Polyelectrolyte complex nanofiltration membranes by surface deposition of polyethylenimine on polyanion supports

Polyethylenimine (PEI) is a water‐soluble polymer with higher density of cations and strong adsorbability. In the present work, loose nanofiltration membranes based on PEI were prepared by surface deposition of PEI on hydrolyzed polyacrylonitrile (PANH) supports through a surface crosslink method without using extra crosslinkers. The thinner selective layer (around 50 nm) of polyelectrolyte complex was formed through the crosslinks (ionic and co‐valent) between amine groups in PEI and carboxyl groups in PANH. The PEI/PAN membranes were characterized by SEM, ATR‐IR, and XPS. Nanofiltration of PEGs and salt solutions were performed to evaluate the membrane performance. Loose nanofiltration membranes, with molecular weight cut‐off from 500 to 950 Da, permeances form 7 to 16 L m−2 h−1 bar−1, were obtained by the simple surface crosslink method. The membrane performance can be facile tailored by controlling the deposition parameters, including deposition time and post‐treatments.