SUMMARY

• This study evaluated the sorption of PFOA and related PFAS compounds by three adsorbents: graphene oxide (GO), an iron-oxide-modified reduced graphene oxide composite (FeG), and RemBind®, with the aim of developing effective in situ remediation strategies for PFAS-contaminated environments.
• PFOA sorption by FeG and RemBind® exceeded 90%, significantly outperforming GO which achieved only 60% sorption.
• While increasing pH hindered PFOA sorption by GO due to increased repulsion of anionic PFOA, variations in pH and ionic strength did not significantly influence PFOA sorption by FeG or RemBind®, indicating that binding is predominantly controlled by non-electrostatic forces.
• Hydrophobic interactions at the graphene or carbon surface were identified across all adsorbents, with additional ligand-exchange mechanisms involving the associated iron and aluminium minerals in FeG and RemBind® respectively, contributing to stronger and more stable binding.
• Desorption testing showed PFOA release was greatest in methanol compared to water, toluene, or hexane. This indicates a low risk of PFOA remobilisation from rainfall events, though the presence of polar organic solvents may increase leaching risk.
• Successful sorption of a range of PFAS compounds from a real contaminated site water sample was demonstrated, confirming the potential of mixed adsorbents such as RemBind® for in situ PFAS remediation through multiple simultaneous sorption mechanisms.
• The study highlights that combining mineral and carbonaceous phases, as evident in the design of RemBind®, significantly increases both the capacity and strength of PFAS binding compared to single-phase adsorbents.