Polydimethylsiloxane/Magnesium Oxide Nanosheet Mixed Matrix Membrane for CO 2 Separation Application.

Carbon dioxide (CO 2 ) concentration is now 50% higher than in the preindustrial period and efforts to reduce CO 2 emission through carbon capture and utilization (CCU) are blooming. Membranes are one of the attractive alternatives for such application. In this study, a rubbery polymer polydimethylsiloxane (PDMS) membrane is incorporated with magnesium oxide (MgO) with a hierarchically two-dimensional (2D) nanosheet shape for CO 2 separation. The average thickness of the synthesized MgO nanosheet in this study is 35.3 ± 1.5 nm. Based on the pure gas separation performance, the optimal loading obtained is at 1 wt.% where there is no observable significant agglomeration. CO 2 permeability was reduced from 2382 Barrer to 1929 Barrer while CO 2 /N 2 selectivity increased from only 11.4 to 12.7, and CO 2 /CH 4 remained relatively constant when the MMM was operated at 2 bar and 25 °C. Sedimentation of the filler was observed when the loading was further increased to 5 wt.%, forming interfacial defects on the bottom side of the membrane and causing increased CO 2 gas permeability from 1929 Barrer to 2104 Barrer as compared to filler loading at 1 wt.%, whereas the CO 2 /N 2 ideal selectivity increased from 12.1 to 15.0. Additionally, this study shows that there was no significant impact of pressure on separation performance. There was a linear decline of CO 2 permeability with increasing upstream pressure while there were no changes to the CO 2 /N 2 and CO 2 /CH 4 selectivity.