Carbon-based electrode materials with ion exchange membranes for enhanced membrane capacitive deionization

Abstract

Potable clean water is in high demand for human life. Numerous technologies like reverse osmosis, flash distillation and electrodialysis are employed and explored to overcome the scarcity of potable water. Last decade has witnessed great attraction of researchers towards membrane capacitive deionization (MCDI) as an alternative technology for water desalination. MCDI holds ability to compete with benchmark desalination techniques as it involves adsorption of ions by porous carbon material on application of low voltage (<1.4 V). Ions are desorbed back into the stream on reversing the potential hence, regenerating the electrodes. Addition of ion exchange membranes enhances the desalination efficiency by reducing the effect of co-ions, which is not possible in traditional capacitive deionization (CDI). Present study aims to synthesize and explore the best fit carbon-based material for MCDI. SPEEK and QPPO polymers were used for CEM and AEM preparation over the porous carbon materials respectively. SEM, XRD and Raman spectroscopy were used to investigate the structural information about carbon materials. Nyquist plots were obtained to analyze diffusive behavior and formation of electrolyte double layer (EDL) on electrode-electrolyte interface. Capacitive behavior of the electrodes was analyzed through cyclic voltammetry (CV) and Galvanostatic charge discharge (GCD). Water desalination performance of membrane coated carbon materials was observed through batch-mode MCDI set-up. Important CDI parameters like salt adsorption capacity (SAC) and specific capacitance were also calculated to evaluate performance of the prepared MCDI electrodes. Among all four synthesized materials, CMGO (carbon spheres modified graphene oxide) reports highest SAC value i.e. 22.5 mg g−1 which suggest CMGO as a promising material for large scale MCDI application.