Enhanced CO2-selective behavior of Pebax-1657: A comparative study between the influence of graphene-based fillers

Mixed matrix membranes (MMMs) containing graphene-based fillers have attracted considerable attention in the field of gas separation. In this study, two types of graphene derivatives (Graphene (G) and Graphene Oxide (GO)) were embedded into the poly-ether-block-amide (Pebax) based MMM to investigate and compare CO2/N-2 separation at various filler loadings (0.3-1 wt%). The morphologies of the prepared neat Pebax and MMMs were characterized by SEM, XRD, FTIR and DSC. Compared with the neat Pebax, the permeability of all gases was increased by adding filler content in the MMMs due to the crystallinity decrement of the polyamide (PA) segment. The best separation performance of the Pebax/G MMMs occurred at 0.7 wt%, where the CO2 permeability increased from 26.51 to 44.78 Barrer (similar to 1.7 times). Also, for the Pebax/GO MMMs, the CO2 permeability was increased up to 58.96 Barrer (similar to 2.2 times) by adding 0.5 wt% filler. This further gas permeation increment for the Pebax/GO sample was attributed to the higher affinity of GO nanosheets to CO2 sorption, which can facilitate CO2 gas transition through the membrane matrix. Moreover, the CO2/N-2 ideal selectivity increased from 74.26 for the neat Pebax to 111.95 (similar to 1.5 times) and 120.72 (similar to 1.62 times) by adding 0.7 wt% G (Pebax/G-0.7) and 1 wt% GO (Pebax/GO-1) into Pebax, respectively. As a consequence, graphene derivatives can be recognized as a promising developer of permselectivity (permeability and selectivity) of the MMMs.