Carboxylated carbon nanofibers as hydrophilic porous material to modification of cellulosic membranes for forward osmosis desalination

In this work, cellulose triacetate (CTA) membranes containing carboxylated carbon nanofibers (CNFs) were synthesized via phase inversion method for the forward osmosis (FO) application. At the first, CNFs were functionalized using carboxyl groups (COOH) in order to make a hydrophilic property. Fourier transform infrared spectroscopy (FTIR) accredited the formation or existence of chemical functional groups on CNFs. Then, the different contents of carboxylated CNFs (0.25, 0.5 and 1 wt%) were added in the casting solution as additive to improve the FO performance of membrane. The synthesized FO membranes were characterized in terms of surface properties, structure of membranes, intrinsic separation properties and as well as FO performance and subsequently compared with commercial membrane. The membrane surface hydrophilicity was enhanced with increasing carboxylated CNFs content in the casting solution. The FO experiments were performed by 10 mM NaCl solution as a feed solution and 1 M NaCl solution as a draw solution in both orientation of membrane. The application of these FO membranes was also investigated for sea water desalination. The modified membrane exhibited superior performance in term of high water flux and low solute diffusion. The water flux of the prepared membrane reached to a maximum of 15.6 L/m2 h which was nearly 2 times as high as that of the neat CTA membrane. The tensile strength measurement confirmed that this parameter of modified FO membrane is greater than that of the unmodified CTA.