Polymeric and mixed-matrix membrane flat sheets in O2/N2 gas separation: Recent advances, magnetism concepts, and future perspectives

Membrane technology has opened a new horizon to oxygen enrichment research studies in order to separate this gas from other gases in the air such as nitrogen. This technology has become popular due to its low cost, low energy consumption, and easy access. Recent events in the world and bitter experience of Covid-19 and SARS epidemics have made human society face the challenge of finding a way to fabricate simple and cost-effective oxygen devices and ventilators. From a medical perspective, oxygen separation can be useful for treating aspiration and breathing difficulties. Also, nitrogen gas is required in the food industry and pharmaceutical chemicals. In this review, we provide an overview of polymeric membrane structures, and focus on organic and inorganic compound fillers in membranes. Particular attention is paid to the role of magnetic nanoparticle fillers with different concentrations, sizes, coercivity, and accumulation in mixed-matrix membranes (MMMs), while also investigating synergistic effects of magnetic modules. The roles of external magnetic field and magnetic module are also highlighted in the fabrication and testing processes. Finally, the results of O₂/N₂ gas separation using polymeric and MMM flat sheets are presented and compared, thereby determining future perspectives.