Switchable thermoresponsive fluorinated hydrogels for reversible and efficient PFAS adsorption-desorption

Regeneration of PFAS-saturated polymer-based adsorbents with organic solvents is costly, operationally complex, and environmentally burdensome. Here, we developed thermoresponsive fluorinated hydrogels (F9-NIPAM) by incorporating fluorophilic moieties into N-isopropylacrylamide networks, enabling reversible PFAS adsorption-desorption. This distinctive design harnesses a synergistic interplay among fluorine-fluorine interactions, temperature-triggered hydrophilic-hydrophobic transitions (contact angle from 72.71° to 95.62°), and tunable pore contraction (from 3.92 to 2.91 μm), collectively governing reversible behavior across 25-50 °C. Consequently, F9-NIPAM achieved 80-100% sorption of long-chain PFAS (PFOA, PFOS, PFHxS, and PFNA) and >95% desorption using mild regenerants (0.1% NaOH+20% MeOH, v/v = 3:7, 50 °C), reducing MeOH consumption by 80% relative to conventional methods (1% NaCl+100% MeOH, v/v = 3:7, 25 °C). Molecular dynamics simulations further revealed thermally assisted desorption by increasing PFAS diffusion (2.17 × 10^-8 cm² s^-1 vs. 1.21 × 10^-8 cm² s^-1) and weakening hydrogen-bond interactions (28 fewer hydrogen bonds), elucidating the molecular basis of reversible release. Techno-economic and life-cycle assessments demonstrated 15-20% improvements in cost efficiency and substantial decreases in carbon emissions (1006.03 and 1231.63 kg CO₂-eq when using waste heat and clean energy, respectively). Overall, this work highlights the value of coupling selective interfacial interactions with stimuli-responsive behavior to enable controlled and reversible PFAS treatment.