Covalent organic framework-poly(acrylic acid)-modified poly(vinylidene fluoride) ultrafiltration membranes towards enhanced antifouling properties and low hydrophilic material leaching

The hydrophilicity is acknowledged critically to raise anti-fouling of membranes conferring a leaching problem over a prolonged operation. To decrease the leaching of hydrophilic material in modified membranes, poly(vinylidene fluoride) (PVDF) ultrafiltration membranes is herein presented using covalent organic framework (COF)-poly(acrylic acid) (PAA) modifier via PAA-catalyzed in-situ COF synthesis method. The modified PVDF membrane with an optimized COF-PAA content showed higher water flux (95 L/m(2) h), greater bovine serum albumin rejection, and superior antifouling properties to sodium alginate (95% FRR values). The stability test conducted on COF-PAA-modified PVDF membrane gave a lower leaching rate of PAA than that of the PAA-modified counterpart. The membrane containing COF-PAA compared with the COF-free counterpart showed a smaller water contact angle down to 55 degrees. The morphologies of the COF-modified membranes and the COF-free counterpart studied with scanning electron microscope found that the COF in tight bonding to PAA was homogeneously bonded to the membrane surface. The surface modification contributes to greater stability and anti-fouling properties of the membrane. The enhanced properties can associate with the reduced pore size of PVDF membrane via in-situ COF synthesis using the catalyst PAA. This work provides a novel strategy towards the further development of efficient composite membranes with enhanced antifouling properties and water flux.

Automated summary

By using PAA-catalyzed in-situ COF synthesis method to apply COF-PAA modifier on PVDF membranes, the water flux, rejection rate, and antifouling properties can be improved, with a reduced leaching rate of PAA. The tight bonding of COF to PAA on the membrane surface contributes to enhanced stability and antifouling properties.