Preparation and Transmembrane Transport Mechanism of Liquid-Catched Supported Membranes with High CO2 Separation Performance

CO2 capture is essential for addressing dual-carbon strategies and achieving carbon neutrality. Membrane separation is favored for CO2 separation due to its high efficiency, low energy consumption, and operational convenience. Combining supported liquid membrane technology with ionic liquids (ILs) enables continuous CO2 separation from flue gas without requiring regeneration, simplifying processes, and reducing steps compared to pure IL absorption or adsorption methods. However, supported IL membranes suffer from liquid leakage. This study proposes a novel mechanism for CO2 capture using liquid-catched supported membranes (LCSMs). The LCSM was formed by adding a liquid-locking polymer layer to a porous support membrane. This study investigates the CO2 separation performance of LCSMs from the perspectives of material optimization and operational conditions. Sodium polyacrylate was selected as the liquid-locking polymer material based on molecular simulations. Experiments were conducted to investigate the effects of the support membrane type, liquid type, and liquid concentration on CO2 separation by LCSMs. Further experiments examined the influence of temperature, pressure, liquid concentration, and gas source composition on the separation performance of LCSMs. The optimal conditions for membrane fabrication and operation were determined. In addition, the transmembrane transport mechanism of CO2 separation using LCSMs was studied using molecular dynamics simulations, modeling analyses, and calculations. The simple solution-diffusion mechanism could not accurately describe the CO2 transmembrane transport behavior. A modified solution-ionization-diffusion mechanism was proposed to elucidate the CO2 transmembrane transport mechanism in LCSMs, showing good agreement with experimental results of CO2/N2 separation. Finally, a process for CO2 separation from the flue gas was developed. Preliminary calculations indicated that the capture energy consumption could be reduced to less than 2 GJ/tCO2, significantly lower than traditional absorption methods, with broader applicability and reduced footprint. This process is simpler, continuous, and less expensive. These results indicate that LCSMs are promising and novel methods for CO2 capture, offering an effective and economical solution for industrial applications.