Enhancing Performance of Capacitive Deionization with Polyelectrolyte-Infiltrated Electrodes: Theory and Experimental Validation

Abstract

The energy efficiency of capacitive deionization (CDI) with porous carbon electrodes is limited by the high ionic resistance of the macropores in the electrodes. In this study, we demonstrate a facile approach to improve the energy efficiency by filling the macropores with ion-conductive polyelectrolytes, which is termed polyelectrolyte-infiltrated CDI (pie-CDI or πCDI). In πCDI, the filled polyelectrolyte effectively turns the macropores into a charged ion-selective layer and thus increases the conductivity of macropores. We show experimentally that πCDI can save up to half of the energy consumption compared to membrane CDI, achieving identical desalination during the charging step. The energy consumption can be even lower if the process is operated at a smaller average salt adsorption rate. Further energy breakdown analysis based on a theoretical model confirms that the improved energy efficiency is largely attributed to the increased conductivity in the macropores.

Membrane-Current Collector-Based Flow-Electrode Capacitive Deionization System: A Novel Stack Configuration for Scale-Up Desalination

“…Fourth, one that few researchers have focused on, is the enormous energy consumption for driving flow electrodes. Although the improvement of dispersibility is generally considered to be an effective method to reduce the viscosity of the carbon slurry, excessive high dispersibility of electrode particles will cause a low collision between the electrode particles and the current collectors. , One exciting option is to replace the pressure drive by noncontact driving forces such as gravitational potential energy and magnetic force to drive the electrode particles directly. , …”

Selective Capacitive Removal of Heavy Metal Ions from Wastewater over Lewis Base Sites of S-Doped Fe–N–C Cathodes via an Electro-Adsorption Process

“…Electro-adsorption has attracted increasing attention because of its distinct advantages such as environmental friendliness and simple and fast electrode regeneration, − making it a promising and sustainable approach for water purification. − The traditional deionization process depends on the electrical double layer mechanism, − which results in low removal capacity of heavy metal ions. In contrast, some novel electrodes can better store ions by an electro-adsorption reaction. − We developed an electrode with iron traced at nitrogen and carbon skeleton (Fe–N–C), which had a high removal capacity of sodium ions up to 36.25 mg/g and good regenerative capacity . This good property is attributed to the fact that trace iron promotes the charge transfer of the electro-adsorption site in this process.…”

Novel Inorganic Integrated Membrane Electrodes for Membrane Capacitive Deionization

“…Spray coating considerably reduced the mass loading of the ion-exchange polymer. By optimizing the properties of the ion-exchange polymer, the composition of the ion-exchange layer, and interface construction, MCDI with a high CE and SAC was realized for desalination. ,− …”