Polyamide thin film nanocomposite membrane with internal void structure mediated by silica and SDS for highly permeable reverse-osmosis application

Abstract

The pursuit of highly permeable thin film nanocomposite (TFNC) membrane is an eternal topic for reverse-osmosis (RO) application. Here, we developed a new avenue based on interfacial polymerization to generate a polyamide TFNC membranes EVOH-SiS-PA by adding silica nanorods (SNRs) and sodium dodecyl sulfate (SDS) in water phase on the surface of EVOH nanofibrous scaffold. The resultant membrane presents a foam-like PA layers with a hierarchical internal voids structure, which is 2–3 μm in thick and distinctly differs to the membranes reported to date. The structure feature can be attributed to the fast reaction between MPD and TMC, Marangoni convection in water phase synergistically determined by SDS molecules on water/hexane interface and SNRs with abundant hydroxyl groups. Comparatively, PA TFNC membranes without SDS and/or SNRs just present a PA layer with smaller thickness (1–2 μm), surface roughness and surface area. As a result, a high permeance of 8.5 L m−2 h−1 bar−1 and a reasonably high rejection to NaCl, CuSO4 and MO feed solution (97.1%–2000 ppm NaCl, 98.2% rejection to 2000 ppm CuSO4 and 99.2% to 20 ppm MO) were obtained towards EVOH-SiS-PA, outperforming the currently reported RO membranes. Here, we provide an approach to fabricate advanced PA TFNC membranes with excellent performance, highlighting their great potential in reverse-osmosis application.