The mobilization of oil, which is either attached to a solid surface or as an emulsion in water, is an ongoing challenge and it has attracted a wide range of researchers. Its recovery could be hindered by the strong interactions of the polar groups of oil to the charged solid surfaces. Moreover, high interfacial tension forces result in low mobility of the oil droplets trapped in porous media. In this study, a new controlled surfactant delivery system via encapsulation of cationic surfactants into mesoporous silica nanoparticles is described. The encapsulation of the cationic surfactant resulted in hexagonal mesoporous particles of around 100 nm in diameter. The responsive release of the surfactant molecules from the mesoporous particles was studied under high salinity conditions that are normally encountered in subsurface environments. The release was affected by the presence of the ions present in the high salinity water. However, when the samples were suspended in deionized water, the surfactant release was negligible. Controlling the release of the surfactant was achieved via functionalizing the surface of the particles with amino propyl groups. The functionalized particles released 10% of the encapsulated cationic surfactants in one day in comparison to 17% of the un-functionalized particles. The ability of the suspension to mobilize oil from solid surfaces was studied using sessile drop contact angle measurements. It was concluded that the release of the surfactant resulted in altering the hydrophobic surface to strongly water-wet. Finally, the interfacial tension between oil-brine was reduced by three orders of magnitude in the presence of the nanoparticles. The slow and controlled-release system described here presents a new delivery system of surfactants for applications in enhanced oil recovery as well as remediation of oil contamination.

Encapsulation of cationic surfactant into silica nano-sized capsules: Mechanism of controlled release, wettability alteration and interfacial tension reduction

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ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.