Mechanistic Insights into Mitigation of Combined Scaling–Biofouling for a Novel Thin-Film Composite Membrane Based on Incorporated Defensive–Offensive Strategy

Combined scaling–biofouling is commonly encountered in practical wastewater treatment and desalination due to the coexistence of inorganic scalants and microorganisms, which is a major obstacle limiting the applications of membrane-based technologies. In this study, we developed a simple and effective modification method for the preparation of an anticombined scaling–biofouling thin-film composite (TFC) nanofiltration membrane via a synergetic strategy based on defensive (i.e., sequestering carboxyl groups) and offensive (i.e., immobilizing antimicrobial peptides (AMPs)) functions. According to the Extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) analysis, the sequestration of carboxyl groups by AMPs diminishes the acid–base polarity interaction between the biofoulants and membranes, playing a critical role in dismantling the bridge of carboxyl–Ca2+–carboxyl and subsequently rendering both scaling ions and carboxyl groups unavailable to fouling. Meanwhile, the immobilization of AMPs on the membranes prevents microbial metabolism and growth by contact-killing mechanisms, endowing the membrane resistance to severe biofouling in the presence of scaling ions. Furthermore, the synergetic effects overcome the permeability–rejection–antifouling trade-off by enhanced water permeance without sacrificing salt rejection. This research provides a novel dimension for developing high-performance TFC membranes for the mitigation of combined scaling–biofouling in the practical application of wastewater treatment and desalination.