Interfacial study on the interaction between hydrophobic nanoparticles and ionic surfactants

The use of hydrophobic nanoparticles to manipulate the foam stability has attracted great interests recently. In this study the interactive behavior is investigated between the hydrophobic nanopartides with the ionic surfactants including ordinarily charged and ionic liquid ones. The concentration of nanoparticles is varied and the surfactant concentration is fixed at below the critical micelle concentration, where the air-water surface property is sensitive to the state of surfactants in the bulk solution. The static and dynamic surface tension, zeta potential and dilational viscoelasticity of the mixed solution are measured at various conditions. It is observed that both surface tension and magnitude of zeta potential increase with nanoparticle addition, suggesting that the nanoparticles are attracting surfactant monomers in competition with the air-water surface and the premicelles in the bulk solution. The dynamic changes of surface tension and dilational viscoelasticity are monitored with changes of nanoparticle concentration. The possible assembly of surfactants with nanoparticles and the consequential effect are discussed with a proposed mechanism. Understanding the interaction and synergy between hydrophobic nanoparticles with ionic surfactants, in particular ionic liquid surfactant, may shed light on the use of such nanoparticles in the industrial practices such as enhanced oil recoveries. (C) 2015 Elsevier B.V. All rights reserved.