The great improvement of the surfactant interfacial activity via the intermolecular interaction with the additional appropriate salt

The typical organic salt benzyltrimethylammonium bromide (BMAB) was used to greatly enhance the interfacial activity of the traditional anionic surfactant sodium dodecyl benzene sulfonate (SDBS). The additional BMAB caused the obvious reduction of the interfacial tension (IFT) between the SDBS aqueous solution with a low concentration and model oil (V-toluene:Vn-decane = 1:1). Based on the special SDBS/BMAB intermolecular interaction, we proposed that the synergistic effect between the electrostatic attraction and pi-pi stacking interaction largely increased the SDBS interfacial concentration, leading to the dramatic IFT reduction. Three organic salts and two surfactants with similar structures, as well as the typical inorganic salt NaCl, were used in control experiments to confirm our speculation. The interaction energies between SDBS molecules and different organic salts were calculated using molecular mechanics to further interpret the mechanism. The salt and temperature tolerances of the SDBS/BMAB system were systematically investigated. Moreover, the availability of the SDBS/BMAB mixture in brine water/crude oil system was evaluated by the core flooding tests.