The high price of newly explored surfactants is a concern in applications, but their mixture with conventional surfactants can bring about desired outcomes. Gemini surface active ionic liquids (GSAILs) have emerged as unique materials in tuning interface properties. Surfactants like sodium dodecyl sulfate (SDS), on the other hand, are known effective and commercially available. This study investigates the simultaneous effects of a benzimidazolium cationic GSAIL, [C4benzim-C6-benzimC4][Br2], and SDS surfactants on the interfacial tension (IFT), emulsification, and wettability alteration of the crude oil water system. The results demonstrate amazing synergies up to 97.6 % in the IFT reduction. An ultra-low IFT of 0.16 mN⋅m 1 was achieved with an optimum GSAIL mole fraction of 0.4, attributed to the attractive interaction between the cationic GSAIL and the anionic SDS. Mixtures also give 54.3 and 72.8 % synergies in emulsification and wettability alteration, respectively. The adsorption of individual and mixture of surfactants were theoretically analyzed using the Frumkin adsorption isotherm and the non-ideal interactions of the binary mixtures (NIBM) theory. The corresponding determined parameters were consistent. To have a more comprehensive analysis, the results were compared with those obtained with an analogous structure imidazolium GSAIL.
