Adsorption–photocatalysis synergistic removal of perfluoroalkyl/polyfluoroalkyl substances by reusable chitin/polyethylene imine/O-g-C3N4 sponges in water environments

Pollution of water environments by perfluoroalkyl substances (PFASs) has attracted global attention because of their potential risk to the human health. Hence, effective methods for PFAS removal in water environments are urgently needed. Therefore, herein, chitin/polyethylene imine/oxygen-doped graphitic carbon nitride (O-g-C 3 N 4 ) sponges (ChPCNs) are prepared for the efficient removal of two representative PFASs, namely, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), via an adsorption–photocatalysis “synergistic” mechanism. All ChPCNs exhibit good compressibility and high mechanical strength, and the combination of O-g-C 3 N 4 and chitin enhances the photocatalytic performance of ChPCNs by reducing the bandgap energy, improving the light absorption ability and suppressing the photogenerated electron–hole (h + ) recombination. A ChPCN prepared with an O-g-C 3 N 4 concentration of 200 mg/100 mL (ChPCN-200) efficiently removes 97.9 % and 99.7 % of PFOA and PFOS, respectively, via electrostatic, hydrophobic, and hydrogen bond interactions and hole filling, while ·OH, ·O 2 − , and h + are confirmed to be the active species participating in photodegradation. Notably, the degradation pathway of PFASs involves Kolbe decarboxylation, HF elimination, and oxidation, removing the –CF 2 groups in a step-by-step manner, resulting in gradual degradation into short-chain PFASs and releasing F − . Importantly, the removal efficiency for PFASs by ChPCNs reaches 93.7 % in simulated reclaimed water, with the sponges exhibiting good reusability. This study successfully develops reusable chitin-based materials for efficient removal of PFASs from reclaimed water, providing a promising method for the control of emerging pollutants in water environments.