Interlayer-modulated polyamide composite membrane for organic solvent nanofiltration

In this work, sandwich-like polyamide (PA) organic solvent nanofiltration (OSN) composite membranes were prepared upon hydrolyzed polyacrylonitrile (HPAN) substrates having interlayers of networked polydopamine (PDA), chained polyaniline (PANI) and porous covalent organic frameworks (COFs). The PA selective layer generated by interfacial polymerization (IP) of 1,3,5-benzenetricarbonyl trichloride (TMC) and polyethyleneimine (PEI). The surface morphology and hydrophilicity of HPAN substrate, and subsequent IP process was successfully regulated by these interlayers. Radar chart representation of the characteristic values of Interlayer/HPAN substrate, PA layer and PA/Interlayer/HPAN OSN membrane was described and analyzed. Compared with the low permeance of PA/PDA/HPAN OSN membrane, PA/PANI/HPAN OSN membrane displayed quite high ethanol permeance (3.1 L∙m−2 h−1 bar-1) and acetone permeance (12.4 L∙m−2 h−1 bar-1), owing to its thinner and rougher PA selective layer. Furthermore, PA/TpTD/HPAN OSN membranes had superior separation performance with 99.0% of rejections to dyes having molecular weights above 350.4 Da, and 95.0% of rejections to crude drugs and natural pigments. Moreover, PA/Interlayer/HPAN OSN composite membranes maintained excellent anti-fouling performance, long-term stability and chemical resistance under strong acidic solution. Therefore, the polymeric interlayers with different structures could manipulate the IP process and provide new insight for preparing of PA based OSN composite membranes with excellent-performance and structural-stability.