Synergistic interfacial adsorption behaviour between amino acid surfactant and sodium dodecyl benzene sulfonate

Zwitterionic/anionic surfactant system is usually employed in the field of enhancing oil recovery attributing to its high interfacial properties and low adsorption capacity. In this work, an amino acid surfactant triethyltetramine sodium lauryl glutamate (TFDA) with the isoelectric point around 5 was synthesized. The synergistic interfacial adsorption behaviour between TFDA and sodium dodecyl benzene sulfonate (SDBS) was investigated. The TFDA/SDBS binary system displayed ultra-low interfacial tension (IFT), high emulsification capability, emulsion pH-response behaviour, high stability in rock wettability alternation and low adsorption capacity on solid. By calculating interaction parameters, analysing work of adhesion and fitting with Langmuir adsorption model, the synergistic interfacial adsorption behaviour of binary system at oil-water, oil-hosting solid and water-solid interfaces were deeply discussed. The results indicated that TFDA and SDBS molecules formed tightly adsorption layer on oil-water interface, which lead to the rapid decrease in IFT. Meanwhile, the ultra-low IFT and strong interaction of TFDA/SDBS binary system reduced the work of adhesion for oil- solid interface, thus the binary system can easily mobilize the oil film from the solid surface. When the solid surface is exposed in the TFDA/SDBS solution, TFDA and SDBS molecules can remain the molar ratio around 1:1 and maintain better interfacial interaction in oil-water interface during the surfactants adsorbing in the solid due to the lower adsorption capacity of TFDA and SDBS. Furthermore, stability of the emulsion stabilized by binary system could be adjusted by varying the pH values. These findings would provide a potential strategy for designing amino acid/anionic surfactant binary systems.