Improved water flux and antifouling properties of cardo poly(aryl ether ketone) ultrafiltration membrane by novel sulfobetaine polyimides additive

To improve the water flux and antifouling properties of cardo poly(aryl ether ketone) (PEK-C) ultrafiltration membrane, a novel amphiphilic zwitterionic polymer sulfobetain polyimide (sPI) is introduced into the membrane matrix. A series of PEK-C blend membranes were prepared via non-solvent induced phase separation. Sulfobetain polyimide can migrate and enrich on the surface of membranes/pores due to hydrophilic-hydrophobic structure transformation, which achieved the pore-forming and antifouling dual function. Surface chemical compositions and wettability of the membrane are characterized. The blend membrane sPI/PEK-C membranes exhibited significantly pure water flux (up to 220.65 L/m2h), which was almost 3 times that of the pristine PEK-C membrane (73.68 L/m2h), whereas the BSA rejection of sPI/PEK-C blend membrane was still maintained at a high level (99.1%). Moreover, the sPI/PEK-C blend membranes exhibited improved antifouling performance. Specifically, the higher flux recovery ratio (FRR) (up to 91.56%) and low irreversible fouling (Rir) (15.35%) after three sequential dead-end filtration cycles were observed. This could be attributed to the formation of the hydration layer near the surface via hydrogen bond between water molecules and the hydrophilic sulfobetain groups in zwitterionic polymer. Overall, the novel zwitterionic copolymer is a promising candidate for developing antifouling membrane due to its high water flux and long-term stability in the membrane.