Synthesis of novel thin film composite (TFC) forward osmosis (FO) membranes incorporated with carboxylated carbon nanofibers (CNFs)

Abstract

In this study, thin film composite (TFC) membranes were modified using carbon nanofibers (CNFs) for forward osmosis (FO) applications. Carboxyl functionalization of CNFs was performed to increase their surface hydrophilicity and dispersion in a polysulfone (PSF) matrix as the membrane substrate. Different concentrations of both carboxyl functionalized CNFs (f-CNFs) (0.1, 0.3, and 0.5 wt%,) and raw CNFs (0.3 wt%) were incorporated in the polymer matrix and hydrophilicity, porosity, surface roughness, tensile strength and morphology of the nanocomposite substrates were characterized. The optimal membrane was achieved based on the best performance (higher water flux and lower reverse solute flux). Thereby, the TFC membrane containing 0.3 wt% of the f-CNFs was selected as the optimal membrane. The FO water flux of this membrane was almost 2 times higher than the neat TFC membrane in both FO (active layer facing FS) and PRO (active layer facing DS) modes of operation. Water flux of 13.08 L m− 2 h− 1 and specific reverse solute flux of 0.24 g L− 1 were achieved when 1 M NaCl was used as the draw solution (DS) and Deionized (DI) water was used as the feed solution (FS) under the FO mode. Furthermore, incorporation of the f-CNFs decreased the structural parameter (S) of the TFC membranes leading to lower internal concentration polarization (ICP). From the results, it was concluded that the f-CNFs is a suitable candidate for TFC-FO membranes modification to achieve high membrane performance.