(Invited) Continuous Low-Cost Separation of Multivalent Ions from Dilute Aqueous Solutions by Shock Electrodialysis

Abstract

Shock electrodialysis (SED) is an emerging separations technology, which opens new possibilities for purification, valorization and recycling of contaminated water. By exploiting novel electrokinetic transport phenomena, SED is able to achieve highly selective, continuous ionic separations that are not possible with other electrochemical methods based on ion adsorption in porous electrodes, such as electro-swing adsorption (ESA) and capacitive deionization (CDI), or ion exchange in membrans (alone), such as its cousins, electrodialysis (ED) and electro-deionization (EDI). Instead, the separation in SED is achieved by a steady deionization shockwave in cross flow, which results from the passage of over-limiting current (faster than diffusion) through a charged porous medium, sandwiched between ion-exchange membranes. This talk will introduce the basic principles and mathematical theory of SED, focusing on the separation of trace multivalent from excess monovalent ionic species. Experimental examples include the separation of lead from drinking water and radioactive contaminants from nuclear wastewater. Similar SED systems could be designed to separate valuable ionic species from mining effluents or industrial recycling streams, especially if combined with ESA, CDI, or other electrochemical methods.