Capacitive deionization (CDI) is an attractive alternative to established technologies such as reverse osmosis for energy-efficient water desalination, with one of its recent innovations, flow-electrode capacitive deionization (FCDI), gaining the popularity because of its excellent salt removal capacity (&gt;20 mg NaCl g-1) and the possibility of simultaneous desalination and concentration of a salt water stream. However, FCDI systems suffer from inefficient charge transfer between the current collectors and flow-electrodes. To overcome this limitation, redox-active flow-electrodes allowing high-performance capacitive deionization have been developed and characterized in this study. Results showed that the reversible redox reactions of aqueous hydroquinone (H2Q)/ benzoquinone (Q) facilitated indirect charge transfer, resulting in desalination rate enhanced significantly (e.g., the average salt removal rate was increased by ~131% as a result of the incorporation of 14 mM H2Q). Moreover, the cycling behavior of the quinoid mediators in the anode flow-electrode demonstrated relatively high stability at the low pH induced, suggesting that the use of quinoid mediators should be economical in long-term operation of FCDIs.

Application of quinoid mediators to develop redox-active flow-electrodes for high-performance capacitive deionization

253rd National Meeting (2017)

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