ABSTRACT:
Mixed matrix membranes (MMM) comprised of multi-walled carbon nanotubes (MWCNTs) inside
polyethersulfone (PES) matrix were fabricated and characterized for gas separation performance. The
MWCNTs were purified with acid mixtures (HNO3/H2SO4; v/v = 1:3) to remove carbonaceous impurities
followed by surface functionalization with 3-aminopropyltriethoxylsilane (APTES) to allow well
dispersion of the tubes in organic solvent such as N-methlypyrrolidone (NMP) during the preparation of
PES/MWCNTs suspension. Effects of purification, functionalization and MWCNTs loading on the gas
permeation properties of the MMM were investigated by varying the MWCNTs loading in the PES matrix
from 0.5–3.0 wt.%. The fabricated MWCNTs/PES MMM were characterized by scanning electron
microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetry analysis (TGA) and pure
gas permeation test. Gas permeation measurement showed that MMMs embedded with different kinds
of applied CNTs exhibited different separation performances. For example, gas permeation
measurement showed that MMM embedded with 1.0 wt.% purified and functionalized MWCNTs
possessed better performances in terms of permeability and selectivity in comparison to raw MWCNTs.
The highest gas selectivity was achieved at 0.5 wt.% MWCNTs loadings (aCO2/CH4 = 250.13; aO2/N2 =
10.65) and decreased as the loadings were increased from 1.0 to 3.0 wt.%. The reduction in
performance possibly due to the presence of interface voids which became prominent at higher
MWCNTs loading. The high selectivity of fabricated MMM suggested that the present works have a
great potential to be utilized practically in gas separation technology.