Changes In Interfacial Tension Research Articles

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 0.5mol/L sodium chloride solution, 10V DC voltage, and a voltage action time of 18 hours, 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.

Preparation of pumpkin seed protein isolate nanoparticles by heat-assisted pH-shifting: Enhanced emulsification performance and dispersibility

A food-grade Pickering emulsifier was fabricated using heat-assisted pH-shifting (HP) method for enhancing the emulsion stability. The emulsification performance of the modified pumpkin seed protein isolate (PSPI) nanoparticles was initially tested. The results showed that the modified PSPI had substantially improved emulsifying capacity, with the internal oil phase volume fraction reaching up to 80%, and the emulsion remaining stable after centrifugation at 10,000 g for 60 min and 30 days of storage. The data from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), UV–visible, intrinsic fluorescence and fourier transform infrared spectroscopy (FTIR) indicated that the primary, secondary and tertiary structures of PSPI were disrupted, resulting in changes in interfacial tension, wettability, particle size, and dispersibility of the protein, which promoted the adsorption of modified PSPI nanoparticles to the surface of oil droplets and improved the emulsion stability. Overall, the HP modified PSPI is a promising Pickering emulsifier for various applications.

Droplet microfluidic system for high throughput and passive selection of bacteria producing biosurfactants.

Traditional methods for the enrichment of microorganisms rely on growth in a selective liquid medium or on an agar plate, followed by tedious characterization. Droplet microfluidic techniques have been recently used to cultivate microorganisms and preserve enriched bacterial taxonomic diversity. However, new methods are needed to select droplets comprising not only growing microorganisms but also those exhibiting specific properties, such as the production of value-added compounds. We describe here a droplet microfluidic screening technique for the functional selection of biosurfactant-producing microorganisms, which are of great interest in the bioremediation and biotechnology industries. Single bacterial cells are first encapsulated into picoliter droplets for clonal cultivation and then passively sorted at high throughput based on changes in interfacial tension in individual droplets. Our method expands droplet-based microbial enrichment with a novel approach that reduces the time and resources needed for the selection of surfactant-producing bacteria.

Research on Flow Patterns of Two-Phase Fracturing Fluid in Hydraulic Fracture Considering the Fluid Leak-off.

In in situ-generated proppant fracturing technology without proppant injection, the distribution of the flow pattern of two-phase fracturing fluid in the fracture determines the concentration of proppant particles formed by phase change in different positions. Therefore, the study of a two-phase fracturing fluid flow pattern is of great significance to reveal the formation mechanisms of different flow patterns and guide the on-site implementation of the technology. This paper establishes a mathematical model for the two-phase fracturing fluids in fractures based on their physical properties and presents numerical experiments on the flow pattern of two-phase fracturing fluids under different conditions of injection displacement, interfacial tension, and phase change liquid (PCL) ratio. The results show that at lower injection displacements, such as 3 or 4 m3/min, it is easier to form striped shape distributions, and at higher injection displacements, such as 5 or 6 m3/min, it is easier to form droplet shape distributions. When the interfacial tension is low (15 mN/m), PCL shrinks less and is distributed in strips; when the interfacial tension is high (25, 35, and 45 mN/m), PCL shrinks more and mainly forms droplet-shaped distributions. PCL tends to form discrete droplet shape distributions at PCL volume fractions of 10, and 20%. At 30% volume fraction, PCL is distributed in strips, and at 40% volume fraction, PCL forms strips of a larger size. These findings reveal the changing pattern of two-phase fracturing fluid flow and enrich the theoretical system of in situ-generated proppant fracturing technology, which can provide theoretical support for the on-site implementation of this technology.

Evaluation of the wettability alteration on sandstone rock by graphene oxide adsorption

AbstractOne of the most important parameters of a crude oil recovery process is the interaction of rock-crude oil. In order to alter the positive interaction rock-crude oil, several chemical systems have been proposed. In this study, we use graphene oxide (GO) to alter the positive interaction between sandstone rock and crude oil. In order to evaluate the alteration of the interaction rock oil, we measured the change in the contact angle water sandstone and oil sandstone. In addition, we have measured the interfacial tension (IFT) modification due to the presence of GO in the fluids. The combined effects of graphene oxide concentration, salinity, and pH on interfacial tension and contact angle have been evaluated. The results show that despite GO has not produced significant changes in interfacial tension, the adsorption of GO on the sandstone surface changes the wettability of the sandstone from being strongly crude oil-wet to intermediate crude oil-wettability. Measurements of the contact angle of the treated rock surface with GO solution under soft salinity conditions and pH of 8 show that adsorbed GO can alter the wettability of sandstone from 150 to 90°. In order to corroborate the change in wettability, Amott-Harvey tests were performed. The formation brine and crude oil were subjected to fluid–fluid compatibility tests. These evaluations confirmed a favorable compatibility with the formulation containing 900 ppm of total dissolved solids (TDS), pH 8, and 900 ppm of GO. As a result, it is considered a potential candidate for coreflooding tests.

Interfacial Tension Hysteresis of Eutectic Gallium‐Indium

AbstractWhen in a pristine state, gallium and its alloys have the largest interfacial tensions of any liquid at room temperature. Nonetheless, applying as little as 0.8 V of electric potential across eutectic gallium indium (EGaIn) placed within aqueous sodium hydroxide (NaOH, or other electrolyte) solution will cause the metal to behave as if its interfacial tension is near zero. The mechanism behind this phenomenon has remained poorly understood because NaOH dissolves the oxide species, making it difficult to directly measure the concentration, thickness, or chemical composition of the film that forms at the interface. In addition, the oxide layers formed are atomically‐thin. Here, it presents a suite of techniques that allow to simultaneously measure both electrical and interfacial properties as a function of applied electric potential, allowing for new insights into the mechanisms, which cause the dramatic decrease in interfacial tension. A key discovery from this work is that the interfacial tension displays hysteresis while lowering the applied potential. It combines these observations with electrochemical impedance spectroscopy to evaluate how these changes in interfacial tension arise from chemical, electrical, and mechanical changes on the interface, and close with ideas for how to build a free energy model to predict these changes from first principles.

Spontaneous imbibition of amphoteric-anionic surfactant and Fe3O4 nanoparticles colloidal mixture for enhanced oil recovery

This study investigates the effects of individual and combined systems on interfacial tension (IFT) and wettability alteration characteristics of a combination mixture of colloidal Fe3O4 nanoparticles and amphoteric-anionic surfactant. Combining a binary of amphoteric-anionic surfactants has resulted in an IFT reduction compared to brine alone. Furthermore, the addition of Fe3O4 nanoparticles at concentrations lower than the critical micelle concentration (CMC) of binary surfactant mixes (<0.15 wt%) resulted in an observed increase in IFT values. However, there is no significant change in IFT around or above the CMC (≥0.15 wt%). The alteration in wettability can be observed through a reduction in contact angle when amphoteric-anionic surfactants and Fe3O4 nanoparticles are combined, resulting in a change from water-wet to strongly water-wet conditions. The findings of the imbibition test also demonstrated that adding 0.01 wt% Fe3O4 colloidal nanoparticles in the surfactant mixture provided an optimal recovery efficiency of 63.17%. The results of this study indicate that a notable improvement in recovery can be observed when the primary mechanism of wettability alteration is achieved and simultaneously supported by IFT reduction.

Enhancing oil recovery by alkane-modified molybdenum disulfide nanosheets with the optimum alkyl chain length: The balance between dispersity and hydrophobicity to achieve high interfacial activity

Alkane-modified molybdenum disulfide (AM-MoS2) nanosheets have attracted widespread interest as oil displacement agents for enhancing oil recovery due to their unique oil-water interfacial properties. However, the relationship between the interfacial activity and alkyl chain structure of AM-MoS2 is not comprehensively understood. In this study, 3AM-MoS2 nanosheets were prepared with MoS2 and alkylamines to study the effect of alkyl chain length on the oil-water interfacial activity of AM-MoS2 nanosheets under different salinity conditions. The AM-MoS2 nanosheets prepared with octylamine, dodecylamine, and octadecylamine were referred to as AM8-MoS2, AM12-MoS2, and AM18-MoS2, respectively. AM18-MoS2, which possesses the longest alkyl chain among all the samples, exhibited the highest oil-water interface adsorption ratio within the experimental concentration and salinity ranges. However, the changes in oil-water interfacial tension (IFT) did not agree with the changes in the interface adsorption ratio of nanosheets. AM18-MoS2 exhibited the best interfacial activity, and the IFT was lower than that of MoS2, AM8-MoS2 and AM12-MoS2 when the salinity was no more than 5000 mg/L, while AM12-MoS2 and AM8-MoS2 exhibited the best interfacial activity and the lowest IFT when the salinity reached 10,000 mg/L and 20,000 mg/L, respectively. Considering that the interface adsorption ratio of AM18-MoS2 was higher than that of the other samples under all the experimental conditions, the change in IFT and interfacial activity could be attributed to the change in the morphology of the adsorption layer of nanosheets. The decreased charge repulsion and the increased hydrodynamic size of nanosheets, which resulted from increased salinity, had positive and negative effects, respectively, on the morphology of the adsorption layer. The competition between the two effects resulted in the inflection point in the relationship between the IFT and salinity of AM-MoS2. The AM-MoS2 nanosheets with the optimum alkyl chain length balanced the dispersity and hydrophobicity, which contributed to achieving the best interfacial activity at a certain salinity.

Effect of Titanium Dioxide Nanoparticles on Surfactants and Their Impact on the Interfacial Properties of the Oil-Water-Rock System.

The application of nanoparticles (NPs) in the oil and gas industry has received wide attention in recent years because it is increasingly being considered a promising approach to recovering trapped oil in conventional hydrocarbon reservoirs. Numerous studies have demonstrated that combining nanoparticles with a surfactant can enhance surfactant performance by changing the interfacial properties of the solution when it comes in contact with crude oil and rock surfaces. However, more information and additional experimental data are required concerning the application of titanium dioxide nanoparticles in alkyl ethoxy carboxylic surfactants. In this study, we measure the changes in interfacial tension and wettability due to the addition of titanium dioxide nanoparticles (0, 100, 250, and 500 ppm) in alkyl ethoxy carboxylic surfactant using a spinning drop tensiometer and contact angle measurements. The interfacial tension of the crude oil-water (surfactant) system decreases by approximately two orders of magnitude with an increasing titanium dioxide concentration, exhibiting a minimum value of 5.85 × 10-5 mN/m. Similarly, the contact angle decreases on the surface of the Berea sandstone by combining the surfactant with titanium dioxide, reaching a minimum contact angle of 8.8°. These results demonstrate the potential of this new approach to maximize the recovery of trapped oil and significantly improve oil production.

Interfacial tension of smart water and various crude oils

The utilization of smart water in EOR (enhanced oil recovery) operations has drawn increased attention in recent years. Nevertheless, the variety and complexity of mechanisms during smart water injection require more research endeavors. In this study, interfacial tension (IFT) for the smart water/crude oil interacting system has been investigated. The investigated parameters included various salts with different salinity, pH, asphaltene type, and aged smart water with two crude oil samples. The results showed that the hydration of ions in smart water would play a key role to discern the primary mechanism of smart water. The interaction of acidic and basic asphaltene with hydration shell of different ions can be considered as primary mechanism for efficacy of smart water. Acidic and basic asphaltenes serve as intrinsic surfactants due to their interaction with OH− in the anion hydration shell and H+ in the cation hydration shell, respectively. The propensity of acidic asphaltene to interact with anions with high hydration energy and the tendency of basic asphaltene to interact with cations with high hydration energy led to an IFT of 0.2 mN/m and 11.3 mN/m for acidic and basic oils, respectively. The impact of pH also revealed that acidic and basic asphaltenes would have lower IFT in alkaline and acidic environments. Finally, it was found that changes in IFT for the aged smart water with crude oil depend on the asphaltene type as well as salt and salinity.

Functionalized Amphiphilic Block Copolymers and Complex Emulsions for Selective Sensing of Dissolved Metals at Liquid-Liquid Interfaces.

Increasing contamination in potable water supplies necessitates the development of sensing methods that provide the speed and selectivity necessary for safety. One promising method relies on recognition and detection at the liquid-liquid interface of dynamic complex emulsions. These all-liquid materials transduce changes in interfacial tensions into optical signals via the coupling of their chemical, physical, and optical properties. Thus, to introduce selectivity, it is necessary to modify the liquid-liquid interface with an interfacially stable and selective recognition unit. To this end, we report the synthesis and characterization of amphiphilic block copolymers modified with metal chelators to selectively measure the concentrations of dissolved metal ions. We find that significant reduction in interfacial tensions arises upon quantitative addition of metal ions with high affinity toward functionalized chelators. Furthermore, measurements from UV-vis spectroscopy reveal that complexation of the block copolymers with metal ions leads to an increase in surface excess and surfactant effectiveness. We also demonstrate selective detection of iron(III) cations (Fe3+) on the μM levels even through interference from other mono-, di-, or trivalent cations in complex matrices of synthetic groundwater. Our results provide a unique platform that couples selective recognition and modulation of interfacial behaviors and demonstrates a step forward in the development of the multiplexed sensing device needed to deconvolute the complicated array of contaminants that comprise real-world environmental samples.

Effect of hydrophobic sucrose esters with different fat acid composition and esterification degree on whipped cream properties

The properties of whipped cream rely on fat droplets partial coalescence phenomena occurring during the whipping process. Sucrose esters, as environmental compatibility lower-molecular-weight emulsifiers can modify partial coalescence by regulating both fat crystallization and interfacial properties due to their different fatty acid composition and esterified degree. In this study, we investigated the effects of five hydrophobic sucrose esters (L195, O170, S170, S370, and S570) with different fatty acid compositions (lauric acid, oleic acid and stearic acid) and esterification degrees (monoesters content from 1% to 30%) on whipped cream properties by analyzing fat crystallization inside droplets and oil/water interfacial properties. First, the crystallization profile and microstructure of fat at bulk and emulsion states were also assessed to characterize fat crystallization properties. Additionally, changes in interfacial tension and rheology during cooling were performed to evaluate oil/water interfacial properties. Finally, we investigated the influence of sucrose ester types on emulsion and whipped cream properties. The smaller size of fat crystals inside fat droplets and the presence of stronger interfacial layers induced by S170 (HLB 1, Sucrose monoester<1%, stearic acid 70%), led to the formation of a more homogeneous fat partial coalescence network in whipped cream, resulting in enhanced firmness and stability. The mechanisms behind the effects of fat crystallization and interfacial properties, particularly interfacial crystallization behaviors, on the properties of whipped cream were thoroughly examined and discussed. The results provide theoretical guidance for the application of hydrophobic sucrose esters or lower-molar-weight emulsifiers in whipped cream systems.

Effect of sodium hydroxide, sodium dodecyl benzenesulfonate, and resin on the interfacial tension of asphaltenic synthetic oil extracted from acidic crude oil under low salinity condition

During the past years, the usage of new oil recovery methods known as enhanced oil recovery methods is increasing because of energy consumption rate enhancement and reservoir pressure depletion. Unfortunately, since most of the investigations were focused on crude oil, it is hard to find a generalized pattern of interfacial tension (IFT) and wettability change for different crude oils because of its complicated composition. So, it is necessary to examine the effect of specific fractions of crude oil especially resin and asphaltene fractions on the IFT and wettability alteration using systematic investigations. Although a limited number of investigations examined the interactions between these specific fractions and salts, there are no systematic reports respecting the possible interactions between asphaltene and resin fractions in the presence of alkaline and surfactant. So, in the first stage, the impact of dissolving asphaltene (0–9 wt%) in the toluene was investigated on the IFT reduction which revealed a decrease in IFT value from 34.8 to 23.3 mN/m as the asphaltene concentration was increased. Further experiments showed that the presence of MgCl2 and NaCl with a maximum concentration of 5000 ppm led to a reduction in IFT to a minimum value of 18.3 and 17.3 mN/m for NaCl and MgCl2, respectively, which means the higher impact of MgCl2 on the IFT reduction. After that, the selected optimum concentrations of MgCl2 and NaCl (5000 ppm) were used in the rest of the experiments in which the effect of resin fraction and other chemicals including sodium dodecyl benzenesulfonate (SDBS) and NaOH concentrations was examined on the IFT reduction and rock wettability. According to the obtained results, it was possible to reach the minimum IFT value of 0.08 mN/m, which is several orders lower than the original IFT value of the binary system without the chemicals using the optimum chemical formulation obtained by mixing proper concentrations of SDBS, NaOH, MgCl2, and NaCl. Moreover, the obtained optimum formulations were used through core flooding experiments which revealed the possibility of increasing the oil recovery to a maximum value of 10.1% based on the original oil in place.

Inhibition of asphaltene deposition by Al2O3 nanoparticles during CO2 injection

Carbon dioxide flooding is of interest due to its high oil-sweep efficiency for enhanced oil recovery and contribution to the reduction of greenhouse gas emissions. However, when CO2 is injected into deep geological strata, asphaltene may precipitate. In this work, the effect of Al2O3 nanoparticles on the deposition of asphaltene was examined by assessing the variations of bond number and interfacial tension at different pressures and a temperature of 60 °C. The asphaltene onset point and intensity were characterized using the bond number, which proved a better indicator of changes in oil droplet shape and interfacial tension with gravity. Synthesized mixtures of toluene and n-heptane that contained two different kinds of asphaltenes were used as M and D oil samples. A 0.06 mass% addition of Al2O3 nanoparticles, which worked best for reduction of interfacial tension, was also applied at various pressures. Addition of nanoparticles to the oils prevented asphaltene precipitation in both synthetic samples by altering the slope of the plot of interfacial tension with pressure by 49.7% for the M sample and 9.0% for the D sample. The Al2O3 nanoparticles were found to be more effective at inhibiting asphaltene precipitation for the M oil sample due to its lower H/C ratio and higher nitrogen content.

Impacting Factors of Changes in Dynamic Viscosity and Interfacial Tension of Wood Xylem Sap

The growth of trees is inseparable from the water transpiration in the xylem. To explore the mechanism of sap rising in the xylem, the monthly variation of the dynamic viscosity and interfacial tension of the xylem sap of different tree species and their impacting factors were analyzed. In this experiment, the dynamic viscosity and interfacial tension of the xylem sap of poplar and metasequoia were measured within one year, as well as the sap velocity of poplar. Gas chromatography–mass spectrometry and atomic absorption spectroscopy were used to detect the organic components and inorganic cations of the xylem sap of poplar and metasequoia. By analyzing the influence of organic components and the inorganic cation concentration of xylem sap on the dynamic viscosity and interfacial tension of xylem sap, this study revealed that the dynamic viscosity and the interfacial tension of poplar and metasequoia samples in different months changed in basically the same manner. However, the dynamic viscosity and the interfacial tension of the metasequoia samples were generally higher than those of the poplar samples. The dynamic viscosity of the xylem sap had an obvious exponential relationship with temperature, while the interfacial tension of the xylem sap had an inconspicuous linear relationship with temperature. In addition, disparate xylem structures of the broad-leaved tree poplar and the coniferous tree metasequoia led to different concentrations of organic components and inorganic cations in their xylem sap, which made a difference in the dynamic viscosity and interfacial tension between poplar and metasequoia samples.

A novel and noninvasive approach to study the shear rheology of complex fluid interfaces

Surfactants at gas-liquid and liquid-liquid interfaces have profound effects on interfacial stresses that strongly influence flow in bulk phases in contact with the interface. These effects include changes in interfacial tension and the development of extra stresses that arise when the interface is deformed. Surfactants are important in nature, biological function, and numerous technologies. Understanding interfacial rheology is critical to the development of improved surfactants for these important applications. Here, we propose a novel and noninvasive technique for the investigation of interfacial rheological behavior in shear deformations. In recent years, several techniques for such measurements have been developed and utilized to study a wide range of surfactant systems. However, existing techniques may inherently be invasive making it difficult to isolate the intrinsic interfacial rheological behavior from disturbances to the interface caused by the measurement itself. The proposed technique is indirect in that it does not require the introduction of a probe to deform the interface making it noninvasive. The viability of the technique is demonstrated through comprehensive fluid dynamics modeling of the flow involving a gas-liquid interface with different rheological behaviors.

Silicon electrodeposition from the KF-KCl-K&lt;sub&gt;2&lt;/sub&gt;SiF&lt;sub&gt;6&lt;/sub&gt; and KF-KCl-KI-K&lt;sub&gt;2&lt;/sub&gt;SiF&lt;sub&gt;6&lt;/sub&gt; melts

Silicon and silicon-based materials find extensive applications in metallurgy, microelectronics, and other emerging industries. The field of use of synthesized silicon varies based on its morphology and purity. This study employs voltammetry, galvanostatic electrolysis, and scanning electron microscopy to examine the impact of KI surfactant (in mol %) to 66.5KF–33.3KCl–0.23K2SiF6 melt at 750°C on the electrowinning kinetics of silicon ions and the morphology of silicon deposits formed on a glassy carbon electrode. The findings demonstrate that the addition of potassium iodide to the KF–KCl–K2SiF6 melt at a concentration of 2 mol % induces changes in interfacial tension at the boundary between the glassy carbon, melt, and atmosphere. Consequently, the wetting of the glassy carbon with the melt decreases, leading to a reduction in the actual working surface area and, consequently, a decrease in cathode current while maintaining current density. Taking into account this effect and employing an algebraic estimation of the influence of the melt meniscus shape, it is postulated that the addition of KI does not significantly affect the kinetics of the cathode process. Nevertheless, the impact of KI addition on the morphology of electrodeposited silicon is mentioned. During the electrolysis of the KF–KCl–K2SiF6 melt, fibrous silicon deposits with arbitrary shapes are formed on the glassy carbon electrode, whereas the addition of 2 and 4 mol % of potassium iodide to the melt leads to the agglomeration and smoothing of silicon deposits under the same electrolysis conditions (cathode current density: 0.02 A/cm2, electrolysis duration: 2 h). The obtained results indicate the potential to manipulate the morphology of electrodeposited silicon for specific applications in various fields.

Calculation of IFT in porous media in the presence of different gas and normal alkanes using the modified EoS

Gas injection can increase oil recovery because the gas–oil interfacial tension is less than the water–oil interfacial tension (IFT) and tends to zero in the miscibility state. However, little information has been provided on the gas–oil movement and penetration mechanisms in the fracture system at the porosity scale. The IFT of oil and gas in the porous medium changes and can control oil recovery. In this study, the IFT and the minimum miscibility pressure (MMP) are calculated using the cubic Peng-Robinson equation of state that has been modified using the mean pore radius and capillary pressure. The calculated IFT and MMP change with the pore radius and capillary pressure. To investigate the effect of a porous medium on the IFT during the injection of CH4, CO2, and N2 in the presence of n-alkanes and for validation, measured experimental values in references have been used. According to the results of this paper, changes in IFT vary in terms of pressure in the presence of different gases and, the proposed model has good accuracy for measuring the IFT and the MMP during the injection of hydrocarbon gases and CO2. In addition, as the average radius of the pores gets smaller, the interfacial tension tends to lower values. This effect is different with increasing the mean size of interstice in two different intervals. In the first interval, i.e. the Rp from 10 to 5000 nm, the IFT changes from 3 to 10.78 mN/m and in the second interval, i.e. the Rp from 5000 nm to infinity, the IFT changes from 10.78 to 10.85 mN/m. In other words, increasing the diameter of the porous medium to a certain threshold (i.e. 5000 nm) increases the IFT. As a rule, changes in IFT affected by exposure to a porous medium affect the values of the MMP. In general, IFT decreases in very fine porous media, causing miscibility at lower pressures.

Synthesis and Enhanced Oil Recovery Potential of the Bio-Nano-Oil Displacement System.

Nanoparticles (NPs) have attracted great attention in the tertiary oil recovery process due to their unique properties. As an economical and efficient green synthesis method, biosynthesized nanoparticles have the advantages of low toxicity, fast preparation, and high yield. In this study, with the theme of biotechnology, for the first time, the bio-nanoparticles reduced by iron-reducing bacteria were compounded with the biosurfactant produced by Bacillus to form a stable bio-nano flooding system, revealing the oil flooding mechanism and enhanced oil recovery (EOR) potential of the bio-nano flooding system. The interfacial properties of the bio-nano-oil displacement system were studied by interfacial tension and wettability change experiments. The enhanced oil recovery potential of the bio-nano-oil displacement agent was measured by microscopic oil displacement experiments and core flooding experiments. The bio-nano-oil displacement system with different nanoparticle concentrations can form a stable dispersion system. The oil-water interfacial tension and contact angle decreased with the increase in concentration of the bio-nano flooding system, which also has a high salt tolerance. Microscopic oil displacement experiments proved the efficient oil displacement of the bio-nano-oil displacement system and revealed its main oil displacement mechanism. The effects of concentration and temperature on the recovery of the nano-biological flooding system were investigated by core displacement experiments. The results showed that the recovery rate increased from 4.53 to 15.26% with the increase of the concentration of the system. The optimum experimental temperature was 60 °C, and the maximum recovery rate was 15.63%.

Effects of Co Addition on Microstructure Evolution and Efficient Hydrogen Evolution of Self-Supported Fe–P@Cu Immiscible Alloy

In this article, the effects of Co addition on microstructure evolution and catalytic efficiency variation of an Fe–P@Cu immiscible alloy were systematically studied. According to the first-principles molecular dynamics simulations, it was found that P in the Fe–P@Cu alloy with Co addition would be preferentially bonded with Fe and/or Co in the first coordination shell, and Cu and (Fe+Co) atoms tended to appear on the opposite side of P atom in the three-dimensional cluster configuration, which would have a significant guiding effect on the subsequent solidification process. Through the microstructure analysis, it was observed that the addition of Co element had an inhibitory action on the liquid phase separation behavior due to the changes of interfacial tension, resulting in the formation of a fine second phase structure. Through the electrochemistry characteristics, it was found that the overpotentials of Fe–P@Cu metallic catalysts containing 8% Co and 16% Co with a current density of 10 mA/cm2 have been improved to be 160 and 155 mV in 0.5 M H2SO4 respectively. This excellent catalytic performance might be mainly attributed to the rapid transport of ions and the remarkable amount increase of electron transfer, resulting in the obvious promotion of the hydrogen evolution reaction of (FexCo1–x)nP@Cu alloys.