Modification of Oil-Water Interfaces by Surfactant-Stabilized Carbon Nanotubes
TV Vu and DV Papavassiliou, JOURNAL OF PHYSICAL CHEMISTRY C, 122, 27734-27744 (2018).
In this research, simulation results for using carbon nanotubes (CNTs) to deliver surfactants to an oil-water interface are reported. Two different surfactants were considered, the anionic sodium dodecyl sulfate (SDS) and the nonionic octaethylene glycol monododecyl ether (C12E8). The surfactants were first allowed to adsorb on the CNT surface in an aqueous environment. It was found that the capacities of SDS and C12E8 to adsorb on the CNT were 2.62 and 2.43 molecules/nm(2), respectively. The electrostatic effect of the anionic surfactant and the steric effect of the nonionic surfactant negatively affected the adsorption process. On the oil-water interface, the surfactant molecules quickly desorbed from the CNT to distribute on the interface, leading to the reduction of the oil-water interfacial tension. At a low surfactant concentration, the CNT also remained on the interface, reducing further the interfacial tension. When the surfactant interfacial concentration reached the value corresponding to the bulk critical micelle concentration, the CNT was forced to migrate into the oil phase. These results suggest that CNTs, or other hydrophobic nanoparticles, can be good candidates for delivering surfactants for applications like enhanced oil recovery.
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