Chapter ten - Membrane-based electrochemical technologies: I. Membrane capacitive deionization and flow-electrode capacitive deionization

Abstract

This chapter introduces membrane capacitive deionization (MCDI) and flow-electrode capacitive deionization (FCDI) as membrane-based electrochemical water treatment technologies based on the capacitive deionization principles. MCDI involves the use of a large number of static electrode pairs (anode and cathode) typically arranged in parallel, whilst FCDI involves the use of a number of pairs of electrodes constructed by flowing slurries of conducting particles between the anodic and cathodic current collectors. In both cases, the ions are removed from the feed stream by the application of an electrical potential across the electrodes, and are stored in the macropores and micropores (and retained in the electrical double layers) of the electrodes. In MCDI, an ion exchange membrane (IEM) is placed in front of each electrode to improve the desalination performance; and, in FCDI, IEMs are used to separate the water and flow electrode channels. By altering the operational configuration or IEM selection, specific ions of interest can be targeted for removal. MCDI and FCDI are low energy water treatment methods and can be applied to water desalination for potable water or water reuse applications, resource recovery, and contaminant abatement.