Effect of a mixed anionic-nonionic surfactant adsorption on bentonite structure and on distribution of pentachlorophenol

The adsorption of an anionic–nonionic surfactant mixture and its effect on bentonite structure and the impact of surfactants on pentachlorophenol (PCP) distribution in solid–liquid system were investigated. The aim was to study and explain the high remediating efficiency of ionic–nonionic mixed surfactants for hydrophobic organic compounds (HOCs) — present in contaminated soils and groundwater. The anionic surfactant not only reduced adsorption of nonionic surfactant, but also significantly enhanced PCP desorption from bentonite, as indicated by the apparent distribution coefficients (Kd⁎) of PCP. Surfactant intercalation modified bentonite specific surface area, pore volume, surface roughness and irregularities, as indicated by the fractal dimension calculated by nitrogen adsorption–desorption isotherms. The co-adsorption of the anionic and nonionic surfactants increased ordering conformation of the surfactants on bentonite surface, and improved the thermal stability of the organobentonite system.

► Anionic surfactant decreases the adsorption of nonionic surfactant on bentonite.
► Surfactant mixture changes surface properties of bentonite.
► Mixed surfactants increase thermal and structural stability of bentonite system.
► Structural changes of bentonite further explain the enhanced desorption of HOCs.