Designing of PVDF-Based Cation Exchange Membranes with Improved Electrochemical Properties for Energy-Efficient Brackish Water Desalination

This study aims to develop a poly(vinylidene fluoride) (PVDF)-based cation exchange membrane (CEM) for brackish water desalination by electrodialysis (ED). The modification process involved ozonation of PVDF, followed by p-benzoquinone grafting and subsequently sulfonation using chlorosulfonic acid. The time for functionalization of Quino-PVDF was optimized to get the desired physicochemical and electrochemical attributes of the synthesized CEM. The formation of sulfonated Quino-PVDF (s-Quino-PVDF) was confirmed through nuclear magnetic resonance (NMR) spectroscopy, while the fabricated membranes were characterized using infrared (IR) spectroscopy, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. Among the membranes, the QuinoCEM-30 membrane exhibits superior mechanical and thermal properties. The EDX analysis revealed that the QuinoCEM-30 shows the highest sulfur content, which contributes to better water uptake (17%), and an ion-exchange capacity (IEC) of 0.87 mequiv g–1. QuinoCEM-30 membrane presents an ionic conductivity of 8 × 10–3 S cm–1. During electrodialysis, QuinoCEM-30 confirms a 91.6% salt removal efficiency. Furthermore, the QuinoCEM-30 membrane exhibited the current efficiency of 90% and the lowest energy consumption of 0.94 kW h kg–1, highlighting its efficiency in desalination processes. These results indicate that QuinoCEM-30 can be a promising candidate for energy-efficient brackish water desalination applications.