbreaking, the correlations yield the average error of 0.59% and the maximum error of 3.45%. The correlations should be very useful in estimating the density of aqueous single and multicomponent electrolyte solut...

Temperature dependence of interaction parameters in electrolyte NRTL model

The electrolyte NRTL model captures the electrolyte solution nonideality over the entire concentration range with two binary interaction parameters. Here, the temperature dependence of the binary parameters is formulated with a Gibbs‐Helmholtz expression containing three temperature coefficients associated with Gibbs energy, enthalpy, and heat capacity contributions. We show the Gibbs energy term is correlated to the excess Gibbs energy of aqueous single electrolyte systems at 298.15 K. With the Gibbs energy term identified, the enthalpy term is correlated to the excess enthalpy at 298.15 K. With the Gibbs energy term and the enthalpy term identified, the heat capacity term is correlated to the excess heat capacity at 298.15 K. Once the temperature coefficients are properly quantified by regressing data of mean ionic activity coefficient, excess enthalpy, and heat capacity at 298.15 K or the equivalents, the model provides a comprehensive thermodynamic framework to represent all thermodynamic properties of electrolyte solutions. © 2015 American Institute of Chemical Engineers AIChE J, 62: 1244–1253, 2016

Double liquid electrolyte for primary Mg batteries

Magnesium will be a very promising anode material for primary high energy density batteries, in the event that the corrosion of Mg electrode in aqueous electrolyte is effectively inhibited. Double liquid electrolyte (DLE) is designed and it reduces the corrosion significantly. DLE consists of an aqueous phase and an organic phase, which is immiscible with the former. Cathodic and anodic reactions proceed in the two phases separately, therefore Mg electrode no longer contacts with aqueous electrolyte. Anodic efficiency of pure Mg is above 90% in DLE, much higher than in single aqueous electrolyte.

Novel Pulse Electrodeposited Co–Cu–ZnO Nanowire/tube Catalysts for C1–C4 Alcohols and C2–C6 (Except C5) Hydrocarbons from CO and H2

Co–Cu–ZnO nanowire/tube catalysts were synthesized using pulse electrodeposition technique from a single aqueous electrolyte solution using a template synthesis technique. They were then tested as catalysts for the hydrogenation of CO to alcohols and higher hydrocarbons. Nanowires/tubes were grown inside the pores of membranes using a three-step sequential deposition process. First, a low current of −6.9 mA/cm2 was applied for 300 ms for Cu deposition, then a high current density of −11.5 mA/cm2 for t ms (t = 500, 600, 750 ms) was applied for Co deposition, and finally no current was applied for 1200 ms so that the ions near the cathode replenish. The surface had a significantly different composition than the bulk. On the surface, there was more Co, less Cu, and more Zn. The catalyst showed the alcohol (C1–C4) selectivity of 20.9 %C at H2/CO = 3/1, GHSV = 16 000 scc/h gcat, temperature = 270 °C, pressure = 15 bar, and time-on-stream = 65 h.

Measurement and Correlation of Surface Tension for Single Aqueous Electrolyte Solutions

In this study, the values of the surface tension for a number of single aqueous electrolyte solutions were measured at various temperatures and electrolyte concentrations using the well-known and computer-aided pendant-drop method. In order to conduct the experimental measurements, a high-pressure IFT-700 apparatus, equipped with a view cell and a data acquisition system, was used. The systems studied in this study were aqueous solutions of KCl, NaCl, CaCl2, and Na2SO4. The pooled standard deviation and the confidence limit of the surface-tension data for a 95 % confidence level were determined to be 0.17 mN · m−1 and \({\bar{\sigma} \pm 0.19}\), respectively. It should be noted that while the surface tension for electrolyte solutions increases as the electrolyte concentration increases, it decreases with an increase in temperature as expected. Finally, data reduction was carried out using an empirical equation to show the effect of temperature, electrolyte concentration, and the nature of ionic species on the surface tension for the systems studied.

Predictions of thermodynamic properties of aqueous single-electrolyte solutions with the two-ionic-parameter activity coefficient model

In this study, the enthalpies of vaporization, freezing point depressions, and boiling point elevations of aqueous single-electrolyte solutions were predicted with the two-ionic-parameter model involving the activity coefficients with two electrolyte-specific approaching and solvation parameters of the individual ions of the electrolyte in an aqueous solution. The results show that the predictions are fairly well with the average absolute relative deviations smaller than 6.0% for enthalpy of vaporization and 7.0% for freezing point depression and boiling point elevation, except for some solutions of high concentration and for that with non-completely dissociated weak electrolytes. The prediction results are numerically listed in the tables and discussed in the text.

Application of several activity coefficient models to water-organic-electrolyte aerosols of atmospheric interest

Abstract. In this work, existing and modified activity coefficient models are examined in order to assess their capabilities to describe the properties of aqueous solution droplets relevant in the atmosphere. Five different water-organic-electrolyte activity coefficient models were first selected from the literature. Only one of these models included organics and electrolytes which are common in atmospheric aerosol particles. In the other models, organic species were solvents such as alcohols, and important atmospheric ions like NH4+ could be missing. The predictions of these models were compared to experimental activity and solubility data in aqueous single electrolyte solutions with 31 different electrolytes. Based on the deviations from experimental data and on the capabilities of the models, four predictive models were selected for fitting of new parameters for binary and ternary solutions of common atmospheric electrolytes and organics. New electrolytes (H+, NH4+, Na+, Cl-, NO3- and SO42-) and organics (dicarboxylic and some hydroxy acids) were added and some modifications were made to the models if it was found useful. All new and most of the existing parameters were fitted to experimental single electrolyte data as well as data for aqueous organics and aqueous organic-electrolyte solutions. Unfortunately, there are very few data available for organic activities in binary solutions and for organic and electrolyte activities in aqueous organic-electrolyte solutions. This reduces model capabilities in predicting solubilities. After the parameters were fitted, deviations from measurement data were calculated for all fitted models, and for different data types. These deviations and the calculated property values were compared with those from other non-electrolyte and organic-electrolyte models found in the literature. Finally, hygroscopic growth factors were calculated for four 100 nm organic-electrolyte particles and these predictions were compared to experimental data and to predictions from other models. All of the newly fitted models show good agreement with experimental water activity data in binary and ternary solutions. One of the models is for activities of non-electrolytes only, but the other three models show quite small deviations from measured electrolyte activities. Because there were not enough experimental data for organic and electrolyte activities, some models show bigger deviation for mutual deliquescence relative humidities of organic-electrolyte particles, but calculated growth factors for liquid droplets are quite close to the experimental data. Even in cases with somewhat bigger deviations, the results can be considered satisfactory, because they were calculated based mainly on the predictive properties of the models.

Estimations of activity coefficients of constituent ions in aqueous electrolyte solutions with the two-ionic-parameter approach

The electrolyte-specific solvation parameter regarding the ionic solvation, and approaching parameter regarding the closest distance of approach between ions, in a electrolyte solution were defined by Lin and Lee [Fluid Phase Equil. 205 (2003) 69–83]. In this study, these two electrolyte-specific parameters of individual ions were correlated with the activity coefficients of ions in different aqueous single-electrolyte solutions from literature. With these two parameters and the two-ionic-parameter approach of Lin and Lee, the individual activity coefficients of the ions in the solutions of fourteen 1:1 type, two 1:2 type, and six 2:1 type electrolytes were calculated and compared to the literature values. Also the comparisons of the predicted and literature osmotic coefficients of aqueous multi-electrolyte solutions were reported. The results showed the estimated values fairly agree to the literature data.

Application of the GV-MSA model to the electrolyte solutions containing mixed salts and mixed solvents

In this work the Ghotbi–Vera mean spherical approximation (GV-MSA) model, coupled with two different expressions for the cation-hydrated diameters, was used in predicting the mean ionic activity coefficients (MIAC) of electrolytes for a number of the mixed-solvent and mixed-salt electrolyte solutions at 25 °C. In all cases the cation diameters in solutions changed with concentration of electrolyte while the anion diameters were considered to be constant and equal to the corresponding Pauling diameters. In application of the GV-MSA model to the electrolyte systems, two different expressions were used for concentration dependency of cation-hydrated diameters, i.e., the GV-MSA1 and GV-MSA2 models. In case of the electrolyte solutions containing the mixed-solvent of water and alcohol, the dielectric constants of the mixed solvents were obtained by simple regression of polynomial equations in terms of weight fraction of alcohol to the pertinent experimental data available in the literature. For the mixed-salt and mixed-solvent electrolyte solutions, in order to directly calculate the MIAC of electrolytes without introducing any new adjustable parameter, the values obtained in this work for the cation-hydrated diameters in the single aqueous electrolyte solutions were used. The results obtained in this work showed that the GV-MSA2 could more accurately correlate the MIAC of electrolytes in the single aqueous electrolyte solutions in comparison to those of the GV-MSA1 and Pitzer models. Also, the results showed that the GV-MSA-based models could accurately predict the MIAC of electrolytes in the mixed-solvent electrolyte solutions in comparison to those obtained from the model of Pitzer. In case of the mixed-salt electrolyte solutions the results of the two GV-MSA-based models studied in this work reasonably predict the MIAC of electrolytes in the mixed-salt electrolyte solutions without introducing any additional adjustable parameters compared to those obtained from the model of Pitzer with two adjustable parameters.

A two-ionic-parameter approach for ion activity coefficients of aqueous electrolyte solutions

The individual ion activity coefficient in an aqueous electrolyte solution is characterized in terms of two physical significant ionic parameters regarding the ionic solvation and the closest distance of approach between ions in a solution. The present approach was illustrated by the estimations of the individual activity coefficients of the ions of four electrolytes, NaCl, KCl, NaBr, and KBr in the aqueous single-electrolyte solutions. The estimation results showed the average absolute deviations (AAD) of the individual ion activity coefficients from the experimental values are <0.01 (except Na + and K + in KCl aqueous solution) for the aqueous single-electrolyte solutions. The vapor pressures of the aqueous two-electrolyte solutions consisted of the binary pairs of electrolytes of NaCl, KCl, NaBr, and KBr were estimated by the present approach and compared to the literature values. The average absolute relative deviations (AARD) of vapor pressures are <1.0% for these two-electrolyte aqueous solutions. The advantages of the present approach include: (1) only two parameters are involved for each constituent ion for the activity coefficient and the thermodynamic property estimations of the aqueous multi-electrolyte solutions. (2) Re-correlation from experimental data to determine new parameters is avoided when the additional electrolytes are involved since all the ionic parameters are simply calculated by a mixing rule. These two advantages make the present approach requires less computation effort than other methods do.

Activity of the electrolyte and the amino acid in the systems water + dl,α-aminobutyric acid + NaCl, +NaBr, +KCl, and +KBr at 298.2 K

The activity coefficients of dl,α-aminobutyric acid in four aqueous single-electrolyte solutions (NaCl, NaBr, KCl and KBr) were obtained at 298.2 K. Electrochemical cells with two ion-selective electrodes, a cation and an anion ion-selective electrode and a double junction reference electrode were used to measure the activity coefficients of the electrolyte. The activities of dl,α-aminobutyric acid in each electrolyte solution were calculated using a cross-differential thermodynamic relation. The results show that the nature of the ions in solution has significant effect on the value of activity coefficient of dl,α-aminobutyric acid. Comparison with literature data for dl,α-aminobutyric acid in NaCl aqueous solutions, shows a strong effect of the chemical structure of the amino acid. In the presence of dl,α-aminobutyric acid, the behavior of the activity coefficients of the electrolytes is distinctively different in the dilute and in the concentrated electrolyte regions.

Surface tension of aqueous electrolyte solutions at high concentrations — representation and prediction

A calculation method was developed for representing and predicting surface tension of aqueous electrolyte solutions over a wide range of concentrations, up to 36 m. Based on the Gibbs dividing surface concept, the Langmuir adsorption equation was adopted for modeling the surface excess of electrolyte(s). The activities of electrolytes in the aqueous solutions were calculated by the Pitzer equation. The surface tensions for 45 aqueous single-electrolyte systems at a single temperature were used to correlate the model parameters, and the correlation yields an overall average absolute percentage deviation (AAPD) of 0.47. Surface tensions for 23 aqueous inorganic electrolyte systems are available at several temperatures. Application of these model parameters to extrapolate surface tensions of these systems to different temperatures yields an overall AAPD of 0.91. The proposed method was successfully applied to predict surface tensions for an aqueous binary electrolyte system containing a free acid (HNO 3) and its salt (KNO 3), which have opposite effects on surface tension with an increase in their concentrations, with an overall AAPD of 1.87. The predicted surface tensions for additional 11 binary and five ternary mixed-electrolyte aqueous systems indicate an overall AAPD of 1.69.

A new equation of state for real aqueous ionic fluids based on electrolyte perturbation theory, mean spherical approximation and statistical associating fluid theory

Based on perturbation theory, a new equation of state is developed for real electrolyte aqueous fluids, which is composed of ion–ion, ion–dipole, dipole–dipole, Lennard–Jones dispersion, hydrogen bonding association and hard sphere repulsion terms. The MSA equation from Blum is adopted instead of the perturbed electrostatic term, which simplifies the calculation. The SAFT equation is adopted for the calculation of hydrogen bond association for water molecules. For each electrolyte, only one adjustable parameter, i.e., the cation soft sphere diameter, is regressed. The experimental mean ionic activity coefficient data of 30 aqueous electrolytes (including 1:1, 2:1 and 1:2 electrolytes) were correlated. The parameters thus obtained can be used to predict the densities of these aqueous single electrolyte solutions and the mean ionic activity coefficients in mixed electrolyte aqueous solutions without any additional adjustable mixing parameters.

A vapor pressure model for aqueous and non-aqueous solutions of single and mixed electrolyte systems

A predictive model with two parameters for the calculation of the vapor pressures of aqueous and non-aqueous, single and mixed electrolyte solutions was developed. In this development, the modified Debye-Hückel equation was employed to account for the long-range contribution, and the concept of solvation was employed to account for the short-range contribution. The proposed model has been tested with experimental data reported in the literature of 144 aqueous single electrolyte solutions, 24 non-aqueous single electrolyte solutions and 14 aqueous mixed electrolyte solutions, of which the temperature range was 298–373 K and the ionic strength was moderate. It was found that one parameter, λ, was dependent on solvent only and could be fixed on 2.11 for water, methanol, and ethanol solutions of all kind of electrolytes systems. The other parameter, S, was independent of temperature. The calculated vapor pressures agreed well with the experimental ones, and the overall average percentage deviation was less than 0.26%.

Activity coefficients of sodium, potassium, and nitrate ions in aqueous solutions of NaNO3, KNO3, and NaNO3+KNO3 at 25�C

Ion selective electrodes have been used to measure the activity coefficients at 25°C of individual ions in aqueous solutions of NaNO3 up to 3.5 molal, KNO3 up to 3.5 molal and mixtures of NaNO3 and KNO3 up to 2.4 molal total nitrate ion concentration. The experimental results confirm that the activity coefficient of anion and cation in aqueous single electrolyte solutions of NaNO3 and KNO3 were different from each other over the whole range of concentrations studied. These effects are attributed to the ion-ion and ion-solvent interactions. The results also show that the activity coefficients of nitrate ions in the presence of sodium and potassium counterions do not depend significantly on the nature of the counterions present in the solution. The experimental data obtained in this study were correlated by a model proposed previously.

Measurement and correlation of ion activity in aqueous single electrolyte solutions

AbstractIon‐selective electrodes were used to measure the activity coefficients at 298.2 K of individual ions in aqueous solutions of NaCl and NaBr up to of 5 molal and of KCl up to 4 molal. The mean ionic activity coefficients of NaCl, NaBr, and KCl, obtained from the values of the activity coefficients of the individual ions, show good agreement with values reported in the literature. The experimental results show that the activity coefficients are different for the anion and the cation in an aqueous solution of a single electrolyte and that, as expected from the ion‐ion and ion‐solvent interactions, the activity coefficient of an ion depends on the nature of its counterion. A modified form of the Pitzer's model, which distinguishes between the activity coefficients of the anion and the cation, was used to correlate the experimental results.