Interfacially polymerized composite nanofiltration hollow fiber membranes for low-pressure water softening

► Composite NF hollow fibers for water softening under 2 bar pressure were developed. ► The thin-film selective layer was formed via IP on inner surface of UF substrate. ► Separation is based on combined mechanisms of Donnan exclusion and steric hindrance. ► They can achieve 20 LMH water flux and 90% MgCl2 (3000 ppm TDS) rejection under 2 bar.