Water Electrolyte Systems Research Articles

Modeling the solubility of light hydrocarbon gases and their mixture in brine with machine learning and equations of state

Knowledge of the solubilities of hydrocarbon components of natural gas in pure water and aqueous electrolyte solutions is important in terms of engineering designs and environmental aspects. In the current work, six machine-learning algorithms, namely Random Forest, Extra Tree, adaptive boosting support vector regression (AdaBoost-SVR), Decision Tree, group method of data handling (GMDH), and genetic programming (GP) were proposed for estimating the solubility of pure and mixture of methane, ethane, propane, and n-butane gases in pure water and aqueous electrolyte systems. To this end, a huge database of hydrocarbon gases solubility (1836 experimental data points) was prepared over extensive ranges of operating temperature (273–637 K) and pressure (0.051–113.27 MPa). Two different approaches including eight and five inputs were adopted for modeling. Moreover, three famous equations of state (EOSs), namely Peng-Robinson (PR), Valderrama modification of the Patel–Teja (VPT), and Soave–Redlich–Kwong (SRK) were used in comparison with machine-learning models. The AdaBoost-SVR models developed with eight and five inputs outperform the other models proposed in this study, EOSs, and available intelligence models in predicting the solubility of mixtures or/and pure hydrocarbon gases in pure water and aqueous electrolyte systems up to high-pressure and high-temperature conditions having average absolute relative error values of 10.65% and 12.02%, respectively, along with determination coefficient of 0.9999. Among the EOSs, VPT, SRK, and PR were ranked in terms of good predictions, respectively. Also, the two mathematical correlations developed with GP and GMDH had satisfactory results and can provide accurate and quick estimates. According to sensitivity analysis, the temperature and pressure had the greatest effect on hydrocarbon gases’ solubility. Additionally, increasing the ionic strength of the solution and the pseudo-critical temperature of the gas mixture decreases the solubilities of hydrocarbon gases in aqueous electrolyte systems. Eventually, the Leverage approach has revealed the validity of the hydrocarbon solubility databank and the high credit of the AdaBoost-SVR models in estimating the solubilities of hydrocarbon gases in aqueous solutions.

Estimation of e-NRTL binary interaction parameters and its impact on the prediction of thermodynamic properties of multicomponent electrolyte systems

The main objective of the current work is to obtain and validate the binary interaction parameters of the e-NRTL model for different salts in water, using the data of mean ionic activity coefficients vs. molality compiled by Robinson and Stokes (Electrolyte Solutions, Dover Publications, 2012). This way, the interaction parameters τsalt,water and τwater,salt of the e-NRTL thermodynamic model for 171 binary (salt + water) electrolyte systems have been calculated by non-linear regression of the data available in the literature. The fitting was performed by the Marquardt-Levenberg algorithm which was computationally implemented in an Excel VBA homemade program. The e-NRTL equation was solved by using two different procedures: (i) included in the Excel VBA code or, (ii) implemented in Aspen Plus by linking the process simulator and the Excel VBA code via automation as the third-party software. The interaction parameters obtained by both approaches were able to adequately fit the experimental results. They were successfully validated by the thermodynamic prediction of multicomponent systems reported by other authors. Additionally, the current predictions were compared with those obtained with the parameters contained in the Aspen Properties database showing a significant improvement for several systems. Finally, this work demonstrates that it is possible enhancing the quality of the prediction of multicomponent systems with proper values of the binary electrolyte interaction parameters, without considering electrolyte-electrolyte interactions foreseen in the original e-NRTL model, which makes possible the simulation of processes containing a variety of chemical species regardless their nature.

Aerosol Optical Tweezers Constrain the Morphology Evolution of Liquid-Liquid Phase-Separated Atmospheric Particles

Summary Chemical models of atmospheric particles are vital in understanding the role of aerosol particles in atmospheric chemistry, air pollution, human health, and climate change. Advancing these models requires new frameworks that can realistically predict how critical particle properties evolve. We present such a framework for predicting particle phase separation and which morphology will prevail; this controls how each particle interacts with and affects the atmosphere. We studied the mixing behavior of α-pinene secondary organic aerosol (SOA) with different organic phases, as relative humidity was varied to determine the interplay between polarity, miscibility, interfacial tension, and the resulting morphology. Using measurements from aerosol optical tweezers experiments and literature data, a general trend in morphology with increasing atmospheric oxidation was observed, from biphasic partially engulfed (where both phases are immediately accessible to the gas phase) to biphasic core shell (where the organic shell conceals the core) and finally to a single-phase, homogeneous morphology.

Development of the ReaxFF Methodology for Electrolyte-Water Systems.

A new ReaxFF reactive force field has been developed for water-electrolyte systems including cations Li+, Na+, K+, and Cs+ and anions F-, Cl-, and I-. The reactive force field parameters have been trained against quantum mechanical (QM) calculations related to water binding energies, hydration energies and energies of proton transfer. The new force field has been validated by applying it to molecular dynamics (MD) simulations of the ionization of different electrolytes in water and comparison of the results with experimental observations and thermodynamics. Radial distribution functions (RDF) determined for most of the atom pairs (cation or anion with oxygen and hydrogen of water) show a good agreement with the RDF values obtained from DFT calculations. On the basis of the applied force field, the ReaxFF simulations have described the diffusion constants for water and electrolyte ions in alkali metal hydroxide and chloride salt solutions as a function of composition and electrolyte concentration. The obtained results open opportunities to advance ReaxFF methodology to a wide range of applications involving electrolyte ions and solutions.

Water–Electrolyte Glass-Forming Systems: A Review

Water–electrolyte systems comprising aqueous solutions of nitrates, iodates, sulfates, acetates, orthophosphates, chlorides, and fluorides of Group I–III metals, transition metals, and lanthanides were studied. Studies of glass formation in the system Al2(SO4)3–H2O serve as an example to give an idea of the original method for studying water–electrolyte glass-forming solutions and glasses developed at the Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, enabling one to predict their structures. This investigation method and analysis of experimental data have no analogues either in Russia or abroad. The results obtained were used to elucidate general glass formation trends in various water–electrolyte systems. We were the first to prove a polymeric structure of glass-forming compositions in some water–electrolyte systems. We were also the first to combine the glasses of water–electrolyte systems in a special class of glasses that are hydrogen-bonded polymeric items.

Solvent‐Limited Ion‐Coupled Electron Transfer and Monolayer Thiol Stability in Au144 Cluster Films

AbstractVoltammetric investigations were carried out for Au144 cluster films protected by 1‐hexanethiol (C6S) and 2‐phenylethanethiol (PET) in acetonitrile (0.1 M TBAPF6) and in water (0.1 M KPF6). The C6S‐protected Au144 cluster films show single electron charging behavior both in acetonitrile and water electrolyte systems. Whereas, the PET‐protected Au144 cluster films show charging behavior only in acetonitrile and not in water, although both electrolyte systems contain a common hydrophobic anion (PF6−). This discrepancy is attributed to solvent‐limited ion‐coupled electron‐transfer phenomena. Furthermore, spectroelectrochemistry was employed to study the thermal and electrochemical stability of PET on curved/3D (Au144 cluster films) and flat/2D (self‐assembled monolayers (SAMs) of PET on a polycrystalline planar Au electrode) Au surfaces. At 4 mW laser power, the SAMs of the curved system remained stable; however, in the flat system, they irreversibly desorb from the surface. This was ascribed to the relative stability differences of the PET monolayer originating from the existence of different Au−S structures on the two types of Au surfaces.

Structural Aspect of Glass Formation in Aqueous Electrolyte Glass-Forming Systems

Water–electrolyte systems containing aqueous solutions of Group I–III metal, transition metal, and lanthanide nitrates, iodates, sulfates, acetates, orthophosphates, chlorides, and fluorides, inorganic acids, as well as aqueous and nonaqueous solutions of some of organic compounds (alcohols, acids, aromatic hydrocarbons) have been studied. The research methodology developed at the Institute of General and Inorganic Chemistry, RAS, and the analysis of experimental data have no analogues in our country and abroad. On the basis of the results obtained, general tendencies of glass formation in various water–electrolyte systems have been revealed. For the first time, a polymeric structure of glass-forming compositions of a number of water–electrolyte systems has been proved. The assumption is made that the nature of glass formation in water–electrolyte systems is the same as in systems containing “classical glass” (phosphates, silicates, and others) and organic glass-forming systems, that is, polymeric nature.

Thermodynamic study of the (NaCl + serine + water) mixtures using potentiometric measurements at T = (298.2 and 303.2) K

This work concerns the obtained results by the thermodynamic investigation of the (NaCl+serine+water) electrolyte system based on the experimental potentiometric data. The potentiometric measurements were performed on the galvanic cells without liquid junction of the type: Ag|AgCl|NaCl (m), serine (wt%), H2O (1wt%)| Na-ISE, in various mixed solvent system containing 0, 2, 4, 6, 8 and 10 mass fractions (%) of serine over ionic strength ranging from 0.0435 to 3.4999molkg−1 at T=(298.2 and 303.2)K. The modeling of this system was made based on the extended Debye Hückel equation, Pitzer and Pitzer–Simonson–Clegg models. The obtained parameters were used to calculate the values of the mean activity coefficients of NaCl, the osmotic coefficients, and the excess Gibbs-free energies based on Pitzer model for the investigated system. Also, the mean activity coefficients of NaClbased on mole fractions and excess Gibbs free energies were determined in according to Pitzer–Simonson–Clegg model.

Empirical equation for evaluating the dispersivity of cohesive soil

As indicated by the theory of a clay–water–electrolyte system, the dispersive mechanism of cohesive soil involves three aspects: low clay content, high sodium ion percentage, and strongly alkaline pH. Accordingly, an empirical equation was established with an associated procedure and criteria proposed for evaluating the dispersivity of cohesive soil. The equation consists of four soil physical and chemical indicators: liquid limit (WL), clay content (PC), sodium percentage in the pore water (PS), and pH. The equation is F = 4 − 0.01(2WL + PC − PS) + 0.1 pH, where F is the soil dispersivity value. Compared with the evaluation based on laboratory tests, the empirical equation had higher accuracy for the evaluation of the dispersivity of cohesive soil, and was thus conducive to greater engineering safety. This indicates that the proposed empirical equation is applicable for evaluating the dispersivity of cohesive soil in general engineering.

Novel procedure for the estimation of swelling pressures of compacted bentonites based on diffuse double layer theory

Bentonite clays are proven to be attractive as buffer and backfill material in high-level nuclear waste repositories around the world. A quick estimation of swelling pressures of the compacted bentonites for different clay–water–electrolyte interactions is essential in the design of buffer and backfill materials. The theoretical studies on the swelling behavior of bentonites are based on diffuse double layer (DDL) theory. To establish theoretical relationship between void ratio and swelling pressure (e versus P), evaluation of elliptic integral and inverse analysis are unavoidable. In this paper, a novel procedure is presented to establish theoretical relationship of e versus P based on the Gouy–Chapman method. The proposed procedure establishes a unique relationship between electric potentials of interacting and non-interacting diffuse clay–water–electrolyte systems. A procedure is, thus, proposed to deduce the relation between swelling pressures and void ratio from the established relation between electric potentials. This approach is simple and alleviates the need for elliptic integral evaluation and also the inverse analysis. Further, application of the proposed approach to estimate swelling pressures of four compacted bentonites, for example, MX 80, Febex, Montigel and Kunigel V1, at different dry densities, shows that the method is very simple and predicts solutions with very good accuracy. Moreover, the proposed procedure provides continuous distributions of e versus P and thus it is computationally efficient when compared with the existing techniques.

Pitzer, Modified Pitzer, and Extended Debye–Hückel Modeling Approaches: Ternary RbF or CsF + Glycine + Water Electrolyte Systems at 298.15 K

This article deals with the mean activity coefficients of RbF or CsF in the glycine + water mixed systems. The Pitzer, the modified Pitzer, and the extended Debye–Huckel equations are used to describe the nonideal behavior of the electrolyte. The osmotic coefficients, the excess Gibbs free energy, and the standard Gibbs energies of transfer were calculated with the corresponding parameters.

A practical method for the calculation of liquid–liquid equilibria in multicomponent organic–water–electrolyte systems using physicochemical constraints

Liquid mixtures containing a variety of organic compounds, water, and dissolved electrolytes are prone to liquid–liquid phase separation, owing to non-ideal interactions between water, ions, and organic compounds. Such systems are of practical importance in the design of chemical separation processes as well as the partitioning of semivolatile species in atmospheric aerosols. In this study, a practical phase separation calculation method based on a system of nonlinear equations is presented, applicable to multicomponent systems containing inorganic ions. Expressions are derived that allow consistent use of activity coefficients defined on molality basis for ionic species in combination with mole fraction-based activity coefficients for nonelectrolyte components. Physicochemical considerations are applied together with preliminary evaluation of generated trial compositions to automatically obtain a set of feasible initial guesses. A successive substitution procedure with component-specific step length damping is then employed, followed by a rapid convergence part using a globally convergent solver for systems of nonlinear equations. We discuss several examples that demonstrate the method's remarkable level of reliability even in the case of systems showing highly non-ideal mixing behavior, and we highlight the importance of providing a good initial guess.

Osmoregulation – an important parameter of bacterial growth

Environmental conditions such as temperature, pH, radiation and osmotic pressure are important factors limiting the growth and multiplication of bacteria. Regular structure and metabolism of bacterial cells are maintained through a stable arrangement of the water-electrolyte system, regulated by osmosis. The rapid changes caused by osmotic shock (dehydration, rehydration) might lead to modifications of the phospholipid structure of the cell membrane and even cell death. Advances disturbing the osmosis, which are a natural part of living cells, may appear for example in colloid systems. The biological identification of the osmotic pressure is connected with an increase or decrease in the environmental osmotic strength of microorganisms' habitat. Cells exposed to osmotic stress, such as an increase in osmotic pressure, initiate mechanisms of active coping with the adverse consequences of its effects. Osmoregulatory processes are designed to maintain cell turgor, hence ensuring proper conditions for bacterial growth. Osmoregulation, which consists of maintaining fluid and electrolyte balance of cells, raising concerns accumulation of specific compatible solutes (osmolytes). Osmolytes are small, soluble organic molecules with a positive influence on membrane stabilization and proteins, without disrupting cellular functions. Storage of compatible solutes takes place by synthesis or by downregulation from the medium by means of special transport systems, activated by mechanical stimuli. Knowledge of the impact of osmotic pressure on microbial cells and the regulation of its activity led to the appropriate use of bacteria in various branches of the biotechnology industry.

Modeling of the Ternary NH4Cl + ROH + Water Electrolyte Systems (with R = Me, Et, 1-Pr, and 2-Pr) by the Pitzer−Simonson−Clegg Approach and Its Modified Forms

Literature data on electrolyte modeling in nonaqueous and in mixed solvent systems are still relatively scarce. In addition, contrary to the currently used Pitzer ion-interaction approach, modeling of the ternary systems containing electrolyte, nonelectrolyte, and water by the more refined Pitzer−Simonson−Clegg (PSC) ion-interaction approach is limited only to the work of three research groups. In this context, we have recently reported the use of Pitzer and Pitzer−Simonson−Clegg (PSC) ion-interaction approaches for modeling the ternary HCl + ROH + water electrolyte systems (with R = Me, Et, 1-Pr, and 2-Pr). The present investigation describes also the results obtained by the application of the simplified PSC, original PSC, and previously reported modified PSC, as well as another proposed modified PSC approach (presented in this work), for modeling the nonideal behavior of the ternary NH4Cl + ROH + water mixture. The calculations were achieved based on the experimental potentiometric data previously obtained in our laboratory. Accordingly, the present calculations were performed for NH4Cl electrolyte molalities ranging from 0.01 up to about 4 mol·kg−1 in several alcohols (ROH) with different percent mass fractions, x = (10, 20, 30, 40, and 50) %, for R = Me, Et, 1-Pr, and up to 30 % for 2-Pr, at (298.15 ± 0.05) K.

Pitzer and Pitzer–Simonson–Clegg Modeling Approaches: Ternary HCl + 2-Propanol + Water Electrolyte System

Despite its success for modeling electrolyte thermodynamics in aqueous media, the use of the Pitzer approach for the investigation of electrolytes in nonaqueous or in mixed solvent media is still very limited. Further, a review of the literature reveals that there are no more than a few research groups who have used the exact form of the Pitzer–Simonson–Clegg (PSC) ion-interaction approach for the investigation of electrolytes in mixed solvent systems. As a continuation of our previous studies, the present investigation reports modeling of HCl in the 2-propanol + water mixed solvent system with the Pitzer, PSC and an extended form of the PSC ion-interaction approaches using the experimental potentiometric data from a cell containing pH glass membrane and Ag/AgCl electrodes. The electrochemical measurements were performed over the HCl molality range from 0.01 to 4.5 mol⋅kg−1 in mixed 2-propanol (x%)+water (100−x%) solvents, with different solvent percent mass fractions (x%=10,20,30,40 and 50%) at 298.15±0.05 K.

Pitzer and Pitzer–Simonson–Clegg modeling approaches: Ternary HCl + 1-propanol + water electrolyte system

A survey of literature reveals that the use of Pitzer approach for modeling electrolyte in nonaqueous or in mixed solvent media is still very scarce. Moreover, only two research groups have used the exact and complete form of the more refined Pitzer–Simonson–Clegg (PSC) ion-interaction approach for the investigation of electrolyte in mixed solvent systems. The present investigation describes the results obtained by the use of Pitzer, PSC as well as an extended PSC ion-interaction approaches for modeling the non-ideal behavior of the ternary HCl + water + 1-propanol systems. These modeling purposes were achieved based on the experimental potentiometric data of a galvanic cell containing a pH glass membrane and Ag/AgCl electrodes. The measurements were performed over the HCl electrolyte molality ranging from 0.01 up to 4.5 mol kg −1 in the ternary HCl + 1-propanol ( x%) + water (100 − x%) system with different alcohol percent mass fractions ( x% = 10, 20, 30, 40 and 50%), at 298.15 ± 0.05 K.

Pitzer and Pitzer–Simonson–Clegg ion-interaction modeling approaches: Ternary HCl + methanol + water electrolyte system

Clegg–Pitzer–Brimblecombe ion-interaction semi-empirical approach was rarely exploited for modeling electrolyte, particularly, in mixed solvent systems. Indeed, a review of the literature shows that the use of an exact and complete form of this model (PSC) was only limited to the works of two research groups for the investigation of electrolyte in mixed solvent systems. In this work, we have used both Pitzer and PSC ion-interaction theoretical approaches for modeling the non-ideal behavior of HCl in the ternary HCl + methanol + water electrolyte system. The modeling purposes were achieved based on the experimental determination of the mean molal activity coefficients for HCl in this ternary system by using the potentiometric data of a galvanic cell containing a pH glass membrane and Ag/AgCl electrodes. The measurements were performed over the electrolyte molality ranging from 0.01 up to 5.75 mol/kg in mixed methanol ( x%) + water (100 − x%) solvent, with solvent mass fraction percents: x% = 10, 20, 30, 40 and 50%, at 298.15 ± 0.05 K.

Pitzer and Pitzer–Simonson–Clegg modeling approaches: Ternary HCl + ethanol + water electrolyte system

We report in this work, for the first time, the results obtained from both Pitzer, Pitzer–Simonson–Clegg (PSC) and an extended PSC ion-interaction approaches for modeling the non-ideal behavior of HCl electrolyte in the mixed ethanol + water solvent systems. In this context, a review of literature shows that the use of an exact and complete form of PSC ion-interaction approach for modeling electrolyte in mixed solvent systems was only limited to the works of two research groups. In this work, the modeling purposes were achieved based on the experimental potentiometric data of a galvanic cell containing a pH glass membrane and Ag/AgCl electrodes. The measurements were achieved over the HCl electrolyte molality ranging from 0.02 up to about 5 mol kg −1 in mixed ethanol ( x%) + water (100 − x%) solvent with different solvent mass fractions percent ( x% = 10%, 20%, 30%, 40% and 50%), at 298.15 ± 0.05 K.

Electrical conductivity of aqueous acids in binary and ternary water-electrolyte systems

We analyze electrical conductivity data for aqueous solutions of strong and weak acids over a wide range of concentrations at various temperatures. Electrical conductivity isotherms in these solutions are characterized by peaks, whose parameters correlate with the molecular structure of solutions. On the basis of the concentration dependence of the activation energy of electrical conductivity, the acid solutions are divided into two groups. One includes HIO3, H2SO4, and H3PO4; the other includes HCl, HBr, HI, HClO4, HNO3, and carboxylic acids. We show that anomalous proton migration is operative only in low-concentration solutions until their concentration reaches the peak on conductivity isotherms. The effect of extrinsic ions on proton mobility and on conductivity in acid-salt-water systems is considered.

A discrete element model for kaolinite aggregate formation during sedimentation

AbstractThe formation of colloidal aggregates during sedimentation is an important process when considering geotechnical and environmental engineering problems including wastewater treatment systems and slurry wall constructions for waste isolation. In this paper, a quasi three‐dimensional discrete element framework is developed to model aggregate formation during sedimentation by considering the following microscopic inter‐particle forces present in the clay–water–electrolyte system: van der Waals attraction, electrical double‐layer repulsion, Born's repulsion, hydrodynamic viscous drag, and gravity. The role of these physico‐chemical forces in the formation of clay clusters during sedimentation is investigated using an integrated numerical and experimental approach. The discrete element method (DEM) framework has been previously shown to accurately model clay behavior at the microscopic level. The model is validated with experimental data for comparison of distributions of aggregate density and aggregate size. Good agreement between the model prediction and the experimental results is obtained, suggesting that the DEM can be a powerful tool to better understand the aggregate formation process at the microscopic scale. For particle sizes ranging from 0.05 to 1 µm it is also shown, through numerical simulations, that ionic strength of the fluid medium is the controlling factor for aggregate size and density and that at aggregate sizes less than 20 µm, face‐to‐face interactions dominate the force regime between a pair of particles. Copyright © 2007 John Wiley & Sons, Ltd.