School of Chemical, Biological and Materials Engineering, The University of Oklahoma, 100 East Boyd Street, Norman, Oklahoma 73019, United States.
J Phys Chem B. 2022 Aug 25;126(33):6314-6323. doi: 10.1021/acs.jpcb.2c03670. Epub 2022 Aug 15.
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.
表面活性纳米粒子和表面活性剂对油水界面行为的影响与多种多相流相关的工业过程有关，包括分离过程、提高石油采收率和环境修复。在这项工作中，研究了在油水界面存在表面活性分子和纳米粒子的情况下，油滴在剪切流中的迁移。使用粗粒化计算研究了纯油（十七烷）在水中和油中存在 Janus 纳米粒子（JPs）和/或辛基聚氧乙烯二醇单十二醚（一种非离子表面活性剂）的情况。通过 Couette 流产生剪切流场，其中通道的上壁以指定速度移动，而下壁保持静止。应用耗散粒子动力学（DPD）方法。将油滴放置在静止壁上，并记录其随时间的位移。当表面活性剂添加到油水界面时，水在油滴上的滑移减小，导致油滴的位移更大。此外，当油滴在流场中移动时，表面活性剂分子倾向于集中在油滴的后侧面而不是前侧面。仅在油水界面存在 JPs 会导致油滴迁移速度变慢。在油水界面存在 JPs 和表面活性剂的情况下，通过改变油滴表面 JPs 的数量而保持表面活性剂浓度不变，研究了 JPs 对油-表面活性剂-水体系的影响。在相同的剪切速率下，与纯油相比，存在表面活性剂和 JPs 的情况下油滴的迁移速度增加。JPs 似乎在靠近固体基底-油滴接触线的位置呈现出重复的运动模式。这些发现阐明了表面活性剂和 JPs 对提高石油采收率或修复受油污染的地下环境中油滴位移的贡献。
