Østedgaard-Munck David Nicolas, Catalano Jacopo, Bentien Anders
Department of Engineering, Århus University, Åbogade 40, 8200 Aarhus N, Denmark.
Membranes (Basel). 2020 Oct 25;10(11):304. doi: 10.3390/membranes10110304.
Investigation of electroviscous effects is of interest to technologies that exploit transport of ions through ion exchange membranes, charged capillaries, and porous media. When ions move through such media due to a hydrostatic pressure difference, they interact with the fixed charges, leading to an increased hydraulic resistance. Experimentally this is observed as an apparent increase in the viscosity of the solution. Electroviscous effects are present in all electrochemical membrane-based processes ranging from nanofiltration to fuel-cells and redox flow batteries. Direct measurements of electroviscous effects varying the applied ionic current through Nafion membranes have, to the best of the authors' knowledge, not yet been reported in literature. In the current study, electroviscous phenomena in different Nafion ion exchange membranes are measured directly with a method where the volume permeation is measured under constant trans-membrane pressure difference while varying the ion current density in the membrane. The direct measurement of the electroviscous effect is compared to the one calculated from the phenomenological transport equations and measured transport coefficients. Within the experimental uncertainty, there is a good agreement between the two values for all membranes tested. We report here an electroviscous effect for all Nafion membranes tested to be κH?κH-1=1.15-0.052+0.035.
对利用离子通过离子交换膜、带电毛细管和多孔介质进行传输的技术而言，电黏滞效应的研究具有重要意义。当离子由于静水压力差而在这些介质中移动时，它们会与固定电荷相互作用，导致水力阻力增加。从实验上看，这表现为溶液黏度的明显增加。电黏滞效应存在于从纳滤到燃料电池和氧化还原液流电池等所有基于电化学膜的过程中。据作者所知，通过改变流经纳滤膜的离子电流来直接测量电黏滞效应的研究尚未见诸文献报道。在本研究中，采用一种方法直接测量了不同纳滤离子交换膜中的电黏滞现象，即在恒定跨膜压差下测量体积渗透率，同时改变膜中的离子电流密度。将电黏滞效应的直接测量值与根据唯象传输方程和测量得到的传输系数计算出的值进行了比较。在实验误差范围内，所有测试膜的这两个值之间具有良好的一致性。我们在此报告，所有测试的纳滤膜的电黏滞效应为κH?κH - 1 = 1.15 - 0.052 + 0.035 。
