Regenerable Water Remediation Platform for Ultrafast Capture and Mineralization of Per- and Polyfluoroalkyl Substances.

Abstract

Concerns about per- and polyfluoroalkyl substances (PFAS) arise from their persistence, toxicity, and widespread presence in aquatic environments. Currently, activated carbon and ion exchange resins have been used to remove perfluorooctanoic acid (PFOA), the most commonly studied PFAS, but these methods face challenges like low adsorption capacity and slow kinetics, leading to secondary waste issues. Here, it is observed that a high interlayer crystallinity of nitrate intercalated Cu_xAl layered double hydroxides (LDH) (Cu_xAl-NO₃ LDH) enables a boundary-breaking performance of maximum adsorption capacity (q_max) of PFOA as 1702 mg g^-1 at neutral pH and room temperature. The Al-Al clash within the cationic layers (basal plane disorder) enhances adsorption kinetics (k₁ = 13.2 h^-1), as determined by a ²H magic angle spinning (MAS) solid-state nuclear magnetic resonance (ssNMR) spectroscopy. Furthermore, PFOA-saturated Cu₂Al-NO₃ LDH can be regenerated through its memory effect, achieving ≈54% defluorination of the adsorbed PFOA in the presence of CaCO₃ after the thermal treatment at 773 K (500 °C). Performance in continuous fixed-bed systems (720 mg g^-1 at 0.5 mL min^-1) and PFOA-spiked real water matrices indicates the practical application potential of Cu_xAl-NO₃ LDH, suggesting an effective integrated ultrafast capture-thermal destruction-recycling (CTR) process for treating PFAS-contaminated water.