Hybrid zwitterionic biochar-PES-SPAES composite membranes for efficient treatment of antibiotic-laden municipal wastewater

Abstract

Antibiotic accumulation in discharged water is a growing global public health concern that demands high-performance membrane materials to mitigate it. Herein, functionalized zwitterionic biochar (ZBC) was incorporated into a novel membrane composite of polyethersulfone/sulfonated poly(arylene ether sulfone) (PES/SPAES) via the phase-inversion process. Several instrumental characterizations confirmed the fabrication of the composite membrane and the incorporation of the nanofiller into its matrix. ZBC integration altered the membrane morphology, pore structure, hydrophilicity, and surface charge, as well as the thermal and mechanical properties. The best-performing composite membrane achieved an outstanding 99.1% tetracycline (TC) removal efficiency at a permeation flux of 64.1 L m −2 h −1 . The membrane maintained its high performance across complex environments, including mixed-antibiotic solutions (98.5%) and antibiotic-loaded real municipal wastewater (94.8%). The membrane exhibited strong antifouling behavior, long-term operation, and high rejection of natural organic matter (NOM). Feed pH variation confirmed its effect on TC separation, achieving superior TC removal under acidic and alkaline conditions (99.9%), with an enhanced flux of 71.8 L m −2 h −1 at pH 3. Density functional theory (DFT) calculations supported the experimental findings, showing enhanced TC–membrane interaction in the PES/SPAES/ZBC system through reduced energy gap, increased electron-transfer capacity, and stable TC-bound configurations. These findings establish ZBC nanofiller and PES/SPAES composite as promising materials for developing high-performance composite membranes for antibiotic removal.