M10 - CONFRONTING PFAS – PERFLUOROOCTANOIC ACID ADSORPTION USING ACTIVATED CARBON MODIFIED BY POLYCHLOROTRIFLUOROETHYLENE AND POLYETHYLENE AMINE.

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: To enhance PFOA adsorption via polyamine-functionalized fluoropolymer–carbon composite through introducing higher ion-exchange and hydrophobicity capacity

Abstract Text:

Per- and polyfluoroalkyl substances (PFAS) are emerging environmental contaminants of global concern due to their persistence, widespread distribution, and potential health risks. Fluoropolymers, despite their relevance, has little work done with them for PFAS adsorption; particularly in mixed-mode systems incorporating ion exchange. Activated carbon is a widely used adsorbent known for its tunability and capacity to serve as a solid support with functional enhancements for improved adsorption performance. Polychlorotrifluoroethylene (PCTFE), commercially known as Kel-F 800, is a thermoplastic chlorofluoropolymer characterized by high crystallinity and a high glass transition temperature (Tg), resulting in desirable thermal and mechanical properties and its low cost makes it attractive for large-scale industrial applications. However, Kel-F 800 lacks sufficient functional binding sites for effective PFOA adsorption. Hydrophobic interactions and ion exchange are key mechanisms driving PFAS adsorption. In this work, we demonstrate a viable synthetic strategy to enhance PFOA binding by grafting polyamines onto Kel-F 800. The approach involves substituting chlorotrifluoroethylene units with polyamine chains, thereby introducing multiple hydrophobic amine groups into the fluoropolymer backbone. Branched polyethyleneimine (PEI) was chosen as the derivatizing agent to synthesize the final product: AC–Kel-F 800–PEI.

Column breakthrough studies, modeled using the Yoon-Nelson equation, revealed a substantial increase in breakthrough time from 84 minutes for the bare clay adsorbent to 549 minutes for the AC–Kel-F 800–PEI composite (flow rate: 1 mL/min, PFOA concentration: 100 ppm, column length: 2 cm). Additionally, Thomas model fitting indicated a dramatic improvement in adsorption capacity, increasing from 68.7 mg/g (bare clay) to 468.7 mg/g (AC–Kel-F 800–PEI). Current efforts are focused on evaluating the regeneration durability and PFOA selectivity of the material in the presence of co-existing contaminants. These results highlight the promise of AC–Kel-F 800–PEI as a cost-effective and scalable adsorbent for industrial PFOA treatment applications.