电迁移
化学
选择性
化学物理
扩散
离子
限制电流
离子运输机
价(化学)
电流密度
膜
热力学
材料科学
电极
物理化学
电化学
催化作用
生物化学
物理
有机化学
量子力学
复合材料
作者
Anil Mani,Sanhita Chaudhury,Ghanshyam Meena
标识
DOI:10.1021/acs.jpcb.3c05051
摘要
Understanding the mechanisms leading to the selective transport of cations in an electrodriven process across a cation exchange membrane is important to design and control the potential gradient-based separation process. In this study, a comprehensive description of the current density (I, over a broad current regime) dependence of transport selectivity (Si) between cations of the same/different valence is presented. The role of conventional transport mechanisms such as diffusion, electromigration, and electroconvection in controlling the Si was identified theoretically as well as by multiple experimental approaches. These parameters were found to be dependent on the limiting current density (Ilim). In general, irrespective of the cations involved, Si (over Na+) decreased gradually with increasing I and then increased slowly (and saturated) after Ilim. This extent of variation of Si was heavily dependent on the charge and hydration state of the cations. At I < Ilim, both diffusion and electromigration processes contributed and, notably, the sorption selectivity outweighed the migration selectivity. At I → Ilim, diffusion was the solitary mechanism responsible for cation transport and migration selectivity was the major contributor in Si. At I > Ilim, as also validated by the Peclet numbers, the overall transport was dictated by electroconvection.
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