Enhancement of ion migration and minimization of pressure loss through spacer optimization in flow-electrode CDI

Abstract

While geometric optimization of the desalination chamber is crucial to enhance salt removal in the flow-electrode capacitive deionization (FCDI) spacer, a comprehensive investigation is still scarce. The results of this study demonstrated that the spacer architecture remarkably affected energy consumption. The specific energy consumption (SEC) for brackish desalination reduced with the mesh number (at a range of 30–100) of the spacer from 0.79 to 0.62 kWh m−3, which could be attributed to the decrease in the setting-up resistance. A tradeoff was observed between the desalination (SECW) and the pumping (SEChw) when the thickness of the spacer was varied. In contrast to the SECW that decreased from 0.90 to 0.49 kWh m−3 when the spacer thickness was reduced to 0.25 mm, the commonly overlooked SEChw jumped to 0.39 kWh m−3. A spacer thickness of 0.50 mm at a mesh number of 100 was the optimal value in the 1.50–0.25 mm range, achieving the lowest overall SEC. The results of this study provide new insights into the design and optimization of FCDI toward high-efficient brackish water desalination.