Preparation of highly permeable electropositive nanofiltration membranes using quaternized polyethyleneimine for dye wastewater treatment

To solve water pollution induced by the electropositive dyeing wastewater, in this study, a loose electropositive nanofiltration (NF) membrane is prepared by the interfacial polymerization between self-prepared quaternized polyethyleneimine (QPEI) and 1,3,5-benzenetricarbonyl trichloride (TMC). Here the QPEI reduces the amine groups required for interfacial polymerization with high Zeta potential at the membrane surface. Meanwhile, the crosslinking reaction between QPEI and TMC is limited by steric hindrance effect, thus achieving a loose structure of the NF membranes. The obtained quaternized polyethyleneimine nanofiltration membranes (NF-QPEI) show a high selectivity based on Donnan effect. Rejections of divalent cations and common dyes are higher than 98%, with the excellent water flux of 8.21 L·m−2·h−1·bar−1. Also, the membrane shows high operation stability for 36 h in dye separation test. Therefore, this work can provide a new strategy for the preparation of the electropositive NF membranes in term of dyeing wastewater separation.