离子交换膜中的反离子迁移率：空间效应和价态相关的静电相互作用,ACS ES&T Engineering

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离子交换膜中的反离子迁移率：空间效应和价态相关的静电相互作用
ACS ES&T Engineering ( IF 7.4 ) Pub Date : 2022-03-10 , DOI: 10.1021/acsestengg.1c00457
Hanqing Fan ₁ , Yuxuan Huang ₁ , Ian H. Billinge ₁ , Sean M. Bannon ₂ , Geoffrey M. Geise ₂ , Ngai Yin Yip _{1,

3}

Affiliation

提高离子交换膜 (IEM) 的选择性是环境分离的重要需求，但由于对基本传输现象的理解不足而受到阻碍。具体来说，现有模型不能充分解释膜内单价、二价和三价离子扩散率的数量级差异。在这项研究中，提出了一个传输框架来使用基于第一性原理的解析表达式来描述反离子迁移迁移率。两种控制机制是用于离子传输的可用分数体积的空间效应以及移动离子和固定电荷之间的静电相互作用。具有不同化合价的抗衡离子的迁移率经过实验表征并显示具有高R ²s 在与建议的运输模型的回归分析中。进一步考虑了不同反离子引起的膜膨胀的影响，以更好地模拟空间效应。静电相互作用的摩擦效应与固定电荷密度和介电常数的膜结构和电性能定量相关。此外，与阳离子交换膜相比，阴离子交换膜表现出较弱的静电效应，这归因于季胺官能团的烃链引起的空间位阻。本研究中提供的见解可以为 IEM 和用于离子特异性分离的膜工艺的合理开发提供信息。

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Counterion Mobility in Ion-Exchange Membranes: Spatial Effect and Valency-Dependent Electrostatic Interaction

Enhancing the selectivity of ion-exchange membranes (IEMs) is an important need for environmental separations but is hindered by insufficient understanding of the fundamental transport phenomena. Specifically, existing models do not adequately explain the order of magnitude disparity in diffusivities of mono-, di-, and trivalent ions within the membranes. In this study, a transport framework is presented to describe counterion migration mobility using an analytical expression based on first-principles. The two governing mechanisms are spatial effect of available fractional volume for ion transport and electrostatic interaction between mobile ions and fixed charges. Mobilities of counterions with different valencies were experimentally characterized and shown to have high R²s in regression analyses with the proposed transport model. The influence of membrane swelling caused by different counterions was further accounted for to better model the spatial effect. The frictional effect of electrostatic interaction was quantitatively linked to the membrane structural and electrical properties of fixed charged density and dielectric constant. Additionally, the anion-exchange membrane exhibited a weaker electrostatic effect compared to cation-exchange membranes, which was attributed to steric hindrance caused by hydrocarbon chains of the quaternary amine functional groups. The insights offered in this study can inform the rational development of IEMs and membrane processes for ion-specific separations.

更新日期：2022-03-10

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