Fig. 5 shows the surface and cross-section FESEM images of different MMMs with 1 and 2 wt.% of nanotubes loading. Cross-sectional images of different membranes were taken to determine the degree of the nanotubes distribution in the polymer matrix. The cross-section images of MMMs indicate well distribution of r-MWNTS and f-MWNTs in the polymer matrix at 1 and 2 wt.% loadings (Fig. 5(b)–(d)). The cross-section FESEM images of MMMs with 4 wt.% loading of both r-MWNTs and f-MWNTs with different magnifications are depicted in Fig. 6.