An Easy-to-Use Tool for Modeling the Dynamics of Capacitive Deionization

Abstract

Capacitive deionization is an emerging method of desalinating brackish water that has been presented as an alternative to the widely applied technologies such as reverse osmosis. However, for the technology to find more widespread use, it is important not only to improve its efficiency but also to make its modeling more accessible for researchers. In this work, a program has been developed and provided as an open-source with which a user can simulate the performance of a capacitive deionization system by simply entering the basic experimental conditions. The usefulness of this program was demonstrated by predicting how the effluent concentration in a continuous-mode constant-voltage operation varies with time, as well as how it depends on the flow rate, applied voltage, and inlet ion concentration. Finally, the generality of the program has been demonstrated using data from reports in the literature wherein various electrode materials, cell structures, and operational modes were used. Thus, we conclude that the model, termed the dynamic Langmuir model, could be an effective and simple tool for modeling the dynamics of capacitive deionization.

Basis and Prospects of Combining Electroadsorption Modeling Approaches for Capacitive Deionization

“…These fundamental equations have been shown to accurately model the charge storage and ion adsorption over varying concentrations and voltages. The full DL model, as derived elsewhere [13,19,20], has also been able to predict performance for multi-ion systems [20] and adsorption over time [19].…”

“…The ion influx, in turn, is derived from the flow Q and the influent concentration c in (Equations ( 12) and ( 13)) [27]. Thus, the mass transport calculation can be simplified by treating the entire cell as one volume (influent concentration c in = c 0 , the cell inlet ion concentration) [19]. Alternatively, the cell volume could be divided into some number of subcells i = [1, .…”

“…Modeling of CDI processes has evolved in different directions [9,[12][13][14][15], wherein models consider the same underlying physics but with widely varying Herein, we discuss the underlying model-independent physics governing electroadsorption. Primarily, this is used as a starting point for comparing the approaches and tools used in three different CDI models: the modified Donnan (mD) model [7][8][9][16][17][18], the Randles circuit [12], and the dynamic Langmuir (DL) model [13,19,20]. Crucially, we add value by discussing how tools used in the respective models could be implemented to enhance the other models.…”

Dynamics and Model Research on the Electrosorption by Activated Carbon Fiber Electrodes

“…The second correction is to include the chemical adsorption energy [17], which is represented by μ att . The latter extension captures the effect that functional groups on the electrode surface can interact with ions to form chemical bonds, which is called fake adsorption capacity [18]. The following equation contains the above two corrections.…”

Disinfection of Bacteria in Water by Capacitive Deionization

“…separated by a non-conductive spacer (Suss et al, 2015 ; Ahmed and Tewari, 2018 ; Oladunni et al, 2018 ; Choi et al, 2019 ; Teow and Mohammad, 2019 ). When a low DC potential (typically <2.0 V DC ) is applied across the electrodes, non-Faradaic processes occur, leading to the electrosorption of charged species in water (cations and anions) onto the electrode surfaces, resulting in deionization of the input water (Nordstrand et al, 2019 ; Tang et al, 2019 ). Following similar principles, the negative charge on the Gram-positive and Gram-negative bacterial cell wall mediates their adsorption onto the positively charged electrode surface through electrosorption processes, thus removing the microbes from the treated water (Laxman et al, 2015a ; Wang et al, 2018 ; Yasin et al, 2018 ).…”