Development of novel composite nanofiltration hollow fiber membranes for niche applications

Abstract

Due to its unique ability to separate divalent and multivalent ions as well as low molecular weight organic species, nanofiltration (NF) has now become a widely applied separation technology. However, it is challenging to develop NF membranes that remain competent permeation flux at ultrafiltration (UF)-range low operating pressure to reduce energy consumption and membrane fouling tendency. This thesis presents the development of novel composite hollow fiber membranes with NF-like selectivity at low operating pressure, and tailored surface properties and structures for various niche applications including water softening and forward osmosis (FO). Novel composite NF hollow fiber membrane for low-pressure water softening were prepared via interfacial polymerization (IP), and the IP thin film formation process was ameliorated to strengthen the capability for softening of more concentrated and complex water sources. Moreover, novel double-skinned hollow fibers with an NF-like secondary selective skin were produced through either surface modification or layer-by-layer assembly method to mitigate the internal concentration polarization, scale formation and organic fouling for practical FO applications.