(Invited) Electrochemical Ion Separation Based on Capacitive Deionization as Promising Water and Resource Recovery Processes

Abstract

To resolve the global issue of the water crisis, capacitive deionization (CDI) has been suggested as a promising water recovery technology via electrochemical ion separation. It is considered as an alternative or competing technology for conventional water purification systems such as reverse osmosis and multistage flash distillation. CDI has attracted numerous academic and industrial attention as a novel desalination process for its unique advantages such as high energy efficiency, environmental friendliness, and a high water recovery rate.In the conventional CDI cell architectures, typically a pair (or multiple pairs) of porous carbon electrodes are used, separated by a spacer.The operation of the CDI system consists of two cycles including charging (purification/electro-adsorption) and discharging (regeneration/electro-desorption) steps. During the charging step, the porous electrode pair is charged with applied potential, and salt ions are electro-adsorbed into the electrical double layer (EDL) generated between the interface of porous electrode and water, leading to the removal of salt ions from the feed aqueous solution. The adsorbed ions are released from the electrodes in the discharging step, which is operated with reversed polarity, or short circuit resulting in a concentrated effluent stream.Since the 21st century, numerous technological advancement has been achieved and the field of application has extended thanks to the efforts of research groups around the world. In this presentation, we aim to introduce the major operating principles and research advances including electrode materials and cell configurations. Also, the various applications of CDI are briefly introduced. Finally, this presentation proposes future research directions for the scientific and industrial challenges in water and resource recovery technologies.