Robust β-FeOOH@Polytetrafluoroethylene Nanocomposite Membrane with Synergistic Adsorption–Photocatalysis for Antimony(III) Removal from Wastewater

To address the challenge of efficient antimony [Sb(III)] removal from wastewater, we developed a hierarchically structured β-FeOOH@PDA/PEI-PTFE composite membrane that combines synergistic adsorption and photocatalytic functions. A conformal PDA/PEI layer was deposited on PTFE membranes to promote Fe 3+ chelation and support the in situ growth of vertically aligned β-FeOOH nanorods. Multiscale characterization (SEM, EDS, ATR-FTIR, XRD, and XPS) confirmed uniform β-FeOOH distribution, covalent Fe–O–C bonding, and the presence of functional groups (−NH 2, Fe–OH), which are critical for Sb(III) uptake. The membrane demonstrated excellent adsorption performance, achieving 95% removal at pH 7, with a capacity of 420.01 mg/m 2 and 5 mg/L Sb(III). Adsorption kinetics and isotherms followed pseudo-second-order and Freundlich models, indicating heterogeneous multilayer chemisorption. The presence of competitive ions (e.g., HPO 4 2–, CO 3 2– ) had minimal impact, highlighting the membrane’s selectivity. Under UV irradiation, photocatalytic oxidation further increased Sb(III) removal to 98% within 60 min through •OH/ h + -mediated oxidation to Sb(V), supported by Fe 3+ /Fe 2+ redox cycling, as confirmed by XPS and ESR analyses. The PDA/PEI matrix enhanced structural stability via π–π conjugation and hydrogen bonding, allowing the membrane to retain 76.3% of its efficiency after five regeneration cycles, despite minor photocorrosion and pore blockage. This study reveals a dual-functional mechanism involving electrostatic attraction, complexation, and photocatalysis, offering a sustainable and scalable strategy for antimony remediation in complex water environments.