Adsorption Layer Research Articles

Insights into Adsorption Behaviors of Multi-Component Shale Oil in Illite Nanopores Under Different Reservoir Conditions by Molecular Simulation

Clay pores are important storage spaces in shale oil reservoirs. Studying the adsorption behavior of shale oil in clay nanopores is of great significance for reserve assessment and exploitation. In this work, illite clay pore models and multi-component shale oil adsorption models considering light hydrocarbon correction are constructed for carrying out molecular dynamics simulation. We studied the adsorption behavior and characteristics of shale oil in illite pores, and analyzed the effects of reservoir environmental factors such as temperature, pressure and pore size on the adsorption behavior. The results show that in illite nanopores, shale oil can form multiple adsorption layers. The heavier the component, the stronger the interaction with the wall. The adsorption ratio of the component is closely related to the solid–liquid interaction and the molar fraction, which preliminarily reveals the reason why the heavy component content in the produced oil is considerable. The increase in temperature promotes the desorption of light and medium components, while the heavy components and dissolved gas are less affected; although the increase in pressure inhibits diffusion, the adsorption amount changes little, and only the light component increases slightly. This study deeply reveals the adsorption mechanism of shale oil in illite pores, providing a theoretical basis for the optimization and development of shale reservoirs.

Optimization of the Preparation Process of Crosslinked Polyvinyl Alcohol and Its Thermal Stability in Cementing Slurry

This study focuses on addressing the limitations of fluid loss additive in cement slurry under higher temperatures. The synthesis process of glutaraldehyde-crosslinked polyvinyl alcohol (PVA) was optimized to develop an efficient fluid loss additive for oil well cement slurries. Using one-factor experiments and the uniform design method, the optimal synthesis parameters were established: a reaction temperature of 50 °C; an acid concentration of 1 mol/L; a PVA mass concentration of 8%; a molar ratio of glutaraldehyde to PVA hydroxyl group of 1.47; and a crosslinking degree of 1.49%. The optimized crosslinked PVA demonstrated the ability to control API fluid loss within 50 mL when applied at 1% concentration in cement slurry under conditions of 30–110 °C and 6.9 MPa. Rheological analysis at medium and high temperatures revealed improved slurry properties, including smooth thickening curves and unaffected compressive strength. Further analyses, including thermogravimetric analysis (TGA), Zeta potential testing, and scanning electron microscopy (SEM), revealed that the crosslinked PVA hydrogel remained thermally stable up to 260 °C. Chemical crosslinking transformed the linear PVA into a network structure, enhancing its molecular weight, viscoelasticity, and thermal stability. This thermal resistance mechanism is attributed to the hydrogel’s high-strength reticular structure which forms a uniform, dense, and highly stable adsorption layer, thereby improving both the additive’s efficiency and the hydrogel’s temperature resistance.

Simulation analysis of radiometer effect and outgassing based on molecular particle source perturbation

The Laser Interferometer Space Antenna (LISA) mission is designed to detect space gravitational wave sources in the millihertz band. A critical factor in the success of this mission is the residual acceleration noise metric of the internal test mass (TM) within the ultra-precise inertial sensors. Existing studies indicate that the coupling effects of residual gas and temperature gradient fluctuations significantly influence this metric, primarily manifesting as the radiometer effect and the outgassing effect. However, current theoretical research methods are inadequate for accurately decoupling and predicting the contributions of these two effects. To this end, this paper conducts an in-depth decoupling analysis of the impacts of the radiometer effect and outgassing effect using a simulation method based on molecular particle source perturbation. By constructing a finite element simulation model that couples residual gas and temperature gradient fluctuations, we simulate molecular thermal motion based on fundamental theories such as Maxwell’s distribution function, the free path distribution law, and Knudsen’s adsorption layer hypothesis, in order to study the two manifestations of the radiometer effect and the outgassing. By analyzing and comparing the simulation results, theoretical results, and ground torsion results, we find that the simulation results align effectively with the measured ground torsion results. This alignment enhances our understanding of how the radiometer effect and outgassing impact the internal pressure changes in the sensitive probe, which cannot be sufficiently decoupled by theoretical calculations alone. This conclusion demonstrates that the simulation method can effectively analyze the coupling effects of temperature gradient fluctuation and residual gas in inertial sensors, providing an important theoretical basis and practical significance for developing physical models of inertial sensors aimed at predicting and optimizing overall performance.

Compound Surfactant System with Superior Oil Displacement Performance: Balanced Synergistic Effects from Oil-Water and Oil-Solid Interfaces.

The oil film formed by the adhesion of crude oil to the resin-asphalt adsorption layer is difficult to peel off due to the strong oil-solid interaction, which severely limits further improvements in oil recovery. Although conventional compound oil displacement systems can effectively reduce oil-water interfacial tension, facilitate oil droplet deformation, and alleviate the Jamin effect, they are insufficient in controlling the wettability of oleophilic rock surfaces. In this paper, sodium nonylphenol polyoxyethylene ether sulfate (NPES) and sodium lauric acid ethanolamine sulfonate (HLDEA) were compounded to construct an efficient oil displacement system that simultaneously achieves wettability control of lipophilic surfaces and ultralow oil-water interfacial tension. The HLDEA + NPES system reduces the interfacial tension to 3.8 × 10-3 mN·m-1 and enhances surface wettability control, with an underwater oil contact angle of 157.2°. The compound system can remain stable at high temperatures (up to 110 °C) and high salinity (1 × 105 mg·L-1 NaCl and 7 × 103 mg·L-1 Ca2+). The oil recovery rate increases by 28.7% compared with water flooding and surpasses by 7.8% compared with a commercial ultralow interfacial tension system (10-4 mN·m-1). The synergistic effect of HLDEA and NPES in the oil/water interface increases the interfacial modulus and phase angle, thereby improving the stability of the interfacial film. The synergistic adsorption of HLDEA and NPES in the oil/water interface creates a denser adsorption layer, achieving enhanced wettability control. The HLDEA + NPES system balances the interactions from the oil-water and oil-solid interfaces, achieving a synergistic effect of oil film peeling and oil droplet migration, thereby significantly improving the recovery rate.

Molecular Insights into the Control Mechanism of the Solid-Liquid Interface Interaction on Shale Oil Occurrence: Grand Canonical Monte Carlo and Molecular Dynamics Simulations Investigation.

The strong solid-liquid interaction leads to the complicated occurrence characteristics of shale oil. However, the solid-liquid interface interaction and its controls of the occurrence state of shale oil are poorly understood on the molecular scale. In this work, the adsorption behavior and occurrence state of shale oil in pores of organic/inorganic matter under reservoir conditions were investigated by using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The adsorption potential energy and interaction energy were quantitatively evaluated, and the control mechanism of the oil-rock interaction on shale oil occurrence was explained. Results show that the density distribution of shale oil is not uniform under the confined space. Multiple layers of adsorption of n-octane occur in graphene pores. The number of adsorbed layers is mainly affected by pore size. With the increasing temperature and pore size, the adsorption site shifts from the high-energy to low-energy site and the solid-liquid interaction weakens. The effect of pressure on the occurrence state can be ignored due to capillary condensation. Minerals and oil chemical compositions also affect the oil-rock interaction and occurrence state. The adsorption intensity of minerals to n-octane decreases in the order graphene > montmorillonite > quartz. Competitive adsorption occurs among oil components. The adsorption order of oil components in graphene is asphaltenes > resin > nonhydrocarbon compound > aromatic hydrocarbons > saturated hydrocarbons. Asphaltenes preferentially adsorb on the surface of organic matter and occupy most of the adsorption surface, while saturated hydrocarbons mainly adsorb on the surface of heavy components or distribute in the pore center. The molecular structure of hydrocarbons also affects the adsorption characteristics. The long-chain hydrocarbons preferentially adsorb on the surface more than short-chain hydrocarbons. The straight-chain hydrocarbons preferentially adsorb more than the branched-chain hydrocarbons. This study provides the microscopic interaction between shale oil and minerals and explores the effect of the control mechanism of the oil-rock interfacial interaction on the occurrence state at the molecular level.

Thickness Profile Measurements of Acoustic Induced Maneuvering of Thin Film Evaporation

The transient and steady-state effects on the thickness profile of an extended meniscus in presence of an surface acoustic wave are reported experimentally in the nanoscale range using spectral reflectance. The fluid flow and heat transfer in the evaporating thin film region are interpreted through the changes in the thickness profile. The measurement of the steady-state thickness profile exhibits thinning of the adsorbed layer along with stretching of the evaporating thin film region in the presence of acoustic energy at different amplitudes (73.50–86.87 µm). The derived pressure difference increases for a thinner adsorbed layer, suggesting a rise in the flow driven toward the evaporating thin film region. The associated average heat flux enhances (109%) for the stretched evaporating thin film. The transmission of acoustic energy into kinetic energy in the liquid results in instability near the interline region. Subsequently, the generation of sessile droplets along the extended meniscus is observed. Further, the changes in the sessile droplets (generation diameter, mean diameter, rate of generation and heat flux) near the extended meniscus for different frequencies are analyzed. The results corroborate enhanced cooling upon application of an acoustic wave.

Research on the tribological properties of kaolin/MoDDP composite lubricant additives under heavy load and impact conditions

PurposeWith respect to severe working conditions such as heavy load and impact, this paper aims to investigate the friction reduction and anti-wear performance of kaolin and molybdenum dialkyl dithiophosphate (MoDDP) composite lubricant additives to improve the lubrication effect of a single additive.Design/methodology/approachA four-ball friction test was carried out to determine the optimal concentration of kaolin and organic molybdenum additives and the tribological properties of the kaolin/MoDDP composite lubricant additives. A ring block test of composite lubricant additives was designed to investigate its lubrication performance under the severe working conditions of low speed, heavy load and impact.FindingsThe results showed that the optimal addition mass fractions of kaolin and MoDDP were 4.0 and 1.5 Wt.%, respectively, when kaolin and MoDDP were used as single lubricant additives. Compared with the single additive, the 4.0 Wt.% kaolin/1.5 Wt.% MoDDP composite lubricant additive showed excellent friction reduction and anti-wear effects under heavy load and impact conditions. Physicochemical analysis of the wear surface revealed that the lamellar kaolin additive and MoDDP had excellent synergistic effects, and the friction process promoted the generation of lubricant films containing a chemically reactive layer of MoS2, MoO2, FeS2 and Fe2O3 and a physically adsorbent layer containing SiO2 and Al2O3, which play important roles in anti-wear and friction reduction.Originality/valueThe excellent friction reduction and anti-wear effects of lamellar silicate minerals and the excellent antioxidant properties and good synergistic effects of molybdenum were comprehensively used to develop the composite additives with great lubricating properties.

Self-assembly of chromatic patchy particles with tetrahedrally arranged patches.

The achievement of selectivity in the formation of cubic diamond is challenging due to the emergence of competing phases such as its hexagonal polymorph or clathrates possessing similar free energy. Although both polymorphs exhibit a complete photonic bandgap, cubic diamond exhibits it at lower frequencies than the hexagonal counterpart, positioning it as a promising candidate for photonic applications. Herein, we demonstrate that the 1 : 1 mixture of identical patchy particles cannot selectively form the cubic diamond polymorph due to the frustrations present in the system that are manifested in the primary adsorption layer and propagate as the film grows. We provide a plausible explanation for why the binary system under confinement, resembling interactions between the complementary DNA bases, cannot yield the selectivity in the formation of cubic diamond crystals, which is based on the similarities to the antiferromagnetic systems. We always observe a mixture of both hexagonal and cubic diamonds; however, the formation of such stacking hybrids is observed for a wider range of patch sizes compared to the one-component system.

Molecular mechanisms of hydrogen leakage and blockage in kaolinite nano-cracks for underground hydrogen storage

Underground H2 storage in saline aquifers is critical for advancing the global energy transition through large-scale H2 utilization. However, cyclic stress-induced nano-cracks in caprocks may lead to leakage due to the small size and high diffusivity of H2. This study employed molecular dynamics simulations exploring the occurrence states of H2 and H2O near kaolinite surfaces, particularly focusing on H2 leakage when a nano-crack formed. We examined the effects of basal surfaces (gibbsite and siloxane), water content, and cushion gases (CH4 and CO2). In gibbsite aquifers, H2O formed adsorption layers; while in siloxane aquifers, it appeared as droplets or bridges. Upon nano-crack formation, initial H2 leakage occurred but halted once a critical number of H2O blocked the crack. H2 leakage was generally higher in siloxane than in gibbsite aquifers, except at low water content. Increased water content significantly reduced H2 leakage in gibbsite aquifers by rapidly achieving the critical H2O number, whereas the effect in siloxane aquifers depended on H2O distribution. Cushion gases effectively mitigated H2 leakage. CO2 outperformed CH4 in gibbsite aquifers, while their effects in siloxane aquifers varied based on H2O distribution. CH4 reduced leakage by hindering initial H2 entry into the crack, while CO2 not only impeded initial H2 entry but also assisted H2O in blocking the crack. Our analysis of density distributions, leakage dynamics, molecular configurations, and excess chemical potentials provides insights into H2 leakage and blockage mechanisms in aqueous environments near caprock minerals, facilitating the evaluation of H2 storage feasibility in saline aquifers.

Mechanistic Analysis of Peptide Affinity to Single-Walled Carbon Nanotubes and Volatile Organic Compounds Using Chemiresistors.

Peptides, due to their diverse and controllable properties, are used as both liquid and gas phase recognition elements for both biological and chemical targets. While it is well understood how binding of a peptide to a biomolecule can be converted into a sensing event, there is not the same mechanistic level of understanding with regard to how peptides modulate the selectivity of semiconductor/conductor-based gas sensors. Notably, a rational, mechanistic study has not yet been performed to correlate peptide properties to the sensor response for volatile organic compounds (VOCs) as a function of chemical properties. Here, we have designed a peptide that has (1) two amino acid residues that bind the sensor surface, (2) two flexible linkers (GG) that eliminate steric strain, and (3) a five amino-acid repeat that can bind the analyte of interest either by formation of a binding pocket (such as from peptides selected by phage display) or by forming a semiselective adsorption layer. The nine peptide sequences containing both a six amino acid constant sequence (WGGWGG) and a five amino acid variable sequence (XXXXX) were synthesized, and their impact on the selectivity and sensitivity of carbon nanotube (CNT) gas sensors was explored. The response of each sensor to the following VOCs with diverse chemical properties: isopropyl alcohol (polar protic), acetone (polar aprotic), isoprene (nonpolar, linear hydrocarbon), and toluene (nonpolar aromatic), was then recorded and analyzed. This study revealed multiple key factors that influence the response of peptides on CNTs to select VOCs. First, the stability of the CNT-peptide aqueous dispersion correlated to the aromaphilicity of the side chain, strongly suggesting that the side chains of peptides are interfacing with the CNT, and not the peptide backbone. Second, the sensing response profile cannot solely be explained by peptides adsorbing to the gas molecules with similar polarities/dielectrics and may instead be due to analyte displacement of the peptide side chain on the CNT surface as measured by changes in the peptide bond orientation using near-edge X-ray absorption fine structure spectroscopy (NEXAFS). These two observations create a new paradigm to explain how peptides confer selectivity to semiconductor-/conductor-based gas sensors and can provide insights into future design and implementation of peptide-coated solid state sensors for gas targets.

Lanthanide binding peptide surfactants at air–aqueous interfaces for interfacial separation of rare earth elements

Rare earth elements (REEs) are critical materials to modern technologies. They are obtained by selective separation from mining feedstocks consisting of mixtures of their trivalent cation. We are developing an all-aqueous, bioinspired, interfacial separation using peptides as amphiphilic molecular extractants. Lanthanide binding tags (LBTs) are amphiphilic peptide sequences based on the EF-hand metal binding loops of calcium-binding proteins which complex selectively REEs. We study LBTs optimized for coordination to Tb3+ using luminescence spectroscopy, surface tensiometry, X-ray reflectivity, and X-ray fluorescence near total reflection, and find that these LBTs capture Tb3+ in bulk and adsorb the complex to the interface. Molecular dynamics show that the binding pocket remains intact upon adsorption. We find that, if the net negative charge on the peptide results in a negatively charged complex, excess cations are recruited to the interface by nonselective Coulombic interactions that compromise selective REE capture. If, however, the net negative charge on the peptide is -3, resulting in a neutral complex, a 1:1 surface ratio of cation to peptide is achieved. Surface adsorption of the neutral peptide complexes from an equimolar mixture of Tb3+ and La3+ demonstrates a switchable platform dictated by bulk and interfacial effects. The adsorption layer becomes enriched in the favored Tb3+ when the bulk peptide is saturated, but selective to La3+ for undersaturation due to a higher surface activity of the La3+ complex.

Tribological Performance of Nano-CeO2/BNH2 Compound Lubricant Additive

To improve lubricant performance and extend the service life of machinery, the friction reduction and anti-wear performance of nano-cerium oxide (nano-CeO2) and nitrogen-containing heterocyclic borate (BNH2) composite additives were studied in this work, with the goal of obtaining better lubrication effects than a single additive. The results showed that the nano-CeO2 modified with Span80 had good dispersion stability in the base oil. The optimal addition mass fractions of single nano-CeO2 and BNH2 were 0.6 wt% and 1.0 wt%, respectively. Compared with the base oil, 0.6 wt% nano-CeO2 reduced the coefficient of friction by 44.9% and the wear spot diameter by 27.8%, while 1.0 wt% BNH2 reduced the coefficient of friction by 49.1% and the wear spot diameter by 32.8%. Compared with the single additions of nano-CeO2 and BNH2, the compound nano-CeO2/BNH2 further improved the friction reduction and anti-wear performance of the lubricating oil. Compared with the base oil, the 0.8 wt% nano-CeO2/1.0 wt% BNH2 composite additive reduced the coefficient of friction by 55.9% and the diameter of the abrasive spot by 48%. Physicochemical analysis of the wear surface revealed that the combination of nano-CeO2 and BNH2 had excellent synergistic effects. The generated lubricant films of nano-CeO2/BNH2 contained a chemical reactive layer of organic nitride (C–N), Fe2O3, FeO, and B2O3 and a physical adsorbent layer of CeO2 that provided great friction reduction and anti-wear effects during friction.

Peculiar Effect of Water on Tribological Properties of Natural Deep Eutectic Solvent.

Deep eutectic solvents (DESs) have emerged as promising green liquid lubricants for solving tribological problems due to their economic and excellent physicochemical and lubrication properties. However, a trace amount of water would affect their structure, physicochemical properties, and tribological properties. The effect of water on the tribological properties of DES is still unclear and needs further investigate. Herein, we carried out a systematic investigation into the chemical structure, rheological properties, and tribological performance of DES-water (DES-W) binary systems constructed by combining DES with varying contents of water. The results revealed that low levels of water in DES had a minimal impact on its chemical structure but affected its fluidity and viscosity. Frictional experiments demonstrated that DES-W binary systems displayed a reduced coefficient of friction from 0.094 to 0.025 compared to pure DESs and manifested outstanding antiwear properties under a high-load condition. This was attributed to the formation of hydration layers, adsorption layers, and tribochemical films at the tribointerface through physicochemical adsorption and tribochemical reactions. Our findings not only foster the design and development of green lubricating materials but also expand the engineering applications of DESs to solve wear-related mechanical failures in practical application.

Study on the Adsorption Mechanism of Hydrophobic SiO2 Nanoparticles: A Molecular Dynamics Study

ABSTRACTIn recent years, with increasing global demand for oil and gas resources and continuous decline in conventional oil and gas production, the global development focus has shifted from conventional medium to high permeability reservoirs to low permeability and tight oil reservoirs. As a result, nanoparticles (NPs) have found a promising role in enhanced oil recovery as potential improved oil recovery agents in low permeability. Despite many experiments that have proved that nanoparticles can be adsorbed on the rock surface in a macroscopic perspective, the adsorption mechanism and the effects of molecular structure on the adsorption behavior of nanoparticles on rock surfaces remain scarce. Here, the fundamental phenomena involved in hydrophobic nanoparticles adsorption on rock surface and the effect of mineral composition on adsorption mechanism were elucidated by the analysis of molecular dynamics simulation. The simulation results show that water molecules could form two adsorption layers on both quartz and kaolinite surfaces. Hydration layer thickness of kaolinite is greater than that of the quartz surface. The solid/liquid interface hydration layer thickness of quartz–water system is approximately 0.71 nm, while the thickness of kaolinite–water system is approximately 0.75 nm. Furthermore, coulombic interactions are the main influencing factor for the stable adsorption of nanoparticles on the wall. Nanoparticles can only break through the first adsorption layer to absorb on the layer. Finally, wetting angle tests were conducted which indicated that SiO2 nanoparticles can be adsorbed on the surface and have a good wetting reversal effect. Our study highlights the adsorption mechanism of nanoparticles on a molecular level, which may help to promote the development of low permeability and tight oil reservoirs.

Development of the equilibrium adsorption layer model for describing the dynamic adsorption of radioactive gases

Development of the equilibrium adsorption layer model for describing the dynamic adsorption of radioactive gases

Enhancing Pb Adsorption on Crushed Microplastics: Insights into the Environmental Remediation

This study investigates the pollution characteristics and environmental risks of crushed microplastics (MPs) generated during plastic recycling, emphasizing their adsorption capacity for heavy metals, particularly lead (Pb). SEM-EDS analysis revealed that crushed MPs exhibit significantly higher adsorption capacity than primary MPs due to their larger surface area and more available adsorption sites, including oxygen-containing functional groups. The adsorption behavior of MPs was influenced by key factors such as MP size, MP quantity, pH, salinity, and biofilm formation. Smaller MPs demonstrated higher adsorption efficiency, while elevated pH enhanced Pb adsorption. Conversely, increased salinity reduced adsorption due to competition for adsorption sites. Increasing MP concentrations improved Pb removal efficiency, but higher MP quantities led to a decrease in maximum adsorption capacity, demonstrating a trade-off between removal efficiency and adsorption capacity. Isothermal adsorption experiments revealed that Pb adsorption on MPs follows a multi-layer mechanism, best characterized by the Freundlich model. The adsorption capacity increased nonlinearly with Pb concentration and stabilized as surface sites became saturated. The formation of biofilms on MPs further enhanced their adsorption capacity by providing additional functional groups and facilitating multi-layer adsorption, increasing ecological risks. Adsorption kinetics were best described by pseudo-second-order and intra-particle diffusion models, indicating chemical adsorption and boundary layer diffusion as dominant mechanisms. Magnetic Fe3O4 nanoparticles demonstrated a high recovery efficiency of 99.3% for MPs, highlighting their potential for environmental remediation. However, the presence of adsorbed Pb slightly reduced recovery performance, emphasizing the need to optimize recovery conditions for maximum efficiency. These findings underscore the dual threat posed by crushed MPs: their capacity to adsorb and concentrate harmful substances, increasing ecological toxicity, and the challenges associated with their recovery. This research provides critical insights into mitigating MP pollution and developing effective recovery strategies under realistic environmental conditions.

Study on Amino Acid Corrosion Inhibitors in Tungsten Chemical Mechanical Planarization

Addition of corrosion inhibitor in the slurry during tungsten (W) chemical mechanical planarization (CMP) process is an effective way to avoid excessive corrosion. In this work, three environmentally friendly amino acids (lysine, leucine, and glutamic acid) were chosen as corrosion inhibitor during W CMP process. A smooth wafer surface was obtained after CMP with the addition of lysine. The static etching rate of the W film decreased from 45.9 Å min−1 to 7.1 Å min−1 while an excellent wafer surface roughness (Ra = 1.267 nm) was obtained with the addition of 0.25 mmol l−1 lysine. The results indicate that increasing the amount of protonated amino acid molecules in the slurry can result in the improvement of corrosion inhibition performance as well as decrease the material removal rate. Electrochemical tests indicated that the corrosion inhibition effect can be attributed to the formation of an amino acids adsorption layer on the wafer surface, inhibiting the formation of peroxotungstic acids by the interaction between H2O2 and W film in the concave region. This work provides valuable guidance for the application of environmentally friendly amino acid corrosion inhibitor in the CMP field.

Molecular dynamics simulation on the density distribution and multilayer adsorption of methane in nanopores

The adsorption behavior of methane (CH4) in nanopores affects its spatial density distribution, which is essential for the shale gas extraction. While the average density of CH4 in nanopores has been commonly utilized in practice, the density distribution and the mechanisms of multilayer adsorption remain unclear. In this study, molecular dynamics simulations were conducted to investigate the formation of adsorption layers in nanopores. The effects of pressure, pressure gradient, pore width, and temperature on adsorption were examined. As CH4 pressure increases from 1 to 80 MPa, the adsorption layer transitions from one layer to three, resulting in multilayer adsorption. Although the increased pressure enhances the interactions between CH4 molecules, the force exerted by the pore walls on the CH4 molecules remains unchanged. When the repulsive force from the preceding adsorption layer exceeds the attractive force from the pore walls, a minimum methane density is reached, leading to the formation of a new adsorption layer. Following the application of the methane pressure gradient, it was observed that the carbon (C) atoms are displaced from their adsorption sites to regions of higher potential energy, reducing the peak density value. Additionally, the pore width has a minimal effect on the density distribution, as it does not alter the force exerted on the C atoms. Furthermore, temperature can increase the thermal motion of CH4 molecules, resulting in a more uniform spatial density distribution. Finally, a model was proposed to predict the spatial density distribution of CH4 in nanopores, accounting for multilayer adsorption.

Enhancing the physical and oxidative stability of hempseed protein emulsion via comparative enzymolysis with different proteases: Interfacial properties of the adsorption layer.

Effects of enzymolysis by seven proteases (Alcalase, Bromelain, Flavourzyme, Papain, Pepsin, Protamex, and Trypsin) with distinct cleavage specificities on the emulsification performance of hempseed protein (HPI) and its correlation with the structural and interfacial characteristics were explored in this study. Upon enzymolysis, a remarkable decrease in α-helix and β-turn was observed in resultant hydrolysates (HPH), accompanied by a rise in β-sheet and random coil, notably by Alcalase, Bromelain, Papain, and Trypsin. Overall, proteolysis led to noticeable reductions in surface hydrophobicity and total sulfhydryls as well as a redshift in intrinsic fluorescence, with Papain showing the most pronounced effects, possibly due to its higher hydrolysis degree (4.00%). Interestingly, among the seven HPHs, Papain-HPH with the highest solubility (67.4%) and smallest molecular weight exhibited compromised interfacial activity, lowest emulsifying activity (EAI, 1.67m2/g), and highest creaming index (CI, 64%). Contrastively, Trypsin hydrolysis significantly improved the interfacial activity, albeit causing a notable decrease in interfacial viscoelasticity of the absorbed layers. Consequently, Trypsin yielded the best EAI (10.5m2/g) and emulsion stability (CI, 4%); yet, the smallest emulsion droplets with homogeneous distribution and high apparent viscosity were spotted. Additionally, the oxidative stability of emulsions was conspicuously enhanced, contingent upon the antioxidative capacity of HPHs.

Effect of dynamic high-pressure microfluidization on the structural, emulsifying properties, in vitro digestion and antioxidant activity of whey protein isolate.

The effects of dynamic high-pressure microfluidization (DHPM) on the structural, emulsifying properties, in vitro digestion and antioxidant activity of whey protein isolate (WPI) were investigated. The results demonstrated that WPI treated with 100MPa DHPM exhibited superior emulsification performance. This can be attributed to the conformational changes induced by 100MPa DHPM in WPI, leading to a transformation from disordered structures to ordered structures and an increased exposure of fluorophore such as tryptophan residues and hydrophobic groups, reduced aggregation state and particle size of WPI. These factors facilitated the migration of WPI towards the oil-water interface, resulting in the formation of a robust and compact adsorption layer which reduces interfacial tension and enhances emulsification stability. Furthermore, it was observed that while DHPM did not significantly affect the digestibility of WPI, it did enhance exposure to antioxidant amino acids in the digestive products thereby enhanced their antioxidant properties. In summary, structural modification induced by DHPM treatment enhanced both emulsification and antioxidant properties of WPI. These findings highlight the significant potential of DHPM treatment for enhancing the quality of meat products with an emulsion-type structure.