Interface Engineering\nof Microporous Polypropylene\nMembranes for Polyamide Thin-Film Composite Nanofiltration Membranes\nwith Robust Structure and Superior Performance

Abstract

Nanofiltration membranes have been widely used in many\nfields owing\nto their high separation efficiency and low energy assumption. However,\ntraditional substrates for thin-film composite (TFC) nanofiltration\nmembranes, such as polysulfone or polyethersulfone ultrafiltration\nmembranes, suffer from low surface porosity and poor stability in\norganic solvents. A microporous polypropylene membrane (MPPM) possesses\nhigh organic solvent resistance, high porosity, but poor hydrophilicity.\nHerein, MPPMs were surface hydrophilized for the preparation of TFC\nmembranes by interfacial polymerization. A green, fast, and stable\ndeposition system based on ferulic acid and Fe³⁺ was employed\nfor surface hydrophilization of MPPM, and thus, the aqueous solution\nof piperazine can homogeneously distribute on the substrate surface,\nwhich was directly visualized by confocal laser scanning microscopy.\nThe 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\nof common organic solvents, demonstrating the potential in organic\nsolvent nanofiltration. The proposed strategy expands the selection\nof porous substrates for interfacial polymerization and harsh application\nenvironments for nanofiltration.