Fabrication of stable polyelectrolyte complexed membrane for dye/salt separation via dynamic self-assembly coupled ice-templating technique

With its charged property and multifunctional merit, polyelectrolyte multilayer (PEM) membrane shows great promise in water purification. However, the time-consumption fabrication and dense microstructure of PEM membrane hamper the development of high-performance PEM membrane for wastewater treatment. In this work, we propose the dynamic self-assembly coupled ice-templating technique to fabricate loose nanofiltration membrane in a rapid speed. By vacuum-assisted filtration, poly(ethyleneimine) (PEI) and sodium alginate (SA) can be rapidly assembled into and onto porous ceramic tube, which was subsequently experienced freeze-drying to tailor the microstructure of the result PEM membrane. The microstructure variation was approved by low-field nuclear magnetic resonance. After further chemical crosslinking, the prepared loose PEM nanofiltration membrane offers a superior water permeability of 57.4 LMH/bar, dye rejection efficiency of >99%, and low rejection to salts (12.1% for NaCl), as well as long-term stability, which can thus be potentially applied for clean water harvesting from dyestuff wastewater. The method we proposed opens a new door to intensify the mass transfer of water through the membrane for high-performance membrane development. • A novel loose polyelectrolyte complexed membrane was constructed by dynamic self-assembly coupled ice-templating technique. • ‘Pore-filling’ composite membrane structure ensures the excellent operation stability. • The microstructure evolution was traced with low-field nuclear magnetic resonance, approving our design. • The loose nanofiltration membrane exhibits superior water permeance and high dye/salt selectivity.