Change of organobentonite interlayer microstructure induced by sorption of aromatic and petroleum hydrocarbons—A combined study of laboratory characterization and molecular dynamics simulations

Abstract

In this study, the impact of secondary sorption of hydrocarbons on the interlayer morphology of organic surfactant modified montmorillonites was studied. Montmorillonites intercalated with two quaternary ammonium surfactants, hexadecyltrimethylammonium (HDTMA+) and bis (hydrogenated tallow alkyl) dimethyl ammonium were chosen as the soil sorbents to uptake naphthalene and gasoline. Laboratory characterization using X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FT-IR) were carried out, and molecular dynamics (MD) simulations were performed. The successive interlayer expansion of montmorillonites due to the intercalation of surfactants and hydrocarbons were measured by XRD and TEM. FT-IR was employed to verify the intercalation of organic surfactants and sorbates. Additionally, the MD modeling was conducted to demonstrate the interlayer microstructure of organoclays and to quantify interactions between minerals, surfactants, and sorbates. The experimental and simulation results validated the transitions of montmorillonite interlayer expansion due to the successive intercalation of organic surfactants and sorbates, yielding insights into the understanding of the microstructures of sorbate/surfactant/clay hybrids and their physical-chemical and mechanical behaviors.