Role of Fluorocarbon Chain Length in the Adsorption of Perfluoroalkyl Substances on Nanoplastic Particles

Emerging contaminants such as nanoplastics (NPLs) or per- and polyfluoroalkyl substances (PFASs) are likely to interact with each other in aquatic environments. Here, adsorption and aggregation processes were studied in systems containing NPLs (AL and SL with positive and negative charge, respectively) and PFASs with different fluoroalkyl chain lengths (C4, C6, and C8 with increasing chain length). The adsorption of the PFASs on the oppositely charged AL-NPLs led to charge neutralization and charge reversal at correspondingly high concentrations. The affinity of the PFASs to the AL surface followed the order C4 < C6 < C8. The particle dispersions aggregated rapidly at the charge neutralization PFASs concentration, while the stability below and after this dose depended on the type of background electrolyte and the fluoroalkyl chain length. The predominant forces between the NPLs and the PFASs adsorbed on their surface were mainly of electrostatic origin. No significant interaction was observed between the SL and like-charged PFASs and the charge of the particles was only influenced by the type of salt constituents present. These results provide valuable quantitative information for the development of predictive tools to describe the transport of PFASs by NPLs in aqueous samples of different ionic environments.