Solutions Of Strong Electrolytes Research Articles

Stimulation of Plant Growth with an Aqueous Solution Activated by Glow Discharge Plasma

Abstract—This paper presents the results on the application of low-concentration aqueous solutions of strong electrolytes activated by glow discharge plasma for plant growth stimulation. We provide experimental evidence that these solutions can be used as an effective regulator of plant growth.

Generation of H+ and OH− ions in anion-exchange membrane/ampholyte-containing solution systems: A study using electrochemical impedance spectroscopy

Generation of H+ and OH− ions at anion-exchange membranes is a phenomenon, which substantially reduces the performance of a number of electromembrane processes, such as the wastewater treatment, fuel cell energy production and others. We show that the mechanisms of this phenomenon are different, when a Neosepta AMX anion-exchange membrane is bathed in a strong electrolyte solution (NaCl and KCl) or in an ampholyte solution (NaH2PO4, KH2PO4, KHT and KH2Cit). The H+ and OH− ions' generation in the case of strong electrolytes requires a voltage threshold (about 0.3 V of the corrected voltage not including ohmic contribution), which relates to a current close to the limiting current. The process occurs mainly through proton transfer reactions involving the membrane functional groups. In the case of ampholytes, this generation takes place without a threshold; this process is separated in space: the generation of H+ occurs at the depleted solution/membrane interface, that of OH− ions, at the membrane boundary with the enriched solution. Electrochemical impedance spectra (EIS) are used for the determination of the effective rate constants for the H+ and OH− ions’ generation. Their values are compared with the rate constants calculated from the acid dissociation constants (Ka).

Neutralization Dialysis for Phenylalanine and Mineral Salt Separation. Simple Theory and Experiment.

A simple non-steady state mathematical model is proposed for the process of purification of an amino acid solution from mineral salts by the method of neutralization dialysis (ND), carried out in a circulating hydrodynamic mode. The model takes into account the characteristics of membranes (thickness, exchange capacity and electric conductivity) and solution (concentration and components nature) as well as the solution flow rate in dialyzer compartments. In contrast to the known models, the new model considers a local change in the ion concentration in membranes and the adjacent diffusion layers. In addition, the model takes into consideration the ability of the amino acid to enter the protonation/deprotonation reactions. A comparison of the results of simulations with experimental data allows us to conclude that the model adequately describes the ND of a strong electrolyte (NaCl) and amino acid (phenylalanine) mixture solutions in the case where the diffusion ability of amino acids in membranes is much less, than mineral salts. An example shows the application of the model to predict the fluxes of salt ions through ion exchange membranes as well as pH of the desalination solution at a higher than in experiments flow rate of solutions in ND dialyzer compartments.

Concentration Dependencies of Diffusion Permeability of Anion-Exchange Membranes in Sodium Hydrogen Carbonate, Monosodium Phosphate, and Potassium Hydrogen Tartrate Solutions.

The concentration dependencies of diffusion permeability of homogeneous (AMX-Sb and AX) and heterogeneous (MA-41 and FTAM-EDI) anion-exchange membranes (AEMs) is obtained in solutions of ampholytes (sodium bicarbonate, NaHCO3; monosodium phosphate, NaH2PO4; and potassium hydrogen tartrate, KHT) and a strong electrolyte (sodium chloride, NaCl). It is established that the diffusion permeability of AEMs increases with dilution of the ampholyte solutions, while it decreases in the case of the strong electrolyte solution. The factors causing the unusual form of concentration dependencies of AEMs in the ampholyte solutions are considered: (1) the enrichment of the internal AEM solution with multiply charged counterions and (2) the increase in the pore size of AEMs with dilution of the external solution. The enrichment of the internal solution of AEMs with multiply charged counterions is caused by the Donnan exclusion of protons, which are the products of protolysis reactions. The increase in the pore size is conditioned by the stretching of the elastic polymer matrix due to the penetration of strongly hydrated anions of carbonic, phosphoric, and tartaric acids into the AEMs.

An equation for the isosbestic point wavelength in aqueous solutions of electrolytes

The existence of an isosbestic point in the OH bond vibration band of H2O molecules in solutions of strong electrolytes has been shown by many research groups but its physical meaning has been only recently read as the equilibrium point between two populations of water molecules where either water-ion or water-water interactions respectively prevail. Thus the isosbestic point provides useful information on the bulk displacement of water molecules in presence of solutes. Herein we show that the isosbestic point occurrence is correctly described by an equation describing the balance of the electrostatic forces. Furthermore, its wavelength is also related to the slope of the density vs. the solute concentration. These results support the view that the effect of the solute can be barely regulated within few hydration shells.

An efficient model for estimation of gypsum (calcium sulfate di-hydrate) solubility in aqueous electrolyte solutions over wide temperature ranges

Thermodynamic solubility of calcium sulfate di-hydrate (gypsum) plays a major role in many operations involved in oilfields and process industries. In this study, several solubility models were developed using the approaches including Multilayer Perceptron (MLP) networks, Radial Basis Function (RBF) networks, Least Squares Support Vector Machine (LSSVM), Adaptive Network-based Fuzzy Inference system (ANFIS), and Committee Machine Intelligent System (CMIS) for estimating the phase behavior of calcium sulfate dihydrate (or gypsum) in strong electrolyte solutions at high temperatures. The developed CMIS model was found to outperform all other modeling approaches indicating an excellent accordance with experimental data and yielding an overall correlation coefficient of (R2) 0.9968. The developed CMIS model was also found to outperform the ion interaction model of Pitzer providing superior predictability for gypsum solubility in aqueous electrolyte solutions. The results of this study indicate that gypsum solubility could be estimated by employing the CMIS approach with high accuracy in Na-Ca-Mg-Fe-Al-H-Cl-H2O system over temperatures ranging from 5 to 98 °C.

Ionic conductivities and diffusion coefficients of alkyl substituted sulfonated resorcinarenes in aqueous solutions

Resorcinarenes are macrocyclic compounds that form supramolecular complexes with a wide range of applications. In this paper, mutual diffusion coefficients and molar ionic conductivities are reported for aqueous solutions of the sodium salts of sulfonated resorcinarenes with two different alkyl groups: sodium C-tetraethyl-resorcin[4]arene sulfonate (Na4ETRA) and sodium C-tetrapropyl-resorcin[4]arene sulfonate (Na4PRRA). The diffusion coefficients and conductivities were measured at 25 °C for dilute solutions of the resorcinarenes (concentration < 0.010 mol·dm−3). The concentration dependence of the conductivities is accurately represented by equations for solutions of strong electrolytes, suggesting that association of the ETRA4− and PRRA4− ions with the Na+ counterions is negligible at the concentrations that were used. Furthermore, the limiting mobilities of the ETRA4− and PRRA4− ions derived independently from the diffusion and conductivity measurements are in good agreement. The change in the hydrodynamic radius of sulfonated resorcinarene caused by increasing the length of alky substituents is discussed.

Application of SAFT-VRE in the Flowsheet Simulation of an Advanced PUREX Process

SAFT-VRE is an extension of the statistical associating fluid theory for potentials of variable range (SAFT-VR) that can be used to describe the thermodynamic properties of strong-electrolyte solutions. Here the SAFT-VRE method is used in a flowsheet simulation code to calculate the densities of uranyl nitrate/nitric acid aqueous solutions and the activities of species that are needed for the calculation of the distribution coefficients of nitric acid and uranium in the nitric acid–30% tributyl phosphate (TBP) extraction system that is used in an advanced PUREX process for the reprocessing of spent nuclear fuels. Simulation results of both single-stage extraction experiments and of a multistage flowsheet test showed that the SAFT-VRE method can be used in flowsheet simulations with reasonable accuracy, thus demonstrating for the first time that thermodynamically-based mesoscale SAFT-VRE models can be linked to the macro-scale model of the PUREX solvent extraction process.

Modified nonelectrolyte Wilson-NRF: A new model for strong and weak electrolyte solutions

In this work, the nonelectrolyte Wilson-NRF model has been modified and a new model composed of a modified nonelectrolyte Wilson-NRF (m-Wilson-NRF) equation and the Pitzer-Debye-Hückel equation has been used to represent thermodynamics properties of strong and weak electrolyte solutions. In the first attempt, the present model is applied to correlate activity coefficients of various aqueous solutions of salt at 25 °C and 1 bar as strong electrolyte systems. Also, the osmotic coefficients of the binary and ternary electrolyte solutions are well predicted using the present model. In following, as weak electrolyte systems the solubility of acid gases such as CO2 and H2S in aqueous N-methyldiethanolamine (MDEA) solutions have been represented by the new model in a wide range of temperature, MDEA concentration and partial pressures of acid gases. Comparisons between the results of the new model with other electrolyte models confirm the good capability of the new equation for strong and weak electrolyte solutions.

Количественные характеристики взаимодействий в растворах электролитов

In aqueous and non-aqueous solutions of strong and weak electrolytes, complex interparticle and intermolecular interactions occur mainly between charged particles, solvent molecules, as well as between ions and solvent dipoles. Depending on the properties of the solvent, the same dissolved electrolyte may exhibit opposite properties. So, for example, acetic acid, weak in water, when interacting with a more protogenic solvent (liquid hydrogen fluoride) exhibits the properties of a base by accepting a proton. This behaviour is understood to be determined by the difference in proton affinity. However, insufficient information has been published on the quantitative characteristics of interactions in solutions of strong and weak electrolytes. The present article considers these processes taking place in dimethylformamide (DMF). The most requested electrolyte solution parameters are evaluated: the solvation number of some ions, as well as the masses and sizes of solvated ions. The calculated values are proved to be consistent with those in the literature data. The thermodynamic constants of diphenic acid dissociation in DMF were determined and calculated using the multilevel modelling method for the energy of hydrogen bonds in solvents, thus accounting for dipolar proton solvents (including DMF). Parameters calculated according to the multilevel modelling equations are shown to be consistent with the known literature. The method of multilevel modelling was used to calculate the energy and dimensional characteristics of ions and chemical compounds, as well as the characteristics of ionisation, heat capacity, critical properties and the isothermal differences of thermodynamic functions from the ideal state of solvents. Calculation methods were developed for predicting and refining the parameters of chemical, biological, medical and other systems, supplemented by constructed models concerning state of the ions in solution. The authors declare no conflict of interests regarding the publication of this article.

Derivation and Experimental Verification of Colligative Equations of Dilute Strong Electrolyte Solution

Derivation and Experimental Verification of Colligative Equations of Dilute Strong Electrolyte Solution

Solubility of hydrocarbon and non-hydrocarbon gases in aqueous electrolyte solutions: A reliable computational strategy

Determining solubility of hydrocarbon and non-hydrocarbon components of natural gas is crucial for theoretical studies and engineering design. In this study, new solubility prediction models were developed for both hydrocarbon gases (methane, ethane, propane, and butane) and non-hydrocarbon gases (CO2 and N2) in aqueous solutions of strong electrolytes using a hybrid modeling strategy, which links the Coupled Simulated Annealing (CSA) to the Least-Squares Support Vector Machine (LSSVM) technique. Comparing the models’ predictions with experimentally determined solubility values, a very good agreement was noticed, leading to the overall correlation coefficients of 0.9880 and 0.9907 for the hydrocarbon and non-hydrocarbon gases, respectively. These models were also found to succeed in capturing the physical trends among experimental datasets through performing sensitivity analysis between the dependent and independent parameters. Developed models can be utilized to predict the solubility of pure and/or a mixture of hydrocarbon and non-hydrocarbon gases in aqueous electrolyte solutions, covering wide ranges of ionic strength, pressures, and temperatures up to supercritical conditions. Such a reliable predictive tool helps researchers and engineers to successfully obtain the key thermodynamic properties (e.g., solubility, vapor pressure, and compressibility factor), which are central to properly design and operate the corresponding units in a variety of chemical plants such as petrochemical plants, natural gas processing plants, and refineries.

Diffusion and conductance properties of aqueous solutions of tetrasodium 5,11,17,23-tetrakissulfonatemethylen-2,8,14,20-tetra(2-(methylthio)ethyl)resorcinarene

Interdiffusion coefficients and molar conductivities of the macrocycle tetrasodium 5,11,17,23-tetrakissulfonatemethylen-2,8,14,20-tetra(2(methylthio)ethyl)resorcinarene (H8Na4RSTio) in non-buffered aqueous solutions at 25.00 °C and at concentrations from (0.001 to 0.020 mol·dm−3) have been measured.The concentration dependence of the conductivities is accurately represented by equations for solutions of strong electrolytes, suggesting that there are no association between anionic species from macrocyclic molecule and Na+ counterions at the concentrations that were used. Furthermore, the limiting conductivities of the H8RSTio4− ions derived independently from the diffusion and conductivity measurements, as well as the Nernst diffusion coefficients derived from diffusion (1.296 × 10−9) m2·s−1 and from conductance (1.298 × 10−9) m2·s−1, are in good agreement.Limiting diffusion coefficient of H8RSTio4− anion was used, together with the Stokes–Einstein equation, to determine the equivalent hydrodynamic radius.

Study of Mass Transfer during Reverse-Osmosis Demineralization of Dilute Solutions of Strong Electrolytes

The results of studies of mass transfer through a polyamide composite reverse-osmosis membrane in the demineralization of dilute solutions of six strong electrolytes are summarized. The relation of the electrolyte concentration at the surface of the reverse-osmosis membrane, at which its true selectivity tends to zero, to the specific water flux and the sum of the hydration numbers of the cations and anions of this electrolyte has been revealed. It has been shown that at a low salinity of the feed solution, the product of the molar electrolyte flux and the sum of the hydration numbers of its cations and anions for the test membrane is almost independent of the electrolyte type. An analysis of the dependence of the solute flux on the transmembrane pressure, concentration, and temperature in the electrolyte concentration range of 0.2 to 20 mol/m3 in the feed solution, as well as the experimentally determined activation energy of the NaCl flux, has led to the conclusion that there is an additive component of the electrolyte flux, whose contribution to the total flux is insignificant at high concentrations and becomes determining at concentrations below 2–5 mol/m3.

In situ synthesis of two-dimensional Co2+-doped β-Ni(OH)2 using nickel complex as template for application in supercapacitors

2D nanostructured Co2+-doped β-Ni(OH)2 as electrode material for application in redox-type supercapacitors was synthesized by a strategy of nickel complex template. The 2D Co2+-doped β-Ni(OH)2 was produced by the in situ reaction of 2D Co2+-doped template in strong alkaline electrolyte solution during electrochemical measurement. Due to the large interface and the promoted conductivity induced by Co2+ doping, the Co2+-doped β-Ni(OH)2 exhibited high electrochemical performance. It had high specific capacitance of about 2100 F g–1 at low current density of ~2 A g−1. It also exhibited excellent high rate performance (1259 F g–1 at high current density of 41.7 A g−1), much higher than the undoped sample. The results in this work indicated that the Co2+-doped β-Ni(OH)2 could be used as an effective electrode material in redox supercapacitors.

Quantification of non-ideal effects on diagenetic processes along extreme salinity gradients at the Mercator mud volcano in the Gulf of Cadiz

We present a transport-reaction model (TRACTION) specifically designed to account for non-ideal transport effects in the presence of thermodynamic (e.g. salinity or temperature) gradients. The model relies on the most fundamental concept of solute diffusion, which states that the chemical potential gradient (Maxwell’s model) rather than the concentration gradient (Fick’s law) is the driving force for diffusion. In turn, this requires accounting for species interactions by applying Pitzer’s method to derive species chemical potentials and Onsager coefficients instead of using the classical diffusion coefficients. Electrical imbalances arising from varying diffusive fluxes in multicomponent systems, like seawater, are avoided by applying an electrostatic gradient as an additional transport contribution.We apply the model to pore water data derived from the seawater mixing zone at the submarine Mercator mud volcano (MMV) in the Gulf of Cadiz. Two features are particularly striking at this site: (i) Ascending halite-saturated fluids create strong salinity (NaCl) gradients in the seawater mixing zone that result in marked chemical activity, and thus chemical potential gradients. The model predicts strong transport-driven deviations from the mixing profile derived from the commonly used Fick’s diffusion model, and is capable of matching well with the profile shapes observed in the pore water concentration data. Even better agreement to the observed data is achieved when ion pairs are transported separately. (ii) The formation of authigenic gypsum (several wt%) occurs in the surface sediments, which is typically restricted to evaporitic surface processes. Very little is known about the gypsum paragenesis in the subseafloor and we first present possible controls on gypsum solubility, such as pressure, temperature, and salinity (pTS), as well as the common ion and ion pairing effects. Due to leaching of deep diapiric salt, rising fluids of the MMV are saturated with respect to gypsum (as well as celestite and barite). Several processes that could drive these fluids towards gypsum supersaturation and hence precipitation were postulated and numerically quantified. In line with the varied morphology of the observed gypsum crystals, gypsum paragenesis at the MMV is likely a combination of two temperature-related processes. Gypsum solubility increases with increasing temperature, especially in strong electrolyte solutions and the first mechanism involves the cooling of saturated fluids along the geothermal gradient during their ascent. Secondly, local temperature changes, i.e. cooling during the transition from MMV activity towards dormancy results in the cyclic build-up of gypsum.The model showed that the interpretation of field data can be majorly misguided when ignoring non-ideal effects in extreme diagenetic settings. While at first glance the pore water profiles at the Mercator mud volcano would indicate strong reactive influences in the seawater mixing zone, our model shows that the observed species distributions are in fact primarily transport-controlled. The model results for SO4 are particularly intriguing, as SO4 is shown to diffuse into the sediment along its increasing (!) concentration gradient. Also, a pronounced gypsum saturation peak can be observed in the seawater mixing zone. This peak is not related to the dissolution of gypsum but is simply a result of the non-ideal transport forces acting on the activity profile of SO4 and Ca profiles.

Physicho and electrochemical characterization of PVC incorporated ZP composite membrane and their important parameters through applying TMS equation

The synthetic organic-inorganic composite membranes have enormous applications in the field of filtration and purification processes. The newly synthesized PVC (polyvinyl chloride) incorporated ZP (zinc phosphate) composite membrane is used as a barrier for the transportation of some strong electrolyte solutions like KCl, NaCl and LiCl. The composite material which used to make the membrane was qualitatively synthesized by sol-gel method of material synthesis. To characterize the structural and thermal properties of membrane there are different techniques like FTIR, XRD, TGA/DTA, SEM-EDX, LCR have been used. By characterizations it is clear that the material has crystalline nature, thermally stable and no breakages or cracks are found on membrane the surface. The electrochemical observation was done by potentiometer, which shows that the membrane is cation selective. To determine the charge density of membrane Teorell-Meyer-Sievers method is used. The observed potential and charge density of the incubated membrane follows KCl&lt;NaCl&lt;LiCl and KCl&gt;NaCl&gt;LiCl order respectively. The other important parameters like transport number, mobility ratio, charge effectiveness are also calculated by observed potential values.

Water molecules ordering in strong electrolytes solutions

Experimental observations of vibrational spectra of strong electrolyte solutions with increase in the molarity suggest a self-organization of water molecules depending on the concentration, and not on the ions’ nature. Three different regimes can be observed. At very low concentrations, ions shielding does not change the water molecules intramolecular bonds. Whenever the concentration increases, a distortion of the vibrational peak is observed that increases linearly on a log-log scale, and can lead up to a maximum deformation limit. This might contribute to shed a light on the nature of the two-fluid structure of liquid water reported in the literature.

Ultra-fast AC electro-osmotic micropump with arrays of asymmetric ring electrode pairs in 3D cylindrical microchannel

AC electro-osmotic (ACEO) micropumps presently involve the planar or nonplanar electrode pair array in the rectangular microchannel. However, this paper presented a theoretical model of an ultra-fast 3D ring ACEO micropump with arrays of asymmetric ring electrode pairs in the cylindrical microchannel. The theory is on the basis of the interaction between the nonuniform electric field and ions of an electric double layer (EDL) on the surface of ring electrodes. Therefore, we first established the equivalent hollow cylinder capacitance of EDL for ring ACEO micropumps. Then, the 3D Poisson-Boltzmann model by solving the electric field and fluidic flow field with the charge conservation and the slip velocity boundary conditions was numerically calculated. For a dilute strong electrolyte solution, the conductivity as a function of the electrolyte concentration can be obtained by the modified Kohlrausch's dilution empirical equation with the molar conductivity. The results revealed that the flow rate of ring ACEO was higher than the planar ACEO, which agreed well with the experiment. The dependences of the time-averaged pumping velocity on the frequency and concentration have similar bell profiles with a maximal value. Moreover, the optimal velocity with proper geometric parameters was obtained at a given frequency, voltage, concentration, and radius. The high-speed ring ACEO micropump will be significant for the experimental studies to further improve the flow rate and be hopeful for applications of microfluidic mixing, particle manipulation, and so on.

Peculiarities of transport-structural parameters of ion-exchange membranes in solutions containing anions of carboxylic acids

The experimental results of the study of the concentration dependence of the electrical conductivity and diffusion permeability of ion-exchange membranes which are in contact with solutions of weak electrolytes (carboxylic acids) are provided for the first time. An attempt was made to correlate the observed properties of the membrane to their structure, based on the microheterogeneous model. Some features have been revealed that differentiate the behavior of membranes in solutions of strong and weak electrolytes. For example, for anion-exchange membranes, the dependence of the electrical conductivity on the equilibrium solution concentration disappears in the concentration above 0.05 M, and there is an insignificant increase in the electrical conductivity in lower concentrations. An explanation for the observed effects is suggested which takes into account that the electrical conductivity of the gel phase is much higher than the electrical conductivity of an electrically neutral solution. An equation is proposed which connects the electrical conductivity of a membrane with its ion-exchange capacity and mobility of the counterion in the gel phase.Recommendations on the practical aspect of electrodialysis technology for the treatment of weak electrolytes are given. From a fundamental point of view, it is concluded that for a full description of the transport-structural organization of ion-exchange membranes which are in a solution of a weak electrolyte, the knowledge of the concentration dependence of the electrical conductivity and diffusion permeability only is not enough, and other experimental methods are required.