Multilayer mixed matrix membranes containing modified-MWCNTs for dehydration of alcohol by pervaporation process

In this work, multilayer mixed matrix membranes containing carbon nanotubes (CNTs), poly(vinyl alcohol) (PVA), polyethersulfone (PES) and polyester as inorganic filler and selective top, intermediate and support layers, respectively, were prepared for dehydration of ethanol/water mixtures by the pervaporation process. For this purpose, the MWCNTs were synthesized by the thermal-chemical vapor deposition (T-CVD) technique and then the CNTs were modified by incorporating carboxyl functional groups and synthesizing titanium oxide (TiO2) nanocrystals on them. The results indicated that the MWCNTs with high purity were prepared and carboxyl functional groups were formed on the CNTs. The membranes containing modified MWCNTs had lower swelling degree and higher crosslinking density which resulted in lower total permeation flux in comparison to the neat membrane and the membranes containing pure MWCNTs. Furthermore, the hydrophilicity, surface roughness and crosslinking of the membranes were improved by increasing the concentration of modified CNTs. All mixed matrix membranes had lower total flux than the neat membranes due to an increase of the membrane top layer resistance by incorporating the MWCNT filler. Finally, it was observed that the modification of CNTs led to better dispersion of MWCNTs into the polymeric matrix and improved the separation performance of the multilayer mixed matrix membranes.