How Does Temperature Affect the Charge Transfer Process in Flow Electrode Capacitive Deionization?

Abstract

In this study, we investigate how temperature variations, a key environmental factor, affect the charge transfer process in FCDI systems across seasonal variation and geographical distributions, which is crucial for optimizing FCDI performance but has not received adequate attention. Therefore, thermal-assisted FCDI systems were proposed by controlling the temperatures of the flow electrode and saline water to simulate the environmental conditions, and the temperature effects on the charge transport and desalting ability of FCDI were investigated. First, the isothermal mode was performed, where the flow electrode and saline water were controlled at the same temperatures (0-50 °C) to simulate the natural atmospheric temperature fluctuations and industrial circulating cooling water system. Experimental results showed a strong positive correlation between temperature and electrosorption dynamics. Elevated temperatures significantly improved ion electromigration and diffusion, thereby enhancing the electrosorption capacity of the FCDI device. On this basis, the nonisothermal mode was designed via maintaining the temperature of the flow electrode at 50 °C to improve the desalination performance of FCDI for saline water at different temperatures (0-50 °C). Finally, the East China seawater and industrial circulating cooling water were both desalted successfully to confirm the feasibility of the temperature field in the practical application of FCDI.