Electroconductivity changing tendency of concentrated of formic and acetic acids binary aqueous solutions and water-formic acid-acetic acid ternary solution

The specific electroconductivity (EC) of concentrated formic acid (FA) and acetic acid (AA) aqueous solutions and water-FA-AA mixtures was studied in a wide temperature range. At higher electrolyte concentration, the specific EC passes the maximum in water-FA, water-AA, and water-FA-AA mixtures containing constant AA concentration. At the given temperature, the maximum specific EC of the studied solutions was used as a generalizing parameter. The reduced EC values (EC ratio to the maximum value at the given temperature) all over the studied temperature and concentration ranges were shown to meet in the same curves.     

Electrical conductivity of associated electrolyte-water systems

The specific electrical conductivity (EC) of concentrated aqueous solutions of tartaric and oxalic acids was measured in the range 15–90°C. Specific electrical conductivity versus concentration and temperature relationships were analyzed for the acids studied in this work and for formic, acetic, propanoic, butanoic, chloroacetic, dichloroacetic, and trichloroacetic acids, as well as for aqueous ammonia. As the electrolyte concentration increases, the EC passes through a maximum whose position is independent of temperature. The maximal EC value of an aqueous solution of an associated electrolyte for a given temperature and the concentration corresponding to this maximal EC were used as generalizing parameters. Over the entire ranges of the temperatures and concentrations studied, normalized EC values (normalized EC is the ratio of the current EC to its maximal value for a given temperature) for all electrolytes considered fall on one curve provided that the argument is a normalized concentration (which is the ratio of the current solution concentration to its value at which specific EC has a maximal value).     

Electrical conductivity of the ammonia-water system

The electrical conductivity (EC) of the ammonia-water system was studied in the concentration range 0.1–10 mol/L ammonia and the temperature range 15–60°C. The maximal EC of aqueous ammonia at a given temperature is proposed as the parameter for generalizing experimental results. The normalized EC was calculated as the ratio of the EC of aqueous ammonia of a given concentration to the maximal EC at a given temperature. Over the ranges of the concentrations and temperatures studied, all normalized ECs fall on one curve. The EC activation energy was analyzed as a function of ammonia concentration and temperature.     

Heterogeneity in binary mixtures of (water + tertiary butanol): temperature dependence across mixture composition

The temperature dependence of solution heterogeneity in binary mixtures of water and tertiary butanol (TBA) and its effects on a chemical reaction have been investigated by using steady-state and time-resolved spectroscopic experiments within the temperature range of 278 ≤ T/K ≤ 373. Eleven different mole fractions of TBA, covering extremely low TBA mole fractions to pure TBA, have been considered. An organic chromophore that undergoes a photoexcited intramolecular charge-transfer reaction is employed to reveal the signature of the solution heterogeneity. Upon increasing the solution temperature, the absorption spectrum of the dissolved chromophore exhibits a red shift at very low TBA concentrations but shifts toward higher energy (blue shift) at higher alcohol concentrations. This is a reflection of temperature-assisted aggregation of TBA molecules in very dilute aqueous solutions. The magnitude of the temperature-induced red shift is the largest at around 0.04 mol fraction of TBA, and a larger variation of the spectral line width across the temperature suggests enhanced solution heterogeneity. Reaction time constants measured at various mixture compositions are found to follow an Arrhenius-type temperature dependence. The average activation energy, when plotted as a function of mixture composition, steeply rises with TBA concentration in the limit of the very low TBA mole fraction and then suddenly levels off to a plateau upon further addition of TBA. The alcohol concentration-dependent activation energy abruptly changes its slope at a TBA mole fraction ～0.1, at which a transition from the three-dimensional water-type network to the zigzag alcohol chain structure is known to occur. The plateau value of the activation energy is ～6k(B)T and agrees well with the earlier estimate for the same chromophore from the pure solvent data at room temperature. The observed increase in the spectral red shift with temperature at low TBA mole fractions is in general agreement with the existing experimental results which support the view that temperature assists the aggregation of TBA molecules in dilute aqueous solutions of TBA. However, unlike in the small-angle neutron scattering study [ Bowron, D. T.; Finney, J. L. J. Phys. Chem. B 2007, 111, 9838], which finds clustering of TBA molecules reaching a maximum at ～353 K, the present data do not indicate any such temperature maximum within the temperature range of 278 ≤ T/K ≤ 373.     

The effect of monoethanolamine on conductivity and efficiency of electrodialysis of acid and salt solutions

Experimental studies of the specific conductivity (SC) are carried out for aqueous solutions of organic and inorganic acids and salts including those containing different amounts of monoethanolamine (MEA), which model the absorption solutions used in purification of gas mixtures from carbon dioxide and containing heatstable salts (HSS). It is shown that the addition of MEA to binary aqueous electrolyte solutions gives rise to changes in the SC: in the MEA concentration range from 0 to ～1.5 M, the SC of the resulting ternary solutions increases but decreases again with the further increase in MEA concentration. This behavior of SC is typical also of aqueous binary amine solutions. It is shown that in the presence of MEA, the quantitative removal of dissolved acids and salts proceeds faster with the simultaneous increase in the specific energy consumption by a factor of 7–9 (up to 85.7–93.6 kJ/dm³). It is assumed that the reason for the decrease in SC and the enhancement of energy consumption at electrodialysis of mixed solutions is the probable existence of monoethanolamine both as free solvated ions and neutral molecules and as self-assembled associated structures (ion pairs and more complex particles) which involve also the ions of salts dissolved in amine-containing solutions.     

High-frequency electric conductivity of mixtures of water with acetone,dimethyl sulfoxide,and carbamide

The high-frequency (HF) electric conductivity (EC) of water-acetone, water-dimethyl sulfoxide (DMSO), and water-carbamide mixtures was analyzed. The limiting high-frequency conductivity decreased as the content of the organic component in the mixture increased. When the acetone and DMSO concentrations increased, the high-frequency conductivity passed through a maximum at 2450 MHz and increased with the carbamide concentration in its mixtures with water. The optimum conditions for the absorption of HF energy by the aqueous organic mixtures under study were determined.     

A thermochemical study of aqueous solutions of sodium naproxene

The enthalpies of solution of sodium naproxene and dilution of its aqueous solutions were measured on an isoperibolic calorimeter at 293.15, 298.15, 303.15, 308.15, 313.15, and 318.15 K. The maximum content of the electrolyte was determined by its solubility at the given temperature (0.038–0.083 mol/kg solvent). The Pitzer model was used to obtain the virial coefficients for calculations of many excess thermodynamic properties of both solutions and their components. Changes in these characteristics depending on the concentration and temperature are considered.     

The conductivity of concentrated aqueous mixtures of NaCl and MgCl2 at 25°C

As part of a cooperative study of the thermodynamic and transport properties of aqueous mixtures of NaCl and MgCl₂ at 25°C, we report values of the molar conductivities of the mixed electrolyte in the concentration range 0.5 to 3.6 molar. It was found that the conductivities in the mixtures differ from those calculated assuming additivity of the conductivities of the component binary solutions by 4.65 S-cm²-mol^–1 at constant total molarity and 0.50 S-cm²-mol^–1 at total ionic strength.     

Pseudolattice theory of charge transport in ionic solutions: Corresponding states law for the electric conductivity

A statistical mechanical framework for charge transport in ionic liquid–solvent mixtures based on the existence of a statistical lattice structure (pseudolattice) throughout the whole range of concentration is reported. The ion distribution is treated in a mean-field Bragg–Williams-like fashion, and the ionic motion is assumed to take place through hops between cells of two different types separated by non-random-energy barriers of different heights depending on the cell type. Assuming non-correlated ion transport, the electrical conductivity is shown to have a maximum, arising from the competition between the concentration of charge carriers in the bulk medium and their mobilities in the pseudolattice. An explicit expression for the concentration at which this maximum occurs is given in terms of microscopic parameters, and the electrical conductivity normalized by its maximum value (κ/κ_max) is shown to follow rather closely a universal corresponding states law in concentration space when represented against the ionic concentration scaled by its value at the conductivity maximum (?_α/?_max). Ion–ion and ion–solvent interactions are explicitly considered combining the path probability method for charge transport in solid electrolytes and the Bragg–Williams approximation for interparticle interactions, and their impact on the deviations of experimental data from the universal behavior of non-correlated transport analyzed. The theoretical predictions are shown to satisfactorily predict experimental values of electrical conductivity of aqueous solutions of conventional electrolytes and of mixtures of room temperature molten salts with typical solvents.     

Ionic studies of sodium alginate isolated from Sargassum terrarium (brown algea) karachi coast with 2,1-electrolyte

Physical and chemical analysis of the polysaccharide isolated from Sargassum Terarrium (brown algae) of Karachi coast showed characteristics of the sodium alginate. Optical rotations and sulphated ash content were found and FTIR spectra showed a sharp and strong absorption band at 1600 cm^?1 representing carboxylate ion which conforms high uronic acid content of the product. The viscosities of aqueous 0.1% sodium alginate solution were measured in the presence of copper II chloride (CuCl₂). The viscosities were found to be increased with the increase in the concentration of electrolyte. Viscosities were also found affected with temperature. ‘A’ and ‘B’ coefficients of Jones–Dole equation were evaluated. The increase in positive values of ‘B’ coefficient with the rise of temperature led to conclusion that given electrolyte in 0.1% aqueous sodium alginate solution behaves as structure maker. Thermodynamic parameters regarding to activated state like energy of activation E_η, change in free energy of activation ΔG_η and change of entropy of activation ΔS_η were also evaluated. Straight-line plots of log η versus 1/T observed with positive slopes show the effect of temperature on the viscosities of solutions. Energy of activation (E_η) was found to be decreased with the rise of temperature. Change in free energy of activation (ΔG_η) was also found to be increased with increase in concentrations of electrolyte and also with rise of temperature. The values of change in entropy of activation (ΔS_η) were also calculated. Negative values of ΔS_η were found to be increased with increase in concentration of electrolyte and also with rise of temperature.     

Regularity of conductivity of concentrated aqueous solutions of strong electrolytes

Conductivity of concentrated aqueous solutions of strong electrolytes is analyzed in a wide range of temperatures and concentrations. The highest conductivity of solutions at a given temperature and the concentration corresponding to the highest conductivity are used as the generalizing parameters. It is shown that in the temperature range from 0 to 100°C and the concentration range from 0.1 to 12 M, the values of reduced conductivity (the ratio between the conductivity and its maximum value at a given temperature) for KOH aqueous solution fall on a common curve, if the reduced concentration (the ratio between the concentration of solution and the concentration corresponding to the highest conductivity) is used as the argument. The reduced conductivities of strong acids, bases, and salts of some I-I, I-II, II-I, III-I, and II-II electrolytes fall on the same curve.     

Redox Flow Batteries: Electrolyte Chemistries Unlock the Thermodynamic Limits

Redox flow batteries (RFBs) represent a promising approach to enabling the widespread integration of intermittent renewable energy. Rapid developments in RFB materials and electrolyte chemistries are needed to meet the cost and performance targets. In this review, special emphasis is given to the recent advances how electrolyte design could circumvent the main thermodynamic restrictions of aqueous electrolytes. The recent success of aqueous electrolyte chemistries has been demonstrated by extending the electrochemical stability window of water beyond the thermodynamic limit, the operating temperature window beyond the thermodynamic freezing temperature of water and crystallization of redox-active materials, and the aqueous solubility beyond the thermodynamic solubility limit. They would open new avenues towards enhanced energy storage and all-climate adaptability. Depending on the constituent, concentration and condition of electrolytes, the performance gain has been correlated to the specific solvation environment, interactions among species and ion association at a molecular level.     

On the use of the activation energy concept to investigate analyte and network deformations in entangled polymer solution capillary electrophoresis of synthetic polyelectrolytes

The activation energy associated with the electrophoretic migration of an analyte under given electrolyte conditions can be accessed through the determination of the analyte electrophoretic mobility at various temperatures. In the case of the electrophoretic separation of polyelectrolytes in the presence of an entangled polymer network, activation energy can be regarded as the energy needed by the analyte to overcome the obstacles created by the separating network. Any deformation undergone by the analyte or the network is expected to induce a decrease in the activation energy. In this work, the electrophoretic mobilities of poly(styrenesulfonates) (PSSs) of various molecular weights (Mr 16 x 10(3) to 990 x 10(3)) were determined in entangled polyethylene oxide (PEO) solutions as a function of temperature (in the 17-60 degrees C range) and the PSS activation energies were calculated. The influences of the PSS molecular weight, blob sizes zetab of the separating network (related to the PEO concentration), ionic strength of the electrolyte and electric field strength (75-600 V/cm) were investigated. The results were interpreted in terms of analyte and network deformations and were confronted with those previously obtained for DNA migration in polymer solutions and chemical gels. For a radius of gyration Rgzetab, suggesting PSS and network deformations in the latter case. Increasing ionic strength resulted in an increase in the PSS activation energy, because of the decrease of their radii of gyration, which makes them less deformable. Finally, the activation energies of all the PSSs are a decreasing function of field strength and at high field strength tend to reach a constant value close to that for a small molecule.     

高电压/宽温域水系碱金属离子电池的研究进展

水系储能器件具有固有的高安全性、环境友好性和成本低的优势，在未来智能电网、便携式/可穿戴电子产品等领域显示出巨大的应用潜力。然而水的热力学分解电压低、冰点高，导致水系电解液电化学稳定电压窗口窄以及凝固点高，极大地限制了水系储能器件的能量密度与宽温域应用。因此，设计耐高电压、抗冻的水系电解液，成为水系储能器件大规模、多场景应用的关键。本文系统综述了高电压/宽温域水系碱金属离子电池电解液设计的研究进展，从热力学和动力学角度出发，分别重点介绍提高电解液电压窗口和工作温度范围的各类策略以及相关作用机制。进一步提出宽温域、高压水系电解液的潜在设计思路，并对高性能水系碱金属离子电池的发展方向进行展望。     

Activity Coefficient Prediction for Binary and Ternary Aqueous Electrolyte Solutions at Different Temperatures and Concentrations

The mean spherical approximation (MSA) model, coupled with two hard sphere models, was used to predict the activity coefficients of mixtures of electrolyte solutions at different temperatures and concentrations. The models, namely the Ghotbi-Vera-MSA (GV-MSA) and Mansoori et al.-MSA (BMCSL-MSA), were directly used without introducing any new adjustable parameters for mixing of electrolyte solutions. In the correlation step, the anion diameters were considered to be constant, whereas the cation diameters were considered to be concentration dependent. The adjustable parameters were determined by fitting the models to the experimental mean ionic activity coefficients for single aqueous electrolytes at fixed temperature. The results showed that the studied models predict accurately the activity coefficients for single electrolyte aqueous solutions at different temperatures. In the systems of binary aqueous electrolyte solutions with a common anion, the GV-MSA model has slightly better accuracy in predicting the activity coefficients. Also, it was observed that the GV-MSA model can more accurately predict the activity coefficients for ternary electrolyte solutions with a common anion, especially at higher concentrations.     

Electroconductivity of the calcium oxide-ethylene glycol-water system

The electroconductivity of calcium oxide-ethylene glycol (EG) and calcium oxide-EG-water systems is measured in wide ranges of temperatures and compositions. With increasing temperature, the conductivity of the former system passes through a maximum, which shifts to lower temperatures with increasing electrolyte concentration. Thermodynamic characteristics of the calcium hydroxy glycolate association in EG are estimated using the Lee-Wheaton equation. The conductivity of the latter system decreases with increasing EG content. Its dependence on the limiting high-frequency conductivity of the mixed solvent is analyzed. The activation energy for conduction in both systems decreases with increasing temperature and electrolyte concentration.     

Electrical conductivity of solutions of the LiIO3-HIO3-H2O system

The electrical conductivity of aqueous LiIO₃ solutions and solutions of the LiIO₃-HIO₃-H₂O system is measured over a wide range of compositions at 25, 50, and 75°C. Isothermal surfaces of electrical conductivity are mapped, and the activation energies of conductivity are calculated. The conductivity isotherms in the LiIO₃-H₂O and HIO₃-H₂O boundary binary systems and in mixed solutions along sections with fixed electrolyte ratios each have a maximum as a function of electrolyte concentration. It is assumed that structure reorganization occurs in solutions in the concentration range corresponding to the peak conductivity. Proton migration features in the solutions in question are considered.     

The influence of temperature and concentration on viscous flow of solutions of Et<Subscript>4</Subscript>NBF<Subscript>4</Subscript> in propylene carbonate

Solutions of tetraethylammonium tetrafluoroborate in propylene carbonate were studied by viscometry and densimetry over the concentration range 0.08–1 mol/kg at 283.15, 298.15, and 308.15 K. The concentration dependence of the viscosity of solutions was described by the Angell and Bachinskii equations. The thermodynamic parameters of activation of viscous flow of solutions of Et₄NBF₄ in propylene carbonate were estimated using the approach suggested by Eyring and Andrade. The solvation of tetraethylammonium tetrafluoroborate in propylene carbonate was found to be insignificant. The activation energy of viscous flow in solutions remained constant over the temperature range studied. Viscous flow was largely determined by solvent destructuring as the concentration of the electrolyte and temperature increased.     

Solvation of calcium ions in methanol-water mixtures: molecular dynamics simulation

Molecular dynamics simulations of CaCl2 solutions in water and methanol-water mixtures, with methanol concentrations of 5, 10, 50, and 90 mol %, at room temperature, have been performed. The methanol and water molecules have been modeled as flexible three-site bodies. Solvation of the calcium ions has been discussed on the basis of the radial and angular distribution functions, the orientation of the solvent molecules, and their geometrical arrangement in the coordination shells. Analysis of the H-bonds of the solvent molecules coordinated by Ca2+ has been done. Residence time of the solvent molecules in the coordination shell has been calculated. The preferential hydration of the calcium ions has been found over the whole range of the mixture composition. The water concentration in the first and second coordination shells of Ca2+ significantly exceeds the water content in the solution, despite the very similar interaction energy of the calcium ion with water and methanol. In aqueous solution and methanol-water mixtures, the first coordination shell of Ca2+ is irregular and long-living. The solvent molecules prefer the anti-dipole arrangement, but, in aqueous solutions and water-rich mixtures, the water molecules in the primary shell have only one H-bonded neighbor.