Novel antifouling positively charged hybrid ultrafiltration membranes for protein separation based on blends of carboxylated carbon nanotubes and aminated poly(arylene ether sulfone)

In this study, an aminated hydrophilic poly(arylene ether sulfone) (APAES) multiblock copolymer was prepared from previously synthesized bromomethylated poly(arylene ether sulfone) (PAES-CH2Br) block copolymer via in situ amination with triethanolamine. Novel positively charged hybrid ultrafiltration membranes were fabricated by film casting with non-solvent induced phase separation of blends of PAES and APAES block copolymers with carboxylated multiwalled carbon nanotubes (MWCNT-COOH). Fourier transform infrared spectroscopy in the attenuated total reflection mode, scanning electron microscopy as well as contact angle and outer surface zeta potential studies were performed to characterize the membranes in detail. The results confirmed that the fabricated membranes were porous, hydrophilic, positively charged, and had improved antifouling capacity. The hybrid membranes were used in ultrafiltration of ovalbumin and lysozyme model solutions (individually) at varied pH values. Membrane performance depended on the contents of MWCNT-COOH, which could be adjusted by varying its fraction in the membrane casting solutions. Due to the combined effects of size exclusion and charge repulsion, the permeability, antifouling properties and separation selectivity of the hybrid ultrafiltration membranes could be improved simultaneously by increasing of charge density and fraction of MWCNT-COOH.