Aqueous Solutions Of CaCl2 Research Articles

Influence of alternating electric fields and impurity Mg2+ on CaCl2 aqueous solution: A study by molecular dynamics simulation

Non-equilibrium molecular dynamics (MD) simulations were performed to study the influence of external alternating electric field and impurity Mg2+ on CaCl2 aqueous solution. It is examined in terms of the activity of particles, the water residence time and hydrogen bonding analysis. The results show that alternating electric fields can enhance the hydration between Ca2+ and coordinated water molecules and enhance the hydrogen bonding between water, the Mg2+ has the opposite effects. Furthermore, an alternating electric field with different frequencies was applied; the results show that the electric field with different frequencies can enhance the hydration between Ca2+ and coordinated water molecules. Additionally, by studying the change of the intensities of the alternating electric field, there is no linear relationship between the electric field intensity and the values of these parameters. The simulations results provide useful guidance for understanding the influence of the presence of impurity Mg2+ ions on the scale inhibition when the electric anti-fouling technology is used practically during industrial water processes.

Ionic diffusion and proton transfer of MgCl2 and CaCl2 aqueous solutions: an ab initio study under electric field

ABSTRACTWe report on a series of ab initio molecular dynamics simulations on MgCl and CaCl aqueous solutions subjected to the effect of static electric fields. The diffusion properties of the solvated cationic species have been investigated both in the low-to-moderate field regime and for intense field strengths, where correlated proton transfers between the water molecules take place. Albeit the Grotthuss-like motion of the protons H dramatically affects the standard relative mobility of monovalent cations such as Li, Na, and K [Phys Chem Chem Phys 2017;19:20420], here we demonstrate that the rule ‘the bigger the cation the higher its mobility’ is preserved for divalent cations – such as Mg and Ca – even when a sustained protonic current is established by the field action. Notwithstanding the presence of charged particles anticipates the field threshold of the molecular dissociation of water from 0.35 V/Å to 0.25 V/Å, such a shift does not depend on the nominal charge the cations hold. Protons flow more easily in the MgCl solution (=2.3 S/cm) rather than in the CaCl (=1.7 S/cm) electrolyte solution because of a twofold reason. Firstly, Ca, being larger than Mg, more strongly hampers the propagation of a charge defect of the same sign (i.e. H). Secondly, we demonstrate that the mobility of Ca is sizably higher than that of Mg. This way, by spanning more efficiently the aqueous environment, Ca further inhibits the proton transfers along the H-bonded network. Finally, the protonic conduction efficiency is inversely proportional both to the ionic radii and to the nominal charge of the cations present in solution.

Optimal synthesis and operation of low-cost polyvinyl chloride/bentonite ultrafiltration membranes for the purification of oilfield produced water

The low-cost PVC/bentonite ultrafiltration membranes are prepared by phase inversion method using different coagulation baths involving de-mineralized water and aqueous saturated solution of NH4Cl, NaCl, KCl, MgCl2 and CaCl2. Effect of coagulation bath on membrane performance is investigated by evaluating ternary-phase diagram, membrane morphology, hydrophilicity, porosity, mean pore size, pore density, pure water flux and antifouling behavior using oilfield produced water. Better performing membrane with 5% bentonite loading is obtained from KCl-coagulation bath with pure water permeance-467.5 L m−2 h−1 atm−1. Response surface method based on central composite design is employed to enhance the ultrafiltration membrane performance using the optimum design of experiments through maximizing permeate flux as well as oil rejection separately considering following decision variables: PVC and bentonite loading in casting solution, membrane thickness, pH and trans-membrane pressure (TMP). The maximum permeation flux of 421.3 L m−2 h−1 is achieved using PVC-loading-15.01 g, bentonite-loading-1.37 g, membrane thickness-100 µm, pH-9 and TMP-250 kPa, while maximum oil rejection is 98.6% at PVC-loading-18.0 g, bentonite-loading-0.0 g, membrane thickness-250 µm, pH-5.1 and TMP-54.4 kPa. Due to conflicting nature of permeation and oil rejection, a multi-objective optimization problem is formulated and solved using an elitist non-dominated sorting genetic algorithm (NSGA-II), resulting the Pareto-optimal solution.

Evaporation modes of LiBr, CaCl2, LiCl, NaCl aqueous salt solution droplets on aluminum surface

The evaporation of droplets of the LiBr, CaCl2, LiCl and NaCl aqueous salt solutions were studied experimentally and their evaporation characteristics were compared to droplets of distilled water. The geometrical parameters of droplets (contact angle, height, and diameter) were measured using three methods of data processing: tangential methods (T) and the Young-Laplace method (Y-L). Scattering of the measured data does not depend on the processing method selected for large contact angles. However, in the case of small contact angles, the Y-L method exhibited the smallest measurement error. An optical method allowed for measuring the contact angle of salt solutions droplets just prior to crystallization. The experiments have shown that crystalline hydrates grow near the contact line and distort the droplet profile. The contact angles of salt solution droplets were found to depend on time in a non-linear manner. Typical evaporation modes of the studied aqueous salt solutions are detected: 1 – increasing the contact diameter; 2 – pinning the droplet; 3 – formation of salt crystals (NaCl) or crystalline hydrates (LiBr, CaCl2 and LiCl).

Evaporation and heat transfer of aqueous salt solutions during crystallization

Evaporation, heat transfer and surface crystallization of thin layers of aqueous solutions of CaCl2, LiBr and LiCl salts have been studied experimentally. The control of crystallization rate is extremely important for a wide range of modern technologies, associated with both slow cooling rates and extremely rapid droplet and film crystallization (for example, in nanocoatings). Usually, when calculating the crystallization, the heat transfer coefficient and the evaporation rate are assumed quasi-constant, and the effect of evaporation rate of solution on the rate of crystallization is not taken into account. In this paper, it is shown that even without crystallization the heat transfer coefficient may vary several times, when the height of the film rapidly decreases. This study has shown that the character of crystallization curve and crystallization rate strongly depend on the rate of solution evaporation before the onset of phase transition. Abnormally high crystallization rates 30–50 mm/s are achieved at extremely low supersaturations of solutions (the salt solution is in the quasi-equilibrium region), and this is associated with the rapid growth of dendritic forms. With the growth of the surface crystalline film, the evaporation rate of the solution in metastable state increases significantly and has a non-stationary “oscillation” character. The coefficient of heat transfer before the onset of crystallization also changes significantly. The formation of dendrites is possible if crystallization is realized in thin supersaturated layers with high gradients of temperature and concentration. In this case, very high crystallization rates will be provided by dendritic forms.

An Empirical Model of the Gibbs Free Energy for Solutions of NaCl and CaCl2 of Arbitrary Concentration at Temperatures from 423.15 K to 623.15 K under Vapor Saturation Pressure

An empirical model for the concentration dependence of the Gibbs free energy for solutions of chlorides of alkaline and alkaline earth metals in water is proposed. A simple analytical form of the Gibbs free energy makes it possible to obtain the equations of state for salt solutions that are equally accurate in the entire range of salt concentrations, from dilute solutions to solubility limits. The high accuracy of the thermodynamic description of solutions of high and intermediate concentration is ensured by the presence in the equation for the Gibbs free energy of two terms related to the Margules decomposition of the Gibbs free energy. Our form of the Gibbs free energy also contains a term that reproduces the thermodynamic behavior of solutions of electrolytes, which ensures high accuracy of the proposed model at low salt concentrations in the solution. Using the model, the equations of state for aqueous solutions of NaCl and CaCl2 at water vapor pressure in the temperature ranges of 423.15 K–573.15 K and 423.15 K–623.15 K were obtained, which corresponds to the parameters of ore-bearing solutions participating in the formation of low-temperature hydrothermal ore deposits.

A novel composite of alginate aerogel with PET nonwoven with enhanced thermal resistance

There is a need to develop new composite fabrics with improved thermal properties. Aerogels are highly porous materials with low thermal conductivities and can be used to develop new composites with standard nonwoven fabrics. In this study, a new composite of alginate aerogel with polyester (PET) nonwoven was synthesized by a sol-gel method. A needle punched PET nonwoven was soaked with an alginate solution and then immersed in an aqueous CaCl2 solution which resulted in the formation of a gel inside the PET nonwoven. The gel was dried with supercritical CO2 after solvent exchange with ethanol leading to alginate aerogel-PET nonwoven composite. The aerogels were porous and were in the form of blocks in between the PET fibers as evident from SEM images. The thermal properties of the composite were measured using a heat flow meter. The thermal diffusivity of the composite was significantly lower than the thermal diffusivity of the pure PET nonwoven. The composite also had a higher thermal resistance and also a higher tensile strength than the pure PET nonwoven. Experiments using a thermal imaging camera indicated that the heat flux in the composite is much lower than in pure PET nonwoven due to the presence of alginate aerogel. The results show that the new composite material is promising for use in thermal clothing applications.

Fabrication of calcium phosphate-loaded carboxymethyl cellulose non-woven sheets for bone regeneration

Calcium phosphate-loaded carboxymethyl cellulose non-woven sheets (CMC/CaP sheet) were fabricated and their potential to induce in vitro osteoblast differentiation and in vivo bone regeneration were investigated. The CMC/CaP sheets were prepared by alternately soaking protonated-CMC non-woven sheets in CaCl2 and Na2HPO4 aqueous solutions. Because of its slow water uptake rate, the protonated-CMC was successfully loaded with a mixed phase of brushite and hydroxyapatite. In vitro, the CMC/CaP sheet induced osteoblast differentiation of human mesenchymal stromal cells (hMSCs), as shown by calcification and the upregulation of osteoblast marker genes. In absence of CaP, hMSCs on the CMC sheet had enhanced expression of alkaline phosphatase (ALP) only, indicative of early osteoblast differentiation. Finally, bone regeneration by the CMC/CaP sheet was demonstrated in a mouse calvarial defect model, based on micro-computed tomography (micro-CT), Masson’s trichrome staining, and immunostaining for osteoblast markers. Cells expressing the transcription factor Sp7/Osterix, which is essential for osteoblast differentiation, were detected around the new bone. The combined effect of CMC and CaP enhanced osteoblast differentiation and the CMC/CaP non-woven sheet was found to be an easy-to-handle and flexible scaffold for bone regeneration.

Lateral movements in Rayleigh-Taylor instabilities due to frontiers. Experimental study.

Lateral movements of the fingers in Rayleigh-Taylor hydrodynamic instabilities at the interface between two fluids are studied. We show that transverse movements appear when a physical boundary is present; these phenomena have not been explained until now. The boundary prevents one of the fluids from crossing it. Such frontiers can be buoyancy driven as, for example, the frontier to the passage of a less dense solution through a denser solution or when different aggregation states coexist (liquid and gaseous phases). An experimental study of the lateral movement velocity of the fingers was performed for different Rayleigh numbers (Ra), and when oscillations were detected, their amplitudes were studied. Liquid-liquid (L-L) and gas-liquid (G-L) systems were analysed. Aqueous HCl and Bromocresol Green (sodium salt, NaBCG) solutions were used in L-L experiments, and CO2 (gas) and aqueous NaOH, NaHCO3, and CaCl2 solutions were employed for the G-L studies. We observed that the lateral movement of the fingers and finger collapses near the interface are more notorious when Ra increases. The consequences of this, for each experience, are a decrease in the number of fingers and an increase in the velocity of the lateral finger movement close to the interface as time evolves. We found that the amplitude of the oscillations did not vary significantly within the considered Ra range. These results have an important implication when determining the wave number of instabilities in an evolving system. The wave number could be strongly diminished if there is a boundary.

Soft x-ray spectroscopy of high pressure liquid.

We describe a new experimental technique that allows for soft x-ray spectroscopy studies (∼100-1000 eV) of high pressure liquid (∼100 bars). We achieve this through a liquid cell with a 100 nm-thick Si3N4 membrane window, which is sandwiched by two identical O-rings for vacuum sealing. The thin Si3N4 membrane allows soft x-rays to penetrate, while separating the high-pressure liquid under investigation from the vacuum required for soft x-ray transmission and detection. The burst pressure of the Si3N4 membrane increases with decreasing size and more specifically is inversely proportional to the side length of the square window. It also increases proportionally with the membrane thickness. Pressures > 60 bars could be achieved for 100 nm-thick square Si3N4 windows that are smaller than 65 μm. However, above a certain pressure, the failure of the Si wafer becomes the limiting factor. The failure pressure of the Si wafer is sensitive to the wafer thickness. Moreover, the deformation of the Si3N4 membrane is quantified using vertical scanning interferometry. As an example of the performance of the high-pressure liquid cell optimized for total-fluorescence detected soft x-ray absorption spectroscopy (sXAS), the sXAS spectra at the Ca L edge (∼350 eV) of a CaCl2 aqueous solution are collected under different pressures up to 41 bars.

Adsorption of CO2 onto Activated Carbons Prepared by Chemical Activation with Metallic Salts

Abstract This article has been retracted due to honest error by the author. For further information, please see https://doi.org/10.1515/ijcre-2017-9198. Activated carbons are obtained by chemical activation of African Palm shells (Elaeis guineensis) with different impregnating agents, i. e. magnesium chloride (MgCl2) and calcium chloride (CaCl2) aqueous solutions at different concentrations (3, 5 and 7 % w/v) and temperatures (between 773 and 1073 K), in order to assess their influence on the development of the porosity. The activated carbons prepared are characterized in terms of both textural and chemical properties. The activated carbons have a surface area and a pore volume ranging between 19–501 m2.g−1 and 0.03–0.29 cm3.g−1, respectively. Based on the obtained results, the samples with higher surface area and pore volume (i. e. those impregnated with MgCl2 and CaCl2 solutions and thermally treated at 1073 K) are selected to evaluate the adsorption capacity and affinity for CO2. CO2 adsorption capacity varies between 1.78 and 2.95 mmolCO2.g−1 at 273 K and low pressure, and the activated carbon impregnated with the solution of MgCl2 3 % and activated at 1073 K (i. e. ACMg3-1073) showed the best performances. Finally, the kinetic results show that adsorption rate for sample ACMg3-1073 is enhanced by its micro-mesoporous nature, being the access routes to the micropores larger.

Adsorption of CO2 onto Activated Carbons Prepared by Chemical Activation with Metallic Salts

Abstract Activated carbons are obtained by chemical activation of African Palm shells (Elaeis guineensis) with different impregnating agents, i. e. magnesium chloride (MgCl2) and calcium chloride (CaCl2) aqueous solutions at different concentrations (3, 5 and 7 % w/v) and temperatures (between 773 and 1073 K), in order to assess their influence on the development of the porosity. The activated carbons prepared are characterized in terms of both textural and chemical properties. The activated carbons have a surface area and a pore volume ranging between 19 and 501 m2.g−1 and 0.03–0.29 cm3.g−1, respectively. Based on the obtained results, the samples with higher surface area and pore volume (i. e. those impregnated with MgCl2 and CaCl2 solutions and thermally treated at 1073 K) are selected to evaluate the adsorption capacity and affinity for CO2. CO2 adsorption capacity varies between 1.78 and 2.95 mmolCO2.g−1 at 273 K and low pressure, and the activated carbon impregnated with the solution of MgCl2 3% and activated at 1073 K (i. e. ACMg3-1073) showed the best performances. Finally, the kinetic results show that adsorption rate for sample ACMg3-1073 is enhanced by its micro-mesoporous nature, being the access routes to the micropores larger.

Dependences of the osmotic coefficients of aqueous calcium chloride solutions on concentration at different temperatures

A model that considers the contributions from hydration, ion association, and electrostatic interactions to the nonideality of 2‒1 electrolyte solutions is substantiated. The parameters of the model’s equations are the mean ion hydration number, the spread of the distribution of hydrated ion stoichiometric coefficients in the standard state, and the number of association. The model is successfully used to describe literature experimental data on the concentration dependence of osmotic coefficients of aqueous CaCl2 solutions at temperatures ranging from 0 to 100°C. The modeling of the above systems shows that as the temperature rises, the hydration number falls slightly, the distribution of the hydration number broadens, and the ion paring of the salt rises by the first degree.

Assessment of soil diuron bioavailability to plants and microorganisms through non-exhaustive chemical extractions of the herbicide

In environmental and soil sciences, bioavailability represents the amount of an element or compound that is accessible to an organism for uptake or adsorption across its cellular membrane. In agricultural applications, almost exclusively plant roots and soil organisms uptake contaminants that are dissolved in the soil water. On this basis, a study was conducted to determine the relationship between diuron bioavailability to plants or microorganisms of aged herbicide residues in 10 selected soil types, and their extraction from these soils using three different solutions: n-butanol, hydroxypropyl-β-cyclodextrin (HPBCD) and CaCl2. The aim of the mineralisation bioassays was to assess the diuron bioavailable fraction mineralised by a diuron soil microbial degrader consortium. The bioassays using plants aimed to assess the diuron biotoxicity employing a selected crop (Hordeum vulgare). Toxicity was determined as the level at which plant growth was inhibited.Aging of diuron contaminated soil during 100days drastically decreased the percentage of diuron recovered by the selected extractants in all the tested soils. Results showed statistical correlations between non-exhaustive chemical diuron extraction and biological measurements when the extractant was n-butanol, showing to be the most reliable chemical technique capable of predicting both, diuron bioavailability for microorganisms and for plants. HPBCD was also capable of detecting diuron bioavailability only for microorganism, although with worse statistical data, while the third extractant, CaCl2 aqueous solution, showed to be the least reliable for both assays. The results presented demonstrated that a non-exhaustive chemical extraction using n-butanol as extractant may serve as the basis for a simple and rapid procedure to assess diuron bioavailability in contaminated soils with different characteristics.

Synthesis of calcium chloroborate whiskers via sedimentation and sintering process

Single crystalline calcium chloroborate (Ca2B5O9Cl) whiskers with uniform diameter have been fabricated by a two-step process. The precursor was firstly prepared by the sedimentation reaction between CaCl2, H3BO3 and NaOH aqueous solutions, and then sintered at different temperatures for 6 h with KCl as flux. The XRD indicates that the product synthesized at 600 °C is Orthorhombic Ca2B5O9Cl. SEM and TEM results show that the Ca2B5O9Cl is whisker with the diameter about 0.2–0.5 μm and the length up to 15 μm. SAED analysis shows that the whisker is single crystalline and grows along [001] direction. The possible formation process and growth mechanism were proposed.

Bioprinting of three dimensional tumor models: a preliminary study using a low cost 3D printer

Abstract The deep understanding of cancer and tumor genesis, as well as the development of new therapy strategies still remains one of the emerging challenges in modern medicine. To meet these challenges it seems to be absolutely necessary to overcome the drawbacks of the established 2D in vitro models. Especially the missing microenvironment of the tumor, which means the absence of stroma and immune cells, results in a missing cell-cell and cell-stroma interaction as well as disrupted functional communication pathways. Modern 3D culture systems and 3D printing or rather bioprinting technologies attempt to solve this issue and aim to closely mimic natural tumor microenvironment. In this preliminary work we are going to present the first steps of establishing an artificial 3D tumor model utilising a low cost 3D printer. Therefore the printer had been modified with an open-source syringe pump to become a functional bioprinter using viscosity modulated alginate hydrogel. In the first attempts L929 mouse fibroblasts, which are an integral component of natural stroma, had been incorporated into the hydrogel matrix and printed into scaffolds. Subsequent to the printing process the scaffolds got ionically crosslinked with a 5% w/v aqueous solution of CaCl2 to become mechanically stable. After three days of cultivation viability testing had been performed by utilising FDG staining and PET CT to obtain a volumetric viability measurement. The viability imaging showed vital cells homogeneously distributed in the scaffold and therefore stands as an evidence for a working low cost bioprinting process and a successful first step for the development of an artificial 3D tumor model.

Free convection and vapor diffusion of droplet aqueous solutions

Evaporation of drops of water and aqueous solutions of salts LiBr and CaCl2 have been studied experimentally. The impact of various key factors on the evaporation has been estimated. The behavior of convection significantly differs in drops of water and salt solution. The contribution of gas convection changes with an increase in salt concentration. With increasing salt concentration in a drop, the role of the convective component first increases, reaches an extremum and then decreases with time. Usually when modeling droplet evaporation, the only considered are the diffusive vapor transport and the molecular heat conduction in liquid. The neglect of gas convection in the simulation leads to essential (manifold) underestimation of the evaporation rate compared with the experimental data. Gas convection may be neglected at intensive bubble boiling in a water drop. The process of drop boiling is divided into 4–5 characteristic time stages with a significant change of both the rate of evaporation and the role of convection.

Surface and Interfacial Tension Behavior of Salt Water Containing Dissolved Amphiphilic Compounds of Crude Oil: The Role of Single-Salt Ionic Composition

A detailed investigation into the effect of dissolved amphiphilic compounds of crude oil in salt water on its surface tension/interfacial tension (ST/IFT) behavior has been conducted in this paper. To simulate water–oil contact during water injection into oil reservoirs, 16 single-salt aqueous solutions of NaCl, CaCl2, and Na2SO4 having ionic strengths of up to 2.0 M were mixed with a natural acidic–basic crude oil. The mixing was performed by a rocking mechanism in a visual pressure–volume–temperature cell at an elevated temperature. After the mixing process, two phases were completely separated from each other using a high-temperature centrifuge. Finally, in addition to pH measurements, the air–water ST and decane–water IFT of salt water were measured using the pendant-drop method. The results reveal that the dissolution of crude oil amphiphilic compounds, especially the acidic or basic compounds, in salt water can considerably decrease its ST/IFT. It seems that there is the same optimal ionic strength ...

A Coarse-Grained Force Field Parameterized for MgCl2 and CaCl2 Aqueous Solutions.

Calcium and magnesium ions play important roles in many physicochemical processes. To facilitate the investigation of phenomena related to these ions that occur over large length and time scales, a coarse-grained force field (CGFF) is developed for MgCl2 and CaCl2 aqueous solutions. The ions are modeled by CG beads with characteristics of hydration shells. To accurately describe the nonideal behavior of the solutions, osmotic coefficients in a wide range of concentrations were used as guidance for parametrization. The osmotic coefficients were obtained from the chemical potential increments of water calculated using the Bennett acceptance ratio (BAR) method. The result CGFF accurately reproduces experimental osmotic coefficients, densities, surface tensions, and cation-anion separations of calcium chloride and magnesium chloride solutions at molalities up to 3.0 mol/kg. As a preliminary application, the force field is applied to simulate aggregations of sodium dodecyl sulfate (SDS) in calcium chloride solution, and the simulation results are consistent with experimental observations.

Characterization of locally available soil as a liner material for solid waste landfills in Sri Lanka

This study aimed to develop a low-cost and effective clay liner material for solid waste landfills in Sri Lanka. A locally available clayey soil and its admixtures with 5 and 10% bentonite were examined for this purpose. Laboratory experiments to determine soil plasticity and swell index were carried out on the tested samples. Hydraulic conductivity (k) tests were carried out in the laboratory using water and an aqueous solution of CaCl2 on unconsolidated samples prepared by either dry or slurry packing and pre-consolidated samples with five different consolidation pressures (p) from 10 to 200 kPa. Measured liquid limits for tested admixtures increased with increasing bentonite contents and correlated well with measured values of the swell index. The difference in permeant solutions had little effect on measured k values for both unconsolidated and pre-consolidated samples. The hydraulic conductivities were highly affected by changing p, i.e., the k values decreased on two orders of magnitude as p increased from 10 to 200 kPa. The Kozeny–Carman equation, a theoretical permeability model that expresses the k-porosity relationship, was applied to measured data including reported values. Results showed the Kozeny–Carman equation captured well the porosity-dependent k values for tested soils and their admixtures with bentonite under a wide range of void ratios, suggesting that the Kozeny–Carman equation is a useful tool to estimate the magnitude of k values for differently compacted soil and its bentonite admixtures.