Enhanced Sorption of Perfluoro-alkyl Substances (PFASs) onto Ottawa Sand

Abstract

Sorption to mineral surfaces is an important process in controlling the fate, mobility, and bioavailability of perfluoroalkyl substances (PFASs) in aquatic systems. Unlike other persistent organic pollutants, PFASs are highly water-soluble due to their hydrophilic head group and thus their solid-phase partitioning is limited under natural conditions. However, recent research has shown that sorption of PFASs to suspended solids in surface water can be enhanced by addition of cationic coagulants, through a combination of electrostatic and hydrophobic effects. Whether coagulant-enhanced sorption can be adapted for in situ remediation of PFAS-contaminated groundwater remains an open question. We investigated sorption of six PFASs at environmentally relevant concentrations in the presence of four cationic coagulants: polyaluminum chloride, polyamine, polydiallyldimethyl ammonium chloride (polyDADMAC), and a tannin-based cationic polymer. PFAS adsorption isotherms were determined on Ottawa sand and on aquifer material from a known PFAS-contaminated site. Preliminary results suggest that this method shows promise for in situ remediation of PFAS-contaminated groundwater.