Crumpled polyamide membranes templated by macroporous scaffolds for ultra-permeable nanofiltration

Abstract

The trade-off between permeability and selectivity remains a long-standing obstacle to the development of next-generation thin-film composite polyamide (TFC-PA) membranes. The creation of crumpled surface morphologies is believed to significantly enhance membrane permeability due to increased surface areas and optimized transport pathways. However, there is still a lack of facile and reliable techniques for fabricating crumpled TFC-PA membranes for ultra-permeable nanofiltration. In this study, we introduce a novel scaffold-templating approach for creating highly crumpled TFC-PA membranes via interfacial polymerization (IP). A pre-decorated macroporous nylon scaffold was adopted as a template for IP, where the water-oil interface was confined within the surface cavities of the scaffold using vacuum filtration. This templating strategy enables the formation of a crumpled, loosely crosslinked PA layer that replicates the geometry of the scaffold, thereby greatly facilitating water transport. As a result, the developed membrane shows an ultrahigh pure water permeance of 54.3 L m⁻² h⁻¹ bar⁻¹ and a satisfactory Na₂SO₄ rejection of 97.4%, alongside excellent mono-/divalent anion (SO₄²⁻/Cl⁻) selectivity of up to 50 under a low applied pressure of 2 bar. Meanwhile, the membrane displays outstanding long-term stability under crossflow conditions. This work opens a new avenue for the development of crumpled TFC-PA membranes for low-pressure desalination and ion sieving.