Magnetic field-induced improvement in O2/N2 gas separation applications of simultaneously co-casted superparamagnetic mixed matrix membranes

• Double-layer PES/Pebax-Fe 3 O 4 membranes were fabricated by simultaneous co-casting. • A variable magnetic field (H = 0–5000 Oe) was applied during the fabrication of membranes. • Thick superparamegnetic channels with root-like structure were created on the surface. • O 2 and N 2 permeances of PES/Pebax membranes increased as a function of magnetic field. • O 2 /N 2 ideal selectivity of PES/Pebax-Fe 3 O 4 membrane improved by 40% under H = 4000 Oe. For industrial purposes and current challenges facing the world, the selective separation of oxygen and nitrogen gases from the air by polymer mixed matrix membranes is crucial. Due to the diamagnetic nature of water molecules used in the fabrication of the polymer membranes, the magnetic field (H) may affect the resulting separation performance. Here, using a simultaneous co-casting method, empty and superparamagnetic Fe 3 O 4 nanoparticle-filled double-layer polyethersulfone (PES)/Pebax®1657 mixed matrix membranes are fabricated under different external magnetic field intensities in the range of H = 0–5000 Oe. The O 2 and N 2 permeances of the PES/Pebax® membranes are found to increase with increasing the magnetic field intensity, arising from an enhancement in the polymer chain mobility. The Fe 3 O 4 nanoparticles form thick root-like superparamagnetic channels on the double-layer PES/Pebax® surface at a magnetic field intensity of 4000 Oe, resulting in an O 2 / N 2 ideal selectivity of 3.59 at a feed gas pressure of 10 bar. This indicates an improvement of 40% in the selectivity compared to a single-layer Pebax® membrane filled with Fe 3 O 4 nanoparticles.