Ultrafast formation of pyrogallol/polyethyleneimine nanofilms for aqueous and organic nanofiltration

Nanofilms are of great interest as a kind of separation membranes for seawater desalination and wastewater treatment. Their fabrication, however, always needs a time-consuming process and shows low atom economy. Herein, we report pyrogallol/polyethyleneimine (PG/PEI) nanofilms spontaneously formed at the gas/liquid interface within ten minutes and composited on microporous substrates. Both the film thickness and the surface charge are facilely adjusted by the reaction time and the mass ratio of PG/PEI in aqueous solution. The solution is repeatedly used to fabricate the nanofilm composite membranes and thus this method is with high atom economy of raw materials. The as-prepared nanofilm composite membranes can be directly applied in aqueous nanofiltration, showing a relatively high water permeation flux (17.5 L m(-2) h(-1) bar(-1)) and salt rejection (> 94% for MgCl2 ) during a long-term operation. The nanofilms are also demonstrated potentials in organic solvent nanofiltration after moderate cross-linking by glutaraldehyde.