A g-C3N4/Fe-MOF heterojunction intercalated graphene oxide membrane with persulfate activation self-cleaning property for efficient crude oil in water emulsion separation

Developing the membrane with splendid anti-fouling ability is urgently desired for the separation of high-viscosity crude oils emulsions. Herein, a novel GO-based membrane with anti-crude oil fouling and persulfate activation self-cleaning properties was fabricated by introducing g-C3N4/NH2-MIL-88B(Fe) (g-C3N4/NMB) heterojunction into graphene oxide (GO) sheets via a sample self-assembling process. Combing with micro-nano structures and hydrophilic properties of g-C3N4/NMB heterojunction, GO@g-C3N4/NMB membrane exhibited resplendently selective wettability and anti-crude oil adhesion performance. Based on this, the resultant membrane effectively realized the separation to different low-viscosity oily wastewaters (all rejections >98%). Facing high-viscidity crude oil emulsions, the permeate flux could reach 1611 ± 63 L m-2 h-1 bar-1 with 99.21% of reject rate, which increased almost 80 times than GO membranes. Moreover, profiting from the distinguished photocatalytic activity of g-C3N4/NMB and electron transport capacity of GO nanosheet, the catalytic degradation rate of GO@g-C3N4/NMB membrane was enhanced over 5 times compared to GO membrane under visible light radiation, reaching 0.1513 min-1 for MB under 0.6 mM peroxydisulfate (PDS). Hence, GO@g-C3N4/NMB membrane could reveal continuous purification of organic wastewater through the synergistic effect of filtration and photocatalysis. Similarly, the crude oil-fouled membrane also accomplished regeneration after 30 min of light irradiation and the Rir of GO@g-C3N4/NMB-3 membrane decreased to only 3.7% by persulfate activation self-cleaning strategy. Therefore, this work provided a beneficial avenue for developing sustainable, renewable separation membranes of crude oil emulsions.