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.