An Extended Randles Circuit and a Systematic Model-Development Approach for Capacitive Deionization

Abstract

© 2021 The Author(s). The global need for freshwater rapidly drives the development of emerging and efficient freshwater-production methods such as capacitive deionization (CDI). To allow the CDI technique to continue to grow, simulations can be important for tractably describing, predicting, and optimizing the desalination processes. Amongst the disparate simulation tools available, the Randles-circuit model is widely used in electrochemical measurements but its simplified structure limits its use for wider CDI operations. Thus, we herein describe a systematic stepwise process for widely developing CDI models, and as a proof-of-concept, transform the core Randles circuit into an extended Randles circuit (ERaC) that is highly relevant for CDI systems. Experimental data from the literature extensively verify that the ERaC model accuracy now describes charge storage, charging rate, ion adsorption, and current leakages for a variety of structural and operational parameters, such as asymmetric electrodes, different ion concentrations, and the applied voltage. In conclusion, this developed stepwise process can systematically and effectively create, enhance, and expand CDI models. Thus, researchers will embrace this method of model development, and benefit from the broad usefulness of the proposed ERaC model for a wide range of CDI operations.