Abstract

The process of capacitive deionization (CDI) is a cost effective and energy efficientmethod that offers many opportunities in terms of desalination of brackish water andthe removal of ionic contaminants. Current research focusses on evaluating differentinfluence parameters to make the CDI process more competitive to other commerciallyavailable methods like reverse osmosis, direct distillation or ion exchange. CDI is basedon the adsorption of ions to highly porous electrodes by applying an external voltagedifference. Although, remarkable progress in CDI modelinghas been achieved during thepast decade, so far, only few models exist which fully describe the CDI process and whichpredict the cell behavior in all its aspects, including e.g., performance under constantvoltage and/or constant current control or pH effects including water dissociation.However, in this paper a new approach to CDI modeling is presented, which opensa path to fast and easy implementation of a digital depictionof complex CDI setupshaving e.g., multiple cells. The model is based on the object-oriented modeling languageModelica that enables the simulation and prediction of the behavior of complete CDI cellsby combining chemical, electrochemical and electrical components. Furthermore, thereis the possibility to predict complex setups with e.g., complex electrolytes, concentrationor voltage fluctuations as they appear due to environmental influences outside laboratoryexperiments. Besides detailed time courses of species concentrations in the bulkand the electrodes or local electrical potentials, the model enables the prediction ofimportant sum parameters such as the salt adsorption capacity, current efficiency andpower consumption. The results of the developed CDI model are validated by usingparameter settings from literature and comparing the resulting predictions of equilibriumand kinetics. In addition, the agreement between our own experimental results and therespective model predictions is discussed.

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