The presence of oil attached to a solid surface or as an emulsion in an aqueous phase is of interest for many research areas including oil recovery. Surfactants and/or nanoparticles can be used to control the properties of the interface, such as obtaining low interfacial tension (IFT). Herein, we report utilizing mesoporous silica nanoparticles (MSNs) as carriers for the responsive and controlled release of surfactants to the oil-water interface for enhanced oil recovery (EOR) applications. The MSNs containing a cationic surfactant were surface functionalized with amino groups and the surfactant release behavior was studied and compared with that of non-functionalized MSNs.<br/>The responsive release of surfactant molecules from the MSNs was studied under high salinity conditions normally encountered in subsurface environments. Scanning electron microscopy (SEM) analysis shows that the amino functionalized MSNs are 100 nm in size. Fourier-Transform Infrared Spectroscopy (FTIR) and zeta potential data confirm the presence of amino groups on the MSN surfaces, and results from Thermal Gravimetric Analysis (TGA) demonstrate that the cationic surfactant concentration is directly affected by the functionalization and amino groups bound to the MSNs. The release of the surfactant in deionized (DI) water was negligible compared to that in high salinity water (HSW). Furthermore, the preferential adsorption to the oil-water interface is vivid when the suspension is in HSW, this is confirmed by IFT measurements where the oil-HSW interfacial tension was reduced to 4×10<sup>-3</sup> mN/m. The IFT is significantly higher when the particles are suspended in DI water which confirms their responsiveness to the ions of the medium. The release kinetics show that the material can release up to 60% of the surfactant encapsulated in 3 days confirming a controlled release mechanism achieved by functionalizing the MSNs.

Responsive and controlled release of surfactant encapsulated in amino functionalized mesoporous silica nanoparticles

ACS Fall 2021

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