Application of poly (amide-b-ethylene oxide)/zeolitic imidazolate framework nanocomposite membrane in gas separation

Abstract

Mixed matrix membranes (MMMs) are gaining increasing interest in academic and industrial research due to their combined, desirable properties of both polymers and organic/inorganic filler as important materials. In this work, synthesized zeolitic imidazolate framework (ZIF-8) suspension (10–50 wt%) was directly incorporated into a [poly (amide-b-ethylene oxide) Pebax® 1657] matrix in order to improve the gas separation performance of the membrane. Dynamic light scattering (DLS) analysis showed an average diameter of 77.4 nm for the prepared nanoparticles. The transparent membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and X-ray diffractometry (XRD). These indicated excellent dispersion of nanoparticles, which was achieved by ultrasonication before casting the solution. Incorporation of ZIF-8 as filler in the polymer matrix led to improved thermal and mechanical stability of the membranes. This was confirmed by TGA and tensile analyses, indicating good contacts provided at the polymer/filler interfaces. The effect of ZIF-8 loading (up to 50 wt%) on membrane performance was investigated and it showed an optimum loading of 30 %. Single gas (CO2, N2 and CH4) permeation tests revealed rapid, enhanced permeability of the nanocomposite membranes without significant changes in selectivity (compared to those of the pristine polymeric membrane). The permeability increases for CO2, CH4 and N2 in the optimum Pebax® 1657/ZIF-8 (30 wt%) membrane were found in the stated order as 111, 88 and 99 %. The study revealed that Pebax® 1657/ZIF-8 membranes displayed better gas permeation properties compared to those of Pebax® 1657.