NaOH Aqueous Solution Research Articles

Стресс-тесты антраценпроизводных растительного происхождения

Objective: to study the stability of solutions of standard samples of sennoside B and glucofrangulin A by stress tests using high performance liquid chromatography (HPLC). Materials and methods. The objects of the study were solutions of standard samples of sennoside B, as well as glucofrangulin A. Stress agents were 0.5M aqueous solution of copper (II) chloride (CuCl2), 0.5M aqueous solution of iron (III) chloride (FeCl3), 0.1M aqueous solution of hydrochloric acid (HCl), as well as 0.1M aqueous solution of sodium hydroxide (NaOH) and a solution of hydrogen peroxide (H2O2) 3%. The study was carried out using an Agilent 1100 liquid chromatograph. For this purpose, a Zorbax SB-C18 reverse-phase column (4.6×250 mm, 5 µm) was used. Elution of the mobile phase (acetonitrile and highly purified water, which was adjusted to pH 2 with phosphoric acid) was carried out in a gradient mode. Detection was carried out at wavelengths of 360 nm and 435 nm. Results. It was found that a solution of a standard sample of glucofrangulin A is stable for 14 days under the influence of 0.1M aqueous solution of HCl and 0.1M aqueous solution of NaOH, as well as 0.5M aqueous solution of FeCl3 and 3% H2O2 solution. When a solution of a standard sample of glucofrangulin A interacts with a 0.5M aqueous solution of CuCl2, its destruction is observed. When a standard sample of sennoside B reacts with a 3% H2O2 solution and a 0.5M aqueous CuCl2 solution, it remains stable. When interacting with other stress agents, its destruction occurs. Conclusion. The results obtained on the stability of solutions of standard samples of anthracene derivatives determine the main physico-chemical factors that cause their destruction, which can be taken into account when validating analytical methods, justifying the conditions of storage, packaging and processing of medicinal plant materials that contain anthracene derivatives.

LaCo1-x-yCuxTiyO3/KIT-6 perovskites: synthesis and catalytic behavior in syngas conversion to higher alcohols.

Highly dispersed LaCo1-x-yCuxTiyO3/KIT-6 perovskites were synthesized by the citrate method with inert mesoporous KIT-6 addition. The KIT-6 matrix was removed by dissolution in 7% NaOH aqueous solution. The dispersity of perovskites probably varies depending on the largest cation and its content at the B position of the perovskite ABO3 structure. The CoS=23+/CoS=03+ ratio increases with the increase in copper content and in the presence of Ti4+. It may be explained by the compensation of the distortion of the perovskite structure. The maximum syngas conversion is achieved at nCo/nCu = 7/3. At a higher copper content, the activity of the samples decreases due to the formation of large copper particles (up to 40 nm) in the course of the reduction. The selectivity for alcohols increases with an increase in the proportion of copper and reaches maximum values at a ratio of nCo/nCu close to 1. The distribution of alcohols is the same for all samples, except for LaCo0.35Cu0.35Ti0.3O3/KIT-6. It can be assumed that the synthesis of alcohols proceeds on bimetallic CoCu particles 3 nm in size and cobalt particles 4-6 nm in size, most likely enriched with copper on the surface.

Carbon dioxide-water bubbly flow in a vertical pipe with or without chemical absorption

CO2 bubbly pipe flows with or without chemical absorption were measured to obtain spatial evolution of dissolving bubbly flows. The experiments were carried out using pure water and aqueous NaOH solution of pH = 13 at two gas volume fluxes. The spatial evolutions of flow patterns, mean void fractions and bubble diameter distributions were obtained using an image processing method. The enhancement factor correlation proposed in our previous study was implemented into a three-dimensional one-way bubble tracking method to examine its applicability to CO2-water bubbly flow with chemical absorption. The numerical prediction agreed well with the measured spatial evolutions with or without chemical absorption, which confirmed the applicability of the enhancement factor correlation to bubbly pipe flows.

Study on Manufacturing and Applicability of Natural Adhesive for Paper Craft Using Corn Starch

A natural adhesive of starch (corn) that can be used to make and repair paper crafts was manufactured. The purpose of this study was to explore a composition of an adhesive having maximum adhesive strength while controlling a catalyst, a reaction initiator, and an oxidizing agent added to an aqueous starch solution at room temperature. The best composition was when a 35% starch aqueous solution was used. The 2.0% NaOH aqueous solution was added to the 35% starch aqueous solution to adjust pH from 10.0 to 11.0, and 0.20 g NiSO4, 20.0 g NaOCl, 30.0 g of 30.0% NaOH solution, and 3.0 g of 1.0% sodium thiosulfate were sequentially added. In the last step, the 3.0% HCl aqueous solution was added to adjust the pH of the adhesive to 7.5, and the adhesive strength of the prepared adhesive was 213 kgf/㎠. It was stable at room temperature for more than 60 days without physical changes such as viscosity, phase separation, precipitation, etc. In addition, TVOC, HCHO, and heavy metals were not detected, and the excellent result was found in antibacterial and reversible tests. This adhesive is an excellent natural adhesive that can be easily used by the user and does not contain harmful substances. It was an adhesive that could maintain the reputation of traditional materials in addition to their production and preservation.

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

Arylene Diimide Derivatives as Anolyte Materials with Two-Electron Storage for Ultrastable Neutral Aqueous Organic Redox Flow Batteries

Adsorption dynamics of quercetin with electrospun konjac glucomannan fabric containing double stranded DNA

Konjac glucomannan nonwoven fabric containing double stranded DNA was fabricated by electrospinning to investigate the adsorption dynamics of quercetin. Insolubilization of the fabric was performed by immersing it in aqueous trisodium metaphosphate and NaOH solution. The time course of the adsorbed amounts of quercetin to the fabric was determined in water-ethanol mixtures with varying the quercetin concentration of the immersing solution and the DNA fraction. The theoretical analyses for the adsorption curves were performed with two theoretical equations based on the diffusion-limited dynamics, and the adsorption/desorption dynamics, respectively, to express the adsorption curves of quercetin to the electrospun fabrics. Two time constants and equilibrium adsorbed amounts of quercetin were discussed from their dependencies on the initial concentration of quercetin solutions, DNA content of the fabric, and the weight of the fabric.

Effective Antibacterial/Photocatalytic Activity of ZnO Nanomaterials Synthesized under Low Temperature and Alkaline Conditions.

The purpose of this study was to evaluate the surface properties of ZnO nanomaterials based on their ability to photodegrade methyl blue dye (MB) and to show their antibacterial properties against different types of Gram-positive bacteria (Bacillus manliponensis, Micrococcus luteus, Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli). In this study, ZnO nanomaterials were synthesized rapidly and easily in the presence of 1-4 M NaOH at a low temperature of 40 °C within 4 h. It was found that the ZnO nanomaterials obtained from the 1.0 M (ZnO-1M) and 2.0 M (ZnO-2M) aqueous solutions of NaOH had spherical and needle-shaped forms, respectively. As the concentration of NaOH increased, needle thickness increased and the particles became rod-like. Although the ZnO nanomaterial shapes were different, the bandgap size remained almost unchanged. However, as the NaOH concentration increased, the energy position of the conduction band shifted upward. Photo current curves and photoluminescence intensities suggested that the recombination between photoexcited electrons and holes was low in the ZnO-4M materials prepared in 4.0 M NaOH solution; however, charge transfer was easy. ∙O2- radicals were generated more than ∙OH radicals in ZnO-4M particles, showing stronger antibacterial activity against both Gram-positive and Gram-negative bacteria and stronger decomposition ability on MB dye. The results of this study suggest that on the ZnO nanomaterial surface, ∙O2- radicals generated are more critical for antibacterial activity than particle shape.

Anodization assisted preparation of diverse nanostructured copper oxide films for solar selective absorber

Copper oxide films with diverse morphologies are prepared on copper (Cu) substrate by anodization method. The concentration of aqueous NaOH solution used as electrolyte during the anodization process is found as crucial towards formation of different nanostructured films. The reaction temperature impact on chemical composition and morphology of films is also determined. X-ray diffraction patterns disclose that CuO and Cu2O are presented in films and the share between both could be altered by changing the NaOH concentration and applied potential. Scanning electron microscopy images unveiled formation of films with diverse morphologies comprised of nanorods, nanoflakes, nanoparticles, and nanoleaves. Raman spectra confirmed the presence of CuO mode and its significant peak intensity has indicated high crystallinity. The prepared films have displayed high solar absorptance (63.5%–77.3%), low thermal emittance (4.5%–5.5%), and better solar selectivity (>14). These results suggest that the anodization method can be employed as a potential technique to prepare facile and affordable solar selective absorbers.

In Situ Monitoring of the Surface Evolution of a Silver Electrode from Polycrystalline to Well-Defined Structures.

Capturing the surface-structural dynamics of metal electrocatalysts under certain electrochemical environments is intriguingly desired for understanding the behavior of various metal-based electrocatalysts. However, in situ monitoring of the evolution of a polycrystalline metal surface at the interface of electrode-electrolyte solutions at negative/positive potentials with high-resolution scanning tunneling microscopy (STM) is seldom. Here, we use electrochemical STM (EC-STM) for in situ monitoring of the surface evolution process of a silver electrode in both an aqueous sodium hydroxide solution and an ionic liquid of 1-methyl-1-octylpyrrolidinium bis(trifluoromethylsulfonyl) amide driven by negative potentials. We found silver underwent a surface change from a polycrystalline structure to a well-defined surface arrangement in both electrolytes. In NaOH aqueous solution, the silver surface transferred in several minutes at a turning-point potential where hydrogen adsorbed and formed mainly (111) and (100) pits. Controversially, the surface evolution in the ionic liquid was much slower than that in the aqueous solution, and cation adsorption was observed in a wide potential range. The surface evolution of silver is proposed to be linked to the surface adsorbates as well as the formation of their complexes with undercoordinated silver atoms. The results also show that cathodic annealing of polycrystalline silver is a cheap, easy, and reliable way to obtain quasi-ordered crystal surfaces.

Investigation of the parameters affecting the morphology of zinc oxide (ZnO) nanoparticles synthesized by precipitation method

In this work, zinc oxide (ZnO) nanoparticles were synthesized using aqueous solutions of ZnSO4 and NaOH at ambient temperature and 70 °C. The nanoparticles synthesized at these two temperatures were identified and analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (FTIR), dynamic light scattering (DLS), and zeta potential (ZP). SEM micrographs showed that temperature, method of mixing, and stoichiometric ratio could significantly affect the formation of particles of different sizes and morphology. Phase analysis of synthesized particles was performed by X-ray diffraction. The result showed that temperature had the tremendous potential to convert precursors into products to form a single-phase compound completely. These results were confirmed by the observed characteristic peaks in FTIR. The crystallite size was calculated using Scherer's equation and Rietveld analysis to investigate the effect of the calcination process on the crystal size of the synthesized particles. The results showed that the calcination process could significantly affect the crystal size of the synthesized particles. Both methods showed an increase in the average crystal size of zinc oxide particles after the calcination process. The absolute magnitude of the zeta potential for zinc oxide particles with a pyramidal rod morphology with an average diameter of 80–90 nm was 33.2 and for star-like morphology with an average diameter of 800–900 nm was 11.8.

Time-Resolved Dynamic Crystallization at Liquid/Vapor Interface

We report the behavior of nanodroplets containing aqueous NaOH solutions of different concentrations, visualized using transmission electron microscopy (TEM). Under e-beam irradiation, highly charged aqueous NaOH droplets dewet with edge crystallization before erupting into satellite nanodroplets. For the first time, we observe dynamic nanocrystal precipitation from nanodroplet followed by redissolution in a periodic manner. Time-resolved images show that the crystalline precipitates occur predominantly in two distinct geometric shapes─hexagonal and square. Through structural, elemental, and morphological analyses, we deduce that the crystalline precipitate is monohydrate NaOH·H2O, whose orthorhombic structure forms the underlying basis for the evolved crystalline shapes. Through numerical simulations, we show how the observed preferential orientation of the crystal precipitate depends on crystal morphology and relative droplet–crystal size, but not on electrical forces, which govern droplet deformations. Together, our results reveal strong dynamics at the interface, including ionic chemistry, nanoscale physics, and hydrodynamics.

A New Force Field for OH- for Computing Thermodynamic and Transport Properties of H2 and O2 in Aqueous NaOH and KOH Solutions.

The thermophysical properties of aqueous electrolyte solutions are of interest for applications such as water electrolyzers and fuel cells. Molecular dynamics (MD) and continuous fractional component Monte Carlo (CFCMC) simulations are used to calculate densities, transport properties (i.e., self-diffusivities and dynamic viscosities), and solubilities of H2 and O2 in aqueous sodium and potassium hydroxide (NaOH and KOH) solutions for a wide electrolyte concentration range (0-8 mol/kg). Simulations are carried out for a temperature and pressure range of 298-353 K and 1-100 bar, respectively. The TIP4P/2005 water model is used in combination with a newly parametrized OH- force field for NaOH and KOH. The computed dynamic viscosities at 298 K for NaOH and KOH solutions are within 5% from the reported experimental data up to an electrolyte concentration of 6 mol/kg. For most of the thermodynamic conditions (especially at high concentrations, pressures, and temperatures) experimental data are largely lacking. We present an extensive collection of new data and engineering equations for H2 and O2 self-diffusivities and solubilities in NaOH and KOH solutions, which can be used for process design and optimization of efficient alkaline electrolyzers and fuel cells.

EVALUATION OF DESULPHURIZATION POTENTIALS OF BARIUM CHLORIDE, CALCIUM HYDROXIDE, SODIUM HYDROXIDE AND HYDROCHLORIC ACID ON DIESEL, KEROSENE AND GASOLINE

The sulphur content in refined petroleum products namely diesel (AGO), kerosene (DPK) and gasoline (PMS) obtained from a commercial Filling Station in Abakaliki, Ebonyi State were determined before and after desulphurization with aqueous ionic solutions of NaOH, BaCl2, Ca(OH)2 and HCl using a single beam UV-Vis spectrophotometer (Genesys 1OS, Thermo-Scientific). Results obtained showed that the amount of sulphur contained in the samples before desulphurization were 1.457, 0.992 and 1.294 mg/L in diesel, kerosene and gasoline respectively. The highest sulphur recovery of 0.676 mg/L (46.4 %), 0.315 mg/L (31.8 %), and 0.555 mg/L (42.9%) in diesel, gasoline and kerosene respectively were obtained with a 10 % w/v solution of NaOH after desulphurization. This was followed by a 10 % w/v solution of BaCl2 which gave 35.0 % and 23.0 % desulphurization in Diesel and gasoline respectively. The performance of Aqueous solutions of Ca(OH)2 and HCl in desulphurizing kerosene and gasoline were relatively low (3.2 %,11.4 % and 15 %, 4.6 % respectively) compared with aqueous NaOH. The results showed appreciable reduction in sulphur content of the samples with NaOH exhibiting the highest desulphurization potential in all the samples assayed. Thus these ionic solutions possess the potential to extract sulphur compounds in petroleum products.

Rheological behavior of the galactomannan fraction from Gleditsia triacanthos seed in aqueous dispersion

The purpose of the current study was to explore the influence of hydrochloric acid and sodium hydroxide, and sodium chloride on the rheological behavior of the galactomannan fraction from Gleditsia triacanthos seeds in aqueous solution. The flow (shear and extensional) and viscoelastic behavior as well as the dielectric properties were analyzed. The results indicated the existence of an interconnected microstructure, mainly in the macromolecular systems dispersed in HCl aqueous-solution, whose macromolecular arrangement leads to higher shear and extensional viscosity profiles, and contributes to improve the resistance to high shear deformation of this systems. The electrical conductivity profile of the Gledi -galactomannan in NaOH, HCl and NaCl aqueous-solution would indicate an increase or improvement in the continuity of the macromolecular arrangements compared to the polysaccharide in water. The conjugation of the galactomannan with Cl − ions would contribute to stabilize the microstructure. These results contribute to understand how the galactomannan fraction from Gleditsia triacanthos seeds could influence the microstructure and texture of ended-products, helping to consider its future applications. • Gledi -galactomannan in HCl-solution showed the highest shear and extensional viscosity. • Gledi -galactomannan developed a more interconected microstructure in HCl-solution. • HCl-solution improved the resistance of the Gledi -galactomannan arrangement. • Gledi -galactomannan and Cl − ions conjugation could contribute to stabilize the microstructure.

Effects of Cu-content and passivation treatment on the corrosion resistance of Al0.3Cu CoCrFeNi high-entropy alloys

This work investigated the effects of Cu-content and passivation treatment on the corrosion resistance of Al 0.3 Cu x CoCrFeNi ( x = 0.3, 0.4, 0.5, 0.6) high entropy alloys. With increased Cu content, the Al, Cu-riched precipitates in the Al 0.3 Cu x CoCrFeNi alloys emerged gradually, resulting in the decreased corrosion resistance and the weakening of the passive film. The passivation treatment in 30 wt% HNO 3 and 1 wt% NaOH aqueous solutions promotes the Cr 3+ content in the passive film of Al 0.3 Cu 0.3 CoCrFeNi and reduces the probability of pitting initiation, which substantially increased the corrosion resistance of the alloy. However, this treatment became less effective as the continuously intensified Al, Cu-riched precipitates which damaged the formation of homogeneous passive film and caused more serious galvanic corrosion. • Al 0.3 Cu x CoCrFeNi is FCC, the Al, Cu-riched precipitates increased with increasing Cu. • The passivation treatment is effective to promote growth of passive film on the HEAs. • The passivation effect is diminished as the Cu increased in the Al 0.3 Cu x CoCrFeNi. • The severe Al, Cu-riched precipitates destroy passive film and cause galvanic corrosion.

Voltage Oscillations during Anodic Polarization of Zinc in Water Solutions of NaOH

The present brief research deals with the appearance of voltage oscillations during galvanostatic anodization of Zn in the NaOH electrolyte. Hence, this research aims to describe the observed voltage oscillations, giving the most probable explication for their occurrence. Following previous results, the anodization was performed at 30 or 50 mA•cm-2 in diluted 0.002 M NaOH aqueous solution for 100 or 240 s at room temperature. The respective voltage alterations were recorded and submitted for further analysis. The obtained curves and the probable reasons for the observed voltage oscillations were analyzed in detail. The main research result has become a concept for the correlation between the oscillations and the alteration of the growing layer resistivity. This suggests that the resistivity alters due to local heating effects inside the film. These effects probably cause irreversible structural changes in the bulk of the growing film, obviously related to the occurrence of oxygen vacations. In this sense, this study initiates an entirely new field of investigation regarding the phenomena related to the Zn anodization in alkaline media at high current densities.

Mechanically strong all-chitin filaments: Wet-spinning of β-chitin nanofibers in aqueous NaOH

Herein, a facile wet-spinning strategy was used for the fabrication of mechanically strong all-chitin filaments from an aqueous NaOH solution using β-chitin nanofibers (β-ChNFs). It is hypothesized that to reach high mechanical performance it is important to preserve the crystalline structure of chitin during fabrication. To explore this possibility, β-ChNFs were disintegrated from squid pens by a mild procedure and showed a uniform diameter of 10–25 nm, length of a few microns, and a high aspect ratio of more than 200. An interesting finding was that gel-like β-ChNF filaments were directly formed in aqueous NaOH without using any organic or ionic agents. The gelation of β-ChNFS under alkali treatments contributed to the construction of strong nanonetworks and thus facilitated the formation of high-strength filaments. The resulting all-chitin filaments showed a high tensile strength and Young's modulus of 251.3 ± 12.45 MPa and 12.1 ± 0.72 GPa, respectively, which were further investigated for utilization as flexible sensors. The advantages of this strategy included the lack of use of any toxic solvents and the achievement of high mechanical performance for the all-chitin filaments. We believe that this wet-spinning approach may promote the functional utilization of chitin to develop high-strength filaments in smart textiles, biosensors, and structural reinforcements.

Nanosheet fabrication from magnon thermal conductivity cuprates for the advanced thermal management

Spin-chain–spin-ladder cuprates, such as La5Ca9Cu24O41, have notable electronic and thermal properties because of their unique electron spin arrangement. Among them, magnon thermal conductivity, which originates from the excitation of paired electron spins, is promising for the advanced thermal management applications that enable dynamic control of heat flow. This is because of its high, anisotropic thermal conductivity at room temperature and its dynamic controllability. In this study, we report nanosheet fabrications from polycrystalline La5Ca9Cu24O41 to enhance the control width. We obtained that the nanosheets with a thickness of about 3 nm are obtained via immersion of the polycrystals in a NaOH aqueous solution. We propose the exfoliation model based on the chemical reaction between the (La/Ca)2Cu2O3 subsystem and NaOH solution. The nanosheet fabrications can also lead to new research development on spin-ladder system and other strongly correlated cuprates.

Mass-Transfer Simulation of Salicylic Acid on Weakly Polar Hyper-cross-linked Resin XDA-200 with Coadsorption of Sodium Ion.

The mass-transfer process of salicylic acid on hyper-cross-linked resin XDA-200 was experimentally and theoretically studied. Undissociated salicylic acid was found to be the favorable form for salicylic acid adsorption on the resin. A pH-dependent adsorption isotherm model established in this paper could well fit the adsorption isotherm data at different pH values. Surface diffusion is the main mass-transfer mode for salicylic acid in resin particles. The salicylate anions and Na+ coadsorbed on the resin. The modified surface diffusion model considering the coadsorption was proposed. The model could satisfactorily fit the concentration decay curves of salicylic acid at different pH values and feed concentrations. NaOH aqueous solution at pH 12 could elute salicylic acid in the fixed bed efficiently. A pH-dependent dynamic adsorption and elution process model considering axial diffusion, external mass transfer, surface diffusion, pH-dependent adsorption equilibrium, as well as coadsorption of salicylate anions and Na+ was established. The model could well predict the breakthrough and elution curves at different feed concentrations. The research carried out in this paper has reference significance for optimizing the separation process of salicylic acid and its analogues.

Effects of sodium hydroxide and calcium hydroxide on the phase equilibria of methane hydrates

Alkalis such as sodium hydroxide (NaOH) and calcium hydroxide [Ca(OH)2] find lots of applications in oil and gas industry where formation of methane hydrates (and resulting flow hindrance) is a common occurrence. While many hydrate inhibitors have been identified to maintain flow assurance, effects of these alkalis on the phase stability of methane hydrate have not yet been explored in detail. In this study, the phase behaviour of methane hydrate has been investigated in the presence of aqueous solutions of NaOH and Ca(OH)2 with varying concentrations of 0.005, 0.01, 0.02, and 0.04 mass fractions in a high pressure stirred tank reactor. The phase equilibrium of methane hydrate in aqueous alkali solutions has been generated in the pressure and temperature ranges of 4.27–7.90 MPa and 276.60–283.22 K, respectively. Both the alkalis have found to exhibit inhibition of methane hydrate formation, and the inhibition effect becomes more pronounced at higher concentrations of the alkalis, with NaOH performing as a better inhibitor than Ca(OH)2. A plausible mechanism for the same has also been discussed. The heat of dissociation has been calculated to show that the presence of the alkalis does not influence the structure (sI) of methane hydrate. In addition, a simple model based on the van der Waals-Platteeuw (vdW-P) thermodynamic model consisting of single parameter has been used to predict the phase equilibrium of methane hydrate in the presence of aqueous alkali solutions. The absolute average relative deviations (AARD%) in pressure for the model were measured for the 40 experimental data points generated in this work. The predictions are well within 4 % of the experimental values, which suggests that the model can adequately predict the methane hydrate phase stability in the presence of alkalis. These alkalis are used in various operations during exploration and production of oil and gas. This study therefore will assist in designing an effective and economic thermodynamic inhibitor for methane hydrate based on alkalis for the oil and gas industry.