PEBA/CNC-EGME mixed matrix membrane with interconnected networks for enhanced CO2 separation

Abstract

To address the constraint of polyether block amide (PEBA) membrane in separating CO₂ from N₂, this study focused on developing PEBA/CNC-EGME mixed matrix membranes featuring an interconnected network. Crystal nano cellulose (CNC) bio-based fillers were employed as fixed fillers in these membranes, while ethylene glycol monophenyl ether (EGME) served as a semi-mobile agent. Various membranes were prepared by adding different ratios of CNC solution to PEBA and PEBA-EGME solutions. The structure and separation performance of these membranes were then examined using various techniques. It was observed that the membranes containing higher ratios of CNC exhibited superior performance compared to the Robeson upper bound line. This can be attributed to an adequate amount of CNC fillers, which enabled the establishment of an interconnected structure across the membrane width. As a result, these membranes were able to overcome the trade-off limitation and achieve higher performance. Among the fabricated membranes, the P1CNC1 membrane demonstrated the top performance, with a CO₂/N₂ selectivity of 113 and CO₂ permeability of 100.75 Barrer. In the membranes where EGME is combined with CNC, the presence of EGME molecules as semi-mobile agents alongside CNC fillers successfully addressed the dissociation of the CO₂ transport mechanism at low CNC ratios. This behavior allowed the establishment of interconnected networks even at low CNC ratios, enabling all membranes containing CNC and EGME to surpass the Robeson upper bound line. Notably, the P3CNC1EGME membrane exhibited the highest CO₂ permeability (111 Barrer), and the P1CNC1EGME membrane demonstrated the highest CO₂/N₂ selectivity (121.9), which were 30 % and 166 % higher than those of the pure membrane, respectively.