Hydrophilic nanofiltration membranes with reduced humic acid fouling fabricated from copolymers designed by introducing carboxyl groups in the pendant benzene ring

In this study, strategy of designing new polymers by copolymerization of carefully chosen monomers was explored to synthesize high performance nanofiltration membranes. A series of copolymers with different content of carboxyl groups were successfully synthesized by polymerization of 2-(bis(4-hydroxyphenyl)methyl)benzoic acid (BHPBA), 4,4'-dichlorodiphenyl sulfone (DCDPS). These copolymers have a high glass transition temperature and decomposition temperature, although a large amount of carboxyl groups was introduced in the chains of copolymers. Membranes fabricated from these polymers kept a reasonable tensile strength, even when 100% carboxyl groups were introduced in the polymer. Furthermore, Prepared membranes had a hydrophilic surface, and a high rejection of dyes and salts with relatively large flux. The antifouling measurements demonstrated that the fouling of both humic acid and BSA were greatly reduced with an increasing amount of carboxyl groups in the copolymer. These copolymer membranes exhibited superhigh antifouling of humic acid with a flux recovery ratio (FRR) of 100%, making them promising to be applied in the treatment of water with high content of humic acid.