The membrane is then immersed in 2.0 M H2SO4 for 24 h for complete cross-linking and then extensively rinsed with water to remove the residual H2SO4. Finally the membrane is dried under vacuum at 30 1C for 48 h. The resulting membranes are designated as CS/HNT-X or CS/SHNT-X representing HNTs or SHNTs as the fillers, where X (X ¼3, 6, 9, 12, or 15) represents the weight percentage of nanotubes to CS. CS control membrane is fabricated in exactly the same way as above without incorporating nanotubes. It should be pointed that membrane thickness is in range of 58–67 μm.