当前位置: X-MOL 学术Macromolecules › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Ion Diffusion Coefficients in Ion Exchange Membranes: Significance of Counterion Condensation
Macromolecules ( IF 5.1 ) Pub Date : 2018-07-16 00:00:00 , DOI: 10.1021/acs.macromol.8b00645
Jovan Kamcev 1 , Donald R. Paul 1 , Gerald S. Manning 2 , Benny D. Freeman 1
Affiliation  

This study presents a new framework for extracting single ion diffusion coefficients in ion exchange membranes from experimental ion sorption, salt permeability, and ionic conductivity data. The framework was used to calculate cation and anion diffusion coefficients in a series of commercial ion exchange membranes contacted by aqueous NaCl solutions. Counterion diffusion coefficients were greater than co-ion diffusion coefficients for all membranes after accounting for inherent differences due to ion size. A model for ion diffusion coefficients in ion exchange membranes, incorporating ideas from counterion condensation theory, was proposed to interpret the experimental results. The model predicted co-ion diffusion coefficients reasonably well with no adjustable parameters, while a single adjustable parameter was required to accurately describe counterion diffusion coefficients. The results suggest that for cross-linked ion exchange membranes in which counterion condensation occurs condensed counterions migrate along the polymer backbone and contribute to a current in the presence of an externally applied electric field. Moreover, diffusion coefficients for condensed counterions were approximately 2–2.5 times greater than those for uncondensed counterions.

中文翻译:

离子交换膜中的离子扩散系数:抗衡离子冷凝的意义

这项研究提供了一个新的框架,可以从实验性离子吸附,盐渗透性和离子电导率数据中提取离子交换膜中的单个离子扩散系数。该框架用于计算与NaCl水溶液接触的一系列商用离子交换膜中的阳离子和阴离子扩散系数。考虑到离子尺寸引起的固有差异后,所有膜的抗衡离子扩散系数均大于共离子扩散系数。提出了一种基于反离子凝聚理论的离子交换膜中离子扩散系数的模型来解释实验结果。该模型在没有可调参数的情况下合理预测了钴离子扩散系数,而需要一个可调整的参数来准确描述抗衡离子扩散系数。结果表明,对于其中发生抗衡离子缩合的交联的离子交换膜,缩合的抗衡离子沿着聚合物主链迁移,并在存在外部施加的电场的情况下贡献电流。此外,凝聚态抗衡离子的扩散系数约为非凝聚态抗衡离子的扩散系数的2–2.5倍。
更新日期:2018-07-16
down
wechat
bug