Enhanced selectivity of O2/N2 gases in co-casted mixed matrix membranes filled with BaFe12O19 nanoparticles

Abstract

While the development of mixed matrix membranes (MMMs) has revolutionized gas separation applications, O2 and N2 gases are hardly separated from each other due to the small difference between their kinetic diameters. Here, magnetic MMMs consisting of polyethersulfone (PES)/Pebax-1657-BaFe12O19 nanoparticles (NPs) are fabricated by using a co-casting method. The PES and Pebax polymers are used as the substrate and top layer, respectively. The Pebax selective layer (~4 µm in thickness) is filled with BaFe12O19 powder in the presence of an external magnetic field (H = 0.5 T), providing efficient dispersion and accumulation of the magnetic NPs in the polymer matrix with high chemical stability. Field-emission scanning electron microscopic images indicate the absence of gaps, collapse, and crush at the contact layers of the two polymers, resulting in a dense top layer. By fabricating magnetic double-layer MMMs with 18 and 24 wt% BaFe12O19 NPs, the respective ideal selectivity of O2/N2 gases in the presence of H = 0.5 T at 25 °C is found to be 4 and 4.01, indicating significant enhancement in the gas separation compared to the non-magnetic MMM with an ideal selectivity of 1.87 in the absence of H.