This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Flow-electrode capacitive deionization (FCDI) technology can achieve continuous desalination via the electrodialysis coupling method. However, electrical energy is still highly consumed. In this work, the flow carbon nanotubes (CNTs) and vanadium redox couples are utilized as the flow electrode material together with AC to achieve the energy-saving desalination process. The V 2+ /V 3+ ions are oxidized/reduced at the positive/negative electrode chambers under the constant current applied. The ions in salt feed can be continuously removed through the electrodialysis process in a three-membrane configuration (AEM|CEM|AEM). The carbon nanotubes play double roles of both electron transporter and capacitive ion capturer together with activated carbon. Excellent electrochemical desalination can be obtained. In the current sample tests, the desalination rate can be up to 0.253 μg cm −2 s −1 , and the energy consumption of 72.62 kJ mol −1 is achievable by adding 1 wt % CNTs and 20 mM/20 mM V 2+ / V 3+ to 6.41 wt % activated carbon flow electrode at the current density 0.43 mA cm −2 . This demonstrates the possibility of low-energy desalination with the continuous process. Our study provides an efficient way to promote the FCDI desalination performance, which will contribute to the development of FCDI technology in the future.

In the redox flow electrode capacitive deionization (FCDI), the solubility of redox electrolyte and flowability of carbon slurry have great influence on the salt removal rate and energy consumption. In this work, a mixed solvent electrolyte is proposed in FCDI, which consists of iodide/triiodide redox couples and carbon slurry in the mixed solvent of water and ethanol (1:1). At the current density of 5 mA cm-2, the salt removal rate can reach up to 2.72 μg cm-2 s-1 in a mixed solvent, which is much higher than 1.74 μg cm-2 s-1 in aqueous solution and 2.37 μg cm-2 s-1 in the ethanol solution. This may be owing to the fast transport of ions during redox reaction in organic solvent and the excellent flowability of carbon slurry in the aqueous condition, which can provide more reaction sites for iodide/triiodide redox reaction and faster electron transportation. This unique FCDI with organic and aqueous mixed solvent electrolyte will provide a new perspective for the development of redox flow electrochemical desalination.