Understanding the influence of sodium chloride concentration on ion diffusion in charged polymers

被引:2
作者
Bannon, Sean M. [1 ]
Kutner, Ethan [1 ,3 ]
Garretson, Benjamin [1 ,2 ]
Geise, Geoffrey M. [1 ]
机构
[1] Univ Virginia, Dept Chem Engn, 385 McCormick Rd, Charlottesville, VA 22903 USA
[2] Univ Virginia, Dept Chem, 409 McCormick Rd, Charlottesville, VA 22903 USA
[3] Eli Lilly & Co, Indianapolis, IN USA
基金
美国国家科学基金会;
关键词
Ion exchange membrane; Transport; Diffusion; Free volume; SALT TRANSPORT-PROPERTIES; SULFONATED POLYMERS; SELF-DIFFUSION; MEMBRANE; WATER; SORPTION; PERMEABILITY; COEFFICIENTS; CONDUCTIVITY; TRADEOFF;
D O I
10.1016/j.memsci.2024.123197
中图分类号
TQ [化学工业];
学科分类号
0817 ;
摘要
Previous observations made on sulfonated polysulfones equilibrated with solutions of increasing salinity, where salt diffusion coefficients increase concurrently with reductions in water content driven by osmotic de-swelling, are currently unexplained. To further explain the molecular underpinnings of these observations, we characterized the influence of external salt solution concentration on the average salt and ion diffusion properties of two sulfonated polymers: a model cross-linked material (XLAMPS) and a series of sulfonated polysulfones (HQ: BP - XX). Analysis of the average salt and co- and counter-ion diffusion coefficients in these polymers suggest that the increase in charge screening (of electrostatic interactions between anionic sulfonate groups and co-ions) that occurs with increasing salinity affects the salt diffusion coefficients of sulfonated polysulfone in a manner that is different from what would be expected based on changes in water content alone and from what was observed for XLAMPS. Free volume theory describes the influence of these electrostatic effects on salt diffusion using a parameter related to the characteristic free volume element size necessary for diffusion. The results and analysis suggest that charge screening reduces the characteristic free volume element size necessary for diffusion in sulfonated polysulfone, which provides an explanation for the observed increase in average salt diffusion coefficients with increased salinity.
引用
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页数:11
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