Values Of Activity Coefficients Research Articles

The SIT model parameters for interactions of carbonate compounds with sodium and potassium ions accounting for association

The current study is devoted to the determination of the SIT coefficients at 298.15 K for interactions, involving CO2(aq), HCO3−, and CO32‐, with mostly Na+ and K+ ions. The SIT model is a simple yet physically sound model for activity coefficients in aqueous solutions, that has just one parameter for each cation-anion or a dissolved gas – electrolyte interaction. Among the issues that were met for carbonate systems are the side reactions of hydrolysis and disproportionation in the carbonate solutions, that complicate the analysis of data and lead to unusually large difference, up to 9%, in the values of activity coefficients, determined in different authoritative laboratories. For Na2CO3 and K2CO3 solutions, it was necessary to take into account the reaction of formation of the ionic pair M++CO32‐=MCO3−, with the equilibrium constants β1o equal to log10β1o= 0.75 ± 0.08 for M+=Na+ and to log10β1o= 0.67 ± 0.11 for M+=K+. In all, there are values for more than 20 binary SIT interaction coefficients. All results are valid at 298.15 K, 0.1 MPa.

Synthesis, antioxidant, DNA interaction, electrochemical, and spectroscopic properties of chromene-based Schiff bases: Experimental and theoretical approach

Two chromene-based Schiff base ligands were synthesized by the condensation of 5-hydroxy-2,2-dimethyl-2H-chromene-6-carbaldehyde with 2-aminodiphenylamine and 1,8-diaminonaphthalene: (E)-2,2-dimethyl-6-(((2-(phenylamino)phenyl)imino)methyl)-2H-chromen-5-ol (2) and (E)-6-(((8-aminonaphthalen-1-yl)imino)methyl)-2,2-dimethyl-2H-chromen-5-ol (3). The compounds were characterized by Fourier transform infrared (FT-IR), absorption (UV-Vis) and nuclear magnetic resonance (NMR) spectroscopies, in addition to mass spectrometry (MS) analyses; the results of which were rationalized using density functional theoretical (DFT) calculations. Antioxidant activity of the Schiff bases was determined using the DPPH free radical scavenging and CUPric Ion Reducing Antioxidant Capacity (CUPRAC) assays. Compound 3 (IC50 = 14 μM) showed greater free radical scavenging ability than compound 2 (35 μM), and was also more effective than ascorbic acid and Trolox. DFT studies indicate that the HAT mechanism is favored over SET for DPPH scavenging. Both compounds exhibited stronger Cu(II) ion reducing capacity than Trolox and ascorbic acid with Trolox equivalent activity coefficient (TEAC) values of 2.0 and 1.6 for compounds 2 and 3, respectively. Furthermore, DNA cleavage and binding properties were determined using gel electrophoresis, UV-Vis spectroscopy, and cyclic voltammetry. The compounds showed copper-mediated cleavage of plasmid DNA and strong binding to DNA, with binding constants on the order of 104 M−1. The strength of DNA binding was verified by molecular docking analysis using two DNA models: a B-DNA dodecamer (-8.4 to -9.3 kcal/mol) and a hexamer (-7.8 to -7.9 kcal/mol). Overall, the chromene Schiff bases show promise as antioxidant and DNA binding agents.

Advanced thermodynamic approach to adsorption of charged adsorbates from aqueous electrolyte solutions

This study present estimation of the thermodynamic parameters and the influence of ionic activity coefficient on the thermodynamic equilibrium constant of adsorption of phosphates on fly ash. The adsorption was conducted over a wide range of initial phosphate concentrations at different pH values pH = (3; 7; 10). The adsorption results were treated using the Langmuir, Freundlich and Sips adsorption isotherms, which provide information about the maximum adsorption capacity. The Langmuir and Sips isotherms were a satisfactory fit to the adsorption data, especially at pH = 3, with an acceptable regression coefficient over the entire concentration range, Langmuir (r2 = 0.9737) and Sips (r2 = 0.9969). The estimated maximum phosphate sorption capacity of fly ash was 6.21 ± 0.68 (mmol·g−1) according to Langmuir and 4.19 ± 0.16 (mmol·g−1) according to the Sips model, at pH = 3.0. However, there is no data in the published literature for estimating the thermodynamic parameters of the phosphate adsorption process using thermodynamic models for activity coefficients. Novel approach of this paper was determination of the thermodynamic equilibrium constant and Gibbs free energy, using the Pitzer ion-interaction model to predict the nature of adsorption. The Pitzer-ion interaction model was used for the mixed ionic systems, taking into consideration the effect of other present ions besides phosphates in the equilibrium solution resulting from fly ash desorption. The procedure for comprehensive estimation of the ion activity coefficient at maximum adsorption capacity and the dimensionless thermodynamic equilibrium constant using Langmuir's and Sips’s constants was presented. The calculated value of the phosphate activity coefficient in the equilibrium solution was γH2PO4,e = 0.7003 ± 0.0027 and the converted molar activity coefficient was γH2PO4,e = 0.6903 ± 0.0027. The estimated values of Gibbs free energy were: ΔGL = −6.788 ± 0.521 kJ·mol−1 based on Langmuir equilibrium constant and ΔGa = −7.707 ± 0.527 kJ·mol−1 based on activity and thermodynamic equilibrium constant. According to Sips model, the adsorption process is even more spontaneous, with the Gibbs free energy calculated using the phosphate activity coefficient and the thermodynamic equilibrium constant, ΔGa = −9.707 ± 0.617 kJ·mol−1. Consideration of the ionic activity coefficient is particularly important for large, charged adsorbates at higher concentrations, as the absolute difference in free energy for adsorption is app. 12 %. The scientific contribution is reflected in obtaining the necessary and more accurate information for the improvement of adsorption processes and possibly for the upgrading of fly ash in overall wastewater treatment technology.

Behavioural and physiological impacts of low salinity on the sea urchin Echinus esculentus.

Reduced seawater salinity as a result of freshwater input can exert a major influence on the ecophysiology of benthic marine invertebrates, such as echinoderms. While numerous experimental studies have explored the physiological and behavioural effects of short-term, acute exposure to low salinity in echinoids, surprisingly few have investigated the consequences of chronic exposure, or compared the two. In this study, the European sea urchin, Echinus esculentus, was exposed to low salinity over the short term (11‰, 16‰, 21‰, 26‰ and 31‰ for 24 h) and longer term (21, 26 and 31‰ for 25 days). Over the short term, oxygen consumption, activity coefficient and coelomic fluid osmolality were directly correlated with reduced salinity, with 100% survival at ≥21‰ and 0% at ≤16‰. Over the longer term at 21‰ (25 days), oxygen consumption was significantly higher, feeding was significantly reduced and activity coefficient values were significantly lower than at control salinity (31‰). At 26‰, all metrics were comparable to the control by the end of the experiment, suggesting acclimation. Furthermore, beneficial functional resistance (righting ability and metabolic capacity) to acute low salinity was observed at 26‰. Osmolality values were slightly hyperosmotic to the external seawater at all acclimation salinities, while coelomocyte composition and concentration were unaffected by chronic low salinity. Overall, E. esculentus demonstrate phenotypic plasticity that enables acclimation to reduced salinity around 26‰; however, 21‰ represents a lower acclimation threshold, potentially limiting its distribution in coastal areas prone to high freshwater input.

Three pesticide-pesticide eutectic systems of boscalid: Mechanochemical preparation, characterization and mechanism analysis

Preparation of eutectic mixture is considered to be an efficient means to improve physical and chemical properties in many fields. In this work, three pesticide-pesticide eutectic systems of boscalid with diniconazole, uniconazole and 3,6-dichloropicolinic acid were prepared by mechanochemical method. The formation of eutectic mixtures was identified by differential scanning calorimetry and powder X-ray diffraction characterizations. From the constructed solid–liquid phase diagrams, it is discovered that these eutectic systems could form a eutectic when the molar fraction of boscalid is 0.500. In addition, all eutectic temperatures are more than 29 K lower than the higher melting points of the constituents in the systems, which eliminates the issue of the poor thermal stability of constituents and enables the treatment of them using melting-based operations. Ideal model and COSMO-RS theory also calculate these solid–liquid phase diagrams relatively accurately, and the calculated activity coefficient values prove that these systems do not deviate significantly from the ideal state. The distinct non-ideality at the eutectic composition of the three systems also suggests that the interactions of the three coformers and the boscalid differ. The formation of eutectic mixtures was further confirmed by other solid state characterizations including mid-infrared spectroscopy, Raman spectroscopy and etc. The accelerated stability test indicates the good stability of the three eutectic mixtures. Furthermore, the water solubility study suggests the boscalid in the eutectic systems has a higher solubility than raw boscalid. By using COSMO-RS modelling, the most typical homo/hetero-molecular complexes of these pesticides were obtained and analyzed. Based on the trend of affinity characterized by the Gibbs free energy of the generation of molecular complexes, it could be inferred that eutectic point could be viewed as the state for which affinity of hetero-molecular complexes is greatest. The affinity of hetero-molecular complexes also presents the interaction between boscalid and 3,6-dichloropicolinic acid is greater than the other two pesticides at the eutectic point. Furthermore, the calculated solvation free energies document the intermolecular interaction plays an important role in stabilizing the three eutectic systems. These eutectic systems solve the problem that the three coformers are unsuitable for melting-based procedures and improve the solubility, making them potential options for future pesticide formulation development.

Determination of the Ionic Association Constants of Na+ with CO32- and HCO3- Ions, in NaCl-NaHCO3-H2O Ternary Systems, at 25 °C.

The ionic association constants of sodium with carbonate ion (K1C') and acidic carbonate ions (K2C') were measured in NaCl-NaHCO3-H2O ternary systems to determine the distribution of sodium among the chemical species present in the growth medium of Chlorella homosphaera 424 algae. The mean activity coefficients of sodium chloride (in pure sodium chloride and in a mixture of electrolytes) were determined experimentally using two electrochemical cells, namely Ag, AgCl| KCl (3 M)|| NH4NO3 (1 M)| NaCl (mNaCl)| Na+-ISE and Ag, AgCl|KCl (3 M)|| NH4NO3 (1 M)| NaCl (mNaCl)| Cl--ISE. The studies carried out show that the values of the association constants of K1C' and K2C' do not depend on the composition of the medium, but only on the effective ionic strength. The experimentally obtained γNaCl0 values in the binary system are comparable to the mean activity coefficients values for NaCl, calculated using data from the literature, with -0.9 to 0.1% relative standard deviation. The obtained results show that the experimentally determined mean activity coefficient in the ternary system, γNaCl, is smaller than γNaCl0 in the binary system over the entire field of ionic strengths studied. The ternary system NaCl-NaHCO3-H2O obeys Harned's rule.

Interaction of promethazine hydrochloride with TX-165 in aqueous, NaCl and urea media: a tensiometry and FTIR analysis

An experiment using surface tension was conducted to investigate the interactions of promethazine hydrochloride (PMT), with TX-165, at the interface in different ratios and solvents (water/50 mmol/kg NaCl, and 500 mmol/kg urea) at 298.15 K. A thorough FTIR study of the employed pure and mixed system was also conducted in the aqueous solution. PMT is a medication employed to manage and cure allergic conditions. Usually, NaCl media improved the surface properties of singular and mixed components over aqueous media, resulting in synergistic/attractive interactions among ingredients. TX-165’s composition at mixed monolayer ( ), surface excess concentration (Γ max), pC 20, activity coefficient, and so on were evaluated. The achieved activity coefficient values are attained below one in each case, indicating the attractive interactions amongst ingredients. A negative Gibbs energy of adsorption was obtained all through, indicating spontaneity in the process. A negative excess free energy ( ) was found at the mixed interface of PMT + TX-165, showing a higher surface stability of mixed monolayer than pure component monolayer. FTIR spectroscopy is used to study the spectrum of single and mixed amphiphiles to validate the interaction between PMT and TX-165. This study suggested that TX-165 surfactant might behave as an able antidepressant drug delivery agent.

Solvent pre-selection for binary mixtures based on the activity coefficient at infinite dilution in deep eutectic solvent: Tetraethylammonium chloride+ Ethylene glycol

The values of activity coefficient at infinite dilution (γ12∞) were reported for 27 solutes in tetraethylammonium chloride + ethylene glycol deep eutectic solvent (DES) system at a molar ratio of 1.000:1.997 by inverse gas chromatography (IGC) method at intervals of 10 K from 303.15 to 333.15 K. Then the measured γ12∞ values were used to determine the thermodynamic functions (ΔH1E,∞, ΔS1E,∞, and ΔG1E,∞). The values of selectivity (Sij∞) and capacity (kj∞) for six extraction problems (that is, heptane/toluene, benzene/methanol, heptane/thiophene, acetone/ethanol, cyclohexane/benzene, and cyclohexane/ethanol.) were calculated from experimental γ12∞ values and compared with literature values of other solvents under the same separation conditions. The results indicate that the studied DES is a potential extractant for separation of cyclohexane/ethanol and heptane/thiophene systems. The Flory-Huggins interaction parameters (χ12∞) were used to evaluate the miscibility between DES and organic probes, and the results reveal that alcohols exhibited the best solubility in tested DES. Furthermore, the Hildebrand solubility parameters (δ2) were calculated for tested DES, and the values of δ2 decreased with the increase of temperature.

Graph neural networks for temperature-dependent activity coefficient prediction of solutes in ionic liquids

Ionic liquids (ILs) are important solvents for sustainable processes and predicting activity coefficients (ACs) of solutes in ILs is needed. Recently, matrix completion methods (MCMs), transformers, and graph neural networks (GNNs) have shown high accuracy in predicting ACs of binary mixtures, superior to well-established models, e.g., COSMO-RS and UNIFAC. GNNs are particularly promising here as they learn a molecular graph-to-property relationship without pretraining, typically required for transformers, and are, unlike MCMs, applicable to molecules not included in training. For ILs, however, GNN applications are currently missing. Herein, we present a GNN to predict temperature-dependent infinite dilution ACs of solutes in ILs. We train the GNN on a database including more than 40,000 AC values and compare it to a state-of-the-art MCM. The GNN and MCM achieve similar high prediction performance, with the GNN additionally enabling high-quality predictions for ACs of solutions that contain ILs and solutes not considered during training.

Study of Thermodynamic Properties of l-Serine and l-Threonine in Aqueous Solutions of 1-(2-Carboxyethyl)-3-methylimidazolium Chloride [HOOCEMIM][Cl

The stability of amino acids in solutions containing electrolytes and the effect of ambient pH on their biological activity is an important research area. In this research work, the volumetric and transport properties of ionic liquid (IL) aqueous solution with special performance of 1-(2-carboxyethyl)-3-methylimidazolium chloride ([HOOCEMIM][Cl]) were studied. The selected IL acts as an electrolyte and allows the study of systems containing amino acids at acidic pH. In this work, the density, speed of sound and viscosity of binary and ternary solutions of IL in aqueous solution of amino acids in the structure of proteins, namely l-serine and l-threonine within IL molality range of (0.05, 0.07 and 0.09 mol·kg−1) were measured at 298.15 K. From these quantities, apparent molar volume, limiting apparent molar volume, apparent molar isentropic compression, limiting apparent molar isentropic compression, transfer standard volumes for amino acids from water to the aqueous IL solutions and viscosity B-coefficients were calculated using the equations of Redlich–Meyer and Jones–Dole. Close examination of literature indicates that there is no data for water activity for solution of l-serine + H2O at 308.15 and 318.15 K. In this way water activity, osmotic coefficient and vapor pressure were measured and using the interaction parameters of Wilson, NRTL, NRF-NRTL and UNIQUAC models, activity coefficient values of l-serine calculated.

Calculation of absorbed dose in paediatric phantoms using Monte Carlo techniques for 18F-FDG and [formula omitted]Tc-DMSA and the new TIAC

The radiopharmaceuticals most commonly used in nuclear medicine are 18F-FDG and 99mTc-DMSA, both of which are administered to paediatric and adult patients using the same time activity coefficient. However, the IAEA recommends specific paediatric dosimetry. The aim of this work (TW) was to estimate the absorbed dose for 18F-FDG and 99mTc-DMSA using two paediatric voxel phantoms (Baby and Child) by Monte Carlo techniques. Biokinetic data for both radiopharmaceuticals were obtained from ICRP 128. In addition, the new time-integrated activity coefficient (TIAC) values from a recent publication were examined for the following organs: Brain, urinary bladder wall, liver, heart wall, and lung. The absorbed dose per injected activity (AD/IA) and effective dose per injected activity (E/IA) values were calculated for both phantoms and the results were compared with simulated data of paediatric phantoms from ICRP 128, MIRDcalc software and available literature. Regarding AD/IA in organs, differences of up to 61% and 115% were found for the Baby phantom and 120% and 167% for the Child phantom using 18F-FDG and 99mTc-DMSA, respectively. For FDG using the new TIAC, a maximum difference of 244% was observed. For E/IA, the maximum differences were 27% and 31% for the Baby and Child phantoms, respectively, for FDG and DSMA. In this study, new dosimetric data were calculated using Baby and Child phantoms and the newly recommended TIAC.

Prediction of carbon-dioxide activity coefficient for solubility in ionic liquids using multi-non-linear regression analysis.

Activity coefficient values offer insight into the intermolecular interactions between the solute and the solvent and the deviation from the ideal behavior. CO2 capture from different industrial processes is a globally pertinent issue and the search for suitable chemicals is required. To address the issue, knowledge of activity coefficient values is crucial for CO2 separation-based process. In this regard, a correlation is developed that predicts the coefficient of CO2 activity in ionic liquids by multi-nonlinear regression analysis. The correlation is developed between the pressure range of 1–50 bar and the temperature range of 298.15–33.15 K for mole fractions of 0.3, 0.5, and 0.7. Outliers’ analysis is performed using the boxplot method to determine the suitability of ranges of the selected input parameters. The preceding literature does not predict the activity coefficient in relatively lower to higher temperature and pressure ranges for CO2 solubility in ionic liquids. Initially, the activity coefficient values from COSMO-RS were obtained and compared with the correlation results. The COSMO-RS and the correlation predicted results were subsequently validated with the experimental data. The average absolute error (AAE%) of the predicted correlation values is 19.53% while the root mean square error (RMSE) value is 0.465. The correlation can be used in the future to predict the CO2 activity coefficient values in ionic liquids to facilitate qualitative analyses of their CO2 capture efficiency.

Determining the solubilities for benzoate, nicotinate, hydrochloride, and malonate salts of bedaquiline

Determining the solubility of a compound is important for predicting its oral bioavailability, the medium to be used for dissolution, and solvents for cleaning during manufacturing. The solubilities of the newly synthesized benzoate, hydrochloride, nicotinate, and malonate salts of bedaquiline were elucidated, and the plausible reasons for the differences observed in their experimental aqueous solubilities were highlighted.The shake flask method was used to determine the experimental solubilities of the bedaquiline free base and all the salts in water, 0.01 N HCl, and pH 6.8 buffer. The molar and mole fraction solubility estimates of the salts were determined using equations for ideal and non-ideal situations. Furthermore, the relative contribution of the lattice and activity coefficient to the overall aqueous solubility of the salts were predicted graphically.The new salts ranked hydrochloride [0.6437 mg/mL] > malonate [0.0268 mg/ml] > nicotinate [0.0024 mg/mL] > benzoate [0.0004 mg/mL], showed improved aqueous solubility over the free base. The general solubility equation [GSE], fairly predicted the solubilities for the benzoate and malonate salts, but the ideal solubility equations provided poor estimates of their experimental values. Based on the ideal solubility estimates, the crystal lattice contributions of all salts were malonate > nicotinate > HCl > benzoate. However, using the activity coefficient values, the order of hydrophobicity of the bedaquiline salts was: benzoate > nicotinate > malonate > HCl.The salts forms of bedaquiline offered additional solubility as a function of their crystallinity and hydrophobicity.

Ionic Composition Thermodynamics for Different Saline Waters in Central Iraq

understand the thermodynamic of ionic composition for different saline water, triplicate water samples were collected from each location. This study required chemical analysis for total cations (Ca+2,Mg+2,Na+1,K+1) and anions (Cl-1, HCO3-1,CO3-2,SO4-2). The following parameters were calculated using the[1] program: ionic strength, activity coefficient, activity, and ion pairs. The findings revealed that, according to the classification of medium salinity[2], There is no issue with the rate of infiltration. The calcium ionic activity coefficient values ranged from 0.332 to 0.587, with active Ca+2 accounting for 23 to 48 percent of total soluble Ca+2 in the samples investigated. The concentrations of ion pairs ranged from 0.749 to 2.716 mM. L-1. The magnesium ionic activity coefficient ranged from 0.385 to 0.609, and active Mg+2 was found to be between 29 and 44 percent of total soluble Mg+2. The concentrations of ion pairs ranged from 0.270 to 6.618 mM.L-1. In general, the findings show that: The following is the ion Paris sequence: (MgSO4) 0, (CaSO4) 0, (NaSO4) -, (MgHCO3) +, (CaHO3) +, (KSO4)-. The free ions were arranged in the following order: Na+, SO4 -2, Mg+2, Ca+2, HCO3-1, K+1.- Changes in the mathematical relationship between ionic strength and electric conductivity were generated by the correction of ion pairs and ionic activity.- Correction of ion pairs and ionic activity increased the adjusted sodium adsorption ratio (adj.RNa). Ion pairs, activity, and saline water are some of the terms used in this paper.

Evaluation of the activity coefficients of ternary molecular solutions from osmotic coefficient data

A method is proposed for the evaluation of the activity coefficients of a solution constituted by a solvent (1) and two non-volatile molecular solutes (2,3) from the experimental dependence of the osmotic coefficient of the ternary solution (1,2,3) on composition. A generalized analytical expression is derived to describe such dependence, based on the sum of the weighted contributions of both binary systems and the contribution due to the mixing effect. With the resulting expression and using the solution of the Gibbs-Duhem differential equation for ternary systems, the equations that allows the evaluation of the corresponding experimental activity coefficients of both solutes in ideal dilute solution reference state (molality scale) are derived. From the comparative analysis and discussion of the results obtained for three ternary systems, it was possible to verify that the proposed methodology provides a rigorous alternative to evaluate suitable values ​​of activity coefficients from experimental data of osmotic coefficients. Finally, in order to facilitate the correlation of these values with equations originated in molecular solution modelling (NRTL, UNIQUAC, etc.), the relationships between the corresponding reference states and concentration scales were established.

Potentiometric properties of the electrochemical cells equipped with ionic liquid salt bridge and its application to determine the solubility of the ionic liquid and the mean activity coefficients of the chloride salt of the ionic liquid-constituent cation in water

Potentiometry of electrochemical cells equipped with ionic liquid salt bridge (ILSB) has been studied and applied for determination of the solubility in water of a sparingly soluble ionic liquid (IL) employed for the ILSB consisting of B + and A − , and also the mean activity coefficient of the chloride salt of the IL-constituting cation, BCl. In the case of an electrochemical cell with ILSB made of BA sandwiched by two electrolyte solutions, one containing only hydrophilic ions and the other containing BCl, the cell voltage, E cell , involves the term of the solubility of the IL, enabling the potentiometric determination of the solubility of BA in water based on the Debye-Hückel limiting law. Experimentally, from measured E cell values the solubility of tributyl(2-methoxyethyl) phosphonium bis(pentafluoroethanesulfonyl) amide ([TBMOEP + ][C 2 C 2 N − ]) is determined to be 0.15 mmol dm −3 at 25 °C. The value obtained is of thermodynamic nature because it does not involve the activity coefficient terms. An estimated value of the mean activity coefficient of tributyl(2-methoxyethyl) phosphonium chloride (TBMOEPCl) in aqueous 0.0093 M TBMOEPCl, 0.88 ± 0.01 at 25 °C, agrees with 0.87 ± 0.02 in aqueous 0.01 M TBMOEPCl obtained by the cell in which the ILSB is sandwiched by two aqueous TBMOEPCl solutions, suggesting the consistency in the present potentiometric approach.

Isopiestic determination of osmotic coefficients in the ionic strength range Im = (0.9670–2.2160) mol⋅kg−1 and activity coefficients determined by electromotive force measurements in the range Im = (0.0897–1.0054) mol⋅kg−1 of the {yKCl + (1 – y) K2HPO4}(aq) system at T = 298.15 K

The mean activity coefficients of KCl in the ternary system {y KCl + (1 – y) K2HPO4}(aq) were experimentally determined at T = (298.15 ± 0.01) K by the electromotive force measurement (EMF method) using the cell of the type, K–ISE∣KCl(mKCl), K2HPO4(mK2HPO4)∣Ag∣AgCl (ISE = ion-selective electrode), in the range of total ionic strength of the solution Im = (0.10 to 1.00) mol·kg−1 at different ionic strength fractions of KCl being y = (0.1011; 0.1997; 0.3016; 0.4027; 0.5006; 0.6018; 0.7018; 0.8051; 0.8988; 1). In addition, the osmotic coefficients of the system have been measured at the same temperature by the isopiestic vapor pressure method over the range of ionic strengths from (0.96698 to 2.21602) mol⋅kg−1 using KCl(aq) as the reference solution, at ionic strength fractions of KCl being y = (0.2063; 0.3849; 0.6099; 0.8011; 1). Values of the mean ionic activity coefficients of KCl and osmotic coefficients in the system {yKCl+(1–y)K2HPO4}(aq) were treated by an extended form of Pitzer’s ion-interaction model, Scatchard’s neutral-electrolyte model and Clegg–Pitzer–Brimblecombe’s equations based on the mole-fraction-composition scale. All three models gave similar quality representations of both sets of experimental results. There are two sets of previously published isopiestic data that were taken into consideration during treatment. The model parameters were fitted and optimized to all available thermodynamic data from EMF and isopiestic measurements to obtain an accurate and self-consistent description of properties and to form a set of parameters that can be used in a wide range of ionic strength of the system. The standard deviation of the fit for the ionic strength range from Im = (0.0897 to 10.4350) mol·kg−1 with two optimized mixing parameters of Pitzer’s model without higher–order electrostatic terms was for the mean ionic activity coefficients of KCl and osmotic coefficients, s.d. (γ±) = 3.5⋅10–3 and s.d. (ϕ) = 4.7⋅10–3 respectively, with two optimized mixing parameters of the Scatchard model standard deviations were s.d. (γ±) = 4.9⋅10–3 and s.d. (ϕ) = 5.0⋅10–3 and with Clegg–Pitzer–Brimblecombe’s model higher–order electrostatic terms not included, standard deviations were s.d. (γ±) = 4.2⋅10–3 and s.d. (ϕ) = 4.8⋅10–3.

Lithium and magnesium separation from brines by hybrid capacitive deionization

Presented work deals with the problem of separating lithium and magnesium from brines. A similar size of ionic radius characterizes the Li+ and Mg2+; hence, separating these elements could be problematic. The hybrid capacitive deionization (HCDI) with lithium‑manganese‑titanium oxides was employed as a potential process for separating lithium and magnesium ions from aqueous solutions. During the investigation, the thermodynamics factors were determined. The enthalpy of activation, the entropy of activation and the Gibbs energy of activation for accumulation Li+ and Mg2+ by Eyring-Polanyi and energy activation by Arrhenius equations were calculated for explanation the separation phenomenon. Next, the HCDI for binary and multicomponent solutions were conducted. The critical role in achieving high βLi/Mg plays the activity coefficient of the initial feed, and the value of a voltage applied in constant voltage electric mode. With the increasing value of brines' activity coefficient, the separation factor βLi/Mg lift when the concentration of lithium ions decreases. HCDI with LMTO material adsorbed lithium ions with βLi/Mg at 2.14 and released Li+ with over 70% efficiency. The proposed HCDI process employed LMTO sorptive material could be considered a potential method for separating lithium and magnesium from lithium sources.

Impact of numerous media on association, interfacial, and thermodynamic properties of promethazine hydrochloride (PMT) + benzethonium chloride (BTC) mixture of various composition

Herein, the impact of numerous media of fixed concentration (H2O, NaCl (50 mmol·kg−1), urea (U, 300 mmol·kg−1) and thiourea (TU, 300 mmol·kg−1)) on the association, interfacial, and thermodynamic properties of promethazine hydrochloride (PMT) and benzethonium chloride (BTC, cationic antimicrobial surfactant)) mixture in several compositions were examined via tensiometry method at room temperature (298.15 K). Along with tensiometry, the interaction between PMT and BTC was also assessed by applying the UV–visible as well as FTIR spectroscopy in an aqueous solution. PMT is used for the symptomatic relief of various allergic conditions. The employed systems critical micelle concentrations (cmc) value was acquired much lower than their calculated corresponding ideal cmc value (cmcid) owing to the interaction between components (PMT and BTC) and the interaction amongst PMT and BTC further increases through increase in mole fraction (α1) of first component (BTC). Diverse solution and surface parameters, thermodynamic parameters, etc. have been processed by use of several purported theoretical models. In NaCl media, the cmc value of singular along with mixed species (PMT + BTC) of each composition were found fewer in magnitude than aqueous media while magnitude increased in U/TU media and TU is more valuable in boosting the cmc than U. Activity coefficient value in each case was continuously found below one due to attractive interaction amongst PMT and BTC. The attained Γmax and Amin value of PMT + BTC implies that the formed mixed interface is the closer packing of PMT and BTC. Excess free energy (ΔGex) was attained negative, exhibiting that the mixed micellar/mixed monolayer stability was higher with the singular component’s micelles/monolayer. The shift in frequency of pure component were attained by FT-IR study by addition of other component that also signifies the straightforward interaction among ingredients. Existing research outcomes revealed a straightforward methodology to design the employed surfactant as an efficient ingredient as a drug delivery vehicle for phenothiazine drug.

Solubility and thermodynamic analysis of vinpocetine in various mono solvents at different temperatures

In the present study, the solubility of vinpocetine in ten commonly used solvents at different temperatures range of T = 298.2–323.2 K was examined and correlate the solubility data with Apelblat and Van’t Hoff models and lastly the dissolution thermodynamic parameters of vinpocetine in each solvent were estimated. It was observed that the vinpocetine solubility found less in water and determined to be better in non-polar solvents. Both (Apelblat and Van’t Hoff) models are found suitable to correlate the measured solubility data, still, the Van’t Hoff equation demonstrated to be more precise for the correlation of solubilities of VPN in investigated solvents. The maximum value of activity coefficients (γ2) for vinpocetine was observed in water, this could be due to low solubility of vinpocetine in water, while the value of γ2 was observed lowest in Transcutol owing to maximum solubility of vinpocetine in Transcutol. The conclusions of thermodynamic parameters analysis of vinpocetine in various studied solvents brought out that the vinpocetine solubilization process was endothermic, non-spontaneous and entropy-driven. The outcomes of the present study would provide enormous support in vinpocetine solubilization, pre-formulation and dosage form development in pharmaceuticals.