Facilitated transport membranes containing graphene oxide-based nanoplatelets for CO₂ separation: Effect of 2D filler properties

Realization of suitable membrane-based technology for efficient CO₂ capture to mitigate climate change relies on the development of thin-film composite (TFC) membranes with superior separation performance. Graphene oxide (GO), due to its 2D morphology, intrinsic strength and chemical compatibility, was used as a nanofiller to enhance CO₂ separation performance and stability of a facilitated transport membrane. SHPAA (sterically hindered polyallylamine)-based blend matrix was selected as the polymeric matrix material in this work. The high aspect ratio of GO-based fillers, when coupled with optimized coating protocol, resulted in TFC membranes of ultrathin (200 nm) selective layers with the in-plane orientation of nanoplatelets, leading to enhanced separation properties that can be retained for long term. Porous graphene oxide (pGO) was also incorporated as nanofillers, resulting in significantly improved gas permeation at a very low filler loading of 0.2 wt%; A CO₂ permeance of up to 607 GPU with a CO₂/N2 separation factor of 36 in flat-sheet configuration was documented. Chemical modification of GO with PEG groups was found to further increase the selectivity of the membranes but reduces the CO₂ permeance, showing a CO₂/N2 separation factor of 90 with a CO₂ permeance of 205 GPU. The effect of various 2D nanoplatelets on CO₂ transport properties in the membranes of hydrophilic PVA (polyvinyl alcohol) matrix and facilitated transport SHPAA/PVA matrix was elucidated with respect to the nanofiller property and loading.