Solutions Of Strong Electrolytes Research Articles

Protic ionic Liquids-Water Interactions: A study on 2-Hydroxypropylammonium formate through experimental analysis and computer simulations

In this study, interactions within a mixture of the protic ionic liquid 2-hydroxypropylammonium formate and water were investigated across the entire range of ionic liquid compositions and a wide temperature range from 283.15 K to 333.15 K. This investigation was based on the measurement results of density, viscosity, and electrical conductivity, and was supported by computational simulations. The synthesized ionic liquid was further characterized thermally using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) techniques. The study focuses on the analysis of excess molar quantities of volume, thermal expansion coefficients, viscosity, and Gibbs energy of viscous flow, aiming to examine the influence of temperature and mixture composition on thermophysical properties. The impact of temperature on the system’s viscosity and Angell’s strength parameter was investigated to assess the influence of the ionic liquid’s content on the system’s structural organization. The dependency of molar conductivity on viscosity was analyzed through the Walden rule. Based on this analysis, the effect of temperature and mixture composition on deviations from the ideal behavior in diluted solutions of strong electrolytes was estimated. Computational molecular dynamics simulations were employed for a more detailed study of the structural organization of the system’s components.

Electrical conductivity of heterogeneous ion exchange membranes in solutions of mono-, di- and tricarboxylic acids and its effect on the process of electrodialysis of solutions containing organic acids

In this study, the electrical conductivity of cation-exchange and anion-exchange membranes was studied in solutions containing both strong (sodium chloride and acetate) and weak (acetic, succinic and citric acids) electrolytes. The results obtained indicate that the concentration dependence of the electrical conductivity of membranes in weak electrolytes differs significantly from that observed for solutions of strong electrolytes. In the case of an acetic acid solution, the electrical conductivity of the membranes is higher than that of the equilibrium solution over the entire range of concentrations that were studied. It has been shown that existing models of the transport and structural organization of membranes allows describing the structural parameters of ion-exchange membranes in contact with strong electrolytes. In sodium chloride and sodium acetate solutions, the obtained dependences were processed within the framework of microheterogeneous and three-wire models to establish the influence of the nature of the electrolyte on the transport and structural characteristics of the membranes. The dependence of electrical conductivity on the concentration of a weak electrolyte solution does not allow the use of either microheterogeneous or extended three-wire models for the description of the structure-property relationship of ion-exchange materials. It has been shown that in acetic acid and partially succinic acid solutions, the solution provides the main contribution to the resistance of the electromembrane system. Based on the results obtained from measuring electrical conductivity, changes in the design of a laboratory electrodialyzer were proposed and experiments were carried out on desalting a solution of acetic acid. It has been shown that the use of thinner intermembrane separators in the desalting chamber leads to an increase in the integral current efficiency (from 0.32 to 0.44 at 0.6 A/dm2 and the same degree of desalination) and a reduction in specific energy consumption (from 3.0 to 1.9 kWh/mol at 0.6 A/dm2) during desalination of acetic acid. The results obtained can be further used to improve the parameters of the process of obtaining weak acids by bipolar electrodialysis.

Modeling of dilution enthalpies within implicit-solvent models for electrolytes

This work deals with the calculation of dilution enthalpies for strong aqueous electrolyte solutions when their thermodynamic properties are described within implicit-solvent models. The solution is modeled as a collection of charged hard spheres in a continuum solvent. A new general expression is obtained that accounts for the variation of the solution permittivity, of the size of the ions, and of the specific volume of the solution, with temperature and concentration. This expression is used to compute the enthalpies of LiCl aqueous solutions at temperatures in the range of 25∘C to 100∘C for concentrations up to 6 mol kg−1. The mean spherical approximation (MSA) model with implicit continuum solvent is employed to describe the thermodynamic properties of these solutions.

Raman spectra characterization of size-dependent aggregation and dispersion of polystyrene particles in aquatic environments

Aqueous environments are generally thought to be a source of pooling and re-distribution for both micro-plastics (MPs) and nano-plastics (NPs); however, significantly less data on NPs than MPs have been reported. The occurrence of salts, proteins, and other organic matter may promote or inhibit the aggregation of NPs to form agglomeration particles, making their detection more difficult. In this study, 80 and 500 nm polystyrene nano-plastics (PS-NPs) modified by four different functional groups (PS-Bare, PS-COOH, PS-NH2, and PS–CHO–500 nm) were selected to mimic the flocculation and/or sedimentation of NPs in salts (NaCl, CaCl2, and Na2SO4) and protein solutions. The results showed that the 80 nm PS-NPs are only colloidal in pure water. All four strong electrolyte solutions that were tested significantly promoted the aggregation of PS-NPs, including those that were protein-coated. In addition, 500 nm PS-CHO did not flocculate but gradually settled into sedimentation. Therefore, Raman spectrometry can be used to analyze assembled PS-NPs, but is not suitable for analyzing normal PS-NPs. By combining fractal morphology, this study provides insight into the comprehensive analysis of PS-NPs in water solutions, including the digestion of biological samples.

Electrodialysis Desalination with Simultaneous pH Adjustment Using Bilayer and Bipolar Membranes, Modeling and Experiment.

A kinetic model of the bipolar electrodialysis process with a two-chamber unit cell formed by a bilayer (bipolar or asymmetric bipolar) and cation-exchange membrane is proposed. The model allows describing various processes: pH adjustment of strong electrolyte solutions, the conversion of a salt of a weak acid, pH adjustment of a mixture of strong and weak electrolytes. The model considers the non-ideal selectivity of the bilayer membrane, as well as the competitive transfer of cations (hydrogen and sodium ions) through the cation-exchange membrane. Analytical expressions are obtained that describe the kinetic dependences of pH and concentration of ionic components in the desalination (acidification) compartment for various cases. Comparison of experimental data with calculations results show a good qualitative and, in some cases, quantitative agreement between experimental and calculated data. The model can be used to predict the performance of small bipolar membrane electrodialysis modules designed for pH adjustment processes.

A model for the electric field-driven flow and deformation of a drop or vesicle in strong electrolyte solutions

A model is constructed to describe the flow field and arbitrary deformation of a drop or vesicle that contains and is embedded in an electrolyte solution, where the flow and deformation are caused by an applied electric field. The applied field produces an electrokinetic flow, which is set up on the charge-up time scale $\tau _{*c}=\lambda _{*} a_{*}/D_{*}$ , where $\lambda _{*}$ is the Debye screening length, $a_{*}$ is the inclusion length scale and $D_{*}$ is an ion diffusion constant. The model is based on the Poisson–Nernst–Planck and Stokes equations. These are reduced or simplified by forming the limit of strong electrolytes, for which dissolved salts are completely ionised in solution, together with the limit of thin Debye layers. Debye layers of opposite polarity form on either side of the drop interface or vesicle membrane, together forming an electrical double layer. Two formulations of the model are given. One utilises an integral equation for the velocity field on the interface or membrane surface together with a pair of integral equations for the electrostatic potential on the outer faces of the double layer. The other utilises a form of the stress-balance boundary condition that incorporates the double layer structure into relations between the dependent variables on the layers’ outer faces. This constitutes an interfacial boundary condition that drives an otherwise unforced Stokes flow outside the double layer. For both formulations relations derived from the transport of ions in each Debye layer give additional boundary conditions for the potential and ion concentrations outside the double layer.

One A3B Porphyrin Structure-Three Successful Applications.

Porphyrins are versatile structures capable of acting in multiple ways. A mixed substituted A3B porphyrin, 5-(3-hydroxy-phenyl)-10,15,20-tris-(3-methoxy-phenyl)-porphyrin and its Pt(II) complex, were synthesised and fully characterised by 1H- and 13C-NMR, TLC, UV-Vis, FT-IR, fluorescence, AFM, TEM and SEM with EDX microscopy, both in organic solvents and in acidic mediums. The pure compounds were used, firstly, as sensitive materials for sensitive and selective optical and fluorescence detection of hydroquinone with the best results in the range 0.039–6.71 µM and a detection limit of 0.013 µM and, secondly, as corrosion inhibitors for carbon–steel (OL) in an acid medium giving a best performance of 88% in the case of coverings with Pt-porphyrin. Finally, the electrocatalytic activity for the hydrogen and oxygen evolution reactions (HER and OER) of the free-base and Pt-metalated A3B porphyrins was evaluated in strong alkaline and acidic electrolyte solutions. The best results were obtained for the electrode modified with the metalated porphyrin, drop-casted on a graphite substrate from an N,N-dimethylformamide solution. In the strong acidic medium, the electrode displayed an HER overpotential of 108 mV, at i = −10 mA/cm2 and a Tafel slope value of 205 mV/dec.

Review on Green Synthesis of Nanoparticles using Various Strong Electrolytic Metal Solutions Mediated by Various Plant Parts

The present review targets the comparative biogenic synthesis and mechanisms of nanoparticles using various plant-parts extracts and various solutions of strong electrolytic metal salts. The metal salts are AgNO3, Zn(OAc)2, Zn(NO3)2, ZnSO4, CuSO4.5H2O, Cu(NO3)2, Cu(OAc)2, CuCl2, HAuCl4.3H2O, Mg(NO3)2, Mg(OAc)2, TiO(OH)2, Fe(NO3)2.6H2O, FeCl3.6H2O, FeCl2.4H2O, Al(NO3)2, BaCl2·2H2O, Bi(NO3)2, PdCl2, H2PtCl6.6H2O, NaHSeO3, Na2SeO3, Ca(NO3)2.4H2O, ZrOCl2.4H2O, Zr(OAc)4, NiCl2, NiSO4.6H2O, Ni(NO3)2, VCl2, Co(NO3)2 6H2O, CoCl2, Hg(OAc)2, Mn(OAc)2, (NH4)6Mo7O24, Sr(NO3)2, SnCl2.2H2O, Na2S2O3.5H2O, K2Cr2O7, Cr(NO)3.9H2O and Pb(NO3)2. These salts are soluble to produce to highly active positive metal ions in deionised water. These ions are effectively nucleated in the plant constituents. The plant acts akin to a huge ‘‘bio-laboratory” comprising of leaves, seeds, steam, root, sprout, fruits, latex, parks, fruits peel, fruits, juices. etc… which are composed of biomolecules and phytoconstituents. These naturally happening biomolecules and phytoconstituents have been recognized to play an energetic role in the formation of nanoparticles with discrete shapes and sizes thus acting as a pouring force for the manipulative of greener, safe and environmentally benign protocols for the synthesis of nanoparticles.

Robust Protection of III-V Nanowires in Water Splitting by a Thin Compact TiO2 Layer.

Narrow-band-gap III–V semiconductor nanowires (NWs) with a suitable band structure and strong light-trapping ability are ideal for high-efficiency low-cost solar water-splitting systems. However, due to their nanoscale dimension, they suffer more severe corrosion by the electrolyte solution than the thin-film counterparts. Thus, short-term durability is the major obstacle for using these NWs for practical water-splitting applications. Here, we demonstrated for the first time that a thin layer (∼7 nm thick) of compact TiO2 deposited by atomic layer deposition can provide robust protection to III–V NWs. The protected GaAs NWs maintain 91.4% of its photoluminescence intensity after 14 months of storage in ambient atmosphere, which suggests the TiO2 layer is pinhole-free. Working as a photocathode for water splitting, they exhibited a 45% larger photocurrent density compared with unprotected counterparts and a high Faraday efficiency of 91% and can also maintain a record-long highly stable performance among narrow-band-gap III–V NW photoelectrodes; after 67 h photoelectrochemical stability test reaction in a strong acid electrolyte solution (pH = 1), they show no apparent indication of corrosion, which is in stark contrast to the unprotected NWs that fully failed after 35 h. These findings provide an effective way to enhance both stability and performance of III–V NW-based photoelectrodes, which are highly important for practical applications in solar-energy-based water-splitting systems.

ВІРТУАЛЬНИЙ ЛАБОРАТОРНИЙ ПРАКТИКУМ ЯК ЗАСІБ ВИВЧЕННЯ ПРИРОДНИЧИХ ДИСЦИПЛІН

In the article the way of using information technology in the natural education is activated, such as computer modeling of chemical, physical or biological phenomenon processes, introduction into the educational process of the virtual laboratory works. The relevance of the introduction of virtual laboratories in educational practice is due, firstly, to the information challenges of the time, and secondly, the regulatory requirements for the organization of the educational process of general secondary and higher education. It is mentioned that the use of virtual laboratories in the educational process allows students to conduct experiments with equipment and materials that he is able to use due to lack of a real laboratory or its lack of technical content, get practical skills of conducting experiments of integrated natural direction initiating computer models and the process of operation of unique equipment of chemical, physical, biological laboratory, to study dangerous in the real situation processes and phenomena of natural origin, without fear of possible consequences. The article reveals the advantages and disadvantages of using a virtual laboratory workshop during the study of natural sciences. Possibilities of modern virtual laboratories of a natural direction which allow to model objects and processes of the surrounding world and also to organize computer access to the real laboratory equipment. The possibility of realization of a virtual laboratory workshop on chemical disciplines of the natural cycle in the environment of a virtual simulator of the laboratory IrYdiumChemistryLab is shown. This virtual laboratory involves the formulation of specific tasks or the formation of its own strategy for planning the experiment,the resource immediately differs in the ability to intervene in the program and design your own virtual experiment Created on the basis of IrYdiumChemistryLab virtual laboratory works allow to prepare diluent of various concentrations, to calculate and measure concentrations of ions in solutions of strong and weak electrolytes, to titrate, etc. Virtual laboratories must be present in the practice of teaching natural sciences (chemistry, physics, biology). The need to use a virtual laboratory workshop during distance learning is especially relevant.

Morphological effects on the electrochemical dissolution behavior of forged and additive manufactured Ti-6Al-4V alloys in runway deicing fluid

The particular microstructure of Ti-6Al-4V fabricated by additive manufacturing (AM) makes it exhibit a different corrosion resistance compared with that of the conventional forged Ti-6Al-4V. Here we utilize the electrochemical impedance (EIS) and potentiodynamic polarization (Tafel) to evaluate the electrochemical dissolution behavior in runway deicing fluids (RDF) of three kinds of Ti-6Al-4V alloy, which are respectively fabricated by forging, electron beam melting (EBM), and selective laser melting (SLM). The microstructure and electrochemical results suggest that EBM samples have a better corrosion resistance than others', which is attributed to an appropriate proportion of α-lath width and the volume fraction of β phase. A higher relative proportion of TiO2 is formed on surface, resulting in the fine-lamellar structure with a higher density of grain boundaries. Besides, the corrosion resistance anisotropy of AMed Ti-6Al-4V samples is ascribed to the existence of β columnar gains. In addition, the acicular martensite α′ phase with metastable structure leads to the worst corrosion resistance of SLMed Ti-6Al-4V samples. This work enriches the corrosion resistance of Ti-6Al-4V alloy in strong electrolyte solutions, which helps to promote the service performance of aviation titanium alloys in harsh environments.

On the Development of a Modified Nonelectrolyte NRTL-NRF Model for Strong and Weak Electrolyte Solutions

The non-electrolyte NRTL-NRF model has been modified to study electrolyte solutions. The modified model for electrolytes is composed of short-range parts expressed by the modified nonelectrolyte NRTL-NRF and the Pitzer-Debye-Huckel equation to represent the long-range interactions of ions in the solution. In this work, a salt-specific parameter is used. Various types of experimental data including binary and ternary activity and osmotic coefficients, solid and gas solubilities in aqueous NaCl, and also aqueous Methyldiethanolamine (MDEA) data at wide temperature and pressure ranges have been implemented to check the performance of the present model. The overall relative standard deviation of 0.046 has been achieved for 130 strong aqueous binary electrolytes by the new model in fitting the experimental data of activity coefficients. The percent of absolute average deviations of the modified model for CO2+ MDEA+ H2O andH2S+ MDEA+ H2O is 30.3% and 24.8%, respectively. The results show the good capabilities of the model for electrolyte solutions.

Electrochemical Properties and Selectivity of Bilayer Ion-Exchange Membranes in Ternary Solutions of Strong Electrolytes

Electrochemical Properties and Selectivity of Bilayer Ion-Exchange Membranes in Ternary Solutions of Strong Electrolytes

Method for Calculating the Density of Mixed Solutions of Strong Electrolytes

A method is proposed for calculating the density of solutions of strong electrolytes using the product of the apparent molar volume of the electrolyte by its molality. This method can be used to calculate the density of mixed electrolyte solutions, for example, when determining the activity by the Gibbs–Duhem equation. According to the literature data on the densities of solutions at 20°C, the apparent molar volumes of NaCl, NaNO3, KCl, KNO3, and SrCl2 are calculated and the high accuracy of calculations is demonstrated.

Applied aspects of acid-base interactions and modelling equilibrium concentrations in two-component acid mixtures

Fundamental and applied research into aqueous and non-aqueous solutions of strong and weak electrolytes remains to be highly relevant, which fact is confirmed by a large number of Russian and foreign publications. In almost all such publications, acid-base interactions are considered exclusively with regard to changes in hydrogen ion concentrations. However, the ionic strength of solutions is determined by all ions present in the system, the concentration of which varies during interactions. This is particularly true for potentiometric titration of strong and weak electrolytes not only in aqueous, but also in more complex non-aqueous solutions, which differ significantly in their basic properties (dielectric constant, ionic product, dipole moment, viscosity, etc.). In the study of equilibria, it is more feasible to develop model representations that would greatly simplify and facilitate the computation and evaluation of certain properties of the system under consideration. In this work, acid-base interactions are presented in the form of equations based on mass action laws and those describing equilibrium processes, solvent ionic product, electroneutrality and material balance in electrolyte systems. The proposed equations consider the effect of the concentrations of all charged particles in the system (not only of hydrogen ions – pH) on the ionic strength of the solution, activity coefficients and, as a consequence, the thermodynamic dissociation constant. In addition, these equations allow the dependence between the equilibrium concentrations of all charged particles and the solution acidity determined by the potentiometric method to be expressed in convenient and objective logarithmic coordinates, thus facilitating estimation of the concentration of all particles at any moment of titration.

Ideal thermodynamic behaviors of aqueous electrolyte solutions at very high concentrations

All physical chemistry textbooks state that solutions of strong electrolytes behave in a non-ideal fashion, except at very high dilution. Examples are provided here for ideal behaviors to very high concentrations, as demonstrated by excellent adherence to Raoult’s law: for NaNO2 solutions up to 12 molal (827.9 g per kilogram of water) and for CsNO2 solutions up to 35 molal (6821.9 g/kg). Improved adherence is reported for previously published almost-ideal RbNO2 solutions up to 62 molal (8151.1 g/kg).

A new method of potenciation of aqueous media using high-frequency glow discharge plasma

A method of activation of aqueous solutions of strong electrolytes using high-frequency glow discharge plasma in water vapor at atmospheric pressure is considered. An experimental setup for activation of aqueous solutions of NaCl and KCl salts, sodium sulfate Na2SO4, potassium sulfate K2SO4, etc. is presented. Experimental studies were conducted using an activated solution based on potassium sulfate K2SO4, at a concentration of 5.7×10−2 M. The limit values of acidity, redox potential (Eh) and hydrogen peroxide concentration of the prepared activated solution were: pH ≍ 8.3, Eh ≍ 800, H2O2 concentration ≍ 5×10−4 mol. %. The effectiveness of the K2SO4 - based activated aqueous solution was evaluated at test sites of typical crops, such as soybeans and corn. Based on the results obtained, it is concluded that the method of activation of aqueous solutions using high-frequency glow discharge plasma is quite simple, technological and low-cost.

Extension of Cubic-Plus-Polar (CPP) equation of state (EoS) for application in aqueous electrolyte solutions

In this study, an extension of Cubic-Plus-Polar (CPP) equation of state (EoS), i.e. electrolyte CPP (eCPP), was proposed to study various aqueous binary electrolyte solutions as well as water-CO2-NaCl, water-CO2-Na2SO4, and water-H2S-NaCl ternary systems. To avoid complexity, polar (dipole-dipole, quadrupole-quadrupole, and dipole-quadrupole) interactions were only considered for water, CO2, and H2S components, not for the studied ionic species in electrolyte solutions. In this work, the long-range electrostatic contribution was taken into account by Pitzer-Debye-Huckel equation. The proposed model has three adjustable parameters for each electrolyte, which were determined by fitting to experimental mean activity coefficient and liquid molar volume data of 79 aqueous strong electrolyte solutions at 0.1 MPa and 298.15 K. The overall average absolute relative deviation (AARD) between model-calculated values and experimental data were 1.05% and 1.44% for liquid molar volume and mean activity coefficient, respectively, while this value was 1.27% for predicted results of osmotic coefficient. Moreover, eCPP EoS predicted the liquid molar volumes of 15 different electrolyte solutions with an overall AARD of 0.6% in a wide range of pressure, temperature, and electrolyte concentration. The reliability of the proposed EoS (eCPP) was verified by the obtained AARDs.

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).