Responsive and Controlled Release of Surfactant Encapsulated in Amino Functionalized Mesoporous Silica Nanoparticles

Abstract

Mesoporous silica nanoparticles (MSNs) have a great potential as carriers for controlled release of surfactants for enhanced oil recovery (EOR) applications. Herein, MSNs containing a cationic surfactant were surface functionalized with amino groups and their surfactant release behavior was studied and compared with that of non-functionalized MSNs. The responsive release of surfactant molecules from the mesoporous particles was studied under high salinity conditions normally encountered in subsurface environments. Fourier-Transform Infrared Spectroscopy (FTIR) analysis was carried out to characterize the functionalized particles spectroscopically. Zeta potential measurements were made to study the alteration in surface charge of the capsules. Thermal Gravimetric Analysis (TGA) was conducted to investigate the amount of encapsulated cationic surfactant in the silica capsules. Dynamic Light Scattering (DLS) and Scanning electron microscopy (SEM) analyses were performed to confirm the morphology and size of these surfactant incorporated particles in saline water containing 56,000 mg/L salts. FTIR and zeta potential data confirmed the presence of amino groups on the MSN surfaces, and the results from the TGA demonstrated that the cationic surfactant concentration is directly affected by the functionalization and amino groups bound to the MSNs. DLS and SEM analyses showed that the amino functionalized MSNs are 100 nm in size and maintain their chemical stability when present in high salinity water (HSW). IFT measurements showed that interfacial tension is reduced when the amino functionalized MSNs are suspended in HSW compared to when suspended in DI water. The oil-brine interfacial tension was reduced up to 3×10-4 mN/m when the amino functionalized MSNs are suspended in HSW. The functionalized MSNs higher IFT values when suspended in DI water indicate that the surfactant release only happens in ion rich environments which is representative of subsurface conditions. The release data indicate that the presence of the amine functional groups in MSNs results in a regulated-release mechanism where the functionalized particles in HSW released 30% of the cationic surfactant in one day. The release data indicated that the presence of the amino functional groups in MSNs improved the release properties of the encapsulated cationic surfactant. Therefore, the slow release of surfactant from these amino functionalized nanocapsules around the wellbore will result in a farther reach and deeper penetration in the reservoir.