Highly dispersed Co/Fe sites with FeCoN6-like structure in chitosan-derived carbon membrane for efficient electrocatalytic removal of sulfamethoxazole

A cathodic EMR equipped with highly dispersed Co/Fe-doped CoFeCM achieves 99.4% removal of high-concentration SMX. • FeCoN 6 -like local sites synergistically generate ·OH and O 2 · − for efficient removal. • Chitosan enhances metal anchoring and membrane flexibility, enabling low-cost fabrication. • Continuous-flow EMR realizes electrocatalytic oxidation and membrane separation in one single unit. To address the low efficiency and poor environmental safety of traditional technologies for degrading sulfamethoxazole (SMX), a cathodic electrocatalytic membrane reactor (EMR) was constructed by integrating CoFeCM as the cathode. CoFeCM was fabricated via a scalable mechanical ball milling-hot pressing‑carbonization route using chitosan-modified activated carbon as the substrate, where chitosan enhanced the anchoring of highly dispersed Co/Fe sites to suppress agglomeration and improved membrane mechanical flexibility. The equimolar Co₅Fe₅CM exhibited optimized porous structure (BET: 541.3 m 2 /g), excellent electrical conductivity (8542 S/m), and superior oxygen reduction reaction (ORR) activity. Under mild conditions (1.2 V, pH 3), the EMR achieved 99.4% removal of 100 mg/L SMX and 45.3% COD removal, with 12.4% TOC removal indicating effective transformation and partial mineralization. Mechanistic investigations confirmed that Fe Co sites formed a FeCoN 6 -like local structure with site-specific synergy. Fe sites thermodynamically favored 2e − ORR for efficient H 2 O 2 production, while Co sites kinetically promoted 1e − activation of H 2 O 2 to ·OH. ·OH and O 2 · − served as dominant active species, enabling multi-pathway SMX removal through sulfonamide bond cleavage and oxazole ring opening, with significantly reduced biotoxicity of intermediates. The EMR maintained stable removal efficiency (93.1% after 10-day continuous operation), and the concentrations of Co and Fe in the effluent were lower than the instrumental detection limit, and exhibited good universality for various refractory pollutants, providing a green, cost-effective, and scalable solution for antibiotic-contaminated wastewater treatment, and further demonstrates great potential for simultaneous organic pollutant elimination and salt rejection in high-salinity desalination wastewater systems, broadening the application boundary of electrocatalytic carbon membranes for seawater desalination and brine resource utilization. Download: Download high-res image (128KB) Download: Download full-size image