Zwitterionic forward osmosis membrane modified by fast second interfacial polymerization with enhanced antifouling and antimicrobial properties for produced water pretreatment

Abstract

In this work, superfast surface modification of forward osmosis (FO) membranes was accomplished using zwitterionic species with improved antibacterial and antifouling properties. Asymmetric thin film composite (TFC) FO membranes were fabricated using superfast second interfacial polymerization (SIP). The active sides of the TFC membranes were modified with zwitterionic polyamide moieties. Subsequently, the effects of surface modification on the surface properties, morphologies, and surface charges of the TFC membranes were investigated. The TFC membranes exhibited drastically improved performance in FO processes with model and real produced water samples. The zwitterion-augmentation significantly enhanced surface hydrophilicity and shielded negative surface charge distribution on the membrane surface. Furthermore, static protein absorption and dynamic protein fouling tests with model foulant sodium alginate (SA) revealed that the antifouling characteristics of the asymmetric TFC membranes had improved remarkably. SIP with zwitterion incorporation reduced protein absorption and promoted consistent flux during permeation with the model foulant solution. The antimicrobial characteristic of these FO membranes is also demonstrated with bacterial attachment on membrane surface using Escherichiacoli. Overall, the zwitterion-augmented surface modification of these FO membranes resulted in enhanced permeability and reduction in surface structure parameter leading to improved antifouling properties with respect to organic proteins and gram-positive bacteria.