Decrease In Interfacial Tension Research Articles

Thermophysical Properties of the Hydrogen Carrier System Based on Aqueous Solutions of Isopropanol or Acetone

One concept for the safe storage and transport of molecular hydrogen (H2) is the use of hydrogen carrier systems which can bind and release hydrogen in repeating cycles. In this context, the liquid system based on isopropanol and its dehydrogenated counterpart acetone is particularly interesting for applications in direct isopropanol fuel cells that are operated with an excess of water. For a comprehensive characterization of diluted aqueous solutions of isopropanol or acetone with technically relevant solute amount fractions between 0.02 and 0.08, their liquid density, liquid viscosity, and interfacial tension were investigated using various light scattering and conventional techniques as well as equilibrium molecular dynamics (EMD) simulations between (283 and 403) K. Polarization-difference Raman spectroscopy (PDRS) was used to monitor the liquid-phase composition during surface light scattering (SLS) experiments on viscosity and interfacial tension. For comparison purposes and to expand the database, capillary viscometry and dynamic light scattering (DLS) from bulk fluids with dispersed particles were also applied to determine the viscosity while the pendant-drop (PD) method allowed access to the interfacial tension. By adding isopropanol or acetone to water, density and, in particular, interfacial tension decrease significantly, while viscosity shows a pronounced increase. The behavior of viscosity and interfacial tension is closely related to the strong hydrogen bonding between the unlike mixture components and the pronounced enrichment of both solutes at the vapor–liquid interface, as revealed by EMD simulations. For an aqueous solution with an isopropanol amount fraction of 0.04, minor variations in interfacial tension and viscosity were found in the presence of pressurized H2 up to 7.5 MPa. Overall, the results from this study contribute to an extended database for diluted aqueous solutions of isopropanol or acetone, especially at temperatures above 323 K.

Dissipative Particle Dynamics Study on Interfacial Properties of Ternary H-Shaped Copolymer–Homopolymer Blends

Dissipative particle dynamics (DPD) simulations is used to study the effect of Am/2BmAm/2 and H-shaped (Am/4)2Bm(Am/4)2 block copolymers on the interfacial properties of ternary blends. Our simulations show the following: (i) The capacity of block copolymers to diminish interfacial tension is closely linked to their compositions. With identical molecular weights and concentrations, H-shaped block copolymers outperform triblock copolymers in mitigating interfacial tension. (ii) The interfacial tension within the blends correlates positively with the escalation in H-shaped block copolymer molecular weight. This correlation suggests that H-shaped block copolymers featuring a low molecular weight demonstrate superior efficacy as compatibilizers when contrasted with those possessing a high molecular weight. (iii) Enhancing the concentration of H-shaped block copolymers fosters their accumulation at the interface, leading to a reduction in correlations between immiscible homopolymers and a consequent decrease in interfacial tension. (iv) As the length of the homopolymer chains increases, there is a concurrent elevation in interfacial tension, suggesting that H-shaped block copolymers perform more effectively as compatibilizers in blends characterized by shorter homopolymer chain lengths. These findings elucidate the associations between the efficacy of H-shaped block copolymer compatibilizers and their specific molecular characteristics.

Non-thermal recovery of a viscous oil with a surfactant-polymer process

The goal of this work is to improve recovery of a viscous oil reservoir at 70 °C using a non-thermal process. Polymer floods can improve sweep efficiency, but leave behind a residual oil saturation. A surfactant-polymer flood has the potential to improve both the sweep as well as the displacement efficiency. Phase behavior experiments with the viscous oil, water and surfactants were conducted to identify surfactants. 1D and 2D sandpack displacements were conducted to evaluate the efficacy of the process. Phase behavior experiments showed Winsor type I behavior with a low interfacial tension using a single surfactant, but not ultralow tension. Water flood recovered about 50% OOIP and reduced the oil saturation to about 45% in 1D floods. The subsequent SP flood increased the cumulative oil recovery to 99% in sandpacks when the viscosity of chemical slugs exceeded the oil viscosity. When the permeability decreased (as in a Bentheimer core), the oil recovery decreased to about 86%. Secondary SP floods also recovered most of the oil and faster than tertiary floods. Reduction of polymer concentration (and viscosity to about 1/4th of the oil viscosity) reduced the oil recovery, especially in 2D sandpack floods. Decrease in interfacial tension increased the requirement of polymer concentration to maintain flood front stability. This flood demonstrates the effectiveness of Winsor type I SP formulation for viscous oil, high permeability reservoirs. Such a SP process would reduce the carbon footprint of viscous oil recovery compared to that of thermal processes.

Interfacial properties of CO2 and liquid sulfur in high-sulfur gas fields: Molecular simulations on carbonate mineral surfaces

As the global energy landscape transforms, the development of high-sulfur natural gas has become increasingly critical. However, sulfur deposition during these gas field developments significantly affects operational efficiency. This study employed molecular dynamics simulation to explore the effectiveness of CO2 in alleviating sulfur deposition on carbonate rock reservoirs. Specifically, it examined the interfacial tension between liquid sulfur and CO2, the wettability of sulfur on carbonate rock mineral surfaces, and the kinetics of CO2 displacing liquid sulfur. Results show that as CO2 pressure increases from 10 MPa to 60 MPa, the interfacial tension between liquid sulfur and CO2 decreases by 84 %, from 35.54 mN/m to 5.53 mN/m. The contact angles of sulfur droplets on calcite and dolomite surfaces stabilize at 41.82° ± 2.10° and 44.33° ± 3.27°, respectively, indicating greater sulfur spread on calcite surfaces. With higher CO2 pressures, sulfur deposition on mineral surfaces and interfacial tension both decrease significantly, while the wetting angle of liquid sulfur increases, particularly on dolomite. At 60 MPa CO2 pressure, the adsorption energy of dolomite for liquid sulfur drops from 364.56 kcal/mol to 25.46 kcal/mol, a 93 % reduction, suggesting CO2′s dual role in displacing sulfur and promoting its desorption from mineral surfaces. Furthermore, the efficiency of sulfur deposition alleviation in carbonate rock slit structures improves and stabilizes at around 40 MPa CO2 pressure. This study presents a potential environmentally friendly approach for efficiently developing high-sulfur gas fields, and its findings provide practical insights for optimizing CO2 injection strategies to mitigate sulfur deposition.

Adsorption behavior of asphaltene aggregates generated by self-association at the oil/water interface

The formation of emulsions is undesirable yet unavoidable in petroleum production. Researchers suggest that asphaltenes adsorb at the oil/water interface, forming a protective film that stabilizes emulsions. This study investigates how asphaltene aggregates, formed through intermolecular interactions, affect emulsion stability and the properties of the oil/water interface. First, the effects of asphaltene concentrations, components, and temperatures on emulsion stability and the association state of asphaltenes were explored using the bottle test method and dynamic light scattering, respectively. The promotion of asphaltene aggregation by higher asphaltene concentrations and liquid paraffin content was confirmed by comparing the average size of aggregates, while higher temperatures were found to inhibit aggregation. Higher temperatures destabilize emulsions containing asphaltenes by increasing water droplet collisions, whereas higher asphaltene concentrations and liquid paraffin content stabilize emulsions. Subsequently, the effects of these conditions on expansion modulus were thoroughly investigated using the pendant drop technology. Pendant drop experiments demonstrate that increasing asphaltene concentration, along with the introduction of liquid paraffin, enhances asphaltene aggregation, thereby reinforcing the structural stability of the interfacial film. Spinning drop experiments were conducted to obtain dynamic interfacial tension (IFT) and analyze the adsorption behavior of aggregates at the oil/water interface. The adsorption process of asphaltenes driven by intermolecular interactions, occurs in three regimes: a short-term diffusion-controlled process, a transition process, and a long-term low-speed descent process, referred to as Regimes I, II, and III. The diffusion coefficient in Regime I increases with temperature, while the equilibrium IFT in Regime III decreases with temperature. In Regime II, adsorbed asphaltene aggregates from Regime I tend to prevent further adsorption, reducing the rate of dynamic IFT decrease. In Regime III, dynamic IFT decreases slowly, primarily due to the continued adsorption of asphaltene aggregates into the sublayer and their subsequent reconfiguration. These findings have significant implications for improving the understanding of oil/water interface properties and emulsion behavior in oil production, transportation, and refining systems.

Macroscopic and molecular scale assessment of thermal effects on soil-water interactions of unsaturated diesel-contaminated soils

The soil-water interactions of unsaturated diesel-contaminated soil are crucial for assessing pollution transport during thermal remediation. This paper aims to improve our understanding of this issue by measuring the matric suction of unsaturated contaminated kaolin and carrying out molecular dynamics simulations under thermal conditions. Results show that the increase in pollutant concentration could reduce the water retention capacity of diesel-contaminated kaolin due to changes in electrochemical properties and pore characteristics of samples, as well as a decrease in interfacial tension. On the other hand, pollutants formed a protective film on the kaolinite surface to act as a liquid bridge and prevent water loss at higher temperatures, as confirmed by Fourier transform infrared spectroscopy. With rising temperatures (50–60 °C), kaolin matric suction generally decreased with higher pollutant concentrations, but this trend was not very evident at lower pollution concentrations (0–10,000 mg/kg). In addition, molecular dynamics simulations were used to demonstrate the validity of these findings. The presence of pollutants might strengthen the interaction energy between kaolinite and water (for example, increasing from 276.52 kcal/mol (25 °C) and 267.95 kcal/mol (40 °C) at 8000 mg/kg to 296.54 kcal/mol (25 °C) and 292.46 kcal/mol (40 °C) at 10,000 mg/kg), thereby enhancing the water retention capacity of kaolin. In short, the study revealed that the coating of pollutants on kaolinite could act as a protective film, which binds water molecules through van der Waals and electric field forces and thereby reduces the sensitivity of water retention capacity to temperature.

PREPARATION OF DEEP EUTECTIC SOLVENTS FOR MAKING AN OIL-DISPLACING COMPOSITION BASED ON TETRAHYDROXY ALCOHOL, CARBAMIDE, QUATERNARY AMMONIUM SALT, AND A SURFACTANTS

The binary systems of deep eutectic solvents (DESs) have been synthesised and investigated: tetraxydroxy alcohol - a salt of a quaternary ammonium base (DES1), tetrahydroxy alcohol - carbamide (DES2), a salt of a quaternary ammonium base - carbamide (DES3), and the ternary system tetrahydroxy alcohol - a salt of a quaternary ammonium base - carbamide (DES4). Eutectic compositions of binary systems DES1, DES2 and DES3 are characterised by significantly lower pour/melting points than those of the initial components. The lowest pour point among the binary mixtures is that of eutectic composition DES3. The ternary system is characterised by an even lower melting point (-14 °C), which is associated with the formation of intermolecular donor-acceptor hydrogen bonds within the system. An aqueous solution of DES4 with the concentration of 26 wt% was prepared, and its pH value was determined depending on temperature during preparation. At room temperature, pH of three-component DES is 6.6-7.1, but after thermostating for 6 h at 150 °C pH increases to 9.2 due to carbamide hydrolysis. It is assumed that further on, using DES4 as the basis for an alkaline oil-displacing composition directly in the reservoir, under the influence of the temperature of injected heat carrier, CO2 is formed, along with the ammonia buffer system with the maximal buffer capacity within the pH range 9-10. Resulting carbon dioxide, dissolving predominantly in oil, will cause a decrease in its viscosity, on the one hand, while the formed alkaline medium, being most favourable for surfactant performance due to a decrease in interfacial tension, liquefaction of high-viscosity layers or films at the oil-water-rock boundaries, on the other hand, will ensure efficient use of this system for oil displacement. In addition, the oil-displacing composition based on DES4 will be low-solidifying, which opens the possibility of its transportation and use in the northern regions and the Arctic zone.

Influence of hydrogen sulfide on gas-water interface in underground hydrogen storage: A molecular dynamics study

In this study, we investigate the dynamics of interfacial tension (IFT) between residual pore water and gas mixtures containing H2, CH4, and H2S within subsurface porous media, essential for underground hydrogen storage (UHS) systems. Utilizing molecular dynamics simulations, we established specific IFT correlations across a spectrum of H2S concentrations, ranging from 5 % to 80 %, under the conditions of 14.5 MPa and 343 K. Our results demonstrate a marked decrease in IFT, with a notable 12 % reduction observed even at a minimal H2S concentration of 5 % for H2S-H2 mixtures, contrasting with a 6 % reduction in H2S-CH4 mixtures, and reaching a saturation point at concentrations exceeding 80 %. The presence of CH4 at the interface mitigates the reduction in IFT caused by H2S, underscoring the complexity of gas interactions in subsurface storage. These insights into the molecular dynamics at the gas-water interface carry significant implications for the optimization of UHS operations, informed by the substantial variations in IFT with different H2S concentrations.

Thermophysical properties of the liquid organic hydrogen carrier system based on benzyltoluene considering influences of isomerism and dissolved hydrogen

The benzyltoluene (BT)-based liquid organic hydrogen carrier (LOHC) system currently considered for large-scale applications represents a mixture of regioisomers. To characterize this complex system, a comprehensive experimental database for various thermophysical properties of synthesized BT isomers and their mixtures without and with the presence of hydrogen (H2) close to vapor-liquid equilibrium is established using optical and conventional techniques at process-relevant temperatures and pressures up to 573 K and 6 MPa. The surface tension varies by less than 4% among the dehydrogenated (H0-BT) or hydrogenated (H12-BT) isomers. The density and viscosity of mixtures of H0-BT or H12-BT isomers can be described by simple mixing rules with average absolute relative deviations of 0.022% and 0.38%. With increasing H2 pressure, the viscosity remains nearly constant, while the interfacial tension decreases by up to 5%. The thermal and mutual diffusivity of H12-ortho-BT containing dissolved H2 at 6 MPa decrease and increase with increasing temperature.

Effects of salinity, temperature, and pressure on H2–brine interfacial tension: Implications for underground hydrogen storage

Underground hydrogen (H2) storage is a long-term, clean, and sustainable solution for a large-scale H2 economy. Hydrogen geo-storage strategies in saline aquifers have gained considerable attention regarding meeting energy demand challenges. Rock-fluid interaction and interfacial tension (IFT) of any given gas determine the fluid flow, storage potential, and containment security. However, the literature lacks sufficient information on the IFT of H2-brine systems at various thermophysical and salinity conditions. This study experimentally measures density using an Anton Paar DMA-HP densitometer and IFT with a Kruss drop shape analyzer (DSA-100). The density and IFT measurements of H2-brine systems were evaluated at various pressures (0.1, 5, 10, 15, and 20 MPa), temperatures (25, 50, and 70 °C), and salinities, including deionized water, seawater (mixed brine), and individual brines (NaCl, KCl, MgCl2, CaCl2, and Na2SO4) at 1 and 3 M concentrations. The results indicate a significant decrease in H2-brine IFT by the increasing temperature at a constant pressure and salinity. A slightly decreasing trend is observed when the H2-brine IFT is plotted against pressure, maintaining a constant salinity and temperature. Increasing the salinity of the salt solutions (from 1 to 3 M), irrespective of the salt type, increases the H2-brine IFT at a constant pressure and temperature. Due to the screening effect, the monovalent and divalent cations behave differently in H2. To the best of our knowledge, this comprehensive dataset for H2-brine IFT is presented for the first time. The provided data are crucial for reservoir simulations and determining the H2 geo-storage potential under natural reservoir conditions.

Laboratory study on the transformation of oil-water interface properties under direct current electric field

Interface tension is one of the important mechanisms that affect crude oil recovery and plays an important role in the development of tight oil reservoirs. Electrical-enhanced oil recovery can be used as a technology to reduce interfacial tension and improve crude oil recovery. In the previous research process of Electrical-enhanced oil recovery, the focus was more on the influence of electric field on wettability, and the understanding of the changes in interfacial tension under electric field action is not yet comprehensive. This article designs an orthogonal experiment to study the effect of electric field on oil-water properties. The degree of influence of three factors, namely sodium chloride solution concentration (C), direct current voltage (V), and voltage action time (t), on interfacial tension is studied. Gas chromatography, four component analysis, and Fourier transform infrared spectroscopy are combined to discuss the mechanism of the influence of changes in solution pH, crude oil components, and oil phase functional groups on interfacial tension. The results show that an external electric field can effectively reduce the interfacial tension between oil and water, and the maximum change in interfacial tension after the experiment can be reduced from 23.21 mN/m to 0.37 mN/m; Through range analysis, it can be concluded that the concentration of sodium chloride solution has the greatest impact on interfacial tension, followed by DC voltage and voltage action time. The optimal experimental conditions are 0.5 mol/L sodium chloride solution, 10 V DC voltage, and a voltage action time of 18 h, and the change in interfacial tension is related to the increase in pH value. The change in crude oil composition is also an important reason for the decrease in interfacial tension under external electric fields. Finally, Fourier transform infrared spectroscopy was used to determine that under the action of an electric field, the increase in pH of the sodium chloride solution resulted in the formation of carboxylate salts through chemical reactions between alkaline substances of solution and acidic substances of the oil, which were the key factors in reducing interfacial tension. This study helps to understand and explore the principles and mechanisms of Electrical-enhanced oil recovery in improving oil recovery, with the aim of contributing to the development and promotion of Electrical-enhanced oil recovery technology.

Investigating the mechanism of interfacial tension reduction through the combination of low-salinity water and bacteria

In the enhanced oil recovery (EOR) process, interfacial tension (IFT) has become a crucial factor because of its impact on the recovery of residual oil. The use of surfactants and biosurfactants can reduce IFT and enhance oil recovery by decreasing it. Asphaltene in crude oil has the structural ability to act as a surface-active material. In microbial-enhanced oil recovery (MEOR), biosurfactant production, even in small amounts, is a significant mechanism that reduces IFT. This study aimed to investigate fluid/fluid interaction by combining low biosurfactant values and low-salinity water using NaCl, MgCl2, and CaCl2 salts at concentrations of 0, 1000, and 5000 ppm, along with Geobacillus stearothermophilus. By evaluating the IFT, this study investigated different percentages of 0, 1, and 5 wt.% of varying asphaltene with aqueous bulk containing low-salinity water and its combination with bacteria. The results indicated G. Stearothermophilus led to the formation of biosurfactants, resulting in a reduction in IFT for both acidic and basic asphaltene. Moreover, the interaction between asphaltene and G. Stearothermophilus with higher asphaltene percentages showed a decrease in IFT under both acidic and basic conditions. Additionally, the study found that the interaction between acidic asphaltene and G. stearothermophilus, in the presence of CaCl2, NaCl, and MgCl2 salts, resulted in a higher formation of biosurfactants and intrinsic surfactants at the interface of the two phases, in contrast to the interaction involving basic asphaltene. These findings emphasize the dependence of the interactions between asphaltene and G. Stearothermophilus, salt, and bacteria on the specific type and concentration of asphaltene.

A resolved CFD-DEM investigation into sand production under water flooding in unconsolidated reservoir

Excessive sand production in the wellbore can impede oil production from unconsolidated reservoirs. The study reports an investigation of numerical simulation of sand production in oil-water two-phase flow. The interaction between fluid and particles is achieved by coupling the discrete element method (DEM) with resolved computational fluid dynamics (CFD). By harnessing the advantages of the method, the numerical model can capture the movement of particles and the changes in fluid field at a scale smaller than fine particles. The model reveals the water flooding process in the granular matrix and effectively visualizes the microscopic mechanisms of particle migration. The results indicate that the model with water flooding exhibits higher produced mass compared to the model without water flooding. Parametric analysis shows that there is a critical fines content, which leads to the maximum sand production. With the increase of viscosity and the decrease of interfacial tension, the sand production increases.

Effect of Alkyl Peroxyl Radical Oxidation on the Oxidative Stability of Walnut Protein Emulsions and Their Adsorbed Proteins.

Walnuts are high in protein content and rich in nutrients and are susceptible to oxidation during production and processing, leading to a decrease in the stability of walnut protein emulsions. In this paper, the effect of alkyl peroxyl radical oxidation on the stability of walnut protein emulsions is investigated. With the increase of 2,2-azobis (2-methylpropionamidine) dihydrochloride (AAPH) concentration, both its protein and fat were oxidized to different degrees, and the droplets of the emulsion were first dispersed and then aggregated as seen from the laser confocal, and the stability of walnut protein emulsion was best at the AAPH concentration of 0.2 mmol/L. In addition to this, the adsorption rate of adsorbed proteins showed a decreasing and then an increasing trend with the increase in the oxidized concentration. The results showed that moderate oxidation (AAPH concentration: 0-0.2 mmol/L) promoted an increase in protein flexibility and a decrease in the protein interfacial tension, leading to the decrease in emulsion droplet size and the increase of walnut protein emulsion stability, and excessive oxidation (AAPH concentration: 1-25 mmmol/L) weakened protein flexibility and electrostatic repulsion, making the walnut protein emulsion less stable. The results of this study provide theoretical references for the quality control of walnut protein emulsions.

Advanced machine learning-based modeling of interfacial tension in the crude oil-brine-diethyl ether system: Insights into the effects of temperature and salinity

Solvent injection, a well-established method for enhanced oil recovery (EOR), has demonstrated significant improvements in oil recovery when compared with conventional water flooding techniques. The interfacial tension (IFT) is pivotal in determining the displacement efficiency and overall performance of innovative techniques like dimethyl ether-enhanced waterflooding (DEW), which has gained substantial attention in recent years. In this study, following laboratory measurements of IFT, six advanced machine learning (ML) techniques were employed: Generalized Linear Model (GLM), Generalized Additive Model (GAM), Random Forest (RF), Support Vector Machine (SVM), Extreme Gradient Boosting (XGBoost), and Boosted Regression Tree (BRT) to model the IFT in both oil-brine and oil-brine-diethyl ether (DEE) systems. The analysis is based on an extensive dataset comprising 7,017 data points for oil-brine and 6,949 data points for oil-brine-DEE systems obtained from experimental studies. The findings indicate that the developed RF model excels in predicting IFT, boasting a remarkable coefficient of determination (R2 = 0.99) along with the lowest root mean squared error (RMSE = 0.2), mean squared error (MSE = 0.04), and mean absolute error (MAE = 0.13). The study underscores the significance of optimizing salinity levels to achieve the most substantial reduction in IFT. This reduction is attributed to the enhanced migration of polar components, such as asphaltene molecules, to the interface of the oil-brine system. Moreover, the research highlights a synergistic decrease in IFT when both DEE and soluble ions are present, resulting in the lowest IFT at around 2 mN/m in 40,000 ppm salinity (S2) at 70 °C (T3). This indicates that the adsorption of DEE at the water–oil interface forms a layer capable of adsorbing ions, thereby enhancing the layer's thickness. As a result, the oil–solvent-ion layer becomes thicker compared to the oil-ion layer, leading to the maximum decrease in IFT. Additionally, with increasing temperature up to 70 °C, the IFT of both systems demonstrated a downward trend, as evidenced by all experiments. The outcomes of this study have the potential to enhance our comprehension of the underlying mechanisms involved in water-soluble solvent EOR techniques.

Investigation of the processes of additional oil displacement by nanosuspension silicon oxide from a model core

The use of nanosuspensions during reservoir flooding is an alternative to chemical methods for enhancing oil recovery. In this work, the effectiveness of using nanosuspensions as a post-displacement agent after the base agent (water) was shown. Filtration tests for additional oil displacement from model rock samples were carried out. Suspensions of nanoparticles were used for post-displacement. The mass concentration of spherical silicon oxide nanoparticles (SiO2) varied from 0.01 to 0.25%wt, and their size varied from 10 to 35 nm. The permeability of the model core was 50 mD. An experimental measurement of the interfacial tension and the contact angle of wettability was performed. It is shown that with an increase in the concentration of nanoparticles, the interfacial tension of the “oil — suspension” decreases. It has been established that at a fixed concentration of nanoparticles (0.1%), with an increase in the size of nanoparticles, the interfacial tension decreases. It was revealed that when using suspensions, the contact angle of rock wetting with oil changes significantly. As a result of filtration tests, dependences of the oil displacement efficiency on the concentration and size of nanoparticles were obtained. It has been shown that additional volume of oil can be recovered after filtering nanosuspensions.

Probing Effect of 6MeV Electron Beam Irradiation on Haemoglobin Protein Using Spectroscopic Techniques.

In this work, we study the effect of 6MeV electron beam irradiation on the physicochemical properties of lyophilized Human Haemoglobin A (HbA). Electron beams generated from Race Track Microtron accelerator with energy 6MeV were used to irradiate HbA at fluences of 5 × 1014 e-/cm2 and 10 × 1014 e-/cm2. Pristine and electron beam irradiated HbA were characterized using UV-visible and Fourier transform infrared spectroscopy (FTIR) spectroscopy. The interfacial tension of the aqueous solutions of HbA are also analysed by pendant drop method. Absorbance intensity, % transmittance and interfacial tension decrease with fluence. The peak position of the Soret band (λsoret = 404nm) remains unaffected by the fluences. FTIR spectroscopy confirms the changes in the secondary structure of the haemoglobin. In the amide band I, the percentage of α-helix reduced from 8% to 1%, and an increase in β-sheet (19% to 29%) and β helix (6.3% to 15%) is observed. Interfacial tension decreases from 46.0mN/m and 44.0mN/m with increase in irradiation dose. These finding provides realistic guideline for biological cells exposure to electron beam radiation doses.

Exploring the Effect of Relaxation Time, Natural Surfactant, and Potential Determining Ions (Ca2+, Mg2+, and SO42−) on the Dynamic Interfacial Tension Behavior of Model Oil-Brine Systems

This study examined how the concentration of asphaltene and divalent ions in various salinities affects the interfacial tension (IFT) between a model oil/brine using the pendant drop method. The oleic phase consisted of a mixture of toluene and n-heptane (heptol), to which asphaltene was added to investigate how asphaltene molecules affect the surface properties. The base fluid was prepared with a salinity of 40,000 ppm, and two additional solutions with concentrations of 4000 ppm (low salinity) and 80,000 ppm (high salinity) were created. The results revealed that increasing the concentration of asphaltene within certain salinity ranges led to a decrease in IFT. The lowest IFT was observed at the 40,000 ppm salinity level, indicating that at this optimal salinity, the maximum asphaltene concentration migrated to the heptol/brine interface, reducing the IFT from 23 mN/m to 16 mN/m. Additionally, a 0.5 % wt of asphaltene demonstrated a significant concentration of micellization of natural surfactants, suggesting that the interface was nearly saturated with asphaltene. Consequently, concentrations higher than this value did not significantly alter the IFT. In the final part of the study, the impact of divalent ions was investigated, revealing that as the concentration of Ca2+ ions increased up to fourfold, the IFT decreased to 15 mN/m, about 10 % less than the base case. This value represented the lowest IFT compared to Mg2+ and SO42−. Moreover, modeling the results indicated that the relaxation time decreased with increasing salinity, suggesting that higher salinity accelerated the process of asphaltene absorption at the interface.

Effect of type of fatty acid attached to sucrose ester on the stability of water-in-oil Pickering emulsion

Water-in-oil (W/O) Pickering emulsions have a broad range of potential for use in the food industries. However, because of the scarcity of edible W/O-type particles, the production and stabilization of W/O Pickering emulsion is challenged. Sucrose esters (SEs) have great promise as W/O-type particles, whose properties vary with fatty acid moiety attached. This study investigated the effect of fatty acid residue type on the interface activity of SE and corresponding emulsion properties, in order to select the most suitable SE. Sucrose stearate (SE-S), sucrose palmitate (SE-P), sucrose laurate (SE-L), sucrose erucic acid ester (SE-E) and sucrose oleate (SE-O) were applied. Results showed that the saturation of fatty acid residues caused the difference of crystallinity of SE: SE-S＞SE-P＞SE-L＞SE-E＞SE-O. The lower crystallinity resulted in the increased hydrophilicity of SE-O with a closer θ (101.4°) to 90°, which facilitated interfacial adsorption and rearrangement, and larger decrease of interfacial tension (3.93 mN/m). Consequently, SE-O was capable of stabilizing more water volume fraction (75%). Moreover, the emulsion stabilized by SE-O was observed smaller droplet sizes, higher gel strength, and physical stability. The results revealed that SE-O was more appropriate for the preparation of W/O Pickering emulsion.

Effect of ionic environment in aqueous solution on nucleation and stabilization of bulk nanobubbles

Bulk nanobubbles have attracted significant interest due to their growing demand for widespread applications. A thorough comprehension of the essential factors dictating nanobubble properties holds immense significance in industrial practices. This study endeavors to examine the characteristics of bulk nanobubbles formed in a complex ionic solution containing surfactants and sodium chloride. The experimental findings demonstrate that both ionic and nonionic surfactants can effectively promote the nucleation of nanobubbles. The introduction of salts has an opposing effect as it reduces both the number concentration and the Zeta potential of nanobubbles. There is a concentration threshold for NaCl above which the nanobubble properties are significantly affected. The salt effectively promotes the adsorption of surfactant ions, which in turn leads to a decrease in interfacial tension. The Zeta potential of nanobubbles is established through the competing interactions between the surface adsorption and ion shielding effect. Subsequently, the critical stable conditions for nanobubbles generated in solutions containing surfactants and salts are calculated, while considering both the kinetic stability of nanobubble populations and the thermodynamic stability of individual nanobubbles. These findings offer valuable insights into the intricate influence of complex aqueous ionic environment on nanobubbles, thereby setting the stage for the deliberate manipulation of them.