Ionic liquid-polymeric membranes for CO2 separation: A new perspective on membrane integrity under pressure

Abstract

Membrane-based CO₂ separation is a promising technology compared to traditional processes, presenting advantages such as superior energy efficiency and reduced operational costs. This study investigates the enhancement of CO₂/N₂ separation performance by incorporating ionic liquid [hmim][Tf₂N] into polysulfone membranes. The membranes were produced with 5, 10, and 20 wt% IL, and their permeability was measured at 25°C under pressures of 1 and 4 bar. Stability tests were also conducted. At 1 bar, the membrane with 20 wt% IL exhibited the highest CO₂ permeability of 342.27 Barrer, while the membrane with 5 wt% IL demonstrated the best ideal selectivity for CO₂/N₂ of 27.87. At 4 bar, the membrane with 5 wt% IL showed the highest ideal selectivity for CO₂/N₂ of 40.81, with a CO₂ permeability of 144.26 Barrer. Leaching tests indicated potential integrity loss in ionic liquid composite polymer membranes at high pressures. Specifically, the CO₂ permeability of the PSF-[hmim][Tf₂N] 5 wt% membrane increased continuously post-testing due to IL leaching. However, the performance of the membranes remained stable at lower pressures (1 bar). These findings suggest that the produced membranes achieve higher permeability, CO₂/N₂ selectivity, and CO₂ diffusivity, making them suitable for post-combustion gas separation applications.