Facile construction of a tight polypeptide-based composite ultrafiltration membrane with antimicrobial activity for sustainable treatment of highly saline organic wastewater

Abstract

The development of tight ultrafiltration membranes has opened new avenues for the fractionation of organics and inorganic salts from highly saline organic-rich wastewaters, showing great potential as alternatives to nanofiltration membranes for the sustainable recovery of high value-added products. In this work, polypeptide-based antimicrobial tight-ultrafiltration membranes were developed through the interfacial polymerization of ε-polylysine (ε-pl) and trimesoyl chloride (TMC) on porous ultrafiltration substrates for the sustainable management of highly saline textile wastewater. Systematic characterization was conducted to demonstrate the formation of continuous, thin and smooth ε-pl/TMC cross-linked networks. The designed tight ε-pl/TMC composite ultrafiltration membrane with a MWCO of 3185 Da showed exceptional dye/salt fractionation performance in highly saline textile wastewater, achieving >99.80 % rejection for various dyes (0.2 g L⁻¹ direct red 80, reactive black 5 or reactive blue 2) and a <3.35 % salt rejection (20.0 g L⁻¹ NaCl), with favorable water permeation (39.13–44.46 L m⁻² h⁻¹·bar⁻¹). In addition, the long-term stability of the polypeptide-based tight ultrafiltration membrane was confirmed to be sufficient for enduring dye/salt separation. Furthermore, the intercalation of ε-polylysine onto the membrane surface strongly enhanced the antibacterial activity (i.e., 99.97 % bacterial inhibition) of the tight ultrafiltration membranes. This competitive performance highlights the potential of tight ε-pl/TMC composite ultrafiltration membranes for the sustainable management of highly saline organic wastewater.