The antifouling and separation performance of an ultrafiltration membrane derived from a novel amphiphilic copolymer containing a crown ether

Abstract

Amphiphilic copolymers have attracted extensive attention for the preparation of ultrafiltration (UF) membranes processed with high separation and antifouling performances. Herein, hydrophilic crown ether (dibenzo-18-crown-6-ether, DE) units were introduced into poly(p-terphenyl, isatin) (PDTI) based on a polycondensation reaction via superacid-catalysis. The copolymers showed good thermal stability and membrane-forming properties, and the UF membranes fabricated by NIPS exhibited excellent separation performance. The content of the hydrophilic DE significantly influenced the morphology structure of the UF membranes. The cross-section structure of the membranes gradually converted from finger-like pores to loose sponge pores during delayed phase separation. The water flux of membranes ascended from 130.9 LMH bar−1 to 286.6 LMH bar−1 while the BSA rejection rate decreased from 99.4% to 90.8% as the DE content increased from 10% to 30%. These changes were associated with an enhanced surface porosity, larger surface pore diameter, and thinner top layer. Moreover, increasing the DE content in the copolymer greatly improved the antifouling performance due to greater hydrophilicity. Upon increasing the molar ratio of DE to p-terphenyl from 1: 9 to 3: 7, the flux recovery rate of the membranes surged from 58.5% to 91.5% and remained >80.2% after three fouling-cleaning cycles. In addition, the surface segregation of the hydrophilic DE segment in the copolymer was confirmed by the higher oxygen element content of the UF membrane on the top surface (18.62%) than that of the polymer (13.97%). Therefore, the amphiphilic copolymer containing a crown ether synthesized by a one-pot polycondensation reaction provides an effective way for the preparation and property adjustment of UF membranes.