Wang Ruoyu, Lin Shihong
Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235-1831, USA.
Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN 37235-1831, USA; Department of Chemical and Bimolecular Engineering, Vanderbilt University, Nashville, TN 37235-1831, USA.
J Colloid Interface Sci. 2020 Aug 15;574:152-161. doi: 10.1016/j.jcis.2020.04.032. Epub 2020 Apr 11.
Conventional capacitive deionization (CDI) with carbon electrodes is a desalination process based on the formation of electrical double layer. Intercalation capacitive deionization (ICDI), a category of CDI based on intercalation materials as electrodes, achieves desalination by inserting ions into the crystal lattice of the electrode when a voltage is applied. It has been proven numerically that a thermodynamically reversible CDI cycle always consumes electrical work that equals the Gibbs free energy of the separation. We conducted a thermodynamic analysis of a four-stage reversible cycle for both symmetric and asymmetric ICDI using Frumkin isotherm to describe the electrode-solution chemical equilibrium. We provided both analytical and numerical proof showing the electrical work to complete a four-stage ICDI cycle is exactly identical to the Gibbs free energy of separation. Our thermodynamic analysis also shows ICDI is typically more energy efficient than CDI if constant voltage charging and discharge are performed to complete the same separation.
基于碳电极的传统电容去离子化（CDI）是一种基于双电层形成的脱盐过程。插层电容去离子化（ICDI）是一类以插层材料为电极的CDI，通过在施加电压时将离子插入电极晶格来实现脱盐。数值证明，热力学可逆的CDI循环总是消耗等于分离吉布斯自由能的电功。我们使用弗鲁姆金等温线描述电极 - 溶液化学平衡，对对称和不对称ICDI的四阶段可逆循环进行了热力学分析。我们提供了分析和数值证明，表明完成四阶段ICDI循环的电功与分离吉布斯自由能完全相同。我们的热力学分析还表明，如果进行恒压充电和放电以完成相同的分离，ICDI通常比CDI更节能。
