Gorobchenko Andrey, Mareev Semyon, Nikonenko Victor
Membrane Institute, Kuban State University, 149 Stavropolskaya St., 350040 Krasnodar, Russia.
Membranes (Basel). 2021 Feb 6;11(2):115. doi: 10.3390/membranes11020115.
The application of pulsed electric field (PEF) in electrodialysis has been proven to be efficient for a number of effects: increasing mass transfer rate, mitigation of scaling and fouling, reducing water splitting. Recently, the improvement of the membrane permselectivity for specific counterions was discovered experimentally by the group of Laurent Bazinet (N. Lemay et al. 604, 117878 (2020)). To better understanding the effect of PEF in electrodialysis, simulations were performed using a non-stationary mathematical model based on the Nernst-Planck and Poisson equations. For the first time, it was not only the condition used when the current density is specified but also the condition when the voltage is set. A membrane and two adjacent diffusion layers are considered. It is shown that when applying the regime used by Lemay et al. (the same current density in conventional continuous current (CC) mode and during the pulses in PEF mode), there is a significant gain in specific permselectivity. It is explained by a reduction in the membrane concentration polarization in PEF mode. In the CC mode of electrodialysis, increasing current density leads to a loss in specific permselectivity: concentration profiles in the diffusion layers and membrane are formed in such a way that ion diffusion reduces the migration flux of the preferentially transferred ion and increases that of the poorly transferred ion. In PEF mode, the concentration profiles are partially restored during the pauses when the current is zero. However, if a different condition is used than the condition applied by Lemay et al., that is, when the same average current density is applied in both the PEF and CC modes, there is no gain in specific permeability. It is shown that within the framework of the applied mathematical model, the specific selectivity depends only on the average current density and does not depend on the mode of its application (CC or PEF mode).
脉冲电场（PEF）在电渗析中的应用已被证明在许多方面是有效的：提高传质速率、减轻结垢和污染、减少水分解。最近，洛朗·巴齐内特团队（N. 勒梅等人，《膜科学杂志》604卷，117878页（2020年））通过实验发现了特定反离子的膜选择透过性有所改善。为了更好地理解PEF在电渗析中的作用，使用基于能斯特 - 普朗克方程和泊松方程的非稳态数学模型进行了模拟。首次不仅考虑了指定电流密度时的情况，还考虑了设定电压时的情况。研究中考虑了一个膜和两个相邻的扩散层。结果表明，当采用勒梅等人使用的模式（传统连续电流（CC）模式下的电流密度与PEF模式下脉冲期间的电流密度相同）时，特定选择透过性有显著提高。这是由于PEF模式下膜浓度极化的降低。在电渗析的CC模式中，增加电流密度会导致特定选择透过性降低：扩散层和膜中的浓度分布使得离子扩散降低了优先传输离子的迁移通量，并增加了传输较差离子的迁移通量。在PEF模式下，当电流为零时，浓度分布在暂停期间会部分恢复。然而，如果采用与勒梅等人不同的条件，即在PEF和CC模式下施加相同的平均电流密度，则特定渗透率没有提高。结果表明，在所应用的数学模型框架内，特定选择性仅取决于平均电流密度，而不取决于其应用模式（CC或PEF模式）。
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