Molecular Assembly of Surfactant Mixtures in Oil-Swollen Micelles: Implications for High Salinity Colloidal Stability

Abstract

Alkylbenzene sulfonates are one of the most important synthetic surfactant families, considering their wide applicability, cost-effectiveness, and overall consumption levels. Nevertheless, their low salt tolerance (especially divalent ion contents) prevented their wider applications such as enhanced oil recovery in high salinity reservoirs. Here, using experiments and atomistic molecular dynamics simulations, we demonstrated that the high salinity colloidal stability of alkylbenzene sulfonates can be dramatically increased by mixing with zwitterionic cosurfactants in oil-swollen micelles. By mixing with cosurfactants we had two important observations. (1) The polydispersity of surfactant mixture oil-swollen micelles were largely decreased due to the less rigid oil/water interfaces with mixed surfactants, which formed fewer but larger uniform micelles. (2) Strong dehydration of sulfonates due to the shielding from protruding more extended zwitterionic cosurfactants at the oil/water interfaces. Both observed molecular assembly characteristics triggered by the cosurfactants effectively reduced the total exposures of sulfonates to water phase that may form divalent ion bridging and large aggregates, and thus increased their high salinity colloidal stability. Lastly, it was observed that the dehydration of sulfonates was the highest at flat oil/water interfaces (very large oil-swollen micelles), which justified that adding trace amount of mineral oils may boost the high salinity colloidal stability even further.

Specific Ion Effects at Calcite Surface Defects Impact Nanomaterial Adhesion

“…Note the acute and obtuse steps can be seen as (3 1 8) and (3 16) vicinal surfaces as well. Three fluids were considered in this work: (1) deionized water, DI, (2) seawater, SW (0.7 M NaCl), and (3) brine, B (1.28 M NaCl + 0.34 M CaCl 2 ), where the latter two are relevant in subsurface hydrocarbon reservoir applications in the Middle East. ,,,, …”

“…Calcium carbonate (CaCO 3 ) is a widely important mineral that is found extensively in biological and geological systems. The interaction of water, ions, organic molecules, macromolecules, and nanomaterials with calcite surfaces controls a broad range of natural and industrial processes such as ion exchange, contaminant migration, , enhanced oil recovery, − biomineralization, − and flocculation . Atomic force microscopy (AFM) is a powerful tool to study calcite surface interactions in air and in solution because of its Angstrom-level spatial and pico-Newton force resolutions.…”

Formation, Physicochemical Stability, and Redispersibility of Curcumin-Loaded Rhamnolipid Nanoparticles Using the pH-Driven Method

“…Traditionally, the surfactant-coated nanoparticles were assembled using small molecule synthetic surfactants, such as sodium dodecylbenzenesulfonate (SDSB), monoglyceride, serine-based bis-quatgemini surfactants, and alkylbenzenesulfonates . However, it is a trend to use natural surfactants instead of synthetic surfactants because of the increasing consumer demand for “clean label” products .…”

Self-Assembly of NaOL-DDA Mixtures in Aqueous Solution: A Molecular Dynamics Simulation Study

“…The PME (Particle Mesh Ewald) was applied to calculate the long-range electrostatics. The NVT ensemble was performed at 300 K in 1,000,000 steps [ 27 , 41 ]. After every 5000 steps, the information, including coordinates, velocities, and energies, was exported.…”

“…Followed by the balance of temperature, the pressure was stabilized by NPT equilibration. In our study, the pressure of the systems was maintained at 1 bar using the Berendsen thermostat with the time constant of 3.0 ps [ 27 , 41 ]. The output information was saved every 50,000 steps.…”