NaCl Aqueous Solution Research Articles

Gamma-irradiated janus electrospun nanofiber membranes for desalination and nuclear wastewater treatment

This study presents the fabrication of double-layer electrospun nanofibrous membranes (DL-ENMs) using polyvinylidene fluoride (PVDF) and polyether sulfone (PES) based polymers with different degrees of hydrophilicity (PES, sulfonated PES, and PES with hydroxyl terminals). A comparative analysis was carried out with single-layer electrospun nanofiber membranes (SL-ENM) with a total thickness of about 375 μm. Using feed solutions, including sodium chloride, sodium nitrate, and simulated nuclear wastewater (SNWW), the performance of DL-ENMs was evaluated for desalination and radionuclide decontamination by direct contact membrane distillation (DCMD) and air gap membrane distillation (AGMD) techniques. The results showed that DL-ENMs, especially those incorporating a sulfonated PES-based hydrophilic layer, exhibited superior permeate fluxes, reaching values of 72.72 kg/m2.h and 73.27 kg/m2.h in the DCMD using aqueous feed solutions of NaCl and NaNO3, respectively, and 70.80 kg/m2.h and 41.96 kg/m2.h using aqueous feed solutions of SNWW in DCMD and AGMD, respectively. Both SL-ENMs and DL-ENMs exhibited high rejection efficiencies and decontamination factors for the feed solutions (>99.9%). In addition, the prepared ENMs were exposed to gamma radiation to evaluate their applicability in real-life applications. The result of irradiation revealed the negative impact of gamma radiation on the fluorine content of PVDF which could be a critical point in using PVDF as a hydrophobic material for decontaminating nuclear wastewater by membrane distillation.

Corrosion resistance of squeeze cast magnesium alloy AM60-based hybrid nanocomposite coated with plasma electrolytic oxidation

ABSTRACT Plasma electrolytic oxidation (PEO) coating with NaAlO2 and KOH electrolytes was applied on the surfaces of as-cast AM60 (PEO-AM60), 7 vol.% Al2O3 fibres/AM60 (PEO-7FC) and 7 vol.% Al2O3 fibres + 3 vol.% Al2O3 nano-sized particles/AM60 (PEO-MHNC-7F3NP) to improve their corrosion resistance. The SEM and EDS analyses indicated that the PEO coating process formed a porous and dense layer on the substrate surface, as well as MgAl2O4 was the major concentration of the coating. The thickness of PEO coating on the 7FC and MHNC-7F3NP composites was slightly less than the coating on the AM60. The electrochemical corrosion tests were carried out in 3.5% NaCl aqueous solution at room temperature for investigating the corrosion behaviour of the as-cast AM60 and the composites after applying the PEO coating. The PEO coating increased the corrosion resistance of the AM60 alloy and the 7FC and MHNC-7F3NP composites to 342.81, 301.73 and 290.44 from 4.07, 2.08 and 1.88 kΩ∙cm2. By comparing the corrosion test results of the coated AM60 and the composites with those of the uncoated counterparts, it was found that the PEO coating significantly improved the corrosion resistance by up to 154 times. The addition of nano-sized particles barely increased the corrosion rate of the composite.

Microbially formed Mn(IV) oxide as a novel adsorbent for removal of Radium

Radioactivity of Ra isotopes in natural waters is of serious concern. Control of 226Ra concentrations in tailings ponds, which store waste from U ore extraction processes, is an important issue in mill tailings management. In this study, we tested microbially formed Mn(IV) oxide as an adsorbent for removal of Ra in water treatment. Biogenic Mn(IV) oxide (BMO) was prepared using a Mn(II)-oxidizing fungus, Coprinopsis urticicola strain Mn-2. First, adsorption experiments of Sr and Ba, as surrogates for Ra, onto BMO were conducted in aqueous NaCl solution at pH 7. Distribution coefficients for Ba and Sr were estimated to be ∼106.5 and ∼104.3 mL/g, respectively. EXAFS analysis indicated that both Sr and Ba adsorbed in inner-sphere complexes on BMO, suggesting that Ra would adsorb in a similar way. From these findings, we expected that BMO would work effectively in removal of Ra from water. Then, BMO was applied to remove Ra from mine water collected from a U mill tailings pond. Just 7.6 mg of BMO removed >98% of the 226Ra from 3 L of mine water, corresponding to a distribution coefficient of 107.4 mL/g for Ra at pH ∼7. The obtained value was convincingly high for practical application of BMO in water treatment. At the same time, the high distribution coefficient indicates that Mn(IV) oxide can be an important carrier and host phase of Ra in the environment.

Fabrication and anti-corrosion performances of robust superhydrophobic surface on NAB via solution-etching

A labyrinth microstructure interconnected by micron and submicron acicular structures was successfully prepared by immersing nickel-aluminum bronze in 9 wt% FeCl3·6H2O solution at room temperature for 40 min. After being modified with 1H, 1H, 2H, 2H-perfluorodecyltriethoxysilane (FAS-17), the microstructure surface displays robustly low-adhesion superhydrophobicity, and the water contact angle is above 160 ° on it. In addition, the superhydrophobic surface exhibits excellent corrosion resistance and stability in 3.5wt % NaCl aqueous solution and corrosion solution with different pH values.

Corrosion performance and mechanisms of tantalum coatings on 316 stainless-steel in subcritical aqueous solutions of NaCl and NaBr

The corrosion behavior of 316 stainless-steel with a tantalum (Ta-316) coating deposited using PVD technology was investigated in subcritical environments containing Cl− and Br− at 290 °C and 6 MPa. The corrosion rate of Ta-316 continuously decreased with increasing exposure time, demonstrating its high corrosion resistance. A thin film, mainly composed of Ta2O5, formed on the surface of the tantalum coating, preventing the diffusion of substrate elements. The corrosion process and mechanism of Ta-316 were also examined.

Solubility of CO in water and NaCl(aq) at high pressures

Experimental measurements of CO solubility in water and in NaCl(aq) solutions are reported at temperatures, pressures and salt molalities of relevance to geological carbon storage: (323.15 to 423.15) K, (2 to 28) MPa and (2 and 4) mol·kg−1, respectively. The expanded relative uncertainty of the CO solubility is estimated to be 4.4% at 95% confidence intervals. This study provides the first data for CO solubility in brine with high molality of salt. The results from this study were used to develop simple models for the solubility of CO in aqueous NaCl solutions as a function of temperature, pressure and salt molality dependent, up to 4 mol·kg−1.

Effect of Scanning Strategy on the Manufacturing Quality and Performance of Printed 316L Stainless Steel Using SLM Process.

In this study, the effects of Z-0°, Z-67°, Z-90°, I-67°, and S-67° scanning strategies on the surface morphology, microstructure, and corrosion resistance of the specimens in SLM316L were systematically studied. The results show that the partition scanning path can effectively improve the manufacturing quality of the specimen, reduce the cumulative roughness layer by layer, and increase the density of the specimen. The scan path of the island partition of the fine partition is better than that of the strip partition; moreover, the 67° rotation between each layer reduces the accumulation of the height difference of the melt pool, fills the scanning gap of the previous layer, and improves the molding quality of the sample. Electrochemical tests were performed in an aqueous solution of NaCl (3.5 wt%), including open-circuit potential (OCP), dynamic potential polarization, and electrochemical impedance spectroscopy (EIS). The results show that the specimen with a 67° rotation between each layer achieves stability of the surface potential in a short time, and the I-67° specimen exhibits good corrosion performance, while the Z-0° specimen has the worst corrosion resistance.

Speciation studies of a Bisphosphonate Drug. New thermodynamic insights of Sodium Alendronate with Ca2+ and Mg2+ in NaCl aqueous solution (0.10 ≤ I/mol kg-1 ≤ 1.02)

The thermodynamics of interaction of a second-generation bisphosphonate drug, 4-amino-1-hydroxy-1-phosphonobutyl phosphonic acid mono sodium (sodium alendronate) with H+, Ca2+ and Mg2+ has been investigated. The protonation constants were determined in NaCl and (C2H5)4NI aqueous solutions at different ionic strengths (0.10 ≤ I/mol kg-1(H2O) ≤ 1.02) and temperatures (288.15 ≤ T/K ≤ 310.15) by using the ISE-[H+] potentiometry. The differences of the log KiH in the two ionic media were interpreted in terms of activity coefficient variations and formation of Na+ weak complexes. The interactions with Mg2+ and Ca2+ were studied in NaCl(aq) (0.10 ≤ I/ mol kg-1 (H2O) ≤ 1.02) and T = 298.15 K. Two different speciation models were obtained; Ca2+: CaH2L, CaHL, CaL. Mg2+: MgH3L, MgH2L, MgHL, MgL. The dependence of the thermodynamic parameters on the ionic strength and temperature was modelled by means of the Specific Ion Interaction Theory (SIT) and a modified Debye-Hückel equation including a term for the dependence on T/K. The first two protonation equilibria are exothermic, and the reactions are not favoured by an increase of the temperature whilst the last two are endothermic. The entropic contribution resulted to be the driving force of the reactions. The sequestering ability of alendronate towards the two metal cations was quantified by means of the pL0.5 parameter calculated at different pHs and ionic strengths. It resulted that alendronate has a higher sequestration toward Mg2+ with respect to Ca2+. A simulation of the alendronate behaviour in human blood plasma was carried out.

Effect of Temperature on Ultrasonic Degradation of Sodium Poly(Styrene Sulfonate): Analysis of Online Viscometric Data with Theoretical Models and Machine Learning Approaches

The effect of temperature (15, 20, 25, 30, and 35 °C) on the ultrasonic degradation of sodium poly(styrene sulfonate) polyelectrolyte (5.10−3 g/ml) in aqueous NaCl solutions (2.75 m) was investigated. Using the thousands of data obtained by an online viscometer monitoring technique, the degradation kinetics, and the effect of temperature on this process were analyzed in detail with 12 theoretical models reported in the literature. The Giz, OHM, and Tang-Goto models were found to give good results, and these models were selected to evaluate the effect of temperature on the ultrasonic polymer degradation. The degradation constant and the limiting molecular weight at which no polymer chain scission occurs were found to decrease with increasing temperature for all models. Furthermore, modeling was performed using popular machine learning algorithms, such as Multilayer Perceptron, Adaptive Neuro-Fuzzy Inference System, Long Short-Term Memory, Gradient Boosting Regression, Light Gradient Boosting Machine, eXtreme Gradient Boosting Regressor, CatBoost, and Random Forest. The best results were obtained with the Long Short-Term Memory, a deep learning approach. In addition, optimization techniques, such as Particle Swarm Optimization, Genetic Algorithm, Artificial Bee Colony, Clustering, and Global Optimization Method based on a parabolic approach, were used to determine the optimum molecular weight evolution and degradation temperature.

Optimization of Zwitterionic Polymers for Cell Cryopreservation.

Cryopreservation techniques are valuable for the preservation of genetic properties in cells, and the development of this technology contributes to various fields. In a previous study, an isotonic freezing medium composed of poly(zwitterion) (polyZI) has been reported, which alleviates osmotic shock, unlike typical hypertonic freezing media. In this study, the primitive freezing medium composed of emerging polyZI is optimized. Imidazolium/carboxylate-type polyZI (VimC3C) is the optimal chemical structure. The molecular weight and degree of ion substitution (DSion) are not significant factors. There is an impediment with the primitive polyZI freezing media. While the polyZI forms a matrix around the cell membrane to protect cells, the matrix is difficult to remove after thawing, resulting in low cell proliferation. Unexpectedly, increasing the poly(VimC3C) concentration from 10% to 20% (w/v) improves cell proliferation. The optimized freezing medium, 20% (w/v) poly(VimC3C)_DSion(100%)/1% (w/v) NaCl aqueous solution, exhibited a better cryoprotective effect.

Investigation on recrystallization of cryoprotectant solutions during warming under alternating electric fields

In the field of cryopreservation, recrystallization during rewarming is a significant factor leading to cryo-injury, causing ice crystal-induced mechanical injury to biological samples. Currently, methods, such as adding ice recrystallization inhibiting agents and increasing warming rates, have been adopted to reduce recrystallization injury. These methods also greatly increase the potential toxicity risk and engineering difficulty of cryopreservation. Accumulating research has progressively demonstrated that application of an electromagnetic field during cryopreservation can influence the preservation efficacy. However, the mechanism of action of the electric field has remained a subject of ongoing debate. We observed the recrystallization phenomenon of cryoprotectant solutions under a polarized light microscope and discovered promising experimental results. The electric field strength did not exhibit a discernible impact on the ice crystal size, while electric field frequency exerted a more significant impact. We found that at specific frequencies, the ice crystal size and growing rate were significantly affected during annealing. Compared to no electric field, an alternating electric field with a voltage of 10 V and a frequency of 5 × 104 Hz increased the recrystallization areas of a 15% (w/v) propylene glycol solution by 57%. And an alternating electric field with a voltage of 3 V and a frequency of 5 × 108 Hz decreased the recrystallization area of a 0.9% (w/v) NaCl aqueous solution by 9.9%. Different types of cryoprotectants exhibit varying responses to alternating electric fields frequency. These findings prompt us to reevaluate the role and mechanism of alternating electric fields in the cryopreservation of biological materials.

An accurate model for the solubilities of anhydrite in H2O–NaCl solutions at temperatures up to 1073 K, pressures up to 14,000 bar, and mole fractions of NaCl up to 0.3

An accurate density-based solubility model is established for anhydrite in H2O–NaCl solutions, which is valid for temperatures up to 1073 K, pressures up to 14,000 bar, and mole fractions of NaCl (xNaCl) up to 0.3. The isobaric linear dependence of the mineral solubility logarithm on the solvent density logarithm should be a common phenomenon similar to isothermal linear dependence, particularly at relatively high pressures. The terms about P in the equations of the density-based model are rational and necessary to elevate the accuracy of mineral solubility models. This model reproduces the complicated changing trends of anhydrite solubility with temperature, pressure, and xNaCl. Compared to numerous experimental data, the average relative deviations of calculated anhydrite solubilities in water and the aqueous NaCl solution are 3.52% and 9.64%, respectively, which are within experimental uncertainties. According to this model, the anhydrite deposition would result from any salinity variation departing from the specified xNaCl in skarn- or porphyrite-type iron ore-forming hydrothermal fluids.

Corrosion Performance of Epoxy/Sulfur–Selenium Coating on Q235 Steel

Sulfur powder (99.99%) and selenium powder (99.99%) were mixed and heated to approximately 300 °C to obtain an S-Se alloy. It has good flowability at 130 °C and can be applied to Q235 steel to obtain a S-Se coating. Epoxy was used as a filler, and the S-Se alloy was applied as a coating. This combination was utilized to create the composite coatings of epoxy/sulfur–selenium (E/S-Se). To investigate the corrosion resistance of this coating on Q235 steel substrate, we conducted measurements and obtained electrochemical impedance spectra (EIS) and linear polarization curves (LPC). These measurements were performed in a three-electrode cell within an electrochemical workstation using a 3.5 wt.% NaCl aqueous solution. By comparing bare Q235 steel, S-Se, and E/S-Se, the study found that the E/S-Se coating had a higher self-corrosion potential (−0.484 V vs. SCE) and the lowest self-corrosion current density (2.361 × 10−11 A/cm2). The purpose was to simulate the corrosive environment experienced by condensate return pipe walls in petroleum refining equipment. Additionally, experiments were carried out using 0.01 mol/L HCl solution as the corrosion medium at different temperatures (40 °C, 60 °C, 80 °C). The results indicated that the E/S-Se coating exhibited a lower corrosion rate compared to the Q235 steel substrate. Under immersion conditions at 40 °C and 60 °C, no corrosive substances were detected on the surface of the coating. The test results demonstrated that the E/S-Se coating exhibited superior corrosion resistance compared to the Q235 substrate, providing up to 99% protection for the substrate.

On the Mechanism of Self-Assembly of Fibrinogen in Thrombin-free Aqueous Solution.

Fibrinogen dissolved in 0.12 M aqueous NaCl solution at a pH of 6.6 exhibits self-assembly in response to a lowering of the NaCl concentration to values equal to or lower than 60 mM. As has been established in a preceding work (Langmuir 2019, 35, and 12113), a characteristic signature of the self-assembly triggered by a drop in ionic strength is the formation of large globular particles. Growth of these particles most likely obeys a coalescence-like process also termed a step growth process. In order to extend this knowledge, the present work first optimized the protocol, leading to highly reproducible self-assembly experiments. Based on this optimization, the work succeeded in identifying an initial stage, not yet accessible, during which rigid short fibrils grow in close analogy to the thrombin-catalyzed polymerization of fibrin. In addition, first suggestions could be made on the transformation of these fibrils into larger aggregates, which upon drying turn into thick fiber-like ropes.

Study of helminth eggs (Ascaris suum) inactivation by anaerobic digestion and electrochemical treatment

Background The use of insufficiently treated wastewater or Faecal sludge in agriculture raises concerns because of the pathogen content. Helminth eggs (HE) are one of the most crucial pathogens for ensuring public health and safety. Widely used disinfection treatment methods do not guarantee the complete inactivation of helminth eggs. The current study evaluated the effectiveness of anaerobic digestion and electrochemical process on helminth (Ascaris suum) egg inactivation. Methods Lab-scale biochemical methane potential (BMP) assay was conducted by spiking A. suum eggs in a serum bottle. Total solid (TS), volatile solid (VS), pH, biogas production and its composition, and volatile fatty acids (VFA) were analyzed along with A. suum inactivation every third day for the initial 15 days and fifth day for 45 days. In the second set of experiments, a hypochlorite (4700 ppm) solution was generated by electrolysis of aqueous NaCl solution in a membrane-less electrochemical cell. The hypochlorite was diluted (940, 470, 235, and 156ppm) in wastewater, spiked with A. suum eggs and then examined for inactivation at regular intervals. Results The results of the anaerobic digestion treatment documented 98% inactivation of A. suum eggs (0.15 eggs/mL) in 35 days and remained at 0.14 eggs/mL until day 45. Correlation analysis revealed a positive relationship between non-viable eggs and pH and a negative relationship with all the other parameters. Electrochemical treatment achieved 10% inactivation at 940 ppm concentration in 24h. Conclusions This study revealed that the inactivation of A. suum eggs by anaerobic digestion or electrochemical treatment is a combined effect of more than one parameter.

Electrogeneration of Hypochlorite Ions using a Dimensionally Stable Anode-Type (Ti/PtPd(10%)Ox) Electrode

<p>The study examined the electrogeneration of hypochlorite ions (ClO<sup>−</sup>) via electrolysis of aqueous NaCl solutions using a dimensionally stable anode-type (DSA-type) electrode based on platinum and palladium oxides supported on titanium mesh (Ti/PtPd(10%)O<sub>x</sub>). The electrogenerated ClO<sup>−</sup> was quantified on the basis of the absorption band at 292 nm (A<sub>λ</sub> = 292) of the UV-Vis spectrum. The effect of initial pH, concentration of NaCl, cell potential difference and electrolysis time were investigated in this study. The results showed that the electrolysis of aqueous NaCl solutions increases the solution pH up to high values (≥ 8.0) that favor the formation of ClO<sup>−</sup> over chlorine or hypochlorous acid. The hypochlorite concentration increases significantly at pH values > 7.0 and shows a linear trend with increasing NaCl concentration and with increasing cell potential difference. When the cell potential and NaCl concentration are held constant, the maximum hypochlorite value during electrolysis depends on both the cell potential and NaCl concentration. The Ti/PtPd(10%)O<sub>x</sub> anode favors the production of hypochlorite ions, making this anode a promising material for use in electrochemical oxidation of wastewater via an indirect mechanism.</p>

Complete thermal characterization of liquids by front photopyroelectric configuration using the reference sample method

We explored the use of the front photopyroelectric (FPPE) configuration and the reference sample method to determine the thermal properties of liquid samples such as extra virgin olive oil and aqueous glycerol (GL), ethylene glycol (EG), and sodium chloride (NaCl) solutions. The thermal diffusivity (α) and thermal conductivity (k) were determined from photopyroelectric phase and amplitude signals, respectively, using water as a reference. The thermal effusivity (e) and volumetric heat capacity (ρc) were also determined based upon both obtained thermal properties. All thermal properties of GL and EG in aqueous solutions decrease as their volume fraction increases at an average rate of 5% for concentrations higher than 20% and between 23% and 10% for concentrations less than 20%. The Matvienko and Mandelis’ model for α and our proposed expression for ρc described this trend with a reliable approximation to the experimental data with R 2 about 0.97 and 0.99, respectively. Moreover, the frequency of a specific angle is proportional to α as established by the theory for the phase signal for thermally thick samples. In the case of aqueous NaCl solutions, the α and k values were slightly below 4.6% and 3% from water values reported at room temperature. The proposed method allows the simultaneous determination of α and k by using only the FPPE configuration with test and reference liquid samples, reducing time and uncertainties from the use of more than one experimental setup, and providing the complete thermal characterization.

L version of the transformed Kedem-Katchalsky equations for membrane transport of electrolyte solutions and internal energy conversion.

One of the important formalisms of non-equilibrium thermodynamics is Peusner network thermodynamics. The description of the energy conversion in membrane processes, i.e., the conversion of the internal energy of the system into the dissipated energy and the free energy used for the work associated with the transport of solution components, allows us to describe the relationship between these energies and the thermodynamic forces acting in the membrane system. The aim of this study was to develop a procedure to transform the Kedem-Katchalsky equations for the transport of binary electrolytic solutions across a membrane into the Kedem-Katchalsky-Peusner equations based on Peusner network thermodynamics. The conversion of electrochemical energy to free energy in the membrane system was also determined. The nanobiocellulose biomembranes (Biofill) were the subject of the study with experimentally determined transport parameters for aqueous NaCl solutions. The research method is the Kedem-Katchalsky-Peusner formalism for binary electrolyte solutions with introduced Peusner coefficients. The coefficients of the L version of the membrane transport equations and the Peusner coupling coefficients were derived as functions of NaCl concentration in the membrane. Based on these coefficients, the fluxes of internal energy of the system, energy dissipated to the surroundings and free energy related to the transport of electrolyte across the membrane were calculated and presented as functions of the osmotic and electric forces on the membrane. The Peusner coefficients obtained from the transformations of the coefficients of the Kedem-Katchalsky formalism for the transport of electrolyte solutions through the Biofill membrane were used to calculate the coupling coefficients of the membrane processes and the dissipative energy flux. The dissipative energy flux takes the form of a quadratic form due to the thermodynamic forces on the membrane - second degree curves are obtained. Moreover, the dissipative energy flux as a function of thermodynamic forces allowed us to examine the energy conversion in transport processes in the membrane system.

Solubility of CO2 in salty water: adsorption, interfacial tension and salting out effect

In this work, we performed Molecular Dynamics simulations to investigate the solubility of CO 2 in both pure water and NaCl aqueous solutions, employing various force fields for water and NaCl. We first focussed on the solubility of CO 2 in TIP4P/2005 and TIP4P/Ice water models. We found that it was necessary to apply positive deviations to the energetic Lorentz-Berthelot combining rules for the cross interactions of water and CO 2 in both models to accurately replicate the experimental solubility of the gas. Then we found a negative adsorption of ions at the NaCl solution– CO 2 interface. We also observed an increase of the interfacial tensions of the system when adding salt which is related with the observed negative adsorption of the ions at the interface. Furthermore, we found that unit charge models tend to highly overestimate the change in the interfacial tension compared to scaled charge models. Finally, we also explored the salting out effect of CO 2 using different force fields for NaCl. Our findings indicate that unit charge force fields significantly overestimate the salting out effect of CO 2 while the scaled charge model Madrid-2019 accurately reproduces the experimental salting out effect of CO 2 in NaCl solutions.

Effect of silicon content on the corrosion behaviors of CrAlSiN thin films deposited by magnetron co-sputtering

One CrAlN and four CrAlSiN thin films containing 0.8–7.3 at. % Si were grown by a magnetron co-sputtering process using pure Cr, Al, and Si targets. The microstructure of the CrAlSiN coating changed from a coarse columnar structure to a dense and compact morphology as Si content increased from 0.8 to 7.3 at. % due to the formation of more amounts of amorphous silicon nitride phase to block the growth of columnar grains. Pitting corrosion was the main corrosion failure mechanism for each coating. According to the potentiodynamic polarization test, the lowest corrosion current density, the highest pitting potential, and the widest passivation range were obtained on the 7.3 at. % Si contained CrAlSiN coating. After the electrochemical impedance spectroscopy study of CrAlN and CrAlSiN thin films in 3.5 wt. % NaCl aqueous solution for 100 h immersion, the corrosion resistance of CrAlSiN thin films was 14 times higher than the CrAlN film due to its fine nanocolumnar microstructure to effectively retard the attack of corrosive electrolyte through the defects of coating.