Multifunctional PVDF-fabric-based bilayer membrane with wettability difference for efficient removal of direct dye from water and high-flux oil/water separation

A novel strategy was proposed to fabricate a multifunctional bilayer membrane to remove organic dyes from wastewater efficiently. The composite membrane (PVDF@FCC-MCF1) consisted of a conductive polymer layer of polyvinylidene fluoride (PVDF) and Fe-Co-loaded carbon nanotubes (FCC) and a hydrophilic cotton fabric layer modified via copolymerization of catechol and polyethyleneimine. Significantly, the incorporation of Fe-Co-loaded carbon nanotubes in a conductive polymer layer enables PVDF@FCC-MCF's own self-cleaning and regenerative performances at 6 V direct voltage. Compared to the PVDF monolayer membrane, PVDF@FCC-MCF has exhibited an excellent water flux (337.36 L·m−2·h−1) under flow-through filtration mode without external pressure, and an increased dye rejection rate from 70.90% to 90.36% for 15 mg/L of direct dye even after 12 cycles. Meanwhile, the f-PVDF@FCC-MCF (turning PVDF@FCC-MCF over) has excellent separation performance (oil/water separation efficiency > 99.00% and dye removal up to 96.14%) for oil/water/dye mixtures. This flexible integration of FCC-based electrochemical self-cleaning capabilities and the super hydrophilicity/ underwater superoleophobicity capabilities of modified cotton fabrics into composite membranes can serve as an effective antifouling of membranes.