Microplastics as an adsorption and transport medium for per- and polyfluoroalkyl substances in aquatic systems: Polystyrene and undecafluorohexanoic acid interactions

Abstract

The assessment of possible interactions between microplastic particles (MPP) and other emerging contaminants such as per- and polyfluoroalkyl substances (PFAS) is of great importance due to their potentially conjunctive harmful effects on the environment. Here, the colloidal behaviour of a polystyrene MPP in the presence of undecafluorohexanoic acid (UFHA), an alternative to the widely used C8 PFAS, was studied in aqueous dispersions. Adsorption of UFHA on MPP was confirmed, where it induced charge neutralization with overcharging at higher UFHA concentrations. Rates of MPP aggregation were rapid with neutral particles, while slow at low and high UFHA doses, where considerable, alternate surface charge persisted and hence, fine particle dispersion was maintained. The addition of multivalent ions influenced the surface charge and aggregation features of MPP, in both their native form and in the presence of UFHA. Concurrent adsorption of electrolytes and UFHA was observed and strongly affected the rate of MPP aggregation under some experimental conditions. This study provides new insights into the possible interactions of PFAS with MPP, which may fundamentally influence the migration of these contaminants in aqueous environments. Aggregated particles will more likely accumulate in the sediments or at the air–water interface, while individual, highly stable MPP-PFAS composites have the potential to migrate together in the water column.