Studying the electrosorption performance of activated carbon electrodes in batch-mode and single-pass capacitive deionization

• Published in: Separation and purification technology 2019-05, Vol.215, p.403-409
• Main Authors: Liu, Nei-Ling, Sun, Shih-Han, Hou, Chia-Hung
• Format: Article
• Language: English
• Subjects: Activated carbon; Capacitive electrodes; CDI Ragone plot; Desalination; Electrosorption
• ISSN: 1383-5866; 1873-3794
• DOI: 10.1016/j.seppur.2019.01.029

[Display omitted] •Electrosorption performance of activated carbons was examined for the desalination.•The effect of pore structure on capacitive characteristics was investigated.•High specific capacitance suggested high salt adsorption capacity.•CDI Ragone provided comprehensive view on desalination capacity and rate.•Single-pass mode CDI was desirable to estimate desalination performance. In the present work, the electrosorption performance of activated carbon-base capacitive deionization (CDI) was evaluated by batch and single-pass mode experiments. Two commercial activated carbon electrodes with raw materials of coal (AC1) and wood (AC2) were selected and their physical and electrochemical characteristics were determined by Brunauer–Emmett–Teller (BET) and cyclic voltammetry experiments. The results indicated that micropores and mesopores are well-balanced in both AC1 and AC2. The specific surface of AC1 (940 m2/g) was higher than that of AC2 (662 m2/g), and the AC1 showed a higher specific capacitance from cyclic voltammetry curves. CDI characteristics could be determined from the batch-mode and single-pass experiment, both AC1 and AC2 showed good electrosorption performance. The batch-mode, however, can only serve as evaluation of basic CDI performance. As evidenced in single-pass experiments with 2 mM NaCl at 1.0 V, AC1 exhibited a higher salt adsorption capacity of 5.08 mg/g-carbon than that of AC2 (2.39 mg/g-carbon). The CDI Ragone plot from single-pass experiments was further used as a functional tool to provide the key performance indicators: salt adsorption capacity and mean deionization rate. In the CDI Ragone plot, AC1 appeared towards the top and right side, showing that AC1 was more well-developed than AC2. In addition, the impact of pore structure on electrosorption performance was clearly observed. Overall, this study can provide a fundamental basis for understanding the estimation of CDI performance.