Flow-electrode capacitive deionization with highly enhanced salt removal performance utilizing high-aspect ratio functionalized carbon nanotubes. (15th March 2019)

• Record Type: Journal Article
• Authors: Cho, Younghyun; Yoo, Chung-Yul; Lee, Seung Woo; Yoon, Hana; Lee, Ki Sook; Yang, SeungCheol; Kim, Dong Kook
• Is Part Of: Water research. Volume 151(2019)
• Page Start: 252
• Page End: 259
• Publication Date: 2019-03-15
• Subjects: Capacitive deionization -- Desalination -- Flow electrode -- Functionalized carbon nanotube -- Activated carbon; Water -- Pollution -- Research -- Periodicals; 363.7394
• DOI: 10.1016/j.watres.2018.11.080
• Languages: English
• ISSNs: 0043-1354

Abstract

Abstract: Flow-electrode-based capacitive deionization (FCDI) has attracted much attention owing to its continuous and scalable desalination process without the need for a discharging step, which is required in conventional fixed-electrode capacitive deionization. However, flow electrode slurry is poorly conductive, which restricts desalination performance, but higher carbon mass loading in the slurry could improve salt removal capacity due to enhanced connectivity. However, increased viscosity restricts higher loading of active materials. Herein, we report a significant increase in salt removal performance by introducing functionalized carbon nanotubes (FCNTs) into activated carbon (AC)-based flow electrodes, which led to the generation of conducting bridges between AC particles. The salt removal rate in the presence of 0.25 wt% FCNT with 5 wt% AC improved four-fold from that obtained with only 5 wt% AC, which is the highest value reported in the literature so far (from 1.45 to 5.72 mmol/m 2 s, at a saline water concentration of 35.0 g/L and applied potential of 1.2 V). Further, FCNTs with a high aspect ratio (∼50, 000) can more effectively enhance salt removal than low-aspect ratio FCNTs (∼1300). Electrochemical analysis further confirms that the addition of FCNTs can efficiently form a connecting percolation network, thus enhancing the conductivity of the flow electrode slurry for the practical application of highly efficient desalination systems. Graphical abstract: Image 1 Highlights: Functionalized carbon nanotubes (FCNTs) were incorporated into a flow electrode slurry. The salt removal rate increases over four times of that obtained without FCNT. FCNTs with a higher aspect ratio effectively enhance the salt removal performance. Overall resistance of a flow-electrode-based capacitive deionization cell decreases by adding FCNTs.