Ionic liquid‐induced deep grafting of polyelectrolyte to reform polyamide layer for antifouling nanofiltration membrane

Abstract

Surface grafting has been widely used to tune hydrophilicity and chargeability of nanofiltration membranes for reducing membrane fouling potential. However, surface grafting typically leads to a significant pore narrowing and resultant permeability loss, and monocharged surface still struggles to resist mixed foulants with different charges. Herein, ionic liquid (IL)‐ethanol (EtOH) solution containing polyethyleneimine (PEI) is used to rearrange the nascent polyamide layer. The high affinity of IL to the PA layer and the low diffusion steric hindrance of EtOH contribute to the polyamide swelling and PEI deep grafting, during which the “self‐regulation” effect (larger pores would be filled with more PEI molecules) narrows the pore size distribution and enhances hydrophilicity. The nearly charge‐neutral and smooth separation layer shows impressive antifouling capacity to hydrophobic macromolecules and mixed charged molecules, along with long‐term operating stability for real wastewater treatment. This study emphasizes the importance of solvent properties on the membrane grafting behavior.

Fabrication of Oligoaniline-Based Electrically Responsive Polyamide Membranes for High-Performance Molecular Nanofiltration

“…The increase in separation layer densification led to a decrease in membrane permeance and an increase in rejection when the IP time was increased from 1 to 7 min. However, the formed polyamide could be swelled by the ILs and methanol solvent as the IP time increases, − which can lead to the formation of a looser PA structure. This is known as a defect-generation process, which would increase the water permeance and decrease the rejection.…”

Coral‐tentacle‐inspired antifouling membrane spacer: A natural solution for biofouling prevention

“…Membrane has been widely used in water treatment 1–3 . To ensure stable and continuous production in membrane separation processes, exceptional anti‐fouling properties and self‐cleaning capabilities of membrane modules are essential 4 .…”