Synergism Between Alkylbenzene Sulfonate and Nonionic Surfactant for Producing Low Interfacial Tension at Oil/Water Interface

Synergism between alkylbenzene sulfonate and nonionic surfactant was studied by measuring interfacial tensions of surfactants and their mixtures against a homologous series of alkanes. Four di-n-alkylbenzene sulfonate homologues and a nonionic surfactant, lauryl alcohol polyoxyethylene(9) ether, were used. Effects of hydrophilic-lipophilic ability of surfactant, mixing ratio, and salinity of aqueous phase on synergism were investigated. It is found that the synergism for producing low interfacial tensions derives from the change of the hydrophilic-lipophilic abilities of the surfactant systems from the individual surfactants to their mixtures, which is confirmed by analyzing the alkane scanning curves, and the method to achieve synergism is adding the hydrophilic nonionic surfactant to the lipophilic alkylbenzene sulfonate, and ultralow interfacial tensions (< 0.01 mN/m) can be obtained in proper mixing ratios. The results are of great significance for enhanced oil recovery.