Aggregation behaviors of SDBSs at oil/water interface: Theoretical and experimental study

Aggregation behaviors of three different sodium dodecyl benzene sulfonates (SDBSs) were studied theoretically and experimentally in this work. The dynamic oil/water interface tension measurements reveal that 6C12 Phi S is most efficient surfactant in reducing interfacial tension. The addition of inorganic salts (NaCl, CaCl2) to SDBS aqueous solutions was found to further decrease the dynamic interface tension. Molecular dynamics (MD) simulation was employed to study aggregation behaviors of SDBSs at oil/water interface. Radial distribution functions (RDFs) results indicate that Ca2+ can improve the aggregation of SDBSs due to strong electrostatic attraction with headgroups of SDBSs. Meanwhile, the electrostatic repulsion among SDBS headgroups was shield by Ca2+. The orientation of SDBSs was changed and the angle between SDBSs and normal of oil/water interface increased with adding Ca2+. Finally, oil recovery measurement shows that alkali/surfactant/polymer (ASP) system with higher-symmetry and branched alkylbenzene is more effective in enhanced oil recovery.