TY - JOUR
T1 - Salt concentration dependence of ionic conductivity in ion exchange membranes
AU - Kamcev, Jovan
AU - Sujanani, Rahul
AU - Jang, Eui Soung
AU - Yan, Ni
AU - Moe, Neil
AU - Paul, Donald R.
AU - Freeman, Benny D.
N1 - Funding Information:
This material is based upon work supported in part by the National Science Foundation (NSF) Graduate Research Fellowship under Grant no. DGE-1110007 , the Welch Foundation Grant no. F-1924–20170325 , and by the Australian-American Fulbright Commission for the award to BDF of the U.S. Fulbright Distinguished Chair in Science, Technology and Innovation sponsored by the Commonwealth Scientific and Industrial Research Organization ( CSIRO ). The authors thank John Barber and Russell MacDonald for numerous fruitful discussions regarding this study. The authors are also grateful to Mike Kostowskyj of Calera for providing the custom-made resistance cells.
Publisher Copyright:
© 2017 Elsevier B.V.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2018/2/1
Y1 - 2018/2/1
N2 - Electric field driven ion transport in ion exchange membranes, often quantified by membrane resistance or ionic conductivity, is important for membrane-based technologies such as electrodialysis, batteries, fuel cells, etc. Various methods for measuring membrane ionic conductivity have been reported in the literature, but no widely accepted, standard protocol exists. Consequently, conflicting ionic conductivity results for widely studied commercial ion exchange membranes have been reported, leading to confusion regarding, for example, the salt concentration dependence of membrane ionic conductivity, especially for membranes equilibrated with dilute aqueous salt solutions. In this study, we report a simple, fast, reliable technique for measuring ionic conductivity based on direct contact between the membrane and electrodes. The technique was used to measure ionic conductivity values for a series of commercial ion exchange membranes as a function of external solution NaCl concentration (ranging from 0.001 to 5 M). The salt concentration dependence of membrane ionic conductivity was rationalized within the Nernst-Einstein framework. At low external solution salt concentrations (< 0.3 M), ionic conductivity values were essentially constant since mobile ion concentrations in the membranes approached a constant value (i.e., the fixed charge group concentration). At high salt concentrations (> 0.3 M), ionic conductivity values increased with increasing salt concentration for three of the membranes, presumably due to increased ion sorption owing to weaker Donnan exclusion, and decreased for one membrane, presumably due to decreased ion diffusion coefficients resulting from osmotic deswelling.
AB - Electric field driven ion transport in ion exchange membranes, often quantified by membrane resistance or ionic conductivity, is important for membrane-based technologies such as electrodialysis, batteries, fuel cells, etc. Various methods for measuring membrane ionic conductivity have been reported in the literature, but no widely accepted, standard protocol exists. Consequently, conflicting ionic conductivity results for widely studied commercial ion exchange membranes have been reported, leading to confusion regarding, for example, the salt concentration dependence of membrane ionic conductivity, especially for membranes equilibrated with dilute aqueous salt solutions. In this study, we report a simple, fast, reliable technique for measuring ionic conductivity based on direct contact between the membrane and electrodes. The technique was used to measure ionic conductivity values for a series of commercial ion exchange membranes as a function of external solution NaCl concentration (ranging from 0.001 to 5 M). The salt concentration dependence of membrane ionic conductivity was rationalized within the Nernst-Einstein framework. At low external solution salt concentrations (< 0.3 M), ionic conductivity values were essentially constant since mobile ion concentrations in the membranes approached a constant value (i.e., the fixed charge group concentration). At high salt concentrations (> 0.3 M), ionic conductivity values increased with increasing salt concentration for three of the membranes, presumably due to increased ion sorption owing to weaker Donnan exclusion, and decreased for one membrane, presumably due to decreased ion diffusion coefficients resulting from osmotic deswelling.
KW - Ion exchange membrane
KW - Ion transport
KW - Ionic conductivity
KW - Nernst-Einstein equation
UR - http://www.scopus.com/inward/record.url?scp=85032222932&partnerID=8YFLogxK
U2 - 10.1016/j.memsci.2017.10.024
DO - 10.1016/j.memsci.2017.10.024
M3 - Article
AN - SCOPUS:85032222932
SN - 0376-7388
VL - 547
SP - 123
EP - 133
JO - Journal of Membrane Science
JF - Journal of Membrane Science
ER -