A novel organic solvent ultrafiltration membrane of polyimide/polyethyleneimine@TiO2 with high solvent permeability

Organic solvent ultrafiltration (OSU) membrane as the crucial supporting layer of thin-film composite (TFC) organic solvent nanofiltration (OSN) membrane can help the OSN technology to satisfy the rapidly growing demand for small-molecular separation and purification in organic solvent systems. Aiming at the two main bottlenecks of poor tolerance to strong polar solvents and low solvent flux of the conventional commercial polyimide (PI) ultrafiltration (UF) membrane, in this study, a facile method was proposed to prepare a novel polyimide/polyethyleneimine@TiO2 (PI/PEI@TiO2) OSU membrane with improved solvent resistance and permeability by synchronously coupling the non-solvent-induced phase transformation (NIPs), chemical crosslinking and interfacial in-situ biomineralization. Dut to the chemical crosslinking between PEI and PI, the PI/PEI@TiO2 membrane exhibited good resistance to more organic solvents including the strong polar aprotic solvents (e.g., DMF, NMP and DMSO), ordinary polar solvents (e.g., ethanol) and nonpolar solvents (e.g., n-hexane). At the same time, PEI synchronously catalyzed Ti-BALDH to in-situ generate the TiO2 nanoparticles via interfacial biomineralization, which improved the solvent flux of the PI/PEI@TiO2 membrane due to the creation of more channels and promoted the compatibility of TiO2 within PI/PEI matrix. Especially, the PI/PEI@TiO2-5 membrane with 5 wt% TiO2 loading showed the optimal solvent resistance and high flux in strong polar aprotic solvents (>50 L·m-2·h-1·bar-1 in DMF). Therefore, the resultant new PI/PEI@TiO2 OSU membrane will have a promising separation application in the organic solvent systems in the future.