Experimental study of the effect of inlet condition of flow-electrode and electrolyte on the water desalination performance of FCDI

Abstract

Global freshwater scarcity poses a significant challenge to sustainable development efforts. Conventional, desalination technologies often suffer from high energy consumption and operational limitations. Among emerging technologies, Flow-electrode Capacitive Deionization (FCDI) presents a promising avenue due to its favorable economics and ease of scalability. This study investigates the influence of the inlet conditions—specifically temperature and flow rate—of both the slurry electrode and the saline feedwater on desalination performance under varying applied voltages. The results demonstrate that at a constant activated carbon concentration, desalting efficiency (E) is critically governed by these parameters. A positive correlation was found between desalting efficiency and the slurry flow rate (FRe), while an inverse correlation was observed the saline water flow rate (FRw), increasing the temperature of either stream enhanced performance. At V = 1 V, increasing Tw from 22.5 to 50 °C, raised E by 12.5% and 35% for FRw = 2 mL min−1 and FRw = 7.2 mL min−1, respectively. Similarly, increasing the electrode temperature improved desalting efficiency by 15–45%. The study identifies an optimal slurry electrode flow rate (FRe = 21.5 mL min−1) that balances high desalination efficiency, salt removal rate, and current efficiency.