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

While the development of mixed matrix membranes (MMMs) has revolutionized gas separation applications, O-2 and N-2 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 (similar to 4 mu m 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 O-2/N-2 gases in the presence of H = 0.5 T at 25 degrees 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.