PIM-1 mixed matrix membranes incorporated with magnetic responsive cobalt-based ionic liquid for O2/N2 separation

Abstract

Membrane technology for O2/N2 separation is a mature industrial unit. Membranes with excellent permeation-separation performance are still one of the critical requirements. The cobalt-based compounds have been well known for their good affinity for O2, which can facilitate O2 transfer and improve the O2/N2 selectivity in membranes. The cobalt-based compounds, moreover, have a magnetic responsive effect, which can lead to a further improvement in O2/N2 separation under a magnetic field. A class of PIM-1 mixed matrix membranes (MMMs), containing cobalt-based ionic liquid (CILs)@polyarylate (aromatic polyester) (PAR) (core-shell) composite nanospheres (CILs@PAR (c-s) CNPs), were prepared. Chemical compositions of CILs@PAR (core-shell) CNPs were determined by Fourier transform infrared spectroscopy (FTIR). Morphologies and structures of CILs@PAR (core-shell) CNPs were observed by transmission electron microscopy (TEM). Gas adsorption properties of CILs@PAR (core-shell) CNPs were tested. Thermal properties of the (CILs@PAR (c-s) CNPs)/PIM MMMs were investigated by simultaneous thermal analysis (TGA-DSC). Gas permeation-separation performances of the (CILs@PAR (c-s) CNPs)/PIM MMMs were also reported. Compared with the original PIM-1 membrane, the (CILs@PAR (c-s) CNPs)/PIM MMMs display higher O2/N2 selectivity because of cobalt-based ionic liquid as O2 carrier, coupled with a reduction in O2 permeability. With increasing the content of the CILs@PAR (c-s) CNPs, the O2/N2 selectivity increases, and the O2 permeability decreases. It is also found that, as a magnetic field on the MMMs, the O2/N2 selectivity further increases; and it increases more, as a higher content of CILs@PAR (c-s) CNPs. Therefore, the (CILs@PAR (c-s) CNPs)/PIM MMMs exhibit excellent O2/N2 selectivity of ∼5 coupled with good O2 permeability of ∼140 Barrer under a 180 mT magnetic field and show great potential for air separation.