Calcium Chloride Aqueous Solution Research Articles

Molecular interaction studies of caffeine in aqueous metal chloride solutions at 308.15 K

Ultrasonic speed (u), density (d) and viscosity (η) of caffeine in aqueous solutions of potassium chloride, sodium chloride, magnesium chloride and calcium chloride have been measured at 308.15 K. From these data, thermodynamic interaction coefficient, isentropic compressibility (β s ), intermolecular free length (L f ), apparent molar volume (Φ v ), relative association (R A ) and acoustic impedance (Z) have been computed. All the derived parameters are correlated with the molar composition of solutions. Depending on the molecular interactions and the nature of the solutions show the change in structure of solvent when solute is added to it. The viscosity coefficients A and B of Jones-Dole equation have been determined and employed to throw light on the mechanism of solute-solute and solute-solvent interactions.

Melting of a Vertical Ice Cylinder Inside a Rotating Cylindrical Cavity Filled with Binary Aqueous Solution

Melting of a vertical ice cylinder into a homogeneous calcium chloride aqueous solution inside a rotating cylindrical cavity with several revolution speeds is considered experimentally. Melting mass and temperature are measured on four initial conditions of the solution and four rotating speeds of the cavity. Temperature of liquid layer becomes uniform by the mixing effect resulting from cavity rotation and it enhances the melting rate of ice cylinder. As cavity-rotating speed becomes fast, melting rate increases. Dimensionless melting mass is related to Fourier number and rotating Reynolds number in each initial condition, therefore the experimental equation that is able to quantitatively calculate a dimensionless melting mass is presented. It is seen that melting Nusselt number re-increases in the middle of melting process. Ice cylinder continues to melt in spite of small temperature difference between ice cylinder and solution.

Minimum Wetting and Distribution Rates in Falling Film Evaporators

Falling film evaporators are used extensively in the food industry for their ability to process heat sensitive liquids. A coherent liquid film is required to maintain heat transfer efficiency and minimize fouling. It is likely that most evaporator fouling occurs after film breakdown as the substance within the evaporator dries out. The minimum flow rate required to maintain a film is known as the minimum wetting rate which is defined as the minimum mass flow rate per unit circumference. In this work, minimum wetting rates were determined in a 1 m long, 48 mm internal diameter, vertical, stainless steel tube. Water and aqueous solutions of glycerol, alcohol and calcium chloride were used. These substances were chosen so as to give a wide range of properties such as viscosity (0.5-39 mPa s), density (950-1410 kg m–3), surface tension (35-90 mNm–1) and contact angle (64-98°). In a separate set of experiments, the minimum flow rate required to distribute liquid and completely wet the top of industrial evaporator tubes was measured using a range of sucrose solutions. The tube wetting results obtained fitted a dimensionless power law relationship well. Surface tension and contact angle had a strong influence on the wetting rate but viscosity and density were found to have very little effect. The minimum flow rates for distribution were found to nearly always exceed the minimum wetting rates showing that more attention needs to be given to distributor design.

Effect of the melting system sizes on the temperature and concentration combined melting of a vertical ice plate in a rectangular cavity

This paper is concerned with the melting of a vertical ice plate into a calcium chloride aqueous solution inside a rectangular cavity. The initial temperature of the ice plate and the mixture are both −5°C and the initial concentration of the mixture is 20 wt%. The effect of the liquid height H, the width W, the aspect ratio of the liquid region A (=H/W) and the initial ice plate thickness δ i on the transient melting mass per unit melting front area, M, is mainly considered numerically. M keeps a similar value in spite of H varied for A = 1 at early melting stage, however, becomes considerably influenced by H as melting progresses. The ice plate melts influenced by A for H = 20 mm fixed at early melting stage due to the fast development of the stagnant region and M decreases with increasing A (=1∼ 10). A dimensionless correlation of the transient melting mass, the aspect ratio and the melting time was presented under the restricted condition of H = 20 mm.

The Effect of Brine Ingredients on Carrot Texture during Thermal Processing in Relation to Pectin Depolymerization due to the β‐Elimination Reaction

ABSTRACT: Thermal texture degradation of carrots was studied at a temperature of 100 °C in aqueous solutions containing sodium chloride, citric acid, ascorbic acid, and ethylenediaminetetraacetic acid (EDTA) at different concentrations. To enhance the texture of the final product, the carrot samples were pretreated at 65 °C for 30 min in an aqueous calcium chloride solution (5 g/L). For all case studies considered, the pH of the solutions was adjusted to pH = 6.0. In parallel, both the changes in degree of esterification (DE) and the progress of the β‐elimination reaction of carrot pectin under the same conditions were investigated. The kinetic parameters for texture degradation (rate constant kt and final texture value [TP∞/TP0]) were estimated using a fractional conversion model. The results indicate that both the rate constant for texture degradation (kt) and the rate constant for the β‐elimination reaction (kb) increased with increasing additive concentration, while the final texture values (TP∞/TP0) and DE decreased with increasing additive concentration in all systems studied. A high correlation was observed between the relative rate constant for texture degradation and the relative rate constant for the β‐elimination reaction on the one hand, and the relative final texture value and the relative rate constant for the β‐elimination reaction on the other hand, suggesting that the influence of the solutes on texture degradation can be explained by their influence on the β‐elimination reaction.

Effect of Calcination Conditions on Phase Formation of Calcium Phosphates Ceramics Synthesized by Homogeneous Precipitation

Phase composition of calcium phosphate ceramics is a characteristic directly related to the biological response of implants due to the differences in mechanical and biochemical properties of these compounds. In this sense, it was evaluated in this work the crystalline phase evolution of calcium phosphates samples synthesized by wet precipitation route. Fixing Ca/P atomic ratio as 1.67, precipitation was carried out from heated aqueous solutions of calcium chloride and ammonium hydrogen phosphate, in ammonium medium (pH = 10). After washing and drying steps, calcination was performed at 600 to 1100 oC for 1 and 3 hours. Milled and pressed powders were sintered at 1250 oC for 1 hour. Samples were characterized by X-ray diffraction, chemical analysis, scanning electron microscopy, gaseous adsorption, laser diffraction and apparent density measurements. Results indicate the formation of a biphasic calcium phosphate ceramic containing hydroxyapatite as a major phase and β - tricalcium phosphate, the later obtained by heat treatment above 600 oC.

Novel Biomineralization for Hydrogels: Electrophoresis Approach Accelerates Hydroxyapatite Formation in Hydrogels

As a first step toward hydroxyapatite (HAp) formation in agarose hydrogels, we have tailored the internal chemistry using an electrophoresis approach. HAp was formed using aqueous solutions of calcium chloride and disodium hydrophosphate, which were set in a conventional agarose electrophoresis apparatus. Calcium and phosphate ions provided cations and anions, respectively, and were shown to migrate into the agarose hydrogel toward the corresponding electrode side. HAp was formed after colliding with each ion. The time needed to reach complete HAp formation was 30 min, and 130 ng of HAp was formed in 1 mg of agarose hydrogel when the equilibrium swelling state was reached. The electrophoresis approach accelerated the HAp formation, and the linear velocity of 1 mm/min was shown to be roughly 15 times larger than that of simple diffusion (0.06 mm/min).

Ion pairing in aqueous calcium chloride solution: Molecular dynamics simulation and diffraction studies

X-ray and neutron diffraction and molecular dynamics simulation studies were performed on 2.5 and 4.0 M aqueous solutions of calcium chloride. The aim of the work, beyond the determination of the solution structure, was to discuss the capability of each method to detect ion pair formation. It has been found that the diffraction methods are performing very well in the determination of Ca 2+–O distances: the obtained values fell in the range 2.43–2.46 Å. Further on, by applying the X-ray diffraction method ion pairs could be observed in the case of higher concentrated solution, but for neutron diffraction study, the most adequate isotope substitution method has to be chosen with care in order to be able to describe ion pairs in solution. The results of diffraction studies were compared to molecular dynamics simulation results; the latter ones were found to be in general accordance with the experimental findings. The smaller discrepancies between the simulation and the experimental results are coming from small differences in the ion–water and ion–ion distances, and they may be due to the potential model applied in the simulation and to the experimental uncertainties.

Development of mammalian cell‐enclosing calcium‐alginate hydrogel fibers in a co‐flowing stream

A jetting technique in a liquid-liquid co-flowing stream was applied to the preparation of mammalian cell-enclosing calcium-alginate (Ca-alg) hydrogel fibers of several hundred micrometers in cross-sectional diameter. One percent alginate aqueous solution was extruded from needles (270, 480, 940 microm inner diameter) into a co-flowing laminar stream of 100 mM aqueous calcium chloride solution. The extruded alginate solution was stretched by the CaCl(2) solution, which is known as a "jetting process", and the Ca-alg hydrogel fibers were formed by gelation of the alginate solution through the uptake of calcium ions in the CaCl(2) solution. The cross-sectional diameter of the hydrogel fibers could be controlled from approximately 100-800 microm by changing the velocities of the alginate and CaCl(2) solution, and the inner diameter of the needle. Approximately 95% of bovine carotid artery vascular endothelial cells remained alive after the process of preparing hydrogel fibers in a co-flowing stream, demonstrating that the cell-enclosing process scarcely influences the viability of the enclosed cells.

Visual observations of flow structure and melting front morphology in horizontal ice plate melting from above into a mixture

Visual observations reveal a complicated flow in the liquid melt and a melting front configuration resulting from horizontal ice plate melting from above into a 20 wt% calcium chloride aqueous solution. The initial temperature of the ice plate and the mixture are both −5°C. Small scale “mountain and valley” structures (∼1 mm) appear on the flat melting front just after melting begins, which have been called “sharkskin”. Innumerable upward and downward flows appear near the sharkskin and are controlled by its “mountain and valley” structure. These typical flows will considerably promote the melting of the ice plate to be 30% larger as compared to the numerically predicted results assuming a flat melting front (i.e., without the sharkskin), and also by three times larger compared with the results for melting from below.

Ion Binding to Cucurbit[6]uril: Structure and Dynamics

Molecular dynamics simulations are used to study the microscopic structure and dynamics of cations bound to cucurbit[6]uril (CB[6]) in water and in aqueous solutions of sodium, potassium, and calcium chloride. The molarities are 0.183 M for the salts and 0.0184 M for CB[6]. The cations bind only to CB[6] carbonyl oxygens. They are never found inside the CB[6] cavity. Complexes with Na(+) and K(+) mostly involve one cation, whereas with Ca(2+) single- and double-cation complexes are formed in similar proportions. The binding dynamics strongly depends on the type of cation. A smaller size or higher charge increases the residence time of a cation at a given carbonyl oxygen. When bound to CB[6], sodium and potassium cations jump mainly between nearest or second-nearest neighbors. Calcium shows no hopping dynamics. It is coordinated predominantly by one CB[6] oxygen. A few water molecules (zero to four) can occupy the CB[6] cavity, which is limited by the CB[6] oxygen faces. Their residence time is hardly influenced by sodium and potassium ions. In the case of calcium the residence time of the inner water increases notably. A simple structural model for the cation activity as "lids" over the CB[6] portal cannot, however, be identified. The slowing of the water exchange by the ions is a consequence of the generally slower dynamics in their presence and of their stable solvation shells.

Properties of Amorphous Calcium Carbonate and the Template Action of Vaterite Spheres

The fast mixing of aqueous solutions of calcium chloride and sodium carbonate could immediately result in amorphous calcium carbonate (ACC). Under vigorous stirring, the formed ACC in the precipitation system will dissolve first and, then, transform within minutes to produce crystalline forms of vaterite and calcite. After that, the solution-mediated mechanism dominates the transformation of the thermodynamically unstable vaterite into the thermodynamically stable calcite. Although ACC is the least stable form of the six anhydrous phases of calcium carbonate (CaCO(3)), it could be, however, produced and stabilized by a variety of organisms. To better understand the formation-transformation mechanism of ACC and vaterite into calcite, ex-situ methods (i.e., scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction spectroscopy) were used to characterize the formation-transformation process of ACC and vaterite in aqueous systems without organic additives, showing that ACC sampled at different conditions has different properties (i.e., lifetime, morphology, and spectrum characterization). It is also very interesting to capture the obviously polycrystalline particles of CaCO(3) during the transformation process from vaterite to calcite, which suggests the formation mechanism for the calcite superstructure with multidimensional morphology.

Viscosity of aqueous calcium chloride solutions at high temperatures and high pressures

Viscosity of six (0.10, 0.33, 0.65, 0.97, 1.40, and 2.00) mol kg −1 binary aqueous CaCl 2 solutions has been measured with a capillary-flow technique. Measurements were made at pressures up to 60 MPa. The range of temperature was from 293 to 575 K. The total uncertainty of viscosity, pressure, temperature, and composition measurements was estimated to be less than 1.6%, 0.05%, 15 mK, and 0.014%, respectively. The effect of temperature, pressure, and concentration on viscosity of binary aqueous CaCl 2 solutions was studied. The measured values of viscosity of CaCl 2(aq) were compared with data, predictions, and correlations reported in the literature. The temperature and pressure coefficients of viscosity of CaCl 2(aq) were studied as a function of concentration and temperature. The viscosity data have been interpreted in terms of the extended Jones–Dole equation for the relative viscosity ( η/ η 0) to accurate calculate the values of viscosity A- and B-coefficients as a function of temperature. The derived values of the viscosity B-coefficients were compared with the values calculated from the ionic B-coefficient data. The physical meaning parameters V and E in the absolute rate theory of viscosity and hydrodynamic molar volume (effective rigid molar volume of salt) V k were calculated using present experimental viscosity data. TTG model has been used to compare predicted values of the viscosity of CaCl 2(aq) solutions with experimental values at high pressures.

Optimization of vaterite synthesis for application to coating pigment of ink-jet paper

Calcium carbonate in the crystal form of vaterite can be expected as a coating pigment because of fineness of primary particles and the spherical secondary structure. So far, the interfacial reaction method has been applied to prepare vaterite particles. However, to avoid using volatile organic solvents, an aqueous system with no organic solvent was developed in this study. Consequently, vaterite was successfully synthesized from only two aqueous solutions of potassium carbonate and calcium chloride with no additive. As parameters of the reaction condition, temperature, agitation rate and effects of surfactants were examined. The optimum temperature of the reacting liquids was around 40 °C. Reduced volumes of the reacting liquids to intensify the agitation effect increased the vaterite ratio for a given homogenizer at a constantly rotating speed. Among surfactants used, there was no difference observed in the effect on vaterite generation. At a suitable condition about other parameters, pure vaterite was obtained even under no surfactant condition. In summary, it was speculated that the vaterite form was generated at an early stage of the reaction. At insufficient levels of shear stress, vaterite growth is not promoted and generated vaterite transfers spontaneously to calcite. Surfactants are assumed to adsorb onto surfaces of primary particles and trigger an orderly aggregation.

Modified carrageenan. 6. crosslinked graft copolymer of methacrylic acid and kappa-carrageenan as a novel superabsorbent hydrogel with low salt- and high pH-sensitivity

A novel, polysaccharide-based, superabsorbent hydrogel was synthesized through crosslinking graft copolymerization of methacrylic acid (MAA) onto kappa-carrageenan (κC), using ammonium persulfate (APS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. A proposed mechanism for κC-g-polymethacrylic acid (κC-g-PMAA) formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The effect of grafting variables, including MBA, MAA, and APS concentration, was systematically optimized to achieve a hydrogel with the maximum possible swelling capacity. The swelling kinetics in distilled water and various salt solutions were preliminarily investigated. Absorbency in aqueous salt solutions of lithium chloride, sodium chloride, potassium chloride, calcium chloride, and aluminum chloride indicated that the swelling capacity decreased with increased ionic strength of the swelling medium. This behavior can be attributed to the charge screening effect for monovalent cations, as well as ionic crosslinking for multivalent cations. The swelling of superabsorbing hydrogels was measured in solutions with pH ranging from 1 to 13. In addition, the pH reversibility and on-off switching behavior, at pH levels of 3.0 and 8.0, give the synthesized hydrogels great potential as an excellent candidate for the controlled delivery of bioactive agents.

Mineralization of calcium phosphate in reverse microemulsion

In the present study, reverse microemulsion was prepared to regulate the mineralization of calcium phosphate. Calcium chloride and sodium hydrogen phosphate aqueous solution were, respectively, dropped into the mixture of Span 80, Tween 80, and n-heptane to get two kinds of emulsions. n-Buranol was used to adjust the emulsions to transparent state. Calcium phosphate was prepared by adding phosphate microemulsion to Calcium microemulsion. Heating method was used to induce the phase separation. After being washed with acetone and ethanol, the mineralized deposition were studied with scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results indicated that the minerals in the deposition were mainly monetite (DCPA) and the nanosized needle-like DCPA exhibited the preferential orientation along 200 direction.

Effects of Salts on Mechanical Properties of Heated Rice Grains

The effects of sodium ion and calcium ion on hardness of rice grains such as Koshihikari, Yukinosei and Akihikari, were investigated using breaking stress and weight uptake measurements, and inner structures of the samples were observed via scanning electron micrographs. When the same rice species was heated in the deionized water, sodium chloride aqueous solution and calcium chloride aqueous solution, the magnitude of breaking stress became higher in a order: the deionized water < sodium chloride aqueous solution < calcium chloride aqueous solution. In the same kind salt solution, the magnitude became higher in a order: Koshihikara < Yukinosei < Akihikari. The value of weight uptake of the same rice grains was larger in a order: calcium chloride aqueous solution < sodium chloride aqueous solution < the deionized water. The circumference structures of rice grains heated in aqueous sodium chloride and calcium chloride solution looked more compact and had finer texture than those heated in the deionized water.

Energy efficient liquid desiccant-based dryer

A liquid desiccant-based dryer is developed that has higher energy efficiency compared to conventional hot air based drying systems used in industrial and agricultural sectors. Two-stage regeneration of the liquid desiccant, an aqueous solution of calcium chloride, is used to improve the energy efficiency. It is demonstrated that the liquid desiccant-based dryer is techno-economically superior. Contacting device is an important component in the absorber and regenerator of a liquid desiccant system. Carryover of liquid desiccant into the process and/or regenerated air streams is eliminated with the novel contacting device, which has 120–185% greater surface density compared to conventional packing. The air side pressure drop through the contacting device is very low. This paper presents the experimental results of a liquid desiccant-based dryer, designed for a paper tray drying application. It also includes the effect of variation of operating parameters and that of solution heat exchanger on specific moisture extraction rate (SMER). The average SMER of the liquid desiccant-based dryer is experimentally found to be 1.5 kg/kW h of heat. Energy savings and resultant reduction in CO 2 emissions is about 56% compared to conventional hot air- based dryer. Benefits will be more while drying temperature sensitive herbal, agricultural and pharmaceutical products.

Effect of cavity inclination on a temperature and concentration controlled double diffusive convection at ice plate melting

This paper is concerned with the double diffusive convection due to the melting of an ice plate into a calcium chloride aqueous solution inside a rectangular cavity. It is mainly considered the effect of the cavity inclination θ on the melting rate and the mean melting Nusselt- and Sherwood-numbers, experimentally as well as numerically. The ice plate melts spontaneously with decreasing temperature at the melting front even if initially there does not exist a temperature difference between the ice and the liquid. The concentration- and temperature-gradients near the melting front induce double diffusive convection in the liquid, which will affect the melting rate. Experiments reveal that the mean melting mass increases monotonically with increasing cavity inclination. The numerical analysis based on the laminar assumption predicts well the melting mass in the range of θ=0–90°, however, under-predicts the melting mass in the range of θ=90–180° as compared with the experimental results.

Apatite-forming ability of alginate fibers treated with calcium hydroxide solution.

Calcium alginate fibers were prepared by extruding an aqueous sodium alginate solution into an aqueous calcium chloride solution. The fibers were treated with a saturated aqueous calcium hydroxide solution for various periods and their apatite-forming ability was examined in a simulated body fluid (SBF). The calcium alginate fibers were treated with the aqueous calcium hydroxide solution for periods longer than five days formed apatite on their surfaces in SBF, and their apatite-forming ability improved with increasing calcium hydroxide treatment time. The amount of calcium ions released from the fibers also increased with increasing calcium hydroxide treatment time, resulting in acceleration of nucleation and growth of apatite on the fiber surfaces. The resultant apatite-alginate fiber composite is expected to be useful as a flexible bioactive bone-repairing material.