Effect of electrode thickness variation on operation of capacitive deionization
Effect of electrode thickness variation on operation of capacitive deionization
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DOI：
10.1016/j.electacta.2012.04.083
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发表时间：
2012-07
影响因子：
6.6
通讯作者：
S. Porada;M. Bryjak;A. J. V. Wal;P. M. Biesheuvel
中科院分区：
文献类型：
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作者：
S. Porada;M. Bryjak;A. J. V. Wal;P. M. Biesheuvel
在电容性去离子（CDI）中，水是通过在两个多孔电极之间施加电场来脱盐的，这两个电极分别位于运输水溶液的间隔通道的两侧。在这项工作中，我们研究了平衡盐吸附和出水盐浓度随时间的动态发展，以及间隔层和电极厚度的函数。电极厚度将以对称的方式（将两个电极加倍）和不对称的方式变化，通过将一个电极加倍和三倍而不是另一个电极。为了描述决定活性炭微孔中盐吸附的静电双层（EDL）的结构，建立了一个改进的donnan模型，该模型成功地描述了数据，也适用于非常显著的电极厚度比。我们建立了一个考虑厚度变化的广义CDI输运模型，该模型与实验数据比较好地反映了出水盐浓度随时间的变化。这些实验旨在进一步测试我们的平衡和输运模型，特别是其中的假设，在第一个近似中，对于由化学未修饰的活性炭颗粒制成的电极，EDL结构与电子电荷的符号无关。为了研究化学表面电荷的相关性，我们还改变了流入细胞的盐溶液的pH值。
In capacitive deionization (CDI) water is desalinated by applying an electrical field between two porous electrodes placed on either side of a spacer channel that transports the aqueous solution. In this work we investigate the equilibrium salt adsorption and the dynamic development of the effluent salt concentration in time, both as function of spacer and electrode thicknesses. The electrode thickness will be varied in a symmetric manner (doubling both electrodes) and in an asymmetric manner, by doubling and tripling one electrode but not the other. To describe the structure of the electrostatic double layer (EDL) which determines the salt adsorption in the micropores of activated carbons, a modified Donnan-model is set up which successfully describes the data, also for situations of very significant electrode thickness ratios. We develop a generalized CDI transport model accounting for thickness variations, which compares favorably with experimental data for the change of the effluent salt concentration in time. These experiments are aimed at further testing our equilibrium and transport models, specifically the assumption therein that in first approximation, for electrodes made of chemically unmodified activated carbon particles, the EDL structure is independent of the sign of the electronic charge. To investigate the relevance of chemical surface charge we also varied pH of the salt solution flowing into the cell.