Amphiphilic molecular brush-grafted nanofiltration membranes via stable initiator immobilization: A dual defense strategy against complex fouling in leachate

Conventional nanofiltration (NF) membranes often encounter severe membrane fouling issue in advanced treatment of leachate, primarily due to the presence of complex foulants. Herein, we developed a novel dual-defense functionalized robust antifouling NF membrane through covalent grafting of initiator α -bromoisobutyric acid (Biba) onto a NF membrane surface followed by sequential grafting of zwitterionic polymer (PSBMA) and fluoropolymer (PHFBM) brushes via surface-initiated atom transfer radical polymerization (SI-ATRP). The chemical grafting of novel initiator Biba supplanted the previously reported toxic initiator and unstable polydopamine coating strategy, thereby facilitating robust covalent immobilization of antifouling functional layers. The modified membrane demonstrated exceptional antifouling capabilities during synthetic wastewater treatment, exhibiting a flux decline ratio (FDR) of only 12.4 % and a flux recovery ratio (FRR) of 94.7 %. Furthermore, it also showed remarkable durability during three cycles of filtration using actual leachate biological treatment effluent, consistently maintaining a FRR of 94.2 %. The molecular dynamics simulations, adhesion force tests, and free energy calculations elucidated the fouling resistance and fouling release mechanisms of the PSBMA and PHFBM brushes. This work provides a new initiator immobilization strategy for fabricating a robust fouling resistant NF membrane with a dual-defense functional polymer brushes coating layer. Meanwhile, this robust NF membrane exhibits substantial potential for sustainable leachate treatment applications.