Janus Nanoparticle and Surfactant Effects on Oil Drop Migration in Water under Shear

Abstract

The effects of surface-active nanoparticles and surfactants on the behavior of oil–water interfaces have implications for a variety of industrial processes related to multiphase flows including separation processes, enhanced oil recovery, and environmental remediation. In this work, the migration of an oil droplet in shear flow is investigated with the presence of surface-active molecules and nanoparticles at the oil–water interface. Pure oil (heptadecane) in water and oil with the presence of Janus nanoparticles (JPs) and/or octaethylene glycol monododecyl ether, a nonionic surfactant, were examined using coarse-grained computations. The shear flow field was created utilizing a Couette flow, where the top wall of a channel moved with a specified velocity and the bottom wall was kept stationary. The dissipative particle dynamics (DPD) method was applied. The oil drop was placed on the stationary wall, and its displacement was recorded over time. When surfactants were added at the oil–water interface, the slip of the water over the oil drop was reduced, leading to a larger displacement of the drop. Moreover, surfactant molecules tended to concentrate toward the rear side of the oil drop rather than the front as the drop moved in the flow field. The presence of only JPs on the oil–water interface resulted in slower droplet migration. In the presence of both JPs and surfactants, the effect of JPs on the oil–surfactant–water system was investigated by changing the number of JPs on the drop surface while keeping the concentration of the surfactant constant. Under the same shear rate, the droplet’s migration speed increased in the presence of both surfactants and JPs compared to the case of bare oil. The JPs appeared to follow a repeated pattern of motion while residing close to the solid substrate–oil drop contact line. These findings elucidate the contribution of both surfactants and JPs on oil drop displacement for enhanced oil recovery or remediation of an oil-contaminated subsurface.

RETRACTED: Preparation and Analysis of Structured Color Janus Droplets Based on Microfluidic 3D Droplet Printing

“…Nonionic surfactants Capstone FS-30 (FS-30) and Triton X-100 (X-100) have excellent emulsifying and wetting properties. They can adjust the interfacial tension, thus forming Janus droplets with stable interfacial morphology [32,33]. Therefore, in this paper, non-ionic surfactants FS-30 and X-100 will be selected as the regulating materials of interfacial tension between n-hexane/perfluorohexane and a carbomer hydrogel to prepare structural color Janus droplets with excellent performance.…”

Effects of Nanoparticle Wettability on the Meniscus Stability of Oil–Water Systems: A Coarse-Grained Modeling Approach

“…It is defined as , where θ Phi and θ Pho describe the contact angle between an oil droplet and a flat surface with the same wettability as the hydrophilic and the hydrophobic faces of the Janus particle, respectively, as seen in Figure b,c . As was shown in previous research, the three-phase contact angle of the oil droplet on a flat surface; i.e., θ Phi or θ Pho , can be determined from the density profile of the droplet. The amphiphilicity of the Janus particle can be tuned by modifying the wetting behavior of the two opposing JP facets.…”

Interfacial rheology insights: particle texture and Pickering foam stability

“…While the impact of various particle attributes on the bulk properties of Pickering foams has been extensively studied in the literature, examples of which are provided above, understanding the impact of particles on the resulting mechanical properties of a fluid-fluid interface is a growing field of research [63][64][65][66][67][68][69][70][71]. The interfacial rheological measurements, which are conducted by either expanding and contracting the interface (i.e.…”