A molecular modeling and experimental study of solar thermal role on interfacial film of emulsions for elucidating and executing efficient solar demulsification

The adsorption and intermolecular interactions of surfactant and polymer at the oil-water interface are related to interfacial property, which determines whether an efficient oil-water separation can be obtained. Taking oil/water emulsion from the ASP flooding as an example, the thermal role of solar demulsification was studied through combined simulation calculation and experiment. First, a molecular dynamics model of an oil/water interface containing sodium dodecyl benzene sulfonate (SDBS) and polyacrylamide (PAM) was constructed and was used to explore the thermal role on interfacial behavior and intermolecular interactions. Then, the variation of interfacial properties was characterized experimentally as interfacial tension and interfacial rheology. Finally, the effect of solar thermal role on the oil/water emulsions was monitored via the particle size distribution and the ratio of oil removal. The results show that the thermal field changes the configuration and motion behavior of SDBS and PAM and weakens their interaction energy, promoting SDBS extension into the oil. Thus interfacial tension is increased and the rigidity and strength of the interface are decreased, which destabilizes and bridges the emulsion droplets, facilitating coalescence and eventual oil-water separation. As a result, the size of oil droplets was promoted and the oil removal ratio of 40.53 % was achieved. This work provided insight into the thermal role of solar demulsification, thus providing theoretical support for effectively coupling solar photo, electric, and thermal energy to high-efficiency solar demulsification.