Incorporating the magnetic alignment of GO composites into Pebax matrix for gas separation

The mixed matrix membranes (MMMs) were developed by incorporating graphite oxide (GO) flakes functionalized with iron oxide (Fe3O4) into Pebax matrix. The Pebax/Fe3O4–GO MMMs were used to separate CO2/CH4 and CO2/N2 gas mixture. The results showed that the MMMs with magnetic alignment presented the better gas separation performance than that of random arrangement of Pebax/Fe3O4–GO mixed matrix membranes. The reason was that the Fe3O4–GO flakes arranged magnetically in the membrane played a multiple role in improving the performance of MMMs. Firstly, under the action of the magnetic field, the magnetic alignment of Fe3O4–GO flakes in Pebax matrix constructed the shorter transfer path for gas molecule, increasing the CO2 permeability. Secondly, the hydroxyl groups in GO flakes and the presence of Fe3O4 have stronger binding force for water, improving the CO2 solubility selectivity. Thirdly, the better interaction between the magnetic alignment of GO composites and polymer matrix, reduced the interface defects. Especially, the optimum gas separation performance was obtained at the Fe3O4–GO flakes content of 3 wt% in Pebax matrix at vertical arrangement with selectivity of 47 and 75 for CO2/CH4 and CO2/N2, respectively, and CO2 permeability of 538 Barrer at 0.2 MPa and room temperature.