Solvent resistant nanofiltration membranes based on crosslinked polybenzimidazole

Solvent resistant nanofiltration membranes based on crosslinked polybenzimidazole (PBI) were designed and fabricated. The modification was carried out by crosslinking PBI asymmetric nanofiltration (NF) membranes with p-xylylene dichloride. The morphology of the membranes was tuned by changing crosslinking time and was investigated in detail by atomic force microscopy (AFM) and scanning electronic microscopy (SEM). The membranes have a typical asymmetric structure with a dense skin layer and a porous sublayer. The roughness of the membranes increases after crosslinking. The results showed that the solvent stability of PBI membranes improved obviously after crosslinking. The modified PBI membranes were applied in solvent resistant nanofiltration (SRNF) processes. Dyes with different molecular weights (ranging from 400 to 1100) and different charges were selected as solutes for filtration experiments. The modified PBI membranes showed very good rejection up to 99.9% for the tested dyes in the selected solvents. Compared to pristine PBI membranes, the modified membranes showed much higher retention of dyes with different molecular weights in different solvents. Therefore, the modified PBI membranes show very promising prospects in solvent resistant nanofiltration processes.