Study of multi-component systems in polybenzimidazole membrane formation and their impact on membrane performance

Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica

Integrally skinned asymmetric polybenzimidazole (PBI) membranes suitable for organic solvent nanofiltration (OSN) were prepared via phase inversion and several changes were implemented in the dope solutions in order to control their molecular weight cut-off (MWCO). Initially, uncrosslinked membranes with different polymer concentrations were tested to investigate their impact on membrane performance. On a second approach, several co-solvents were added in the dope solutions of PBI membranes. Coupling this methodology with chemical crosslinking, using an aromatic bi-functional crosslinker, provided solvent stable membranes with several MWCOs in the nanofiltration range and high permeance. Further variation of membrane dope parameters was tested in order to study membrane formation impact on membrane performance. Total solubility parameters of the chosen co-solvents were calculated, and a correlation between this tool and membrane performance was studied. Even though it was not possible to withdraw conclusions on a fundamental level, from the correlation of the total solubility parameters with membrane performance, this work demonstrates the possibility of developing PBI OSN membranes using different co-solvents and opens up future possibilities for controlling the MWCO of these membranes. A post-treatment study was also conducted in order to examine its impact in membrane performance.