关键词: Oil–soil interface, Thermal desorption, Isothermal adsorption, Extended-DLVO (EDLVO), Molecular dynamics

Abstract: The mineral species in soils vary in a wide variety of places, thus resulting in the petroleum-contaminated soil (PCS) with complex characters. Thus, the research on the effect of mineral species on oil-soil interactions in PCS takes on a critical significance. In this study, the desorption and adsorption behaviors of aromatic hydrocarbons (Ar) on two minerals surfaces were examined. Meanwhile, the interfacial forces between minerals and Ar were studied and the sources of these forces were analyzed. Moreover, molecular dynamics (MD) simulations were conducted to gain insight into the interfacial interaction mechanisms. As revealed by the results of this study, in comparison with Qs–Ar (quartz sand, Qs), Mnt–Ar (montmorillonite, Mnt) contaminants required higher temperature and activation energies for thermal desorption (201.95 kJ·mol^-1 vs. 127.82 kJ·mol^-1). The above difference was generated since the adhesive forces between Ar and Mnt surfaces were greater than those between Ar and Qs. As indicated by the analysis of the adhesion force sources, the van der Waals forces were responsible for facilitating oil adhesion to mineral surfaces, even though the electrostatic force prevented oil–mineral adhesion. Furthermore, the hydrophobic forces facilitated adhesion in 3 nm. The MD results demonstrated that compared with the Qs system, there existed larger binding energies between Ar and Mnt, a lower diffusion coefficient for Ar on the Mnt surface, as well as more significant adsorption of Ar on Mnt. In general, the different mineral species affect the strength of the interaction at the oil–soil interface, which is a guideline for proposing targeted oil-soil separation measures.

Key words: Oil–soil interface, Thermal desorption, Isothermal adsorption, Extended-DLVO (EDLVO), Molecular dynamics