Effects of surface modification Nano-SiO2 and its combination with surfactant on interfacial tension and emulsion stability

[Display omitted] •The surface of Nano-SiO2 is quantitatively modified by using silane coupling agent (KH570) at first time.•The modification degree of Nano-SiO2 particles has great influence on the interfacial tension of the combined system.•The synergistic effect between the modification degree of Nano-SiO2 and anionic surfactant (PS) was explained. Nano-silica (Nano-SiO2) particles have some limitations in their application as an oil displacement agent due to the easy aggregation characteristics. Therefore, it is necessary to modify the particle surface to enhance its dispersibility. A silane coupling agent (KH570) was used to organically modify Nano-silica, the relationship between the dosage of KH570 with the zeta potential, contact angle, particle size, sedimentation rate of modified Nano-SiO2 particles before and after modification was studied. And a displacement system (KH570-G-Nano-SiO2/PS) was fabricated by compounding modified Nano-SiO2 particles with the petroleum sulfonate (PS) molecules, the interfacial tension, emulsification property of the system with crude oil were systematically investigated, finally the synergistic effect of modified particles on the reduction of interfacial tension was explored. Results showed that when the dosage of KH570 was 5 %, the wettability of the particles changed from hydrophilic to hydrophobic, and the dispersion stability was significantly improved. The modified Nano-SiO2 (0.2 %)/PS (0.3 %) system can reduce the oil/water interfacial tension to 5.42 × 10−3 mN/ m. At this point, zeta potential of the system was 54.8 mV, and the stability of the emulsion prepared by this system reached its best level. The modification of Nano-SiO2 particles and the mechanism of reducing the oil/water interfacial tension after compounded with petroleum sulfonate (PS) is analyzed. The modification degree of Nano-SiO2 particles has great influence on the interfacial tension of the system compounding with surfactant.