Electrosprayed g-C3N4/ZnO photocatalytic membrane for self-cleaning dye degradation and fouling mitigation

Azo dyes are persistent in wastewater due to their stable aromatic structures, posing environmental and health concerns. Although photocatalytic oxidation is effective for dye mineralization, powdered catalysts suffer from agglomeration and difficult recovery. In this study, a g-C 3 N 4 /ZnO nanocomposite was immobilized onto a PVDF membrane via electrospraying to enable simultaneous dye degradation and antifouling performance. The modified membrane exhibited enhanced hydrophilicity (contact angle reduced from 83.4° to 52.7°), increased pure water flux (252.1 L/m 2 h), and reduced surface roughness. Antifouling evaluations demonstrated improved flux recovery across different foulants, increasing from 62.6% to 79.8% for sodium alginate, 88.1% to 98.4% for bovine serum albumin, and 63.9% to 72.1% for humic acid. Photocatalytic degradation of Reactive Red 241 achieved 79.2% removal within 200 min, with a flux recovery ratio of 96.25% after UV-assisted self-cleaning. Scavenger experiments and ESR spectroscopy revealed a Z -scheme mechanism, with •O 2 − and h + as the dominant reactive species. Compared to powder-form catalysts, the immobilized membrane showed superior reusability, retaining 76.4% of its activity after five cycles. These results highlight the potential of g-C 3 N 4 /ZnO-coated membranes as a durable and low-maintenance platform for sustainable azo dye wastewater treatment. • g-C 3 N 4 /ZnO coating enhanced membrane hydrophilicity and water permeability. • Modified membranes resisted protein, polysaccharide, and organic fouling. • g-C 3 N 4 /ZnO/PVDF achieved 79% RR241 dye removal in 200 min and 96.3% flux recovery. • UV-assisted self-cleaning maintained long-term flux and catalyst stability. • ESR and trapping confirmed ROS-mediated degradation mechanisms.