Carbon nanotubes (CNTs) were synthesized by CVD method using cyclohexanol and ferrocene as carbon precursor and catalyst, respectively. Nitric acid was used for purification and functionalization of CNTs. TEM image of CNTs before and after purification revealed that acid treatment could remove encapsulated catalyst particles. Afterward, highly pure and functionalized CNTs were incorporated in poly (vinyl alcohol) (PVA) to synthesize PVA-CNTs nanocomposite membranes. FESEM characterization was carried out to investigate dispersion of different CNTs loading in PVA matrix. The results showed that 2 wt.% CNTs loading is better dispersed in the polymer and increasing CNTs loading more than 2 wt.% agglomerates CNTs. Degree of swelling results for nanocomposite membranes showed that present of CNTs in the PVA membranes reduce the degree of swelling. Furthermore, pervaporation (PV) results revealed that incorporating of CNTs in PVA matrix increases significantly water selectivity due to rigidification of the polymer chains. The water selectivities for the pristine PVA and 2 wt.% CNTs loading nanocomposite membranes were evaluated as 119 and 1794, respectively. (C) 2011 Elsevier B.V. All rights reserved.