Effect of incorporation of multi-walled carbon nanotubes on the CO2/CH4 separation performance of sulfonated poly (ether ether ketone) / polyetherimide composite membranes using design of experiments and molecular dynamics simulation methods

Blend membranes were prepared based on sulfonated poly (ether ether ketone) (SPEEK) and poly (etherimide) (PEI) using different amounts of multi-wall carbon nanotubes (MWCNTs) (up to 2 wt.%). PEEK has been sulfonated directly to reach 70% degree of sulfonation. The manufactured membranes were examined by X-ray diffraction (XRD), scanning field emission electron microscopy (FESEM), Fourier transformed infrared spectroscopy (FTIR). The effect of the composition of SPEEK / PEI on membrane selectivity was investigated under different feed pressures (2 to 8 bar) and temperatures (25 to 55 °C). The values of selectivity and gas permeability were varied between the value of the individual polymers, fluctuating systematically with SPEEK / PEI content variation in the blends. TGA and tensile tests result obtained for prepared membranes shown that the hybrid membrane had good thermal and mechanical properties. The addition of MWCNTs to the blend led to simultaneously improve the selectivity and permeability of the pair gases of CO2 and CH4. The permeability of CO2, as well as CH4/CO2 selectivity for the membrane with the same weight of SPEEK and PEI, and 1 wt.% of MWCNTs (coded SP55M1) experienced an increase of about 22% compared with the neat membrane. Molecular dynamics simulations (MDS) were performed by employing the COMPASS force field to estimate the diffusivity of CH4 and CO2 gases through selected membranes. At last, with compared to the obtained experimetal data, the optimized nanocomposite membrane, integrated with MWCNTs was efficient, which makes it promising platform to separate mixed gase flows of CO2 and CH4 and other related environmental processes.