Polyethylene Battery Separator as a Porous Support for Thin Film Composite Organic Solvent Nanofiltration Membranes

Organic solvent nanofiltration (OSN) has made significant advances recently, and it is now possible to fabricate thin film composite (TFC) membranes with a selective layer thickness below 10 nm that gives ultrafast solvent permeance. However, such high permeance is inadvertently limited by the support membrane beneath the selective layer, and thus there is an urgent need to develop a suitable support to maximize TFC performance. In this work, we employed a commercially available polyethylene (PE) battery separator as a porous support to fabricate high performance TFC OSN membranes. To deposit a uniform polyamide selective layer onto the porous support via interfacial polymerization, the PE support was hydrophilized with O₂ plasma and the reaction efficiency was optimized using a surfactant. Owing to the high surface porosity of the PE support and the high permselectivity of the PA layer, the PE-supported TFC membrane outperformed the previously reported OSN membranes and its performance exceeded the current performance upper bound. A solvent activation step dramatically improved the solvent permeance by 5-fold while maintaining nanoseparation properties. In addition to the superior OSN performance, the commercial availability of the PE support and simplified TFC fabrication protocol would make the PE-supported OSN membranes commercially attractive.