Solubilization and remediation of polycyclic aromatic hydrocarbons in groundwater by cationic surfactants coupled nanobubbles: Synergistic mechanism and application

Polycyclic aromatic hydrocarbons pose a severe threat to groundwater and the soil environment. Improving the efficiency of the surfactant-enhanced remediation (SER) technique is a research hotspot. Nanobubbles (NBs) were introduced to enhance the solubilization effect of cationic surfactant dodecyltrimethylammonium bromide (DTAB) on phenanthrene (PHE). The interaction between NBs and DTAB was favorable in reducing the critical micelle concentration of DTAB. The equilibrium solubilization of DTAB to PHE was upgraded by up to 30.4% with the synergy of NBs. The effect of DTAB concentration on the stability of NBs was an essential reason for the different upgrade rates. The kinetic study showed that the process of equilibrium solubilization was accelerated, while NBs were "consumed". Based on the classic DLVO framework, OH– and inorganic ions in groundwater can participate in the formation of micelles and change the double electric layer thickness of bubbles, which are the key factors affecting the stability of NBs. The results revealed the colloidal interface characteristics and the particle behavior of micelles with NBs, providing new insight into the combined application of micelles or vesicles with NBs.