Interface Engineering of Microporous Polypropylene Membranes for Polyamide Thin-Film Composite Nanofiltration Membranes with Robust Structure and Superior Performance

Abstract

Nanofiltration membranes have been widely used in many fields owing to their high separation efficiency and low energy assumption. However, traditional substrates for thin-film composite (TFC) nanofiltration membranes, such as polysulfone or polyethersulfone ultrafiltration membranes, suffer from low surface porosity and poor stability in organic solvents. A microporous polypropylene membrane (MPPM) possesses high organic solvent resistance, high porosity, but poor hydrophilicity. Herein, MPPMs were surface hydrophilized for the preparation of TFC membranes by interfacial polymerization. A green, fast, and stable deposition system based on ferulic acid and Fe3+ was employed for surface hydrophilization of MPPM, and thus, the aqueous solution of piperazine can homogeneously distribute on the substrate surface, which was directly visualized by confocal laser scanning microscopy. The nanofiltration membranes show rejection of 98.1% to Na2SO4 and water permeation flux of about 16 L/m2·h·bar. Moreover, the membranes are stable in a variety of common organic solvents, demonstrating the potential in organic solvent nanofiltration. The proposed strategy expands the selection of porous substrates for interfacial polymerization and harsh application environments for nanofiltration.