Employing a green cross-linking method to fabricate polybenzimidazole (PBI) hollow fiber membranes for organic solvent nanofiltration (OSN)

A solvent resistant polybenzimidazole (PBI) hollow fiber membrane has been designed and fabricated by a dry-jet wet-spinning process and subsequently cross-linked with a K2S2O8 aqueous solution at 35 °C. This green cross-linking process not only dramatically improves the membrane stability in harsh solvents including N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF) and dimethylsulfoxide (DMSO), but also enhances the mechanical properties of the PBI hollow fibers. A cross-linking duration of 14 h is found to produce PBI hollow fibers with most balanced separation performance. The newly developed cross-linked PBI hollow fiber membrane shows a rejection of Rose Bengal (RB) more than 99% in acetone, exhibiting very good prospects for solvent resistant nanofiltration (SRNF) applications. To effectively mitigate hollow fibers from damage due to membrane swelling during organic filtration, it is recommended that the module configuration for SRNF has one end of hollow fibers free from the module housing. A simple backwash cleaning process has also been developed to restore the membrane performance of a fouled membrane.