Investigation of the synergistic effects of SiO2 and Al2O3 nanoparticles with SDS and CTAB surfactants on the stability and improving phase behavior of water-oil emulsions

The stability of emulsions is a significant challenge across various industries, including food, pharmaceutical, and petroleum. Surface-active agents utilized for enhanced oil recovery often exhibit inadequate performance under reservoir conditions with high salinity, presenting a critical barrier to effective emulsion stabilization. Furthermore, due to the extreme hydrophilic or hydrophobic nature of nanoparticles (NPs), they are not effective in stabilizing emulsions on their own. To address this limitation, a minimal quantity of surfactant was introduced into the NPs to improve their wettability and achieve dual wettability. This research has examined the synergistic effects of SiO₂ and Al₂O₃ NPs combined with sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB) surfactants on water-oil emulsion stability. This approach enhances emulsion stability by combining the stabilizing effects of both the NPs and the surfactants, an aspect that has not been previously addressed in phase behavior studies through the examination of the interactions and surface behavior of surfactant-nanoparticle complexes at the oil-water interface. Several experiments, including phase behavior, FT-IR, zeta potential, contact angle, and interfacial tension (IFT) tests, were performed to evaluate the interaction of surfactants with NPs. The results demonstrate that combining NPs with surfactants, especially those with opposite charges, significantly reduces IFT to the order of 10⁻⁶ mN/m, which can overcome capillary pressure, and enhances optimal salinity levels even up to 75000 ppm. Interactions between CTAB-SiO₂ and SDS-Al₂O₃ notably improve the hydrophobicity of NPs, resulting in IFT reductions of 11.4 and 7 mN/m, respectively, compared to NPs alone.