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Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone
Published on: February 23, 2017
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Multi-component ion equilibria and transport in ion-exchange membranes
Alaaeldin A E Elozeiri1, Jouke E Dykstra1, Huub H M Rijnaarts1
1Environmental Technology, Wageningen University & Research, Bornse Weilanden 9, 6708 WG Wageningen, the Netherlands.
Journal of Colloid and Interface Science
|June 27, 2024
Summary
This study experimentally investigates Donnan equilibrium in ion-exchange membranes with multiple electrolytes. Findings show ion fractions shift with ionic strength, validating Donnan equilibrium theory and enabling accurate flux predictions.
Area of Science:
- Electrochemistry
- Membrane Science
- Physical Chemistry
Background:
- Charged species redistribute at ion-exchange membrane interfaces to minimize system free energy.
- Understanding Donnan equilibrium is crucial for predicting ion behavior in multi-electrolyte solutions across membranes.
Purpose of the Study:
- To experimentally investigate Donnan equilibrium in cation-exchange membranes (CEMs) with quaternary electrolyte solutions (Na+/Mg2+/K+/Ca2+/Cl-).
- To calculate ion activity coefficients and assess their impact on ion concentrations and fluxes in a simulated Donnan dialysis.
- To validate Donnan equilibrium theory concerning ion fraction shifts with varying solution ionic strengths.
Main Methods:
- Experimental determination of equilibrium concentrations in multi-electrolyte solutions across six commercial CEMs.
- Calculation of ion activity coefficients using experimental data and fitting parameters.
- Simulation of Donnan dialysis using a transport model incorporating fitted activity coefficients.
Main Results:
- Mean relative error of 3% achieved in describing equilibrium concentrations of ionic species.
- Equivalent ion fractions of monovalent counter-ions increased with ionic strength, displacing multivalent ions, consistent with Donnan equilibrium theory.
- An arbitrary assignment of one activity coefficient did not impact predicted internal ion concentrations or modeled ion fluxes.
Conclusions:
- The study successfully determined ion activity coefficients for CEMs in quaternary electrolyte solutions.
- Donnan equilibrium principles accurately predict ion redistribution under varying ionic strengths.
- The methodology provides a robust framework for modeling ion transport and predicting fluxes in complex electrochemical systems.
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