Exploring the role of γ-Oryzanol on stabilization mechanism of Pickering emulsion gels loaded by α-Lactalbumin or β-Lactoglobulin via multiscale approaches

The research explored the role of γ-oryzanol (γs) on stabilization behavior of Pickering emulsion gels (PEGs) loaded by α-lactalbumin (α-LA) or β-lactoglobulin (β-LG), being analyzed by experimental and computer methods (molecular dynamic simulation, MD). Primarily, the average particle size of β-LG-γS was expressed 100.07% decrease over that of α-LA-γS. In addition, γs decreased the dynamic interfacial tension of two proteins with the order of β-LG < α-LA. Meanwhile, quartz crystal microbalance with dissipation proved that β-LG-γS exhibited higher adsorption mass and denser rigid interface layer than α-LA-γS. Moreover, the hydrophobic group of γS had electrostatic repulsion with polar water molecules in the aqueous phase, which spread to the oil phase. β-LG-γS had lower RMSD/Rg value and narrower fluctuation compared with α-LA-γS. This work strength the exploration of interfacial stabilization mechanism of whey protein-based PEGs, which enriched its theoretical research for industrial-scale production as the replacement of trans fat and cholesterol.

Methane-Water Interfacial Tension in Nanopores: A Dissipative Particle Dynamics Study

Imbibition of fracturing fluid in deep shale nanopores has a significant effect on shale gas production. One of the key parameters affecting imbibition is the interfacial tension of the methane-water system. However, studies on the methane-water interfacial tension in nanopores are very limited, and obtaining the accurate value of the methane-water interfacial tension at the nanoscale is difficult and time-consuming. In this work, a dissipative particle dynamics simulation model was built to study the methane-water interfacial tension in nanopores. This model provides reliable access to methane-water interfacial tension for deep shales under high-temperature, high-pressure conditions at low computation cost. It can be easily used to compute the methane-water interfacial tension in nanopores or the confined space in wide application scenarios. A sensitivity study of methane-water interfacial tension on a variety of factors was conducted. Results demonstrate that under high-pressure conditions, the increase in pressure leads to the rise of interfacial tension. When pressure increases from 20 to 120 MPa, interfacial tension rises from 0.0275 to 0.12 N/m, which contributes to the severe imbibition of fracturing fluid in deep shales. The confinement effect was observed by investigating the influence of pore size. Interfacial tension almost remains unchanged in pores smaller than 7 nm because most of the confined space is occupied by interface layer molecules in these pores. When pore size increases from 7 to 15 nm, the confinement effect is reduced. The interfacial tension experiences a growth from 0.1155 to 0.27 mN/m. Compared with pressure and pore size, the effect of temperature on interfacial tension can be neglected during deep shale gas production.

Dissipative Particle Dynamics-Based Simulation of the Effect of Asphaltene Structure on Oil-Water Interface Properties

Asphaltenes are the main substances that stabilize emulsions during the production, processing, and transport of crude oil. The purpose of this research is to investigate the process of asphaltenes forming interfacial films at the oil-water interface by means of dissipative particle dynamics (DPD) and the effect of asphaltenes of different structures on the oil-water interface during the formation of interfacial film. It is demonstrated that the thickness of the interfacial film formed at the oil-water interface gradually increases as the asphaltene concentration rises and the amount of asphaltene adsorbed at the oil-water interface gradually multiplies. Both the number and type of heteroatoms in asphaltenes affect the interfacial behavior of asphaltenes. The interface activity of asphaltenes can be enhanced by increasing the number of heteroatoms in the asphaltene, and the type of heteroatom affects as well the interfacial activity of the asphaltene as it affects the aggregation behavior of the asphaltene in the system. As the number of asphaltene aromatic rings increases, the oil-water interfacial tension (IFT) trends down gradually, while the effect of alkyl side chains on the reduction of IFT of asphaltenes is different, and asphaltenes with medium length alkyl side chains can reduce IFT more efficiently.

Comprehensive review of the interfacial behavior of water/oil/surfactant systems using dissipative particle dynamics simulation

A comprehensive understanding of interfacial behavior in water/oil/surfactant systems is critical to evaluating the performance of emulsions in various industries, specifically in the oil and gas industry. To gain fundamental knowledge regarding this interfacial behavior, atomistic methods, e.g., molecular dynamics (MD) simulation, can be employed; however, MD simulation cannot handle phenomena that require more than a million atoms. The coarse-grained mesoscale methods were introduced to resolve this issue. One of the most effective mesoscale coarse-grained approaches for simulating colloidal systems is dissipative particle dynamics (DPD), which bridges the gap between macroscopic time and length scales and molecular-scale simulation. This work reviews the fundamentals of DPD simulation and its progress on colloids and interface systems, especially surfactant/water/oil mixtures. The effects of temperature, salt content, a water/oil ratio, a shear rate, and a type of surfactant on the interfacial behavior in water/oil/surfactant systems using DPD simulation are evaluated. In addition, the obtained results are also investigated through the lens of the chemistry of surfactants and emulsions. The outcome of this comprehensive review demonstrates the importance of DPD simulation in various processes with a focus on the colloidal and interfacial behavior of surfactants at water-oil interfaces.