Review of concepts and applications of electrochemical ion separation (EIONS) process

Sustainability has become a global issue that arouses the need for efficient allocation of resources such as water and energy. Over the recent decade, vast research activities were conducted to electrochemical processes, which utilize fundamentals of electrochemistry to achieve ion separation. Owing to its facile, energy-efficient, and environmentally benign characteristics, electrochemical processes are widely applied to various industries such as desalination, and resource recovery to separate ions either non-selectively or selectively. Although electrochemical processes have been designed for different target ions and industrial purposes, they have in common that ions are captured and released by electrodes sharing similar fundamental separation principles. In this review, electrochemical ion separation (EIONS) was proposed to encompass electrochemical processes utilized in various applications. The concept of EIONS is established in detail through chemical process classification. In addition, the state-of-art of EIONS in desalination, resource recovery, impurity removal, and control of hardness and nutritive ions are provided as example applications. Furthermore, perspectives on the development and potential expansion of EIONS application are provided.