A novel loose-NF membrane based on the phosphorylation and cross-linking of polyethyleneimine layer on porous PAN UF membranes

In this study, a novel loose-NF membrane was fabricated by coating the polyethyleneimine (PEI) layer on a hydrolyzed polyacrylonitrile (HPAN) ultrafiltration membrane, followed by phosphorylation with inositol hexaphosphate (IP6) and cross-linking process. The cross-linked network was constructed by the coordinative cross-linking of Fe (III) ion and phos-(PEI), and the electrostatic attraction of PEI and IP6. At the optimized fabricating conditions, the loose-NF membrane exhibited both high rejection to dyes and transmission to different salts. The rejections of 0.1 g/L methyl blue (MB), congo red (GR), acid fuchsin (AF) and crystal violet (CV) aqueous solutions respectively were 99.92%, 99.53%, 98.99% and 92.86%, and the corresponding fluxes were 11.54, 10.96, 11.40 and 11.76 L m⁻² h⁻¹ at operating pressure of 0.2 MPa. Meanwhile, the membrane exhibited low rejections to different salt solutions with the order of MgCl₂ (30.51%) > MgSO₄ (20.57%) > NaCl (7.46%) > Na₂SO₄ (5.89%) and fluxes around 19 L m⁻² h⁻¹ at 0.2 MPa. Moreover, the prepared membrane possessed high stability for dealing with biologically treated textile effluent (100 h).