Post-treatment of polysulfone/zeolite-templated carbon mixed matrix membranes by heating and surface coating for enhanced gas separation performance

Gas separation is crucial in industries such as natural gas sweetening, CO2 removal, and oxygen/nitrogen enrichment. Mixed matrix membranes (MMMs) have emerged as a promising solution, and zeolite-templated carbon (ZTC), with high surface area and uniform pore structure, serves as an effective filler to enhance performance. In this study, polysulfone (PSF)/ZTC MMMs with 0.25-0.5wt% ZTC were fabricated using the dry-jet wet spinning technique. However, avoiding interfacial voids in MMMs proved challenging, resulting in reduced separation efficiency. This research aims to enhance separation performance by modifying membrane surfaces through post-treatment (heating and coating) to minimize these voids. The MMM PSF/ZTC was altered by heating at 200°C for 30, 120, and 240min, surface coating with polydimethylsiloxane, or a combination of both. The 0.25wt% ZTC MMM modified by heating for 240min followed by coating exhibited remarkable selectivity improvements: O2/N2 increased from 1.93 to 8.56, CO2/N2 from 6.05 to 45.38, and CO2/CH4 from 5.28 to 46.42 (via coating alone). SEM analysis revealed denser and smoother surfaces after modification, while DSC indicated that prolonged heating reduced permeance due to decreased polymer chain mobility. These results demonstrate that heating and coating synergistically enhance adhesion between polymer and filler particles.