Search Results (7)

In this paper, sodium alginate (NaAlg) was used as functional monomers, bovine serum albumin (BSA) was used as template molecules, and calcium chloride (CaCl₂) aqueous solution was used as a cross-linking agent to prepare BSA molecularly imprinted carboxylated multi-wall carbon nanotubes (CMWCNT)/CaAlg hydrogel films (MIPs) and non-imprinted hydrogel films (NIPs). The adsorption capacity of the MIP film for BSA was 27.23 mg/g and the imprinting efficiency was 2.73. The MIP and NIP hydrogel film were loaded on the surface of the printed electrode, and electrochemical performance tests were carried out by electrochemical impedance spectroscopy (EIS) and differential pulse voltammetry (DPV) using the electrochemical workstation. The loaded MIP film and NIP film effectively improved the electrochemical signal of the bare carbon electrode. When the pH value of the Tris HCl elution solution was 7.4, the elution time was 15 min and the adsorption time was 15 min, and the peak currents of MIP-modified electrodes and NIP-modified electrodes reached their maximum values. There was a specific interaction between MIP-modified electrodes and BSA, exhibiting specific recognition for BSA. In addition, the MIP-modified electrodes had good anti-interference, reusability, stability, and reproducibility. The detection limit (LOD) was 5.6 × 10⁻⁶ mg mL⁻¹. Full article

Equilibrium molecular dynamics simulations are performed to examine the hydration behavior of Ca²⁺ and Cl⁻ across a wide range of salt concentrations (from 1 wt.% to 60 wt.% CaCl₂) in an aqueous solution. The predicted radial distribution functions (RDFs) and coordination numbers (CNs) of Ca²⁺–water, Cl⁻–water, and Ca²⁺–Cl⁻ agree with the previous studies conducted at concentrations below the solubility limit at room temperature. The hydration limit of aqueous calcium chloride solution is identified at 10 wt.% CaCl₂ as the CNs remain constant below it. Beyond the bulk solubility limit ~44.7 wt.% CaCl₂, a noticeable decrease in the CN of Cl⁻ and water is recorded, implying the saturation of the solution. The solvating water molecules decrease with increasing salt concentration, which can be attributed to the growth in the number of ion pairs. Full article

Fine powders of brushite CaHPO₄·2H₂O, ardealite Ca(HPO₄)_x(SO₄)_1−x·2H₂O (Ca(HPO₄)_0.5(SO₄)_0.5·2H₂O), and calcium sulfate dihydrate CaSO₄·2H₂O—all containing sodium chloride NaCl as a reaction by-product—were synthesized from 0.5 M aqueous solution of calcium chloride CaCl₂, sodium hydrophosphate Na₂HPO₄ and/or sodium sulfate Na₂SO₄. Powder of ardealite Ca(HPO₄)_x(SO₄)_1−x·2H₂O (Ca(HPO₄)_0.5(SO₄)_0.5·2H₂O) was synthesized by precipitation from aqueous solution of calcium chloride CaCl₂ and mixed-anionic solution simultaneously containing the hydrogen phosphate anion HPO₄²⁻ (Na₂HPO₄) and sulfate anion SO₄²⁻ (Na₂SO₄). Sodium chloride NaCl, presenting in compacts based on synthesized powders of brushite CaHPO₄·2H₂O, ardealite Ca(HPO₄)_x(SO₄)_1−x·2H₂O (Ca(HPO₄)_0.5(SO₄)_0.5·2H₂O) and calcium sulfate dihydrate CaSO₄·2H₂O, was responsible for both low-temperature melt formation and the creation of phase composition of ceramics. Heterophase interaction of components led to the resulting phase composition of the ceramic samples during heating, including the formation of chlorapatite Ca₅(PO₄)₃Cl in powders of brushite and ardealite. The phase composition of the ceramics based on the powder of brushite CaHPO₄·2H₂O containing NaCl as a by-product after firing at 800–1000 °C included β-Ca₂P₂O₇, and Ca₅(PO₄)₃Cl. The phase composition of ceramics based on the powder of ardealite Ca(HPO₄)_x(SO₄)_1−x·2H₂O (Ca(HPO₄)_0.5(SO₄)_0.5·2H₂O) containing NaCl as a by-product after firing at 800 and 900 °C included β-Ca₂P₂O_7, CaSO₄, and Ca₅(PO₄)₃Cl; after firing at 1000 °C, it includedCaSO_4, Ca₅(PO₄)₃Cl and Ca₃(PO₄)₂/Ca₁₀Na(PO₄)₇, and after firing at 1100 °C, it included CaSO₄ and Ca₅(PO₄)₃Cl. The phase composition of ceramics based on powder of calcium sulfate dihydrate CaSO₄·2H₂O containing NaCl as a by-product after firing at 800–1100 °C included CaSO₄ as the predominant phase. The phase composition of all ceramic samples under investigation consisted of biocompatible crystalline phases with different abilities to biodegrade. For this reason, the created ceramics can be recommended for testing as materials for treatment of bone defects using regenerative medicine methods. Full article

The glucosinolates which are specialized plant metabolites of Brassica vegetables are prone to hydrolysis catalyzed by an endogenous enzyme myrosinase (thioglycoside hydrolase, thioglucosidase) that exists in Brassica plant tissue causing volatile isothiocyanates release. Currently existing literature data on the inactivation of myrosinase is insufficient in particular for use in the analysis of volatile and odor compounds in vegetables rich in glucosinolates. In this study, the impact of different metal salts in effective inactivation of enzyme activity was investigated by solid-phase microextraction (SPME) and GC/MS system in aqueous samples and kohlrabi matrix. A saturated solution of calcium chloride which is commonly used to stop enzyme activity in plant tissue inactivates the myrosinase–glucosinolate system. However, even without the participation of myrosinase, it changes the reaction pathway towards nitrile formation. The model experiment shows that optimum efficiency in inhibition of the enzyme system shows iron(III) ions, silver ions, and anhydride sodium sulfate resulting in no volatile products derived from glucosinolates. However, in the kohlrabi matrix, the strongest enzyme inhibition effect was observed for silver salt resulting in no volatile products, also both anhydrous Na₂SO₄ and saturated CaCl₂ solution seem to be useful inhibitors in flavor studies. Full article

This paper addresses the analysis of the applicability of water as a working fluid for the new adsorptive heat transformation (AHT) cycle "Heat from Cold" (HeCol). The cycle proposed for cold countries operates at the ambient temperature below 0 °C. In this work, an aqueous solution of calcium chloride is proposed instead of liquid water to prevent the ice formation in the evaporator and condenser. The proposed water-based cycle is compared with the common methanol-based HeCol one in terms of the specific useful heat generated per cycle. The effect of the CaCl₂ solution on the cycle boundary pressures and its useful heat is studied both theoretically and experimentally. This approach can be extended to other adsorptive heat transformation cycles working at an evaporator or condenser temperature below 0 °C. Full article

In the last few years, the use of ionic liquid-based membranes has gained importance in a wide variety of separation processes due to the unique properties of ionic liquids. The aim of this work is to analyze the transport of nutrients through polymer inclusion membranes based on different concentrations of methyltrioctylammonium chloride, in order to broaden the application range of these kinds of membranes. Calcium chloride (CaCl₂) and sodium hydrogen phosphate (Na₂HPO₄) nutrients were used at the concentration of 1 g·L⁻¹ in the feeding phase. The evolution of the concentration in the receiving phase over time (168 h) was monitored and the experimental data fitted to a diffusion-solution transport model. The results show very low permeation values for CaCl₂. By contrast, in the case of Na₂HPO₄ the permeation values were higher and increase as the amount of ionic liquid in the membrane also increases. The surface of the membranes was characterized before and after being used in the separation process by scanning electron microscopy coupled to energy dispersive X-Ray spectroscopy (SEM–EDX) and elemental mapping analysis. The SEM–EDX images show that the polymer inclusion membranes studied are stable to aqueous solution contacting phases and therefore, they might be used for the selective transport of nutrients in separation processes. Full article

An existing idle cooling tower can be reversibly used as a heat-source tower (HST) to drive a heat pump (HP) in cold seasons, with calcium chloride (CaCl₂) aqueous solution commonly selected as the secondary working fluid in an indirect system due to its good thermo-physical properties. This study analyzed the effect of CaCl₂ mass fraction on the effectiveness (ε) of a closed HST and the coefficient of performance (COP) of a HP heating system using an artificial neural network (ANN) technique. CaCl₂ aqueous solutions with five different mass fractions, viz. 3%, 9%, 15%, 21%, and 27%, were chosen as the secondary working fluids for the HSTHP heating system. In order to collect enough measured data, extensive field tests were conducted on an experimental test rig in Changsha, China which experiences hot summer and cold winter weather. After back-propagation (BP) training, the three-layer (4-9-2) ANN model with a tangent sigmoid transfer function at the hidden layer and a linear transfer function at the output layer was developed for predicting the tower effectiveness and the COP of the HP under different inlet air dry-/wet-bulb temperatures, hot water inlet temperatures and CaCl₂ mass fractions. The correlation coefficient (R), mean relative error (MRE) and root mean squared error (RMSE) were adopted to evaluate the prediction accuracy of the ANN model. The results showed that the R, MRE, and RMSE between the training values and the experimental values of ε (COP) were 0.995 (0.996), 2.09% (1.89%), and 0.005 (0.060), respectively, which indicated that the ANN model was reliable and robust in predicting the performance of the HP. The findings of this paper indicated that in order to guarantee normal operation of the system, the freezing point temperature of the CaCl₂ aqueous solution should be sufficiently (3–5 K) below its lowest operating temperature or lower than the normal operating temperature by about 10 K. The tower effectiveness increased with increasing CaCl₂ mass fraction from 0 to 27%, while the COP of the HP decreased. A tradeoff between the tower effectiveness and the COP of the HP should be considered to further determine the suitable mass fraction of CaCl₂ aqueous solution for the HSTHP heating system. The outputs of this study are expected to provide guidelines for selecting brine with an appropriate mass fraction for a closed HSTHP heating system for actual applications, which would be a reasonable solution to improve the system performance. Full article