Ultrathin polyamide nanofiltration membrane prepared by triazine-based porous organic polymer as interlayer for dye removal

Abstract

Separation membrane with high flux is generally encouraged in industrial application, because of the tremendous needs for decreasing membrane areas, usage costs and space requirements. The most effective and direct method for obtaining the high flux is to decrease membrane thickness. Polyamide (PA) nanofiltration membrane is conventionally prepared by the direct interfacial polymerization (IP) on substrate surface, and results in a thick PA layer. In this work, we proposed a strategy that constructing triazine-based porous organic polymer (TRZ-POP) as the interlayer to prepare the ultrathin PA nanofiltration membranes. TRZ-POP is firstly deposited on the polyethersulfone substrate, and then the formed TRZ-POP provides more adhesion sites towards PA based on its high specific surface areas. The chemical bonding between terminal amine group of TRZ-POP and the amide group of PA further improves the binding force, and strengthens the stability of PA layer. More importantly, the high porosity of TRZ-POP layer causes the higher polymerization of initial PA owning to the stored sufficient amino monomer; and H-bonding interaction between amine groups of TRZ-POP and piperazine (PIP) can astrict the release of PIP. Thus, IP process is controlled, and the thinnest thickness of prepared PA layer is only < 15 nm. As expected, PA/TRZ-POP membrane shows a more excellent water flux of 1414 L·m−2·h−1·MPa−1 than that of the state-of-the-art nanofiltration membranes, and without sacrificing dye rejection. The build of TRZ-POP interlayer develops a new method for obtaining a high-flux nanofiltration membrane.