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Flow electrode capacitive deionization (FCDI), a novel ion removal technology, is influenced by various factors such as electrode material properties, fluid flow rate, and device structure. In the FCDI system, the intermediate chamber is the core element where ions migrate towards the cathode and anode to complete the adsorption process. In this study, we designed a hollow plastic plate with channels (PP) and a hollow graphite plate with channels (GP) as the intermediate chamber, compare and study with conventional plastic mesh (PM) chambers. CFD simulations revealed that the newly designed PP and GP chambers significantly reduced the hydraulic stagnation zone. The results of the desalination experiments revealed that the desalination efficiency of the GP-FCDI was 1.5 and 1.9 times higher than that of the PP-FCDI and PM-FCDI, respectively. At the same time, in situ potential measurement (ISPM) was used to monitor the voltage drop of each component in FCDI, thereby accurately calculated the proportion of energy consumption in the intermediate chamber. The results indicate that the energy consumption of the intermediate chamber of GP-FCDI was 54 % less than that of PM-FCDI. The current work will help us provide new insights for the design and optimization of FCDI systems. • Replaced conventional FCDI intermediate chamber with flow channel • Innovative introduction of graphite plate into the intermediate chamber • The effects of hydraulic distribution on desalination performance were analyzed. • The SEC of each component of the FCDI device was calculated separately. [ABSTRACT FROM AUTHOR]

Flow electrode capacitive deionization (FCDI) is a new ion removal technology with sustainable deionization performance. However, the interface resistance has a significant impact on ions migration in FCDI. We therefore introduced a novel FCDI device that incorporated a layer of carbon felt as an "ionic capacitor" between the flow electrode and the ion exchange membrane, termed CF-FCDI. Mechanism exploration results revealed that the addition of carbon felt reduced device resistance, shorten electron transfer pathways, improved charge efficiency, and increased ion migration rate. Experimental results demonstrated that the improved CF-FCDI device achieved 44 % higher desalination rate compared to traditional device. In addition, long term operation experiments confirmed the stability of CF-FCDI device, highlighting its potential as a viable desalination solution. The findings of this study provided valuable insights for further development of FCDI and offered a promising solution for its applications such as seawater desalination. [ABSTRACT FROM AUTHOR]

[Display omitted] • The series connection method of flow electrode ST-SC and MT-SC in multi-stage FCDI were proposed. • Flexible current control each level device to decrease ENRS. • MT-SC operating mode was more energy-efficient and efficient than traditional single stage devices. • The MT-SC operating mode could fully utilize the energy released during the desorption process. This article proposed a three-stage flow electrode capacitive deionization (FCDI) device, in which the flow electrodes were connected in series and circulated among the three stages. Four different methods of flow electrode series connection (ICC, SCC, ST-SC, and MT-SC) were investigated. The results showed that the MT-SC mode achieved the best desalination performance and saved 43.47 % of energy. To further reduce energy consumption, the current of the three-stage device was further optimized using flexible current, and the mode with gradually decreasing current (15 mA-10 mA-5 mA) was the most effective. Moreover, the effects of flow rate, influent salt concentration and current on the desalination performance of the three-stage FCDI device were studied. A fair comparison was made between the desalination performance of three-stage and single-stage FCDI devices, and the results showed that the multi-stage FCDI device with series flow electrodes can fully utilize the energy released during the short-circuit desorption process to reduce the energy consumption of desalination. Therefore, the multi-stage FCDI devices were more energy-efficient and economical than traditional single-stage devices. [ABSTRACT FROM AUTHOR]

Flow electrode capacitive deionization (FCDI) has great advantages in high salinity wastewater desalination. However, due to the limited adsorption capacity of electrode material, membrane concentration polarization would form and increase energy consumption, and affect the continuity of desalination. In this work, milling technology was used to modify original activated carbon (AC), the obtained ball milled activated carbon (BAC) was used as FCDI electrode material. The milling process modified multiple physical and electrochemical characteristics of original AC. The highest average salt removal rate (ASRR) of BAC was 2.2 times of that of AC, which was attributed to the modified surface properties including more oxygenated functional group, larger electrostatic gravitation characteristics and better hydrophilicity. The reduced concentration polarization during the desalination was responsible for the increased adsorption capacity, which was due to larger electrolyte contact area, enhanced ions capacity by more suitable pore structures, and 5 times higher energy normalized removal salt (ENRS) of BAC flow electrode than that of AC. Because of its simple operation and remarkable modification effect, ball milling technology shows great potential in large scale modification of electrode materials. [ABSTRACT FROM AUTHOR]