Effect of chitosan as a functionalization agent on the performance and separation properties of polyimide/multi-walled carbon nanotubes mixed matrix flat sheet membranes

▶ Raw MWCNTs were generally closed ended and after functionalization, open ended chitosan-wrapped MWCNTs were obtained. ▶ Chitosan-functionalized MWCNTs increased the CO 2 and CH 4 permeabilities of the mixed matrix flat sheet membranes. ▶ A very good dispersion and adhesion of the chitosan-functionalized MWCNTs in the polyimide matrix were observed. The effect of chitosan as a functionalization agent on the performance and separation properties of polyimide/multi-walled carbon nanotubes mixed matrix flat sheet membranes were investigated. Polyimide (PI)/raw multi-walled carbon nanotubes (r-MWCNTs) and polyimide (PI)/chitosan-functionalized multi-walled carbon nanotubes (C-f-MWCNTs) mixed matrix membranes were fabricated by phase inversion method. Raw and functionalized multi-walled carbon nanotubes were characterized by transmission electron microscope (TEM). The membrane samples were characterized by SEM, FESEM, DSC and gas permeation tests using He, CO 2 and CH 4 as test gases. TEM results and gas permeation test using He as test gas showed that r-MWCNTs were generally closed ended and after functionalization, well dispersed open ended chitosan-wrapped MWCNTs were obtained. Gas permeation results showed that addition of 1 wt.% (solid base) C-f-MWCNTs into casting dope can increase the CO 2 and CH 4 permeabilities by 20.48 and 0.71 Barrer, respectively. The increase in permeabilities of CO 2, CH 4 and He in this study can be attributed to the presence of high diffusivity tunnels in the MWCNTs within the polyimide matrix. It is interesting that the CO 2/CH 4 selectivity was also increased by 51.4% (from 10.9 to 16.5) by addition of C-f-MWCNTs. DSC and FESEM results also revealed a very good dispersion and adhesion of the C-f-MWCNTs in the polyimide matrix.