Aqueous Sodium Chloride Solutions Research Articles

Formation of Hybrid Membranes for Water Desalination by the Method of Membrane Distillation

A method has been developed for the formation of hybrid membranes consisting of a hydrophilic microporous substrate and a hydrophobic nanofiber polymer layer deposited by electroforming. A track-etched membrane made of polyethylene terephthalate was used as a hydrophilic microporous substrate, on the surface of which a thin layer of titanium was applied by magnetron sputtering to ensure adhesion of the nanofiber layer. Simultaneously, the titanium coating was used to make a conductive track-etched membrane that served as a collector electrode. It is been shown that the application of this method for the formation of polymer coatings when used as a starting material for the formation of polyvinylidene fluoride nanofibers makes it possible to obtain a layer with highly hydrophobic properties, the water contact angle of the surface of which, depending on the deposition density, averages 143.3 ± 1.3°. A study of the morphology of the nanofiber coating shows that it has a microstructure typical of non-woven materials. The nanofibers forming the porous system of this layer have a wide range in size. The study of the molecular structure of the nanofiber layer by IR-Fourier spectroscopy and X-ray diffraction analysis showed that its structure is dominated by the β-phase, which is characterized by a maximum dipole moment. It is been shown that the hybrid membranes of the developed sample provide high separation selectivity when desalting an aqueous solution of sodium chloride with a concentration of 26.5 g/l by membrane distillation. The salt rejection coefficient for membranes with a nanofiber layer density from 20.7 ± 0.2 to 27.6 ± 0.2 g/m2 in the studied mode of the membrane distillation process is 99.97−99.98%. It has been established that the use of a highly hydrophobic nanofiber layer with a developed pore structure in combination with a hydrophilic microporous base makes it possible to increase the productivity of the membrane distillation process. The value of the maximum condensate flow through the membranes is on average 7.0 kg m2/h and its depends on the density of the deposited nanofiber layer.

A Computational Study of the siRNA-Silica Nanoparticle Binding Process.

Molecular dynamics simulations were performed to investigate the structural and energetic features related to the direct binding of a short interfering RNA (siRNA) molecule on a silica nanoparticle functionalized with 3-aminopropyltriethoxysilane (APTES) groups, immersed in a sodium chloride aqueous solution at physiological concentration. Three different grafting densities of APTES were evaluated, namely, 2.7, 1.3, and 0.65 nm-2. Structural features as a function of the grafting density were analyzed and characterized in terms of density field profiles, pair correlation functions, and hydrogen bonding. The analysis of the orientation of siRNA during the binding process suggested that the oligonucleotide anchors to the surface by one of their ends in a tilted arrangement and subsequently, it rotates toward a surface-parallel stabilized configuration. Free energy of binding between siRNA and the silica nanoparticle was computed using the adaptive biasing force scheme. The results indicate that the binding process is essentially barrierless and consistent with a thermodynamically spontaneous reaction, yielding the largest binding free energy, of about ∼-36 kcal/mol at the largest APTES grafting density. However, a favorable binding was also observed at the lowest APTES density (∼-16 kcal/mol). a fact that would be advantageous to facilitate the further release of siRNA within the cell.

Thermodynamically Traceable Calorimetric Results for Aqueous Sodium Chloride Solutions from T = (273.15 to 373.15) K up to the Saturated Solutions: Part 2 —The Quantities Associated with the Partial Molar Heat Capacity

AbstractIn previous articles (Partanen and Partanen in J. Chem. Eng. Data 65: 5226 − 5239 (2020), J. Solution Chem. 52: 1352 − 1385 (2023)), we presented a traceable and transparent three-parameter model for thermodynamic activity and enthalpy quantities in aqueous NaCl solutions. The model is based on extended Hückel equations with parameters B, b1, and b2 and it applies from T = 273.15 to 373.15 K up to the saturated solutions. These studies demonstrate that the model explains the literature data of almost all thermodynamic quantities including apparent and partial molar enthalpies within experimental error. In the model, the ion-size parameter in the Debye–Hückel equation, B, is regarded as a constant while the parameters of the coefficients of the linear and quadratic molality terms, b1 and b2, respectively, possess quadratic temperature dependences. In this study, the results obtained for the heat capacity quantities of NaCl(aq) are considered. We show that the available heat capacity literature for these solutions can be predicted at least satisfactorily up to the saturated solutions with our new model. Following this success, we supplement the existing thermodynamic tables with the new values for the relative apparent and partial molar heat capacities for NaCl solutions. It is likely that the new tables contain the most reliable values determined so far even though no calorimetric data were used in the parameter estimation of our model. Graphical Abstract

Effect of Aqueous Electrolyte Composition on Efficiency of Electrochemical Post-Processing of Additive Manufacturing Products from Ti-6Al-4V Alloy Obtained by Selective Electron Beam Melting

The influence of the anionic composition of an aqueous electrolyte on the efficiency of the electrochemical leveling of the initial microgeometry of samples obtained by the selective electron beam melting (SEBM) at the following mode parameters was studied: current density – 20 A/cm2, initial interelectrode gap – 0.3 mm, average speed of electrolyte pumping – 12 m/c. Aqueous solutions of sodium chloride, nitrate, perchlorate and bisalt electrolytes based on them were studied. It was that aqueous solutions of sodium perchlorate have the best microleveling properties among the studied working media, which provides the ability to reduce the parameters Ra and Rz from values of 35 and 180 μm, respectively, to values of 3.2 and 20 μm during electrolysis of 30 s in a direct-flow electrolyzer. It was established that the microgeometry leveling corresponds to the model of the secondary distribution of dissolution rates; two main factors were identified that significantly influenced on the result: polarization of the electrodes and a decrease in the oxidation state of metal ions passing into the solution during electrochemical machining in the vicinity of the depression in relation to the protrusion due to changes in the local conditions of electrolysis. Microetching along grain boundaries in the studied electrolytes was not detected at the accepted parameters of the electrolysis mode.

An Electronic “Tongue” Based on Multimode Multidirectional Acoustic Plate Wave Propagation

This paper theoretically and experimentally demonstrates the possibility of detecting the five basic tastes (salt, sweet, sour, umami, and bitter) using a variety of higher-order acoustic waves propagating in piezoelectric plates. Aqueous solutions of sodium chloride (NaCl), glucose (C6H12O6), citric acid (C6H8O7), monosodium glutamate (C5H8NO4Na), and sagebrush were used as chemicals for the simulation of each taste. These liquids differed from each other in terms of their physical properties such as density, viscosity, electrical conductivity, and permittivity. As a total acoustic response to the simultaneous action of all liquid parameters on all acoustic modes in a given frequency range, a change in the propagation losses (ΔS12) of the specified wave compared with distilled water was used. Based on experimental measurements, the corresponding orientation histograms of the ΔS12 were plotted for different types of acoustic waves. It was found that these histograms for different substances are individual and differ in shape, area, and position of their extremes. Theoretically, it has been shown that the influence of different liquids on different acoustic modes is due to both the electrical and mechanical properties of the liquids themselves and the mechanical polarization of the corresponding modes. Despite the fact that the mechanical properties of the used liquids are close to each other, the attenuation of different modes in their presence is not only due to the difference in their electrical parameters. The proposed approach to creating a multi-parametric multimode acoustic electronic tongue and obtaining a set of histograms for typical liquids will allow for the development of devices for the operational analysis of food, medicines, gasoline, aircraft fuel, and other liquid substances without the need for detailed chemical analysis.

Corrosion Behaviour of Weld Metal of Ultra-High-Strength Steel Weldments in a Sodium Chloride Aqueous Solution.

As high-strength and ultra-high-strength steels are widely used in all kinds of modern welded constructions, a lot of research is carried out to investigate the mechanical properties of the weldments of these steels, but there is little information on such important characteristics as their corrosion behaviour. This research focuses on the corrosion behaviour of the weld metal of the weldments of S906QL and S700MC steels. The weld metal was tested electrochemically in a 3.5% NaCl aqueous solution via a potentiodynamic scan to determine the corrosion rate and its dependence on the welding gap. No influence of the welding gap on the corrosion rate was found, but the experimental results suggested that the corrosion rate depended on the chemical composition of the filler material and the microstructure of the weld metal.

Assessment of the Amino Acid L-Histidine as a Corrosion Inhibitor for a 1018 Carbon Steel in Aqueous Sodium Chloride Solution

Assessment of the Amino Acid L-Histidine as a Corrosion Inhibitor for a 1018 Carbon Steel in Aqueous Sodium Chloride Solution

Reflection coefficient of a natural sodium bentonite in aqueous mixed electrolyte solutions: positive and negative anomalous osmosis

A natural sodium bentonite was tested in the laboratory to measure its reflection coefficient, ω, in equilibrium with mixed aqueous solutions of sodium chloride (NaCl) and potassium chloride (KCl), with the aim of assessing the relative contribution of chemico-osmosis and diffusion induced electro-osmosis to the non-hydraulic component of the liquid flux in the presence of two cationic species, which diffuse at different rates in the pore solution. The former chemico-osmotic contribution is only related to the ionic partition effect in the bentonite pores, and causes ω to vary in the 0 to 1 range, whereas the latter electro-osmotic contribution is controlled by the diffusion potential, which spontaneously builds up across the bentonite layer in response to the different aqueous-phase diffusion coefficients of the ionic species. The theoretical interpretation of the obtained test results demonstrated that chemico-osmosis was the major contribution to ω when the testing solutions only comprised KCl. However, significant deviations in the values of ω from those expected for pure chemico-osmosis were observed for mixtures of NaCl and KCl, with both negative ( ω = −1.234) and positive ( ω = 1.040) anomalous values of the reflection coefficient, resulting from the enhanced influence of diffusion induced electro-osmosis.

Microstructures and Corrosion Behaviors of Non-Equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox)(x = 0, 0.23) High-Entropy Alloy Coatings Prepared by the High-Velocity Oxygen Fuel Method

The non-equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox) (x = 0, 0.23) high-entropy alloy (HEA) coatings were prepared by the high-velocity oxygen fuel (HVOF) method. The microstructures and corrosion behaviors of the HVOF-prepared coatings were investigated. The corrosion behaviors were characterized by polarization, EIS and Mott-Schottky tests under a 3.5 wt.% sodium chloride aqueous solution open to air at room temperature. The Al0.32CrFeTi0.73Ni1.50 coating is a simple BCC single-phase solid solution structure compared with the corresponding poly-phase composite bulk. The structure of the Al0.32CrFeTi0.73Ni1.27Mo0.23 coating, combined with the introduction of the Mo element, means that the (Cr,Mo)-rich sigma phase precipitates out of the BCC solid solution matrix phase, thus forming Cr-depleted regions around the sigma phases. The solid solution of large atomic-size Mo element causes the lattice expansion of the BCC solid solution matrix phase. Micro-hole and micro-crack defects are formed on the surface of both coatings. The growth of both coatings’ passivation films is spontaneous. Both passivation films are stable and Cr2O3-rich, P-type, single-layer structures. The Al0.32CrFeTi0.73Ni1.50 coating has better corrosion resistance and much less pitting susceptibility than the corresponding bulk. The corrosion type of the Mo-free coating is mainly pitting, occurring in the coating’s surface defects. The Al0.32CrFeTi0.73Ni1.27Mo0.23 coating with the introduction of Mo element increases pitting susceptibility and deteriorates corrosion resistance compared with the Mo-free Al0.32CrFeTi0.73Ni1.50 coating. The corrosion type of the Mo-bearing coating is mainly pitting, occurring in the coating’s surface defects and Cr-depleted regions.

Influence of Starch Admixtures and Silver Colloids Stabilised with Starch Hydrolysates on the Course of Electrochemical Potential Difference of Reinforcing Steel in High-chloride Environment

The purpose of the conducted study was to verify whether the use of concrete admixtures with modified starches and starches modified with stabilised silver colloids affects the course of electrochemical potential difference, and hence corrosion, of reinforcing steel in a chloride environment. In the tests, cross-linked starches and products of acid hydrolysis of starch (dextrins) were used as admixtures. The 1-molar aqueous solution of sodium chloride was used as an aggressive environment. The tests consisted of measuring the potential difference generated in the reinforcement corrosion cell on the surface for a period of 60 days and then assessing the risk of corrosion. The effect of the addition of starch derivatives on the properties of cement paste was investigated through a one-way ANOVA analysis of variance followed by post hoc tests. The test results showed that the use of concrete admixtures with cross-linked starches positively affects the passivation of the steel. The likelihood of reinforcing steel corrosion when using distarch phosphate, acetylated distarch phosphate and acetylated distarch adipate admixtures is less than 5%. The results obtained showed an improved effect on the passivation of reinforcing steel in cement composites. Additionally, concrete samples may have microbicidal properties.

Pattern transition of flow dynamics in a highly water-absorbent granular bed

An aqueous sodium chloride solution was injected at a controlled rate into a granular bed in a quasi-two-dimensional cell. The granular bed was made of dried, highly water-absorbent gel particles whose swelling rate was controlled by the salinity of the injected fluid. At a high salinity level (low swelling rate), high injection rate, and short timescale, the injected fluid percolated between the gel particles in an isotropic manner. Meanwhile, at a low salinity level (high swelling rate), low injection rate, and long timescale, the gel particles clogged the flow path, resulting in anisotropic branch-like structures of the injected fluid front. The transition of the injection pattern could be understood based on the ratio of the characteristic timescales of swelling and injection. Moreover, the clogged pattern showed an oscillatory pressure drop whose amplitude was increased with higher salinity. Such an oscillatory behavior observed in an injection process in swelling gel particles may be relevant in geological situation, such as fluid migration underground.

Effects of different freezing methods on muscle qualities and myofibrillar protein properties of red drum (Sciaenops ocellatus) during storage

The freezing of aquatic products without causing significant changes in quality is recently attracting much attention. In this study, the effects of air freezing (AF, -20 °C), blast freezing (BF, -35 °C), liquid nitrogen freezing (LNF), and immersion freezing (IF, -35 °C) by 20 % ethanol, 20 % propylene glycol, 10 % glycerol, and 10 % sodium chloride aqueous solutions, respectively, on muscle qualities and myofibrillar protein properties of the red drum were investigated. The results indicated that the freezing rate of IF was 2.66 cm/h, which was 6.33 times higher than that in AF groups. Compared with AF and BF, the ice crystals were smaller and more uniformly shaped, with properties of lower water migration and less texture softening after cryogenic liquid freezing of IF and LNF group aquatic products. Immersion freezing showed the same superiority in maintaining the freshness of fish fillets and retaining the protein structure as liquid nitrogen storage. Overall, IF has similar effects to LNF in maintaining muscle qualities and myofibrillar protein properties. This study describes a new freezing method that uses 20 % ethanol, 20 % propylene glycol, 10 % glycerol, and 10 % sodium chloride aqueous solutions as immersion freezing medium. The multi-compound freezing medium has the potential to be used for the freezing of aquatic products.

Effects of electric double layer on nanoscale boiling: Molecular dynamics approach

Electric double layers (EDL) are formed in aqueous solution of electrolytes near electrically charged wall. Such EDLs play a crucial role in many interfacial phenomena, among which a nanoscale boiling process was studied with molecular dynamics simulations. Evaporation and boiling were investigated with aqueous solution of sodium chloride (NaCl), a typical inorganic electrolyte, in contact with an artificially charged platinum substrate. The heating area temperature of the substrate was controlled in a range from 500 to 800K. The results indicate that the surface charge and the formed EDL suppress the bubble nucleation due to strengthened interaction between liquid molecules and the substrate. It was also shown that water molecules in the EDL exhibit orientational ordering even at higher temperatures.

A New Concept for Interpretation of the Viscoelastic Behavior of Aqueous Sodium Carboxymethyl Cellulose Systems.

Viscoelastic behaviors of aqueous systems of commercially available sodium carboxymethyl cellulose (NaCMC) samples with the degrees of substitution (DS) of approximately 0.68 and 1.3, and the weight-average molar masses (Mw) higher than 200 kg mol-1 dissolved in pure water and aqueous sodium chloride solutions were investigated over a wide concentration (c) range of NaCMC samples. The dependencies of the specific viscosity (ηsp), the average relaxation time (τw), and the reciprocal of the steady-state compliance (Je-1) on c were discussed. The relationships ηsp ∝ c3, τw ∝ c2, and Je-1 ∝ c, characteristic of the rod particle suspensions, were clearly observed in a range lower than the c where the critical gel behavior was observed. Thus, a new concept based on the rheology of rod particle suspensions was employed to interpret the viscoelastic behaviors obtained in the c range. In this context, NaCMC polymer molecules are assumed to behave as extended rod particles with length (L) and diameter (d), including effective electrostatic repulsive distances, due to the dissociation of Na+ in aqueous systems. Thus, the number density of polymer molecules is given to be ν = c/Mw, and viscoelastic parameters such as ηsp, τw, and Je-1 are calculated using the theoretical model for rod particle suspensions proposed by Doi and Edwards. This concept reasonably described not only the viscoelastic data obtained in this study but also those from other groups using NaCMC samples with different DS and Mw values.

Anti‐fouling capacity enhancement of thin‐film composite polyamide membrane by chitosan graft polymerization methods

AbstractThis study aimed to improve the anti‐fouling properties of a thin‐film composite polyamide membrane by modifying it with chitosan and acrylic acid using UV‐induced and Redox‐initiated graft polymerization methods. The modified membrane's separation performance was evaluated by measuring the flux and retention of sodium ions in water during filtration. The anti‐fouling capacities of the modified membranes were determined by measuring the maintained flux ratios and irreversible fouling factors during the 8‐h filtration of aqueous solutions of sodium chloride at different concentrations (1000 and 10,000 ppm). In addition, by evaluating the membrane's surface properties using various methods, including field emission scanning electron microscopy, attenuated total reflection – Fourier transform infrared spectroscopy, and water contact angle measurements, we have demonstrated the validity of the experimental results. Our results showed that the grafted membranes under UV irradiation or redox initiators had enhanced anti‐fouling properties while maintaining salt retention. The modified membranes fabricated by UV‐induced or Redox‐initiated technique had superior anti‐fouling capabilities, with irreversible fouling factors and maintained flux ratios of around 8% and 43%, respectively, after 8 h of filtration, compared to only 12% and 36% for the unmodified membrane. These findings suggest that the modified membranes have the potential for use in filtration systems to prevent the fouling phenomenon.

Diffusivities in water or aqueous solutions of sodium chloride with dissolved hydrogen and methane by dynamic light scattering

Knowledge of diffusion in water or aqueous solutions of sodium chloride with dissolved hydrogen and methane is important for geological hydrogen storage. This study examines the accessibility of diffusivities in the corresponding mixtures through dynamic light scattering at macroscopic thermodynamic equilibrium and provides corresponding data for hydrogen-storage-relevant temperatures T up to 393 K and pressures up to 20 MPa. The thermal and mutual diffusivities are simultaneously accessible in mixtures of water and hydrogen. Moreover, for water with dissolved mixtures of hydrogen and methane, the thermal diffusivity and an apparent diffusivity related to the diffusion of the gas mixture can be accessed. In aqueous solutions of sodium chloride at T > 300 K, a strong molecular association leading to a quasi-static light-scattering pattern in the liquid sample was observed, which hindered the determination of the molecular gas diffusivities. However, the salt diffusion coefficient was accessible for all T values.

Robust and stable organic sulfonate sodium salt-coated superhydrophilic mesh for ultra-fast gravity-drive oil-water separation

Due to its special wetting behavior and high selectivity, super-wetting mesh is considered as an ideal candidate material for efficient separation of water/oil mixture. However, the oil-water separation mesh suffers from the problems of poor stability and durability, leading to the failure of the separation. In this paper, a robust and stable superhydrophobic/superhydrophilic copper mesh had been successfully prepared by decorating the copper mesh via the chemical grafting of the 3-thiol-propyl trimethoxysilane (KH590) and the subsequent reaction with 2-acrylamide-2-methylpropane-1-sulfonate sodium (AMPS). It showed that the KH590 condensation compound was tightly coated on the surface and the superhydrophobic copper mesh (SUCM) possessed excellent superhydrophobicity towards various liquid droplets with a WCA of higher 150° and a sliding angle lower 5°, while the superhydrophilic copper mesh (SICM) had promising anti-oil pollution property with WCA near 0°. The SUCM and SICM also had excellent acid and alkali resistance. The obtained SICM had preeminent separation efficiency higher 99% and extremely high permeability flux of 33,441 L·m−²·h−¹ for gravity-driven toluene-water separation, and possessed excellent recyclability even after 20 cycles. Moreover, the SICM could be used to separate the oil-water mixture of aqueous solution with different pH (pH=5/7/8) and aqueous sodium chloride solution with different concentrations (5%/25%/50%/saturated aqueous sodium chloride solution). In addition, the SICM had outstanding anti-abrasion mechanical stability. This work provided a simple and effective method for the preparation of special wettability materials with excellent acid/alkali resistance and mechanical stability, and promoted the practical application of oil/water separation mesh.

Corrosion behavior of two Cu‐based shape memory alloys in NaCl solution: An electrochemical study

AbstractThe corrosion behavior of two different Cu–Al–Mn–Ni alloys, pseudoelastic and pseudoplastic, was studied in a 0.6 M sodium chloride aqueous solution by monitoring the open circuit potential for 100 h and characterizing the resulting corrosion products. Electrochemical impedance spectroscopy analysis detected three processes related to the electrochemical double layer, a passive film and a diffusive contribution associated with the dissolution/precipitation of corrosion products. Potentiodynamic scans revealed a cathodically controlled corrosion mechanism and the presence of active–passive behavior at anodic potentials for both alloys studied. Polarization of the samples at selected potentials in the anodic branch allowed the investigation of the reactions involved, highlighting an improved corrosion resistance of the pseudoelastic alloy. The corrosion rates of the pseudoelastic and pseudoplastic alloys, after 100 h of immersion, were determined to be 0.007 and 0.011 mmpy, respectively. The post‐experiment characterization was carried out by means of scanning electron microscopy, micro‐Raman spectroscopy and X‐ray diffraction, supporting the electrochemical results.

Electrochemical conversion of contaminant p-nitrophenol to p-aminophenol and high-value p-quinones: Mechanism, kinetics and modeling

Understanding the chemistry of contaminant p-nitrophenol (p-NP) in electrochemical systems is of importance to remove it from wastewater and to produce high-value products such as quinones. In this study, redox experiments in a system initially containing an aqueous solution of sodium chloride and p-NP at pH 5 and 25 °C were performed in an electrochemical reactor with low-cost steel electrodes. The reactor was operated at 0.1 and 0.2 A, and at initial p-NP concentrations of 4.04×10−5, 6.97×10−5 and 10.3×10−5 M. Air and argon were bubbled at the bottom of the cathode to have solutions saturated with O2 (7.7 mg L−1) and free of dissolved O2. At these conditions p-NP was completely converted to less toxic and more valuable p-hydroquinone and p-aminophenol in an hour. The reaction rates were individually controlled by the steps of electron transfer and adsorption of p-NP at the cathode surface. In the presence of dissolved O2, p-hydroquinone and p-aminophenol were intermediate species oxidized to p-benzoquinone, and p-quinoneimine in the greatest amount, respectively. The rate constants for the reactions were determined on the basis of kinetic results obtained by liquid chromatography and spectrophotometry. The suggested mechanism, and the innovative kinetic model involving Langmuir-Hinshelwood rate expressions for the surface reactions, were consistent with results from mass spectrometry and total organic carbon. For the first time for this kind of kinetic model, it was also able to reproduce a large set of kinetic data of electroreduction of p-NP with iron electrodes obtained by independent researchers at several different conditions.

Corrosion Behavior of Chromium Conversion Coated AZ91C Magnesium Alloy in Sodium Borate and Sodium Chloride Aqueous solutions

A chromium containing film was deposited on the surface of the investigated AZ91C magnesium alloy by chemical conversion process. The microstructure and surface morphology of the as- received and coated alloys were initially characterized by optical microscope. The corrosion behavior of AZ91C before and after coating was studied through weight loss technique by immersion in 3.5% NaCl and borate solutions at various concentrations and pH values. Surface corrosion products and passivation films were analyzed by X-ray diffraction. The obtained results showed that AZ91C coated with chromium conversion coating exhibits enhanced corrosion resistance, furthermore X-ray diffraction revealed that corrosion damage was mainly caused by formation of crystalline phase Mg(OH)2. The addition of borate with different concentration enhanced the protection with efficiency of 86% recorded at 0.2N sodium borate concentration and 3.5% NaCl.Corrosion behavior