Preparation and Property of Polyethersulfone Ultrafiltration Membranes with Mesoporous-graphitic-C3N4/Ag

Membrane fouling is still the major problem for the application of membrane separation. In this study, different amounts of silver doped mesoporous graphitic carbon nitride (m-g-C3N4/Ag) were introduced into casting solution by blending. The polyethersulfone (PES) nanocomposite membrane was prepared via the phase-inversion method. The impacts of m-g-C3N4/Ag addition on the morphology, filtration, antibacterial, photocatalytic, and antifouling properties of nanocomposite membrane were systematically studied. The results showed that the addition of m-g-C3N4/Ag can improve the cross-section structure of the nanocomposite membrane as well as its surface hydrophilicity. Compared with pure PES membrane, the pure water flux of the modified nanocomposite membrane increased significantly with the increase of doping amount. The protein rejection rates of all samples were over 90%, indicating that the addition of m-g-C3N4/Ag can significantly improve the filtration performance of the nanocomposite membrane without sacrificing the rejection performance. The anti-bacterial activity of the nanocomposite membranes was improved with the increase of m-g-C3N4/Ag content in which the anti-bacterial activity to P. aeruginosa was much more significant than that to E. coli. The pure PES membrane almost had not photodegradation under light irradiation. By contrast, all nanocomposite membranes exhibited good photocatalytic properties under visible light irradiation, and the photocatalytic activity improved with increase of m-g-C3N4/Ag. The nanocomposite membrane in which the m-g-C3N4/Ag content was the highest that showed the optimal photocatalysis, and the decolorization rate of methyl orange reached 63% in 120 min. The comprehensive antifouling performances of all membranes were characterized by four-step filtration experiments. It can be seen that the flux recovery ratio (FRR) of all nanocomposite membranes is much higher than that of PES membrane. The FRR of all membranes was further increased after washing with water and irradiating with visible light. In summary, the addition of m-g-C3N4/Ag can endow the PES membrane with the antibacterial and the photocatalytic properties under visible light irradiation, thereby improving its comprehensive antifouling performance.