Competitive adsorption of perfluoroalkyl substances on anion exchange resins in simulated AFFF-impacted groundwater

Abstract

The historical use of aqueous film forming foams (AFFF) containing perfluoroalkyl substances (PFASs) for firefighting and training activities has resulted in groundwater contamination. The competitive adsorption of PFASs and the effect of co-existing compounds on the removal of PFASs by anion-exchange resins were studied in this study. Perfluorohexane sulfonate (PFHxS) was selected as the representative PFAS, and resin IRA910 was found to be effective for PFHxS removal. When PFHxS was co-removed with other PFASs in bisolute system, it replaced the adsorbed PFASs with shorter C-F chains on the IRA910, while perfluorooctanesulfonate (PFOS) was not replaced by PFHxS. The competitive adsorption among PFASs decreased in the order of PFOS > PFHxS > PFOA > PFBS>PFHxA > PFBA, closely related to the hydrophobicity and functional groups of PFASs. The nonionic organic compounds could not interfere with the PFHxS removal, while ionic ones can reduce the sorption amount and their influence to the sorption of PFHxS was concentration dependent. The presence of inorganic anions slightly decreased the removal efficiency of PFHxS and the influence of different inorganic anions was similar due to multiple effects including competitive anion, screening effect, and salting-out effect in the adsorption process.