Water Activity In Solutions Research Articles

Effect of anion α-functionalization on the water affinity of thermo-responsive phosphonium acetate-derived ionic liquids

This study presents a facile method for assessing the effect of anion functional group substitution on the water affinity of phosphonium-acetate ionic liquids. By combining the same cation with three different α-substituted carboxylate anions, the effect of anion functional group substitution on the IL miscibility with water and hygroscopicity was experimentally evaluated and rationalized using COSMO-RS sigma profile analysis. Lower critical solution temperature (LCST) phase separation experiments and water vapor partial pressure measurements revealed that there is a stark α-substitution dependency on the affinity of water for acetate [AcO], pivalate [PivO], and trifluoroacetate [TFA] derived tributyl(octyl)phosphonium [P4448] ILs. It was found that the IL water affinities varied as: [P4448][AcO] > [P4448][PivO] > [P4448][TFA]. With the lowest water partial pressure and no LCST driven phase separation, [P4448][AcO] exhibited a high affinity for water. On the other hand, [P4448][PivO] and [P4448][TFA] exhibited LCST-driven phase separation and room temperature immiscibility, respectively, with higher water partial pressures, as a result of relatively weak water affinities. COSMO-RS sigma profile analysis revealed that the aliphatic carboxylate anions should incorporate apolar interactions commensurate with or greater than the polar hydrogen bond acceptor interactions for phase immiscibility of the corresponding IL with water. It was found that the relative magnitudes of apolar and polar interactions, assessed using the anion sigma profile peak intensity ratio (Ir), are directly correlated with the IL water affinity, and inversely correlated with the solution water activity coefficient. Therefore, it was concluded that Ir forms a quantitative link between the structural changes at the molecular level and the bulk water affinity exhibited by the ionic liquid as a whole.

Machine learning for determination of activity of water and activity coefficients of electrolytes in binary solutions

Activity of water and electrolytes in aqueous solutions is of utmost importance for multiple industrial applications. However, experimental determination of such values is time-consuming, while calculation of activity coefficients using numerical methods is challenging. By training neural networks models on literature data, one could predict activity of water and electrolytes easily, without requiring any experiment. In this paper, multiple descriptors (or features) are compared to predict activity coefficients of electrolytes and activity of water in electrolyte solutions. A neural network based on the Levenberg-Marquardt algorithm (LM-NN) showed high accuracy to calculate values, despite the small size of the training datasets. Both activity coefficients of electrolytes and activity of water in electrolyte solutions can be predicted accurately even on unseen data, using simple descriptors such as electrolyte concentration, ion sizes and charges. However, some discrepancies were observed due to the lack of representativeness of the training dataset. This could be solved by selecting training data sets that are similar (e.g. same group of the periodic table) to the unknown values, or by including available experimental data for the salt considered. The ability of the LM-NN to solve non-linear least square curve fitting problems makes it a good candidate to fit experimental activity coefficient data, with the advantage of simplicity as compared to e-NRTL or UNIQUAC methods. This method paves the way for accurate and quick determination of thermodynamic data for electrolyte solutions (and beyond) using machine learning, without necessitating large training datasets.

UPTAKE OF TIGHTLY BOUND TRITIUM BY PLANTS

A study of the bioavailability of a tightly bound tritium in the soil in situ under the conditions of the Semipalatinsk test site (STS) and in a laboratory vegetation experiment was conducted. Significant concentrations of organically bound tritium (OBT) were recorded in Stipa capillata plants growing on the territory of the STS. At the same time, tritium in the free water of plant tissues (TFWT) was not detected. In a model experiment using Cucumis sativus culture, the specific activity of tightly bound tritium in the composition of the solid phase of the soil and tritiated water (HTO) in the composition of the soil solution at the beginning and at the end of the experiment differed significantly. At the same time, TFWT activity in Cucumis sativus was 2 orders of magnitude less compared to the activity of tightly bound tritium in the soil and slightly differed from the activity of tritiated water in the soil solution, which is accessible to the root system of plants. The results of vegetation studies have shown that the direct source of tritium for experimental plants was a soil solution. However, changes in the tritium activity in the soil liquid and solid phases in vegetation vessels indicate that the source of tritiated water in the soil solution was a tightly bound form of radionuclide as a result of leaching processes. It is assumed that the possible causes of leaching of tightly bound radionuclide from the solid phase into the soil solution are the moisture regime, as well as the influence of the rhizosphere of plants.

Elimination of Unspecific Amplification in the Exponential Amplification Reaction Using Polyethylene Glycol 200 (PEG 200) as a Cosolute

Exponential amplification reaction (EXPAR) enables extremely rapid nucleic acid measurements. However, the nonspecific amplification in EXPAR limits its application, especially for low abundance target nucleic acids. Herein, polyethylene glycol 200 (PEG200), a widely available small-molecular cosolute, is described to suppress this nonspecific amplification. This cosolute generates molecular crowding and reduces the solution water activity, thereby weakening the template-template interactions and catalysis of enzymes, the major causes of nonspecific amplification. The additional of PEG200 greatly reduces the background and thereby improves the sensitivity of EXPAR by 4 orders of magnitude without extending the analysis time. Hence, the determination of target miRNAs at 1 aM was obtained within 20 min, outperforming most conventional strategies. This work provides an efficient and affordable strategy of applying water soluble cosolutes to eliminate the nonspecific amplification in EXPAR, which is expected to be widely employed to eliminate the background in nicking enzyme assisted amplification (NEAA).

Physicochemical properties and anthocyanin content of commercially manufactured elderberry jams from Patagonia (Argentina)

Abstract Commercially manufactured elderberry jams elaborated in Patagonia, Argentina, were analyzed for physico-chemical characteristics. Water activity (a w) ranged between 0.758 and 0.972 and total monomeric anthocyanin (TMA) content varied from 2.4 up to 55 mg Cy-3G/100 g jam. Relationship between a w and °Brix in jams was described using an equation for correlating water activity in non-electrolyte solutions. Elderberry jam samples were stored at 38 °C and samples periodically withdrawn for analysis. TMA degraded following first order reaction kinetics and color parameter a* decreased during storage while parameter h° increased. Water activity and presence of fructose in jams increased rate of TMA destruction and adversely affected color changes. Studies with sugar solutions containing anthocyanins confirmed TMA degradation is faster in models having reducing sugars than in the presence of sucrose. It is shown that sucrose may undergo hydrolysis during acid catalyzed storage at 38 °C and pH 3.5.

Optimization of osmotic pretreatment of tomato slices using response surface methodology and further hot-air drying

Tomato is one of the most cultivated vegetables, playing important role in the human feed. Due to its characteristics and composition, tomatoes present reduced shelf life, and preservative techniques are required. In this study, response surface methodology was used to optimize process conditions during the osmotic dehydration (OD) of tomato slices, through the desirability function. Optimization factors were absolute pressure (21-89 kPa), vacuum application period (7-15 min), and osmotic solution water activity (0.893-0.943), while investigated responses were sodium incorporation (NaI), water loss (WL), solid gain (SG), weight reduction (WR), and osmodehydrated product water activity (ODaw). The optimized conditions were achieved, and a further hot-air drying (HAD) was conducted at different temperatures and air velocities. During the OD, lower absolute pressure, and osmotic solution water activity led to lower NaI and higher WL and WR. Shorter drying time and higher diffusivity were obtained at higher temperature and air velocity, during the HAD. The dried tomato slices with sodium incorporation reduction were evaluated with regard to the final water activity, rehydration and color, in which no significant differences (p > 0.05) were observed between the treatments.

Thermodynamic Model of the H2O–H2SO4–UO2SO4 System Incorporating Novel Experimental Data on Water Activity

Activity of water in aqueous solutions containing sulfuric acid and uranyl sulfate has been determined at 298.15, 310.65, and 323.15 K by means of the apparatus AQUALAB 4TE. The data obtained, along with literature information about activity of water and solid–liquid equilibria in the H2O–UO2SO4 and H2O–H2SO4–UO2SO4 systems, were used to develop a thermodynamic model of the ternary system mentioned. The resulting model, employing Pitzer–Simonson–Clegg (PSC) equations to represent the properties of a liquid phase, is valid within a wide range of temperatures and concentrations. Apart from introducing novel experimental data and a thermodynamic model, the reported study discusses advantages and disadvantages of the PSC-based thermodynamic descriptions of the H2O–H2SO4 subsystem presented in the literature.

Mean activity coefficients of KCl in the KCl–K2B4O7–H2O solutions at 288.15 K determined by cell potential method and their application to the prediction of solid–liquid equilibria of the KCl–K2B4O7–H2O system

• The unreported mixed ion interaction of Pitzer parameters in KCl–K 2 B 4 O 7 –H 2 O solutions at 288.15 K were obtained in this work. • The experimental and predicted solubilities were compared to verify the rationality of fitting parameters. After measuring the cell potential of the cell without liquid junction K-ISE | KCl ( m 1 ), K 2 B 4 O 7 ( m 2 ) | Cl-ISE with the calibrated potassium ion and chloride ion selective electrode, the mean activity coefficients of KCl in KCl–K 2 B 4 O 7 –H 2 O solutions are calculated by the Nernst equation. The single parameters β (0) , β (1) , C Φ of K 2 B 4 O 7 , and the mixed ion interaction parameters θ Cl, B 4 O 5 (OH) 4 and ψ K,Cl, B 4 O 5 (OH) 4 of the Pitzer model were determined by programming solver and mean activity coefficients in this work. Furthermore, Pitzer equation is also used to evaluate the mean activity coefficient of potassium tetraborate in the KCl–K 2 B 4 O 7 –H 2 O solutions, as well as the osmotic coefficients, water activity and excess Gibbs free energy of the mixed solutions. Additionally, the experimental measurements of phase equilibria in the ternary system KCl–K 2 B 4 O 7 –H 2 O at 288.15 K are investigated in this work. The solubilities of the salts in the ternary system at 288.15 K are predicted by using Pitzer equation and the obtained ion parameters. The comparision of experimental and calculated phase diagram is presented in detail. The prediction results show that the predicted data are in accordance with the experimental data.

Investigate the Water Activity of Different Solutions According to Solute Concentration for Preparing Wet Filtration Solution

According to the World Health Organization (WHO), air pollution ranks 6th among the leading causes of death globally. The wet porous membrane filter has been widely used in dust removal, VOCs, and acid gas absorption. The wet filtration solutions need to ensure a low water activity that limits the release of moisture into the air, inhibits microbial growth, and can absorb dangerous gases. This study investigated the water activity of NaCl, NaNO3, K2CO3, KCl, K2SO4, Mg(NO3)2, MgCl2, and CaCl2 solutions at different concentrations to saturation at 25 °C. NaCl and NaOH solutions are not only investigated at different concentrations but also investigated the effect of temperature in the range of 0-40 °C. Some solution formulas are suggested that ensures the following properties: low water activity, antifungal, antibacterial and acid gas absorption.
 
 

Calculation of water activity in electrolytic solutions using the Electrolattice and Q-Electrolattice equations of state

Water activity directly influences the deterioration, texture, pigmentation, and preservation of nutrients in food. This property quantifies the availability of water for the enzymatic, chemical, or microbiological activity that defines the shelf life of food. In this way, the food industry needs to measure, predict, and control this property. In this context, the present work aims to evaluate the performance of the Electrolattice and Q-Electrolattice equations of state in predicting and correlating the water activity of solutions containing electrolytes. Parameters available in the literature were used to compare the performance of the Electrolattice and Q-Electrolattice equations in predicting the water activity (in binary, ternary, and quaternary solutions of salts). The Q-Electrolattice model presented better performance than the Electrolattice equation, with a relative mean deviation (RMD) of 1.95%, 0.14%, and 0.06% for binary, ternary, and quaternary aqueous electrolytic solutions, respectively. Then, the Q-Electrolattice equation was used to correlate experimental data of systems containing water + NaCl + sugar (fructose, sucrose, glucose, and xylose) at 25°C and water + sugar (fructose, sucrose, glucose, and xylose) at 35°C in aqueous solutions of salts and sugar. The general weighted average of the RMD% was equal to 0.29%. Finally, the procedure was validated with solutions containing water, NaCl, and sugar (fructose, sucrose, glucose, and xylose) at 35°C, a condition that was not used in the parameter fitting process. The overall weighted average of the RMD for predicting the water activity of water + NaCl + sugar solutions at 35°C using the Q-Electrolattice equation was 0.57%, thus validating the parameters estimated in this work. The results obtained in this study showed the feasibility of using the Q-Electrolattice equation to predict water activity in aqueous solutions of salts and sugars used as a basis for the osmotic drying of food.

Evaporation Dynamics of Sessile Saline Microdroplets in Oil.

The occurrence of concentration and temperature gradients in saline microdroplets evaporating directly in air makes them unsuitable for nucleation studies where homogeneous composition is required. This can be addressed by immersing the droplet in oil under regulated humidity and reducing the volume to the picoliter range. However, the evaporation dynamics of such a system is not well understood. In this work, we present evaporation models applicable for arrays of sessile microdroplets with dissolved solute submerged in a thin layer of oil. Our model accounts for the variable diffusion distance due to the presence of the oil film separating the droplet and air, the variation of the solution density and water activity due to the evolving solute concentration, and the diffusive interaction between neighboring droplets. Our model shows excellent agreement with experimental data for both pure water and NaCl solution. With this model, we demonstrate that assuming a constant evaporation rate and neglecting the diffusive interactions can lead to severe inaccuracies in the measurement of droplet concentration, particularly during nucleation experiments. Given the significance of droplet evaporation in a wide array of scientific and industrial applications, the models and insights presented herein would be of great value to many fields of interest.

Modeling of CH4/CO2 hydrate phase behavior in organic and electrolyte inhibitors by dickens’ model

The main purpose of this study is investigating a reliable and convenient model based on Dickens and Quinby-Hunt approach to predict CH4/CO2 gas hydrate equilibrium temperature in presence of organic inhibitors (e.g., methanol, ethanol, ethylene glycol, triethylene glycol, glycerol), and electrolyte inhibitors (e.g., NaCl, KCl, NaBr, KBr, CaCl2, CaBr2, MgCl2, EMIM-Cl, BMIM-Cl, BMIM-Br, BMIM-I, BMIM-DCA, EMIM-HSO4, EMIM-EtSO4, and EMIM-MeSO4). This model named as Dickens’ model is an activity-based model and to calculate water activity of organic solutions the nonrandom two-liquid (NRTL) and Margules was used. Also, Pitzer model was employed to calculate activity of water in electrolyte solutions. A correlation was suggested to determine enthalpy of hydrate dissociation in terms of inhibitor weight percent and equilibrium pressure. Due to no data in open literature, the virial coefficients of Pitzer model in ionic liquid solutions were adjusted. The model results were compared with available experimental data from open literature and observed to be in good agreement with the reported literature.

Determination of clathrate hydrates stability conditions and water activity in aqueous solutions containing natural amino acid and its blend with ionic liquid, alcohol, and salt using a thermodynamic approach

Owing to the necessity of precise calculations in gas hydrates systems comprised of novel environmentally friendly materials such as natural amino acids (NAAs), as well as their blends with ionic liquids (ILs), alcohols, and salts, the present study reports a new method concerning the water activity computation coupled with the van der Waals-Platteeuw (vdW-P) model. The developed activity model consists of two terms, namely Free-Volume modification of the Flory-Huggins (FVFH) equation taking into account the molecular (short-range) interactions, and the extended Debye-Hückel (EDH) equation considering the ionic (long-range) interactions. The model's performance is then assessed against a comprehensive databank (11 NAAs, 9 blends, 475 data points) collected from open literature and data of 3 gaseous hydrate formers (CH4, CO2, and natural gas). The overall deviation of the determined gas hydrates dissociation temperatures for the whole databank is found to be 0.40 K (0.14%), while the most significant individual deviation does not exceed 1.76%, proving the remarkable performance of the developed calculation procedure. Not only does not the model benefit from parameter regression, but it also offers accurate predictions in the complex systems of the inhibitors’ blends. When NAAs are employed solely (409 data points), the deviations of the model results from real data of gas hydrates dissociation temperatures are 0.39 K. On the other hand, in the presence of NAAs mixtures with ILs, alcohols, and salts (66 data points), which represent highly complex systems, the deviation is 0.41 K.

Effect of 1-Butyl-1-methylpyrrolidinium trifluoromethanesulfonate on water activity of ternary aqueous ionic liquid solutions containing [BMIm]Br, [BMIm]Cl, [HMIm]Br, and [HMIm]Cl, at 298.15 K

In improved isopiestic method, the effect of 1-butyl 1-methylpyrrolidinium trifluoromethanesulfonate ([BMP][TfO]) on the activity of water of aqueous solutions of 1-butyl 3-methyl imidazolium bromide ([BMIm]Br), 1-butyl 3-methyl imidazolium chloride ([BMIm]Cl), 1-hexyl 3-methyl imidazolium bromide ([HMIm]Br), and 1-hexyl 3-methyl imidazolium chloride ([HMIm]Cl) was determined. Some quantities of vapor liquid equilibrium were calculated from the experimental values. The activity coefficients of [BMIm]Br, [BMIm]Cl, [HMIm]Br, and [HMIm]Cl in binary and ternary systems were calculated by the results obtained from correlating the activity of water measured in these systems with TNRF-mNRTL local composition based model. Through it, the transfer of these ionic liquids from water to aqueous ternary solutions containing [BMP][TfO] was investigated with respect to the transfer Gibbs energy. The interactions between solute and solvent were highlighted using the transfer Gibbs energy, water activity and partial pressure of water data.

A thermodynamic framework for determination of gas hydrate stability conditions and water activity in ionic liquid aqueous solution

The formation of gas hydrates in pipelines and plugging of the gas flow path are a major cause of operating expenses, safety issues, pressure drop, and fatal accidents. Therefore, the inhibition of gas hydrate formation is of paramount importance. The utilization of a new class of inhibitors such as ionic liquids (ILs) is currently of great interest. In this regard, adjusting water activity in the inhibitor blend (water + IL) is a vital factor. Several models have been developed to calculate the activity of water in the presence of IL(s). The major disadvantage of these models is their correlative basis. This study aimed to propose a rigorous predictive model for the calculation of water activity in the presence of IL(s), which would then be applied in the prediction of the gas hydrate stability conditions. The model is made up of a molecular term (the short-range interactions from Free-Volume-Flory-Huggins (FVFH) activity model) as well as a contribution from ionic interactions as a result of IL(s) dissociation in water (the long-range electrostatic interactions from the extended Debye–Hückel (EDH) model). The overall absolute temperature deviation and the average absolute relative deviation percent in the calculated gas (methane and carbon dioxide) hydrate dissociation temperatures for the whole databank (500 data points including 37 ILs) were found to be 0.61 K and 0.22%, respectively. This proves the superiority of the model over the previous correlative-basis ones. Finally, it is concluded that the higher temperature, the higher the IL(s) concentration, and the lower IL(s) molecular weight(s) result in larger model deviations.

Extending Zavitsas’ hydration model to the thermodynamics of solute mixtures in water

While Zavitsas’ hydration model has been used to determine the activity of water in electrolyte solutions, it has not previously been demonstrated to model the activities of solutes. The present study derives the equations for the activity of solutes in aqueous electrolyte solution mixtures for Zavitsas’ hydration model. The derived equations are tested by predicting the solubility of sodium nitrite (NaNO2) in aqueous sodium chloride (NaCl) and sodium hydroxide (NaOH) solutions, electrolytes of interest to nuclear waste processing. The solubility of NaCl in aqueous NaNO2 solutions was also modeled. The solubility of NaNO2 and NaCl were accurately calculated in these systems, even though no solubility data from those mixtures was used in model parametrization. These results demonstrate that Zavitsas’ hydration model can be used to model the activities and solubilities of solutes in electrolyte solutions, in addition to the activity of water.

Natural gas hydrate stability conditions and water activity in aqueous solutions containing mono ethylene glycol (MEG) and salt: Experimental measurements and thermodynamic modeling

Gas hydrates can form in the presence of saline water produced from the gas and oil reservoirs under specific thermodynamic conditions. One of the best ways to prevent gas hydrate formation is to inject hydrate inhibitors like mono ethylene glycol (MEG) or methanol aqueous solutions in the pipelines. To design productive facilities and overcome operation faults, studying the stability conditions of natural gas hydrates in the presence of aqueous solutions of salt(s) and/or inhibitor(s) is necessary. However, a few studies have been conducted on stability conditions of natural gas hydrates while salt mixtures and MEG are present in aqueous solution. Here, the hydrate stability conditions of a synthetic natural gas in aqueous mixtures of 20 and 30 wt% of MEG, and 2.5 wt% NaCl + 2.5 wt% KCl were experimentally measured under 272–293 K and 3.30–12.70 MPa. An isochoric pressure-search method was employed to conduct the measurements. Then, a thermodynamic model was developed to estimate hydrate stability conditions in the presence of the aforementioned inhibitors. In this developed model, the aqueous phase fugacity is estimated using a combined form of the Cubic-Plus-Association Equation of State with the modified Debye-Hückel electrostatic term and the hydrate phase is modeled using the van der Waals and Platteeuw solid solution theory. To improve model accuracy, the aqueous phase activity was measured in various concentrations at atmospheric pressure and 298.15 K using a standard activity meter called Novasina LabMaster-aw neoAS, Switzerland. These measured data were used to correlate the activity coefficient parameters in the thermodynamic model. Finally, it is noted that the modeling results and the experimental data are in satisfactory agreement.

Hygroscopicity of Microplastic and Mixed Microplastic Aqueous Ammonium Sulfate Systems.

A growing body of research suggests the presence and long-range transport of microplastics in the atmosphere. However, the interactions between these microplastics and atmospheric aerosol are poorly understood. Environmental microplastics vary in color, morphology, and chemical composition and become oxidized over time by UV, mechanical, and biological action. Once introduced to the atmosphere, these microplastics will likely become mixed with atmospheric aerosol. Determining how microplastics interact with aerosol particles and how they may alter aerosol physical properties, including water uptake and loss, is necessary to understand the impact of these microplastics on our environment. Herein, we investigate the effect of microplastics on the water activity of bulk water and ammonium sulfate solutions. We compare a variety of plastic compositions and microplastic morphologies including plastics that have been aged by UV irradiation and mechanical forces in the lab. In addition, we investigate the water uptake and loss in microplastic samples through dynamic vapor sorption. We find an increase in total water sorption for UV-aged plastics compared to pristine plastics. Finally, we investigate the effect of fractional surface coverage on the equilibration time scale.

Water Activity in Aqueous Solution of Sucrose in the Presence of Some Deep Eutectic Solvents

In this work, the effect of some deep eutectic solvents (DESs) based on choline chloride on water activity (aw) in aqueous solutions of sucrose was investigated. Activity of water (aw) and vapor pr...

An accurate water activity model for sulfuric acid solutions and its implementation on moisture sorption isotherm determination

Because of a lack of reliable models to predict the water activity (a w) of H2SO4 solutions, the standard sulfuric acid solution (SSL) method requires a periodic check and adjustment of the acid concentration to ensure that equilibrium will be reached at a predetermined a w point. To establish a reliable equation describing the a w of H2SO4 solutions, five molecular activity models, i.e. nonrandom two-liquid (NRTL), Wilson, universal quasi-chemical (UNIQUAC), modified NRTL-1 (M-NRTL 1) and modified NRTL-2 (M-NRTL 2), were introduced and compared in this study. Each of the models was applied to the 542 literature vapor-liquid equilibrium data points of H2SO4 solutions. The results showed that the NRTL model was the best with respect to its accuracy and simplicity. This NRTL model significantly simplified the implementation of the sulfuric acid solution method for MSI measurements. Excellent agreement was found between this simplified SSL method and the conventional saturated salt solution (SSS) method for MSI measurements of both microcrystalline cellulose (MCC) and apples at 25 °C. Therefore, this newly improved SSL method, based on the NRTL model, could be an inexpensive, convenient and reliable alternative to the conventional SSS method in food MSI measurements in the future. Highlights The NRTL model can accurately predict the a w of H2SO4 solutions. The NRTL model can significantly simplify the known sulfuric acid solution (SSL) method. This improved SSL method is valid and reliable for use in MCC and apples. A working table of the a w of H2SO4 solutions was developed for ease of use.