Improvement of the filtration and antifouling performance of a nanofibrous sterile membrane by a one-step grafting zwitterionic compound

Abstract

Engineering a porous membrane with an amphiphilic zwitterionic surface is effective for the improvement of the permeability and antifouling performance of sterilization filtration. Here, we prepared a zwitterionic EVOH nanofibrous membrane (NFM) through nanofiber suspension coating (nanofiber coverage density of 6 g m⁻²), alkaline solution activation and a simple one-step addition reaction with isocyanate-sulfopropylbetaine (NCO-SB). As indicated by experimental analysis, the nanofibrous membrane possesses a thin nanofiber active layer (about 8 μm), narrow pore size distribution and high hydrophilicity, which is beneficial for the absolute interception of Escherichia coli, Staphylococcus aureus and Brevundimonas diminuta as well as a relatively high and stable permeability (11032.3 L m⁻² h⁻¹, 0.2 MPa). The dynamic fouling experiments and protein adsorption experiments illustrated that the modified membrane exhibited strong antifouling properties and excellent permeation recovery abilities mainly due to the grafting of zwitterions on the membrane surface. Specifically, the higher flux and flux recovery ratio (65.1%) after three sequential cross-flow filtration cycles were still obtained compared to the nascent NFM. The ameliorated physical–chemical performance of the membrane can be attributed to the synergistic effect between the uniformly distributed small pore size and the zwitterionic surface of the modified NFM. This work provides a valuable approach for manufacturing high-performance sterilization membranes in bio-separation applications.