(755g) Effects of Pore Size in Polybenzimidazole Membranes on the Performance of Organic Solvent Nanofiltration

Organic solvent nanofiltration (OSN) through a membrane is an economically viable technology for the separation and recovery of organic solvents. The pore size in the membrane is crucial to the membrane performance (based on solvent flux and solute rejection). In this work, we report a molecular simulation study to investigate the effects of pore size (centred at 0.75, 0.85 and 0.95 nm, respectively) in three polybenzimidazole (PBI) membranes. Quantitative relationships between the pore size and the microscopic properties of solvent (methanol) in the membranes are established. Methanol in the membranes is revealed to possess two states: a bound state that strongly interacts with the polymer matrix and a bulk-like state that can move freely in the membrane. The movement of methanol can induce the formation of pores and the variation of pore size distribution in the membranes. Methanol flux and solute rejection are estimated at different pore sizes. It is unravelled that methanol flux is primarily governed by the percentage of the bulk-like methanol, while solute reject is largely determined by the pore size. This simulation study highlights the crucial effects of pore size on the performance of OSN membranes, and would facilitates the development of new membranes for high-performance OSN.