Polyethylenimine grafted hollow fiber membranes for fast dye separation

Hollow fiber membranes (HFMs) are widely used in nanofiltration for dye separation. However, the majority of HFMs suffers from the "trade-off" relationship between permeance and rejection. Here, we demonstrate a facile strategy to prepare polyethylenimine (PEI) grafted polyethersulfone (PSF-PEI) HFMs for fast dye separation with high rejection. Different from traditional interfacial polymerization, the nanofiltration HFMs were directly fabricated via quaternarization of PEI on brominated polyethersulfone (PSF-Br) ultrafiltration HFMs. Compared to other reported works, the prepared PSF-PEI HFMs exhibit ultra-high water permeance of 150 L m-2 h-1 bar- 1 along with outstanding rejection of over 98% for several kinds of dyes and low rejections (<20%) for inorganic salts. Impressively, the PSF-PEI HFMs also have excellent stabilities and antifouling abilities, which can be operated stably at complex environment for a long time with dye rejection of higher than 99%. Therefore, the prepared HFMs show great potential in industrial application for fast dye separation.