Electrical Conductivity Of Aqueous Solutions Research Articles

Electrical conductivity of stevia rebaudiana-surfactant mixture aqueous solution: Roles of temperature and sugar substitute concentration

The investigation of stevia-surfactant systems is of significant importance for the extraction process of steviol molecules as well as for the formulation of food products. The present study investigates the electrical conductivity of aqueous solutions containing a sugar substitute and surfactant over a temperature range of 25–50 °C. The sugar-substitute, Stevia Rebaudiana, concentration Cs (g/mL), is ranged from 0.047 to 0.6. The surfactant, Sodium bis(2-ethylhexyl) sulfosuccinate (AOT), has a concentration range of 1.4 ≤CAOT (g/L)≤ 6. The degree of ionization in ionic micelles, α, is determined by examining the conductivity of AOT in Stevia-free water, where complete micelle dissociation is observed. In the presence of Stevia Rebaudiana, a significant exponential decay in system conductivity with respect to the concentration of the sugar substitute is observed. Empirical equations were introduced to describe this behavior. The temperature dependence of conductivity is modeled using an Arrhenius equation. We postulate the formation of pseudo-micelles arising from interactions between the sugar substitute and surfactant, characterized by an effective degree of ionization in ionic micelles, αe.

SODIUM, MONOETHANOLAMMONIUM AND POLYETHYLENE POLYAMMONIUM CITRATES AQUEOUS SOLUTIONS ELECTROCHEMICAL PROPERTIES

pH and conductometric study of aqueous (0.1 ÷ 9.0)⋅10-3 mol/l solutions of sodium (Na3Cit), monoethanolammonium (H3Cit⋅3MEA) and polyethylenepolyammonium (kH3Cit⋅3PEPA) citrates was carried out. Features of the electrochemical behavior of monoethanolamine and polyethylenepolamine ammonium citrates aqueous solutions were revealed in comparison with Na3Cit. As the temperature increases from 293 to 303 K, the pH values and Na3Cit solutions molar electrical conductivity increase. Due to hydrolytic processes, when diluting H3Cit⋅3MEA solutions, a change in pH is observed from slightly acidic to slightly alkaline, in contrast to Na3Cit. An increase in temperature (in the region of 293–308 K) leads to an increase in the medium acidity, in contrast to sodium citrate solutions, which is accompanied by an atypical decrease in molar electrical conductivity at the same H3Cit⋅3MEA content. It has been shown that an increase in temperature in the range of 293-308 K leads to a decrease in H3Cit⋅3MEA aqueous solutions pH, in contrast to Na3Cit and kH3Cit⋅3PEPA solutions, which is accompanied by an atypical decrease in molar electrical conductivity at the same H3Cit⋅3MEA content. The component composition of Na3Cit, H3Cit⋅3MEA and kH3Cit⋅3PEPA aqueous solutions was calculated. The probability of the existence of negatively charged ion-molecular complexes in H3Cit⋅3MEA and kH3Cit⋅3PEPA aqueous solutions is shown. The concentration and temperature dependence of citrate ions hydrolysis constant was obtained. The concentration and temperature dependence of these complexes was assessed. The atypical negative effect of heating on H3Cit⋅3MEA aqueous solutions molar electrical conductivity is associated with a change in the radius of the ion-molecular complex and its stability. The value of the limiting molar electrical conductivity of sodium, monoethanolammonium and polyethylenepolyammonium citrates aqueous solutions in the range of 293–313 K was estimated. Correlations were revealed between the values of the limiting electrical conductivity and ion-molecular complexes formation constants in H3Cit⋅PEPA aqueous solutions. The values of energy, enthalpy and entropy of activation of molar electrical conductivities of aqueous solutions were calculated. For the solutions studied, compensation effects were noted in the activation parameters of molar electrical conductivity.

Method for measuring the mineralization of aqueous solutions in pipeline flows

A description of the hardware–software complex designed and manufactured for the operational assessment of the concentration of a dissolved substance in a water stream on the lower surface of metal pipes in various technological lines without sampling is presented. At the Trofimuk Institute of Petroleum Geology and Geophysics SB RAS the dependences of the electrical conductivity of aqueous solutions on temperature were studied under specific conditions – in an electrically conductive cell. Physical experiments were performed using solutions of different mineralization (from 0.5 to 300 g/L), in a measuring cell made of steel of small volume (8.14 cm3). Mathematical modeling of solution mineralization assessment has been performed.

Thermodynamic analysis of methyl orange anion association with α-cyclodextrin using a conductometric approach

The electrical conductivities of aqueous solutions of the azo dye methyl orange (sodium salt) were measured at 25.0 °C in the concentration range between 2.103 × 10–4 and 9.255 × 10–4 mol L−1. Molar conductivity values fit the Debye–Hückel–Wager equation for a symmetric electrolyte. The estimated value of the molar conductivity of the sodium salt of methyl orange at infinite dilution is found to be 77.93 ± 0.38 S cm2 mol−1. The calculated ionic conductivity at infinite dilution of the anion of methyl orange is 27.82 S cm2 mol−1. Using the same methodology, a thermodynamic analysis of the association between methyl orange anion and α-cyclodextrin was conducted at 20.0, 25.0, 32.0, and 40.0 °C. The measured molar conductivities decreased as the mole ratio of α-cyclodextrin to methyl orange went below 3. The conductivity measurements were analysed using a model 1:1 stoichiometry at the four different temperatures. The values of the thermodynamic quantities ∆H° and ∆S° for the inclusion process were calculated by using Van’t Hoff plot, their values are − 27.35 kJ mol−1 and − 9.70 J K−1 mol−1 respectively. For this case of the studied inclusion process this inclusion was disfavored through entropy change and favored through enthalpy change.

Studies of the Formation of Inclusion Complexes Derivatives of Cinnamon Acid with α-Cyclodextrin in a Wide Range of Temperatures Using Conductometric Methods.

The electrical conductivities of aqueous solutions of sodium salts of trans-4-hydroxycinnamic acid (trans-p-coumaric acid), trans-3,4-dihydroxycinnamic acid (trans-caffeic acid), trans-4-hydroxy-3-methoxycinnamic acid, (trans-ferulic acid) and trans-3-phenylacrylic acid (trans-cinnamic acid) with α-cyclodextrin were measured in the temperature range of 288.15 K–318.15 K. For the first time in the literature, using the limiting molar conductivity obtained from conductivity measurements, the values of the complexation constants (Kf) of the salts of phenolic acid derivatives with α-cyclodextrin were determined using a modified low concentration chemical model (IcCM). An attempt was also made to analyze the individual thermodynamic functions , and describing the complexation process as a function of temperature changes. The obtained results show that the process of formation of inclusion complexes is exothermic and is spontaneous.

Modeling of the density, viscosity and electrical conductivity of aqueous solutions saturated in boric acid in presence of lithium sulfate or sodium sulfate at 293.15 to 313.15 K

The modeling of the density, viscosity and electrical conductivity of aqueous solutions saturated with boric acid, in the presence of sodium sulfate or lithium sulfate, are presented. The salt concentrations range studied were from (0 to 3.3242) mol·kg−1 for sodium sulfate and from (0 to 2.9336) mol·kg−1 for lithium sulfate at temperatures from (293.15 to 313.15) K and at 1 atm pressure. A model for the density was derived using the Pitzer model. The Eyring's absolute rate theory and the Pitzer model were combined to represent the viscosity. The Casteel-Amis equation was modified to describe the electrical conductivity with temperature and boric acid effects where necessary. The results showed that the models successfully represented the properties studied and are robust for estimation purposes within and beyond the experimental range studied. Also, it was found that short range interactions of boric acid, sulfate, sodium and lithium ions with water molecules are relevant to determine the volumetric and transport properties of these solutions and that the electrical conductivity is determined by charged species (Na+, SO42−, NaSO4−, HSO4− and Li+, SO42−, LiSO4−) and the solution viscosity; that is mainly influenced by these salts concentrations, boric acid solubility behavior with these salts and temperature. This is valuable information to improve the processes of boric acid production.

Influence of a Constant Magnetic Field on Some Properties of Water Solutions

The effect of a static magnetic field with induction up to 7 T on the concentration of dissolved molecular oxygen, the concentration of hydrogen peroxide, the redox potential, and the electrical conductivity of aqueous solutions with a low concentration of active impurities is studied. It was shown that the concentration of dissolved molecular oxygen in water under the exposure of a magnetic field with induction up to 7 T does not change significantly, while the concentration of hydrogen peroxide increases linearly. It has been established that the pH value of water with field amplification in this induction range tends to decrease within 10%. With an increase in induction, an increase in the redox potential of water is observed. The change in its value is approximately 7 mV/T. It was shown that, with an increase in induction up to 2 T, the electrical resistivity of the water under study drops to about 0.6 MΩ cm, while at higher values of induction it practically does not change.

Localized Apparatuses in Teaching Electrical Conductivity of Aqueous Solutions

Localized Apparatuses in Teaching Electrical Conductivity of Aqueous Solutions

HYDROLYSIS AND ELECTRICAL CONDUCTIVITY OF METHYLAMONIUM SULFAMATE AQUEOUS SOLUTIONS

The pH-metric, conductometric and spectrophotometric study of the acid-base and electrochemical properties of methylammonium sulfamate aqueous solutions (1·10-4 – 1·10-2 М) in the temperature range 293 – 313 K has been done. The increase in pH and molar conductivity of the studied solutions during their storage over time is explained by the hydrolytic decomposition of sulfamate anions with the formation of sulfate anions and ammonium cations. In the concentration range (0,1 – 1,0)·10-3 М, the degree of hydrolysis of sulfamate anions depends slightly on the initial salt content and reaches 100%. A further increase in the salt content results a directly proportional decrease in the hydrolysis degree. Limit molar conductivity values by Shydlovsky extrapolation are calculated. The influence of the initial concentration of methylammonium sulfamate on the electrochemical properties of aqueous solutions was revealed. The experimental values of the limit molar electrical conductivity of aqueous solutions obtained with an extrapolation of Shidlovsky with an initial concentrations of methylammonium sulfate (1,0 – 10,0)·10-3 М increase with increasing temperature from 293 to 308 K. For solutions with a higher concentration, the values of the limit molar electrical conductivity is independent on temperature and l0 equals 206±19 Om -1 ·sm 2 ·mol -1 . The activation parameters of the conductivity of the investigated solutions at 293 – 313 K were obtained. A relative decrease in the mobility of hydrogen ions in the test solutions was observed, comparable to the valve of the mobility during the transfer along the H-bonds of water. The negative values of ΔS# indicate that the atoms in the activated complexes are located more «compactly» than in the original systems, that is, in the formation of the activated complexes the number of rotational and oscillatory degrees of freedom decreases. The compensatory effects in the activation parameters of the molar electrical conductivity of aqueous solutions of methylammonium sulfamate in the temperature range 293 – 313K are indicated.

Исследование влияния температуры на электропроводность растворов неорганических солей в этаноле

The electrical conductivity of the solutions depends on the nature of the solute and solvent. For a solvent, the main parameter is the dielectric constant. Since the dielectric constant of alcohols is much less than the dielectric constant of water, the electrical conductivity of alcoholic solutions of salts is less than the electrical conductivity of their aqueous solutions. Therefore, alcoholic solutions of inorganic salts are weak electrolytes. We previously studied the electrical conductivity of inorganic salts in a number of alcohols (ethanol, propanol-2 and butanol-1) at room temperature. It is of interest to study the effect of temperature on the electrical conductivity of salts in alcohols. Obviously, an increase of temperature salt solutions leads to an increase in their electrical conductivity. To study the temperature dependence of the electrical conductivity of aqueous solutions electrolytes, we proposed an approach based on the study of the effect of temperature on the equivalent electrical conductivity of solutions at infinite dilution λ∞. Using this approach, we studied the electrical conductivity of aqueous solutions of a number of inorganic salts, carboxylic acids, and amino acids as a function of temperature. It has been established that for these solutions the dependence λ∞(Т) is described by the exponential Arrhenius equation λ∞ = Аexp(-E/(RT)). However, such studies have not been conducted for alcoholic salt solutions. In this regard, this article explores the possibility of describing the experimental data λ∞(Т) for solutions of certain inorganic salts in ethanol by this equation. It is shown that the Arrhenius equation with the found activation energies adequately describes the temperature dependence of the ultimate equivalent conductivity for solutions of a number of inorganic salts (chloride and calcium nitrate, cadmium iodide, lithium and potassium chloride, chloride, iodide and ammonium nitrate, silver nitrate and sodium bromide) in ethyl alcohol.

Исследование влияния температуры на электропроводность спиртовых растворов алкоголятов натрия и калия

Earlier, we studied the electrical conductivity of inorganic salts in a number of alcohols (ethanol, propanol-2, and butanol-1) at room temperature and found that alcoholic solutions of inorganic salts are weak electrolytes. It is known that an increase in the temperature of salt solutions leads to an increase in electrical conductivity due to an increase in the mobility of their ions in the solvent medium. To study the temperature dependence of the electrical conductivity of aqueous solutions of electrolytes, we proposed an approach based on the study of the effect of temperature on the equivalent electrical conductivity of solutions at infinite dilution λ∞. Using this approach, we studied the electrical conductivity of aqueous solutions of a number inorganic salts (nitrates, acetates, and phosphates), carboxylic acids, and amino acids as a function of temperature. It was found that for these solutions the dependence λ∞(Т) is described by the exponential Arrhenius equation λ∞ = Аexp(-E/(RT)). This equation was used to describe the temperature dependence of the ultimate equivalent conductivity for solutions of a number of inorganic salts (calcium and nitrate calcium, cadmium, lithium and potassium iodides, chloride, iodide and ammonium nitrate, silver nitrate and sodium bromide) in ethanol. This article investigated and demonstrated the possibility of describing the experimental data λ∞(Т) for solutions of ethylates, propylates and isopropylates of sodium and potassium in the corresponding alcohols (ethylates in ethanol, propylates in propanol, isopropylates in isopropyl alcohol) using the same equation.

About changes in the physicochemical properties of aqueous solutions used as a liquid electrolyte cathode

The gas discharge between liquid electrolyte cathode and metal anode was experimentally investigated. Aqueous solutions of sodium chloride, potassium chloride, sodium sulfate, sodium hydroxide, and potassium hydroxide were used as the electrolyte cathode. Decrease aqueous solution was compensated by adding distilled water (solvent) in a continuous mode in the discharge burning process. It was found that, despite the significant dilution with a solvent, the specific electrical conductivity of aqueous solutions of alkali metal salts and alkalis varies slightly.

Electrical conductivity of aqueous solution of KOH at atmospheric pressure

Measurements of the electrical conductivity ratio of a 20% aqueous solution of KOH depending on temperature, intensity of electric field and frequency of changing direction of current are being studied. To ensure and conduct the measurements a conductivity meter was made with a current that changed the direction by means of a “meander” voltage. The measurement results of the study are processed in the form of analytical dependencies.

Conductometric studies of dissociation constants of selected monocarboxylic acids a wide range of temperatures

The electrical conductivities of aqueous solutions of formic acid, acetic acid, propionic acid, butyric acid, valeric acid and caproic acid were measured in the temperature range from T = (283.15 to 313.15) K and in the concentration range m = (0.03048·10−3–25.69·10−3) mol∙dm−3. The data were analyzed according to Barthel's low-concentration chemical model to obtain the values of dissociation constant (Kd) and association constant (KA). The changes in the determined thermodynamic functions ΔHd, ΔSd, and ΔGd were also compared with changes in aliphatic chain length and carboxylic acid structure.

Molar conductivity and association constants of sodium salts of selected cinnamic acids in water at temperatures from 288.15 to 318.15 K

The electrical conductivities of aqueous solutions of sodium salts of cinnamic acid, 4-hydroxycinnamic (p-coumaric) acid, 3,4-dihydroxycinnamic (caffeic) acid, 4-hydroxy-5-methoxycinnamic (ferulic) acid and 3,5-dimethoxy-4-hydroxycinnamic (sinapinic) acid were measured over the temperature range (T) of 288.15 to 318.15 K at 5 K intervals. The limiting molar conductivity Λmo and ionic association constants (KAo) were obtained using the low concentration Chemical Model (lcCM). The limiting ionic conductivity and the Eyring's activation enthalpy of charge transport of the investigated anions were determined.

Electrochemical microfiltration treatment of bisphenol A wastewater using coal-based carbon membrane

A novel electrochemical microfiltration process, in which the coal-based carbon membrane (CCM) serves as the membrane filter and anode simultaneously, was designed for the decontamination of bisphenol A (BPA) wastewater in this work. Effects of operational parameters, including residence time (RT), initial BPA concentration and electrical conductivity of aqueous solution, on the treatment performance were also investigated. Morphology and electrochemical properties of carbon membrane were analyzed by scanning electron microscope (SEM) and electrochemical workstation, respectively. As expected, the electrochemical microfiltration process demonstrated excellent BPA removal ability due to the synergistic effect between membrane filtration and electrochemical oxidation. Under the optimal conditions of applied voltage 2.0 V, initial BPA concentration 50 ppm, 0.1 mol/L Na2SO4 and residence time 0.88 min for the electrochemical microfiltration of CCM, the BPA and COD removal efficiency was up to nearly 97% and 90%, respectively, and the energy consumption was only 0.50 kWh kgCOD−1. During the treatment, the degradation of BPA was attributed to the combination of direct and indirect oxidation. And a possible degradation pathway of BPA was proposed based on the intermediates detected by high-performance liquid chromatography-mass spectrometry (HPLC-MS).

Conductance studies of aqueous solutions of sodium salts of selected benzoic acid derivatives at temperatures from (288.15 to 318.15) K

The electrical conductivities of aqueous solutions of sodium salts of benzoic acid, 2-hydroxybenzoic (o-salicylic) acid, 3-hydroxybenzoic (m-salicylic) acid, 4-hydroxybenzoic (p-salicylic) acid, 3,4-dihydroxybenzoic (protocatechuic) acid, 4-hydroxy-3-methoxybenzoic (vanillic) acid and 4-hydroxy-3,5-dimethoxybenzoic (syringic) acid were measured over a temperature range (T) of 288.15 to 318.15 K and a concentration range (c) of ~1 · 10−4 to ~1,5 · 10−2 mol·dm−3. The results were analyzed with Barthel's low concentration Chemical Model (lcCM) to obtain the ionic association constants (KAo) and the limiting molar conductivity (Λmo) of the electrolytes. The limiting ionic conductivity and hydrodynamic radius of the investigated anions were determined, as well as the value for Eyring's activation enthalpy of charge transport. The study also analyzes and discusses the influence of hydrolysis of the salts on their limiting molar conductivity.

Characterising a PCB electrical conductivity sensor using electromagnetic simulation and a genetic algorithm

Measuring electrical conductivity makes it possible to determine the concentration of dissolved ionic compounds in the water. Presented is a sensor developed for easily measuring the electrical conductivity of aqueous solutions. This sensor is comprised of two planar electrodes integrated onto a printed circuit board (PCB). PCB technology enables this sensor to be manufactured at high volumes for a modest cost. However, when the sensor is integrated into a PCB, it becomes difficult to analytically determine the influence the dimensions of the sensor's electrodes have on its measurements. In this research, a genetic algorithm was used to derive an equation predicting the behaviour of a PCB sensor with any reasonable electrode dimensions. Afterwards, the accuracy of this equation was evaluated by comparing its predictions to the measurements taken using actual sensors.

Ion-Pair Formation Constants of Lithium Borate and Lithium Hydroxide under Pressurized Water Nuclear Reactor Coolant Conditions

A custom-made high-precision flow AC conductance instrument was used to measure the frequency-dependent molar electrical conductivities of aqueous solutions of lithium borate from T = 298 K to T = 548 K at a constant pressure, p = 20 MPa. Ion-pair formation constants of lithium borate, KA,m[LiB(OH)40], were derived from these measurements using the Turq–Blum–Bernard–Kunz (TBBK) conductivity model. Our results are consistent with previous low-temperature studies and are the first to be reported at temperatures above 318 K. Under ambient conditions, the degree of association of LiB(OH)40 is half an order of magnitude higher than that of NaB(OH)40 and KB(OH)40, but at T ≥ 448 K, the association constants of all three ion-pairs are equal within the combined experimental uncertainties. The results have been used to derive new equations to represent the temperature dependence of the limiting conductivity of lithium, and the ion-pair formation constant of lithium borate under PWR operating conditions. A new mode...

Correction to "Electrical Conductances of Aqueous Na2SO4, H2SO4, and Their Mixtures: Limiting Equivalent Ion Conductances, Dissociation Constants, and Speciation to 673 K and 28 MPa".

The electrical conductivities of aqueous solutions of Na(2)SO(4), H(2)SO(4), and their mixtures have been measured at 373-673 K at 12-28 MPa in dilute solutions for molalities up to 10(-2) mol kg(-1). These conductivities have been fit to the conductance equation of Turq et al.(1) with a consensus mixing rule and mean spherical approximation activity coefficients. Provided the concentration is not too high, all of the data can be fitted by a solution model that includes ion association to form NaSO(4)(-), Na(2)SO(4)(0), HSO(4)(-), H(2)SO(4)(0), and NaHSO(4)(0). The adjustable parameters of this model are the dissociation constants of the SO(4)(-) species and the H(+), SO(4)(-2), and HSO(4)(-) conductances (ion mobilities) at infinite dilution. For the 673 K and 230 kg m(-3) state point with the lowest dielectric constant, epsilon = 3.5, where the Coulomb interactions are the strongest, this model does not fit the experimental data above a solution molality of 0.016. Including the species H(9)(SO(4))(5)(-) gave satisfactory fits to the conductance data at the higher concentrations.