Effects of surfactants on oil/water interface are studied using dissipative particle dynamics (DPD) at the mesoscopic scale. With a surfactant model, the effects of concentration of three types of surfactants, including ionic surfactant, nonionic surfactant, and the compound system of ionic and nonionic surfactant, on interfacial tension are analyzed in this study. Also, the distributions of interfacial tension and mean interfacial density are predicted. Simulated results indicate that the interfacial tension decreases with an increase of surfactant concentration. As the surfactant concentration increases to a certain value, the surfactant at the oil-water interface is saturated, and the interfacial tension will in-depend on surfactant concentration. It turns out to be that surfactants can be saturated just at the oil-water interface once its concentration reaches a certain value. A proper mixed ratio of compound system can reach a prime effect. Moreover, the inorganic salts can improve the interfacial efficiency of both ionic and nonionic surfactants, and lower interfacial tension. In addition, the temperature influences on surfactant aggregation behavior at the oil-water interface is discussed. Copyright Figure 1. Equilibrated morphology in oil/water system at different water content with nonionic surfactant ( a) water content of 10%; ( b)water content of 50%; (c) water content of 90% (The blue particles (W) represent the water beads, the red particles (O) represent the oil beads, the green particles (A) represent EO, the pink particles (B) represent PO).S. WANG ET AL.

No abstract