N-Oxide connected zwitterionic polyamide nanofiltration membrane for efficient antibiotic/salt separation

Nanofiltration membrane technology for antibiotic desalination in fermentation broth represents a low-energy and high-purity approach. However, it is constrained by the low perm-selectivity and susceptibility to membrane fouling. Here, we develop a novel zwitterionic nanofiltration membrane by incorporating an N-Oxide directly connected zwitterion N,N-bis(3-aminopropyl)methylamine N-oxide (DNMAO) into the nascent polyamide layer via interfacial polymerization. The N-Oxide derived zwitterion created a looser crosslinking network in addition to the trimesoyl chloride-piperazine (TMC-PIP) network, which was supported by Stokes radius related with molecular weight cut-off measurement, and Brunauer-Emmett-Teller Ar adsorption isotherms. Moreover, the directly connected groups (N+-O-) without spacers endow excellent hydration ability and mitigate membrane fouling. The optimized membrane exhibits a water flux of 114.9 L m−2 h−1 and exceptional anti-fouling performance with a flux recovery ratio as high as about 96.4 %. Furthermore, the salt/antibiotic separation factor maintained at 41.1 when continuously filtrating NaCl/erythromycin (ERY) mixed solution for 7 h, which showed a great potential in antibiotic purification.