In-situ sequestration of perfluoroalkyl substances using polymer-stabilized ion exchange resin

Abstract

Remediation of groundwater impacted by per- and polyfluoroalkyl substances (PFAS) is challenging due to the strength of the carbon-fluorine bond and the need to achieve nanogram per liter drinking water targets. Previous studies have shown that ion exchange resins can serve as effective sorbents for the removal of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) in conventional water treatment systems. The objectives of this study were to evaluate the in situ delivery and PFAS sorption capacity of a polymer-stabilized ion exchange resin (S-IXR) consisting of Amberlite® IRA910 beads and Pluronic® F-127 in a quartz sand. At concentrations below 100 µg/L, individual and mixed PFAS adsorption on resin beads exhibited linear isotherms with no apparent competitive effects. However, at concentrations up to 100 mg/L, PFAS adsorption isotherms were non-linear and a mixture of six PFAS exhibited strong competitive effects. In columns packed with 40–50 mesh Ottawa sand, injection of the S-IXR suspension created a uniform sorptive zone that increased PFOA or PFOS retention by more than five orders-of-magnitude compared to untreated control columns. Multi-solute column studies revealed earlier breakthrough of shorter-chain length PFAS, which was consistent with the mixed PFAS adsorption data. These findings indicate that injectable ion exchange resins could provide an effective in situ remediation strategy for PFAS-impacted groundwater plumes.