Efficient surface ionization and metallization of TFC membranes with superior separation performance, antifouling and anti-bacterial properties

Membrane-based forward osmosis (FO) technology has attracted increasing interest in the field of water treatment due to its high economical and separation efficiency. However, the availability of a FO membrane with superior separation and antifouling properties is still the critical issue for its real application in wastewater purification. In this work, novel thin-film composite (TFC) membranes are developed by surface ionization with various metal ions and subsequent metallization with the assistance of pre-grafted polyethyleneimine (PEI) and N-containing organic phosphonic acid (OPA), where the latter provides abundant and stable complexing sites. The grafting of hydrophilic PEI/OPA and the attachment of silver atoms endow the resulting membrane a dual defensive and offensive functionality associated with anti-adhesive property and antibacterial activity, respectively. Compared with the control TFC membrane, the surface-modified membranes show significantly improved anti-adhesive property against bovine serum albumin (BSA) and antibacterial property against S. aureus and E. coli bacteria, and thereby improved antifouling property towards the local lake water. Additionally, compared with the silver-metalized TFC membranes prepared by the direct method or indirect PEI binding, the silver-metalized membrane prepared by the indirect OPA binding exhibits a much higher silver loading (34.38 μg/cm²), as well as better, more stable and long-term antibacterial property. Moreover, compared with the control membrane, the modified membranes also have much higher water fluxes (87–141% increase) and comparable or even lower reverse salt fluxes. The influences of the metal ion type used for ionization and the method used for metallization are systematically investigated.