Desalination, 2nd Edition

Chapter 12Electrosorption of Heavy Metals with Capacitive Deionization: Water Reuse, Desalination and Resources Recovery

Pei Xu¹, Brian Elson² and Jörg E Drewes³

¹New Mexico State University, Las Cruces, New Mexico, USA

²The Water Company, Pueblo, Colorado, USA

³Urban Water Systems Engineering, Technische Universität München, Germany

Abstract

Capacitive deionization (CDI) is an emerging electrosorption process that simultaneously produces deionized water for reuse and recovers valuable heavy metals from waste streams. Bench-scale experiments were conducted to investigate the electrosorption selectivity of metals and cyanide by activated carbon electrodes. Over the course of 158 treatment cycles, CDI remained high efficiency in removing heavy metals and meeting drinking water standards. Within 25 to 30 minutes retention time, the percent removal of conductivity achieved 97.9–96.4% and the effluent conductivity increased slightly from 13 μS/cm in the beginning of experiments to 22 μS/cm at the end of the testing period. Activated carbon electrodes adsorbed trivalent and tetravalent ions preferentially compared to divalent ions. Uranium-238 (IV), iron (III) and chromium (III) were reduced by 98.9±0.6%, 99.9±0.06% 99.6±0.3% while nickel (II), copper (II), lead (II) and zinc were retained 89.0±7.3%, 94.8±2.7%, 94.0±3.3%, 85.2±9.0%, respectively. Nearly all the metal concentrations in the deionized water met the USEPA drinking water standards, except lead (II). CDI reduced the lead ...