A loose nano-filtration membrane prepared by coating HPAN UF membrane with modified PEI for dye reuse and desalination

A novel method to fabricate loose NF membrane for textile wastewater treatment was reported. PEI was reacted with gallic acid by condensation reaction and then the modified PEI was deposited on hydrolyzed polyacrylonitrile (PAN) substrate through electrostatic interaction followed by thermal treatment. With increases in the concentration of gallic acid and PEI in the coating solution, the selective layer became dense and rejection for dyes increased. The membrane prepared at optimized condition achieved a high flux for dyes (51 L/(m2·h) at 0.2 MPa) and the rejection of Methyl Blue and Gongo red are 97.3% and 97.1% when gallic acid and PEI concentration are fixed at 0.1 wt% and 1 wt%, respectively in coating solution at crosslinking temperature of 45 °C. Meanwhile, this membrane also exhibited the good hydrophilicity (contact angle 50.2°), the flux recovery ratio (91.7%) and the lowest irreversible fouling ratio (8.1%) for humic acid (HA), and the best satisfactory antifouling stability in the long-term operation for dyes and salts mixture solution. The novel fabricated membranes exhibited an impressive prospect for the dye reuse due to the high rejection of dyes with a high flux, as well as low salt rejection.