Aqueous Ethanol Solution Research Articles

Electrospun fibers of zein and pea protein to create high-quality fibrous structures in meat analogs

IntroductionThe importance of developing plant-based meat similar to animal meat lies in the fact that sensory similarity is a crucial factor in encouraging consumers to adopt this alternative.MethodologyThe present study reports the morphology, hydrophilicity, and thermal analysis of different fibers obtained by the electrospinning method. In the first step of this work, zein and zein/poly(ethylene oxide) (PEO) in 80% aqueous ethanol solution with varying concentrations of these polymers were investigated.Results and DiscussionIt was observed that the diameters of the electrospun fibers are related to the concentration and viscosity of the solutions. Moreover, the addition of small percentages of PEO makes the fibers more hydrophilic and leads to an increase in the polymeric solution viscosity. Because of its low toxicity, PEO is used in various edible products. In the second step of this work, an ideal zein/PEO combination was found to allow the pea protein (PP) to be electrospun. Adding PP to the zein/PEO blend (20:1) leads to a more hydrophilic fiber and improves thermal stability. The results suggest that the zein/PEO and zein/PEO/PP blends can offer an innovative solution to enhance the texture and appearance of plant-based meats. These simulated electrospun fibers can mimic the fibers in animal meat and are a potential alternative to provide a sensory experience as close to animal meat as possible.

Spectral properties of tolan and its supramolecular complexes in solution and silicate hydrogel

The complexation process of tolane and α-cyclodextrin in water, aqueous-ethanol solution and silicate hydrogel based on tetrakis(2 hydroxyethyl)orthosilicate was studied. The complex formation in solutions were confirmed by electron and 1H NMR spectroscopy, and the stability constant of the complex was determined using spectrofluorimetric titration (lgK1:1 = 1.5). The preservation of the inclusion complex during the preparation of the gel was confirmed by electron spectroscopy.

Composite photocatalysts g-C<SUB>3</SUB>N<SUB>4</SUB>/TiO<SUB>2</SUB> for hydrogen production and dye decomposition

The photocatalytic activity of the g-C3N4 /TiO2 composite samples in the processes of dye (methylene blue) decomposition and hydrogen evolution from an aqueous ethanol solution under the action of visible radiation (400 nm) has been studied. A new original method for the synthesis of the g-C3N4 /TiO2 composite by depositing g-C3N4 /TiO2 to TiO2 nanoparticles during sol-gel synthesis is proposed. The synthesized photocatalysts were characterized by X-ray diffraction, low-temperature gas adsorption, X-ray photoelectron spectroscopy, high-resolution transmission microscopy, and diffuse reflectance spectroscopy in the UV and visible regions. The maximum activity in the hydrogen evolution reaction was 1.3 mmol h–1, which exceeds the rate of hydrogen evolution on the unmodified g-C3N4 and TiO2 samples.

Control of photothermal liquid jets through microbubble Regulation: Fundamental mechanisms and Developing Strategies

Plasmon-induced photoacoustic streaming, considered as a potential application for micro-pumps in microfluidics, currently encounters ongoing debates concerning its fundamental mechanisms. In this study, we investigate the crucial role played by microbubbles in generation of jets in an ethanol aqueous solution. The power density threshold for bubble generation and its dependency on jet initiation are confirmed and the microbubble behavior is well regulated by manipulating the laser and liquid properties. Through simulations coupling fluidic and thermal fields, the significant role of Marangoni effect is validated in jet formation. Specifically, the temperature gradient of microbubbles is determined to be a pivotal factor in the generation of collimated jets. Additionally, factors influencing jetting, such as microbubble size and temperature gradients are studied, and noticeably, a stabilized jet lasting over 4 h is achieved based upon.

Sanguisorba officinalis L. ethanolic extracts and essential oil - chemical composition, antioxidant potential, antibacterial activity, and ex vivo skin permeation study.

Sanguisorba officinalis L. is classified as a medicinal plant and used in traditional medicine. The root of this plant is mainly used as a medicinal raw material, but the above-ground parts are also a valuable source of health-promoting biologically active compounds. The study aimed to evaluate the antioxidant activity and total polyphenol content (TPC) of extracts prepared in 70% and 40% aqueous ethanol solution (dry extract content 50-500g/L) from the aerial parts of S. officinalis. The essential oil was isolated from the tested raw material, and its composition was determined using GC-MS. Ethanolic extracts and essential oil have been tested for antibacterial activity. The extract in 70% v/v ethanol (dry extract content: 500g/L) was subjected to HPLC analysis for the content of selected phenolic acids and an ex vivo skin permeation study. The ability of these metabolites to permeate and accumulate in the skin was analysed. Extracts prepared at both ethanol concentrations showed similar antioxidant activity and TPC. Depending on the method, concentration of solvent, and dry extract content (50-500g/L), the activity ranged from 1.97 to 84.54g Trolox/L. TPC range of 3.80-37.04gGA/L. Gallic acid (424mg/L) and vanillic acid (270mg/L) had the highest concentrations among the phenolic acids analysed. Vanillic acid (10μg) permeates the skin at the highest concentration. The highest accumulation in the skin was found for 2,5-dihydroxybenzoic acid (53μg/g skin), 2,3-dihydroxybenzoic acid (45μg/g skin), and gallic acid (45μg/g skin). The tested ethanolic extracts exhibited antibacterial activity. Samples with a dry extract concentration of 500g/L showed the largest growth inhibition zones. The most sensitive strains to these extracts were P. aeruginosa (24mm), S. lutea (23mm), and S. pneumoniae (22mm). The smallest inhibition zones were observed for B. subtilis (17mm). The essential oil showed weaker antimicrobial activity (growth inhibition zone 8-10mm). The GC-MS method identified 22 major components of the essential oil, including aliphatic hydrocarbons, unsaturated terpene alcohols, aliphatic aldehydes, unsaturated and saturated fatty acids, sesquiterpene, phytyl ester of linoleic acid, nitrogen compound, phytosterol, terpene ketone, phenylpropanoids, aliphatic alcohol, diterpenoid, aromatic aldehyde, and aliphatic carboxylic acid. The conducted research has shown that ethanolic extracts from Sanguisorbae herba are a valuable source of compounds with antibacterial and antioxidant potential, including phenolic acids. The fact that selected phenolic acids contained in the tested extract have the ability to permeate and accumulate in the skin provides the basis for conducting extended research on the use of extracts from this plant raw material in cosmetic and pharmaceutical preparations applied to the skin.

Antisolvent crystallization of rare earth sulfate hydrates: Thermodynamics, kinetics and impact of iron

The thermodynamics and kinetics of ethanol antisolvent crystallization of rare earths from sulfate solutions has been explored, with a view towards separating the rare earths as part of a NdFeB magnet recycling process. The solubility of single and binary metal (Nd, Pr, Fe) phases in aqueous ethanol solutions has been determined. The impact of Fe and Pr on the crystallization of Nd is evaluated, the oxidation kinetics of Fe(II) to Fe(III) quantified, and the influence of Fe oxidation state on the thermodynamics and kinetics of crystallization investigated. Oxidation to Fe(III) is slow, with a half life of approx. 600 h. For pure Nd, the solubility of the obtained, stable sulphate octahydrate decreases exponentially with increased molar organic:aqueous (O/A) ratio, and is well described by the OLI model until O/A=0.2. Pr crystallizes as an isostructural octahydrate with similar solubility. Fe(II) precipitates as a mixed solid phase, with a solubility approximately 40 times higher than the rare earths at O/A=0.2. Fe(III) solutions exhibit liquid–liquid phase separation without precipitation at all evaluated concentrations. Nd and Pr coprecipitate together in proportion to their relative concentrations, with Pr precipitating at concentrations well below its pure component solubility. Fe(II) does not precipitate with Nd at O/A≤0.2 even at high concentration, with significant precipitation as separate particles at higher O/A for all concentrations. The crystallization kinetics and the morphology of the Nd phase is affected by the Fe oxidation state. The work highlights the potential of antisolvent crystallization for selective and efficient separation of REE from Fe.

Sonochemical synthesis of bismuth sulfide-based nanorods for hydrogen production

Bismuth-based nanostructures have been used as promising materials for catalytic hydrogen production. Herein, a sonochemical method was developed to prepare solid solutions like Bi2-xZn1.5xS3 in order to strengthen the Bi2S3 redox ability. Thioglycolic acid (TGA) was used as a complexing agent of Bi3+ to slow down Bi2S3 precipitation, making zinc insertion into the sulfide structure easier. The results of XRD, TEM, EDS, XPS, and DRS analyses suggest the formation of nanocomposites consisting of nanorods of Bi2-xZn1.5xS3 covered by ZnS nanoparticles, with bandgap widening from 1.16 eV (Bi2S3) to 2.37 eV (Bi1.53Zn0.6S3/ZnS/Zn(OH)2). The hydrogen generation in an ethanol aqueous solution was investigated under sonolysis, photocatalysis and simultaneous sonolysis and photocatalysis (sonophotocatalysis) in the presence of bismuth sulfide-based nanorods. The hybrid action of light and ultrasounds determined a remarkable synergistic effect on the hydrogen production of the solid solutions. The most outstanding results were found in the presence of nanocomposites containing Bi2-xZn1.5xS3, which can have an origin in better charge separation after zinc incorporation.

Simultaneous extraction of tocochromanols and flavan-3-ols from the grape seeds: Analytical and industrial aspects

Grape processing generates large amounts of by-products, including seeds rich in hydrophilic and lipophilic antioxidants. This study demonstrates, for the first time, that subjecting grape seeds to a single ultrasound-assisted extraction (UAE) with aqueous ethanolic solutions yields both flavan-3-ols and tocochromanols in the final extract. Notably, the water content in ethanol significantly influences the extractability of tocochromanols more than flavan-3-ols. Solid-to-solvent ratios of 1:50 to 1:2 were tested for both analytical and industrial applications. A sustainable analytical approach for recovering flavan-3-ols and tocochromanols using 60% and 96.4% ethanol extractions was validated and employed to profile nineteen genotypes of lesser-studied interspecific grape crosses (Vitis spp.). Different genotypes showed a wide range of concentrations of tocopherols (1.6–6.3 mg/100 g), tocotrienols (1.0–17.4 mg/100 g), and flavan-3-ols (861–9994 mg/100 g). This indicated that the genetic background and maturity of the plant material are crucial factors from an industrial perspective due to the initial concentration of bioactive compounds. Finally, the study also discussed the fundamental aspects of hydrophobic antioxidant extractability from the lipid matrix with aqueous ethanol solutions and the limitations of the workflow, such as the non-extractable tocochromanols and their esters and the losses of these lipophilic antioxidants during extraction.

A High-Quality Mixed Matrix Membrane with Nanosheets Assembled and Uniformly Dispersed Fillers for Ethanol Recovery.

A high-quality filler within mixed matrix membranes, coupled with uniform dispersity, endows a high-efficiency transfer pathway for the significant improvement on separation performance. In this work, a zeolite-typed MCM-22 filler is reported that is doped into polydimethylsiloxane (PDMS) matrix by ultrafast photo-curing technique. The unique structure of nanosheets assembly layer by layer endows the continuous transfer channels towards penetrate molecules because of the inter-connective nanosheets within PDMS matrix. Furthermore, an ultrafast freezing effect produced by fast photo-curing is used to overcome the key issue, namely filler aggregation, and further eliminates defects. When pervaporative separating a 5 wt% ethanol aqueous solution, the resulting MCM-22/PDMS membrane exhibits an excellent membrane flux of 1486g m-2 h-1 with an ethanol separation factor of 10.2. Considering a biobased route for ethanol production, the gas stripping and vapor permeation through this membrane also shows a great enrichment performance, and the concentrated ethanol is up to 65.6 wt%. Overall, this MCM-22/PDMS membrane shows a high separation ability for ethanol benefited from a unique structure deign of fillers and ultrafast curing speed of PDMS, and has a great potential for bioethanol separation from cellulosic ethanol fermentation.

Morphology evolution of lipid nanoparticle discovered by small angle neutron scattering

The structure of mRNA lipid nanoparticles (LNPs) is still under debate, with different studies presenting varying morphological characteristics, significantly hindering their biomedical potential. A typical formulation process of mRNA LNPs involves three steps: initial rapid mixing of lipids in an ethanol phase and mRNA in an acidic aqueous phase, followed by the swift removal of ethanol, and finally adjusting the solution to a neutral environment. In this study, we utilize Small Angle Neutron Scattering (SANS) with contrast matching to reveal the kinetic pathway-dependent of mRNA LNPs morphology. We find that the formulation process of the Moderna COVID-19 vaccine is controlled by a competition between aggregation and microphase separation, dictating the diverse morphologies observed in mRNA LNPs. The first step leads to the formation of polydisperse spherical droplets with an average diameter of 42±6.0 nm in an acidic ethanol aqueous solution. Ethanol removal initiates both aggregation and internal microphase separation, resulting in a polydisperse core-shell structure with an average diameter of 48±3.7 nm. Heptadecan-9-yl 8-((2-hydroxyethyl) (6-oxo-6-(undecyloxy) hexyl) amino) octanoate (SM-102) binds to mRNA via electrostatic interaction to form a reverse-wormlike micelle structure inside. The 1,2-Distearoyl-sn‑glycero-3-phosphocholine (DSPC) and PEG-lipid are just in the shell and cholesterol acting as a filler throughout the core-shell structure. Upon transitioning to a neutral environment, SM-102 loses its charge and neither the periphery nor the reverse-wormlike micelle can maintain their stabilities, leading to further aggregation and microphase separation. The average diameter of core-shell structure turns to be 66±5.2 nm. In the actual formulation process of the Moderna COVID-19 vaccine, steps 2 and 3 occur simultaneously, and the competition between aggregation and microphase separation determines the final morphology. These findings offer crucial insights into optimizing the morphology of mRNA LNPs, thereby facilitating advancements in vaccine development and mRNA vaccine delivery technologies.

Salting-out and Competitive Adsorption of Ethanol into Lipid Bilayer Membranes: Conflicting Effects of Salts on Ethanol-Membrane Interactions Studied by Molecular Dynamics Simulations.

Small amphiphilic molecules, such as ethanol, disturb the structure of lipid bilayer membranes to increase the membrane permeability, which is important for applications such as drug delivery, disinfection, and fermentation. To investigate how and the extent to which coexisting salts affect membrane disturbance, we performed molecular dynamics (MD) simulations on lipid bilayer membranes composed of zwitterionic lipids in aqueous ethanol solutions containing 0-631 mM NaCl, KCl, and KI salts. The addition of salts at low concentrations induced cationic adsorption on the lipid membrane, which competes with ethanol adsorption, thereby reducing the hydrogen bonds between ethanol and lipid molecules. This competitive adsorption mitigated the membrane disturbance and decreased the permeation of ethanol molecules into the membrane. In contrast, higher salt concentrations enhanced the membrane disturbance and permeability, which was caused by the salting-out of ethanol from the aqueous phase to the lipid bilayer. These conflicting effects appearing at different concentrations were stronger with the chloride salts than with the iodide salt. Among the two chloride salts, NaCl and KCl, the latter showed a greater enhancement in ethanol permeation at high concentrations. This seeming anti-Hofmeister salting-out behavior resulted from greater Na+ adsorption, preventing the ethanol-lipid interactions.

Preparation and application of highly oriented MFI zeolite membranes for efficient pervaporation recovery of organic solvents

Membrane-based pervaporation (PV) is highly efficient and energy-saving, and is poised to emerge as a promising technology for recovering biofuels from aqueous solutions. In this study, we prepared two versions of zeolite membranes, randomly oriented and highly (h0h)-oriented silicalite-1, with similar thicknesses on α-alumina tubes, and performed the first-reported systematic comparison of their PV performances in recovering organic solvents such as methanol, ethanol, acetone, n-propanol, isopropanol, and n-butanol from water. The contribution of the intrinsic properties of these membranes to PV was explored through permeance and selectivity analysis. The highly (h0h)-oriented membrane exhibited a significantly higher level of PV performance. In addition, the permeation behavior of PV and single-gas molecules through the highly (h0h)-oriented membranes was investigated, along with the influence that operating conditions (feed temperature and concentration) exert on PV. The results suggest that the PV permeation mechanism of organic solvent/water systems through the (h0h)-oriented silicalite-1 membranes involves a combination of adsorption-diffusion and molecular sieving. Furthermore, compared with other MFI-based membranes reported in the literature, the highly (h0h)-oriented silicalite-1 membrane demonstrated outstanding comprehensive separation performance due to its highly hydrophobic, preferentially oriented, and uniform silicalite-1 layer. For example, the separation factors for 10 wt% binary aqueous solutions of methanol, ethanol, acetone, and n-propanol were 12 at 50 °C, 32 at 70 °C, 145 at 70 °C, and 37.7 at 50 °C, respectively, with corresponding total flux values of 4.18, 2.63, 2.5, and 0.29 kg/(m2 h), respectively. These unique properties suggest its potential for PV recovery of organic solvents in sustainable chemical engineering.

Asymmetric PDMS/PVDF Pervaporation Membrane for Separation of Ethanol/Water System

AbstractPreparing asymmetric pervaporation membranes is a kind of promising method to enhance pervaporation membrane flux. Hydrophobic PVDF polymer can be used to prepare asymmetric pervaporation membranes, but its separation factor is relatively low. In this work, to improve the performance of PVDF membrane pervaporation, PDMS polymer was added to the PVDF membrane, and asymmetric PDMS/PVDF permeable membranes were prepared by the non‐solvent induced phase separation (NIPS) method. The effects of mass ratios of PDMS to PVDF on the membrane structures and the membrane properties were characterized by SEM, XRD, FTIR, TGA, water contact angle and mechanical strength. The results showed that the ratios of the PDMS: PVDF affect its phase‐separation behavior. As the addition of PDMS increased, the finger‐like pores on the membrane section gradually became longer, the upper surface changed from less porous to porous structure, and the lower surface structure changed from interconnected flocculent structure to porous, and the best structure of the blend membrane was achieved when the PDMS: PVDF mass ratio was 1 : 5. Therefore, the membrane had the best separation performance in separating 15 wt. % ethanol aqueous solution with a permeate total flux of 273.65 g/(m2 h) and a separation factor of 9.09 when the mass ratio of PDMS: PVDF was 1 : 5.

Ethanol activation of polyester membrane for superior dye/salt separation performance

Dye wastewater poses a severe danger to the environment and human health. The purification of dye wastewater is the focus and hotspot of most researchers. In this work, ethylene glycol (EG) was selected as an aqueous phase monomer to fabricate polyester membranes through an interfacial polymerization reaction. Then the polyester membrane was activated by ethanol aqueous solution. By adjusting the activation time and concentration of the ethanol, the network of the polyester membrane can be reshaped to endow the membrane with excellent performance. The activation mechanism was also explored here. Compared to the membrane without activation (PE-0%), the permeability of the optimized membrane (PE-40%) was increased by 8.3 times, and a high rejection was maintained (CR: 99.2%). Importantly, the PE-40% membrane also presented good acid and alkali resistance, chlorine resistance, and excellent antifouling performance. Our work provides an effective and feasible strategy for the development of high-performance polyester membranes.

Enhanced gelling property and freeze-thaw stability of potato, tapioca and corn starches modified by mild heating in aqueous ethanol solution.

Physically modified starches can be classified as natural ingredients on food labels and clean label products. Thus, the market demand for physically modified starch is increasing. Potato, tapioca and corn starches were physically modified by mild heat treatment in an alcoholic solution to enhance their gelling property and freeze-thaw stability. During mild heating of starch suspension (40% w/w) in 10% ethanol solution at the onset gelatinization temperature, granular swelling of starch occurred, followed by amylose leaching with medication of the surface structure of the starch granules. All treated starches exhibited increased gelatinization and pasting temperatures and decreased breakdown for pasting as a result of improved stability against shear and heat. The treated starches had higher hardness, cohesiveness and springiness of gel than the respective native starches, and these gel properties were more pronounced in potato starch than in tapioca and corn starches. The treated starches showed substantially reduced gel syneresis during freeze-thawing. Physical modification of starch by mild heat treatment in an alcoholic solution substantially improved its gelation ability and freeze-thaw stability. © 2024 Society of Chemical Industry.

Synergistic corrosion inhibition of rubber seed extract with KI on cold rolled steel in sulfuric acid solution

BackgroundPlant-based inhibitor has emerged an important topic owing to the combing merits of eco-friendly, low cost, rich natural resources as well as easy preparation. Rubber seed is the agricultural waste, and is mainly composed of oil and fatty acids those contain many polar oxygen atoms, and so it can be extracted to prepare the potential corrosion inhibitor. MethodsRubber seed extract (RSE) is prepared using reflux extraction method with the extracting solvent of ethanol aqueous solution. The synergistic inhibition effect of RSE and potassium iodide (KI) on the corrosion of cold rolled steel (CRS) in 0.50 M H2SO4 solution is firstly studied by weight loss, potentiodynamic polarization (PDP) curves and electrochemical impedance spectroscopy (EIS) methods. CRS surface was thoroughly characterized using metallographic microscope, scanning electron microscope (SEM), atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. FTIR, UV–vis and liquid chromatography mass spectrometry (LC-MS) compositional analysis of RSE were used to analyze the efficient components in RSE. Significant findingsThe results indicate that individual RSE or KI cannot function as a successful inhibitor to prevent CRS corrosion, but the mixture of RSE/KI performs better at inhibiting, with a maximal inhibition efficacy of up to 96.4% of 200 mg L−1 RSE/100 mg L−1 KI. The synergistic coefficient of the mixture is larger than 1, indicating that a true synergism. RSE/KI can drastically retard both cathodic and anodic processes, and interfacial capacitance falls as the charge transfer resistance of CRS/solution rises. It exhibits remarkable inhibition properties when the capacitor arc grows. There is only a small corrosion response in the inhibited media, as evidenced by the variations in electrical conductivity and ultraviolet spectrum before and after immersion. The hydrophilicity and surface roughness of CRS surface is dropped as a result of the introduction of RSE/KI. A series of metallurgical microscopy, AFM, SEM or contact angle tests indicate a synergistic inhibition effect is more pronounced for RSE/KI. XPS results clearly demonstrate that elements including Fe, S, N, and I are bonded to the surface of CRS. The primary ingredients of oleic acid, polyphenols, phenylpropanoids can also produce a strong synergism with KI.

High sensitivity terahertz biomedical sensing with graphene metamaterial

Identification of biomedical molecules by terahertz (THz) sensing is a quite promising noninvasive technique. Here, we present a THz graphene metamaterial with plasmon-induced transparency (PIT) for high sensitivity biosensing. The strong PIT effect is generated by the destructive interference between the plasmon modes excited by two graphene strips. For testing different biomedical analytes, a distinct frequency shift at PIT resonance can be observed due to the effect of surrounding refractive index variation. The metamaterial scheme for noninvasive biomedical sensing can achieve the sensitivity as high as 2.6 THz/RIU. Particular, it can not only detect the phase of red blood cell infected by malaria but also the concentration of ethanol aqueous solution. The underlying mechanism is discussed for understanding the THz sensing operation.

Construction of PDMS@ZIF-8 composite membrane on PVDF hollow fiber inner surface for ultrafast ethanol/water separation

Construction of ultra-thin and defect-free separation membrane on inner surface of hollow fiber supports is significant but challenging for molecular separation. In this study, the highly permeable PDMS@ZIF-8/PVDF composite membranes were successfully fabricated upon the inner-surface of polyvinylidene fluoride (PVDF) hollow fiber membrane for pervaporation (PV) ethanol/water separation. The efficient preparation of hierarchical PDMS@ZIF-8/PVDF composite membranes benefited from the precise regulation of ZIF-8 layer through interfacial synthesis and sequential coating of PDMS matrix. The thickness of the PDMS layer was only 16 ± 2 nm, which admirably eliminated the non-selective defects in ZIF-8 layer. Owning to the optimal combination of MOF layer and ultra-thin polymer layer, the as-prepared membrane exhibited the excellent ethanol flux of 1.34 kg m−2 h−1 with an ethanol concentration in permeate of 31.3 wt% for separating 5 wt% ethanol aqueous solution at 40 °C. The separation performance of the resultant membrane was superior to that of the other ethanol selective PV membranes. These findings herein provided a new way for preparing high-performance hollow fiber composite membranes for PV separation.

THE DEPENDENCE OF ACID-BASE EQUILBRIA AND ACIDITY CONSTANTS OF CONGO RED IN BUFFER SOLUTIONS ON THE IONIC STRENGTH

In this study, the spectrophotometric studies of aqueous ethanol solution of Congo red in various buffers solutions at room temperature 25oC and at different ionic strength of 0.05, 0.1, 0.3, and 0.5 KCl mol L-1 were investigated. The acidity constants of Congo red were estimated by three different methods. The two protonation stages were observed in pH range 2 - 4 and 4 - 6 as result as protonation of amino group and azo groups. The dependence of absorption spectra of Congo red on the ionic strength of solutions which exhibited blue shift with increases ionic strength in addition the shape and intensity were varied. Therefore, the acid-base equilibria shifted toward the higher pHs with the rise in ionic strength. Also, the acidity constants were affected by the ionic strength which the acidity constants decrease with increasing ionic strength of solution because the electrostatic interaction force increased.

Experimental study on the upward annular two-phase flow of nitrogen and ethanol aqueous solutions with different concentrations

Vertical upward annular flow experiments of nitrogen gas and ethanol aqueous solutions with volume fractions of 30 %, 60 %, and 95 % under 0.2 MPa were conducted. The characteristics of the liquid film including base, average, and maximum film thickness and height, velocity, and frequency of disturbance waves were obtained and studied based on the constant electric current method in a 5 mm inner diameter polycarbonate tube. The flow behavior was observed using a high-speed camera simultaneously. It is found that a large number of bubbles in the liquid film is critical to these characteristics. A connection between ethanol concentration and bubbles in the liquid film is found and interpreted by considering bubble stability which arises from the dynamic rise in surface tension. Our experimental investigation suggests that the effect of bubbles in the liquid film on the flow characteristics is not negligible in such annular flows under high liquid flow rates and bubble stability should be considered for annular flows employing solutions consisting of two or more components with large differences in surface tension.