High performance g-C₃N₄-ZnO@CNTs incorporated cellulose acetate membranes for oil-water and organic foulant separations and fouling mitigation

Despite substantial progress in oily wastewater treatment, challenges such as poor dispersion of carbon nanotubes (CNTs), low surface area of bulk g-C₃N₄, and the limited utilization of g-C₃N₄-ZnO in composite membrane development remain unaddressed. Current approaches are unable to integrate CNTs and g-C₃N₄-based materials into stable and efficient membranes for oil-water separation with enhanced fouling resistance. To overcome these limitations, we developed a novel cellulose acetate (CA) membrane modified with g-C₃N₄-ZnO heterojunctions and CNTs, which are engineered to achieve excellent oil-water separation and antifouling performance. This hybrid design utilizes CNTs for structural stability, g-C₃N₄-ZnO for antifouling, and the CA matrix for scalability and cost-effectiveness. Comprehensive physicochemical characterizations confirmed uniform distribution of the g-C₃N₄-ZnO@CNTs membrane, enhanced hydrophilicity (24.33°), and strong underwater oleophobicity. Notably, the developed membrane exhibited outstanding separation performance, maintaining >99 % oil rejection even under elevated pressures (up to 4 bar) and during long-term operation, while demonstrating exceptional antifouling resistance with only 3–15 % irreversible fouling. Furthermore, the g-C₃N₄-ZnO@CNTs membranes achieved effective rejection (>99 %) of organic foulants, including Eriochrome Black T dye and humic acid, which consistently surpassed conventional CNT-modified membranes in both selectivity and stability after 10 cycles. These results establish the g-C₃N₄-ZnO@CNTs composite membranes as a durable and efficient platform for oil-water separation and wastewater treatment.