Fabrication of multifunctional membranes via integrating g-C3N4 with Fe single-atom sites for efficient wastewater treatment.

The development of multifunctional membranes that combine rapid adsorption with photo-Fenton-like degradation capabilities is of great significance for enhancing the purification efficiency of wastewater containing diverse pollutants. Herein, a heterogeneous photo-Fenton-like catalyst featuring Fe single-atom sites stabilized by polydopamine on graphitic carbon nitride (denoted as Fe-PDA-CN) was synthesized and embedded into a polyvinylidene fluoride (PVDF) matrix to fabricate a Fe-PDA-CN/PVDF composite membrane through a non-solvent induced phase separation (NIPS) method. Polydopamine not only provides abundant terminal hydroxyl and amino groups for stabilizing Fe2+/Fe3+ active sites but also enhances the hydrophilicity and contaminant adsorption capacity of the composite membrane. The resulting membrane exhibited exceptional removal efficiency for various contaminants, including antibiotics and hexavalent chromium, and maintained high performance over ten consecutive cycles. Moreover, the leaching of Fe2+/Fe3+ ions remains negligible throughout the long-term operation. Possible degradation pathways of tetracycline hydrochloride (TC) were proposed based on the identification of intermediates, and toxicity analysis indicated that TC was gradually transformed into low-toxicity or non-toxic molecules. The mechanisms underlying TC degradation and Cr(VI) reduction were systematically elucidated. This work presents a promising strategy for designing multifunctional membranes toward sustainable wastewater treatment.