Adsorption behavior of perfluorochemicals (PFCs) on boehmite: influence of solution chemistry

Abstract

With global distribution, persistence nature, and strong bioaccumulation, the fate and transport of perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) in natural environment have recently attracted strong attentions. As boehmite is a common form of hydrated aluminum oxide existing in soils and sediments, this study successfully revealed the adsorption behavior of PFOS and PFOA on boehmite and the influence from solution chemistry. The results of kinetic experiments show that the adsorption equilibrium can be achieved within 48 hours and the boehmite surface is generally receptive to PFOS and PFOA adsorption. The adsorption isotherms estimated the maximum adsorption capacities of PFOS and PFOA on boehmite to be 0.877 μg/m2 and 0.633 μg/m2, respectively. The increase of pH can lead to a moderate decrease of PFOS and PFOA adsorption, owing to the increase of ligand exchange reaction and the decrease of electrostatic interaction. With the compression of electrical double layers, the competitive adsorption from the other ions and the Ca2+ bridging effect between perfluorochemicals have demonstrated their negative influence for PFOS and PFOA adsorption on boehmite surface. Finally, humic acid (HA) also showed significant retardant effects on the sorption of perfluorooctanesulfonate (PFOS) and perfluorobutanesulfonate (PFBuS) on boehmite.