Salt‐Induced Constructions of Gemini‐like Surfactants at the Interface and Their Effects on the Interfacial Tension of a Water/Model Oil System.

It is an urgent issue to enhance oil recovery for unconventional reservoirs with high salinity. Focused on this topic, salt addition is a powerful tool to motivate the surfactant assembly at the water/oil interface and improve the interfacial activity. We used a cationic surfactant cetyltrimethylammonium bromide (CTAB) and an anionic salt dicarboxylic acid sodium (CnDNa) to construct gemini‐like surfactants at the interface and evaluated their ability to reduce the interfacial tension (IFT) between model oil (toluene and n‐decane, v:v = 1:1) and water. Interestingly, the fabrication of a (CTAB)2/C4DNa gemini‐like surfactant was hardly achieved at the fresh water/model oil interface, but accomplished at the brine/model oil interface. At a high NaCl concentration (100,000 mg L−1), the IFT value is reduced to 10−3 mN m−1 order of magnitude, which is generally desired in practical applications. The control experiments displacing the surfactant type and the spacer length further confirmed the NaCl effects on the interfacial assembly. [ABSTRACT FROM AUTHOR]