Highly permselective polyvinylidene fluoride-based cation-exchange membranes containing phosphorated graphene oxide for electrodialysis

Phosphorated graphene oxide (PGO) was used to prepare polyvinylidene fluoride (PVDF)-based cation-exchange membrane for the electrodialysis (ED) process. The influences of PGO wt% on the physicochemical and electrochemical characteristics of the PVDF/PGO membranes were studied using different characterization methods. The morphology, oxidative stability, permselectivity, ion transport number, and electrochemical properties of the best PVDF/PGO membrane were compared with those of the bare Nafion-117 membrane and PVDF/GO membrane containing the same wt% of GO. The membrane containing 60 wt% PGO (PVDF/PGO60) exhibited a high water uptake of 44.69%, which was about 2.5 and 2 times higher than that achieved from PVDF/GO60 and Nafion, respectively. PVDF/PGO60 provided a considerably higher (∼10 times) ion exchange capacity (IEC) than Nafion. Electrochemical analysis revealed that Na+ ions enjoyed a high diffusion coefficient within PVDF/PGO60, which was comparable to Nafion-117. This resulted in a low area resistance of 2.4 ± 0.3 Ω cm2, high permselectivity of 96.4%, and transport number of 97.8%. Moreover, PVDF/PGO60 exhibited a low weight loss of 1.90%, and a moderate resistance change of 19.79% after being immersed in the Fenton reagent for 9 h. The desirable electrochemical properties, and oxidative and mechanical stability of PVDF/PGO60 suggest that the PGO-containing PVDF-based membranes can be considered promising CEMs for application in the electromembrane desalination processes.