A novel crosslinking technique towards the fabrication of high-flux polybenzimidazole (PBI) membranes for organic solvent nanofiltration (OSN)

A green crosslinking method has been proposed to design high-flux polybenzimidazole (PBI) membranes for organic solvent nanofiltration (OSN). Integrally skinned asymmetric PBI membranes were crosslinked using a solution containing trimesoyl chloride (TMC) and environmentally benign 2-methyl tetrahydrofuran (2-MeTHF) for the first time. The separation performance of the crosslinked PBI (X-PBI) membranes towards various solutes and solvents, including polar and nonpolar solvents, have been carefully studied. The X-PBI membrane shows a rejection of 99.6% to remazol brilliant blue R (MW of 627 g/mol) while it has pure acetonitrile, acetone, ethanol, and isopropanol permeances of 40.7, 29.0, 13.8, and 5.8 LMH/bar at 10 bar, respectively. Moreover, the X-PBI membrane exhibits superlative performance during the 2-step filtration of tetracycline, an antibiotic compound with a MW of 444 g/mol. It has rejections of 90.4% and 97.8% in the first and second steps of filtration, respectively. The X-PBI membrane is also able to concentrate solutions containing L-a-lecithin, a food additive with a MW of 758 g/mol, from hexane. It has a L-a-lecithin rejection of 92% and a pure hexane permeance of 80.8 LMH/bar at 10 bar. Besides, it shows great potential to separate mixed dyes and stable OSN performance during 96-h continuous tests.