Deionization shocks in microstructures
Name
Mani-2011-Deionization shocks in microstructures.pdf
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2.01 MB
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Adobe PDF
Checksum (MD5)
4ef557de1d37d9c843170723320b3b50
Author(s)
Mani, Ali
Bazant, Martin Z.
Date Issued
December 2011
Journal
Physical Review E
Publisher
American Physical Society (APS)
Citation
Mani, Ali, and Martin Z. Bazant. “Deionization Shocks in Microstructures.” Physical Review E 84.6 (2011): n. pag. Web. 2 Mar. 2012. Mani, Ali, and Martin Z. Bazant. “Deionization Shocks in Microstructures.” Physical Review E 84.6 (2011): n. pag. Web. 2 Mar. 2012. © 2011 American Physical Society
Version
Final published version
Abstract
Salt transport in bulk electrolytes is limited by diffusion and advection, but in microstructures with charged surfaces (e.g., microfluidic devices, porous media, soils, or biological tissues) surface conduction and electro-osmotic flow also contribute to ionic fluxes. For small applied voltages, these effects lead to well known linear electrokinetic phenomena. In this paper, we predict some surprising nonlinear dynamics that can result from the competition between bulk and interfacial transport at higher voltages. When counterions are selectively removed by a membrane or electrode, a “deionization shock” can propagate through the microstructure, leaving in its wake an ultrapure solution, nearly devoid of coions and colloidal impurities. We elucidate the basic physics of deionization shocks and develop a mathematical theory of their existence, structure, and stability, allowing for slow variations in surface charge or channel geometry. Via asymptotic approximations and similarity solutions, we show that deionization shocks accelerate and sharpen in narrowing channels, while they decelerate and weaken, and sometimes disappear, in widening channels. These phenomena may find applications in separations (deionization, decontamination, biological assays) and energy storage (batteries, supercapacitors) involving electrolytes in microstructures.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
Massachusetts Institute of Technology. Department of Mathematics
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Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
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DOI of Published Version
https://doi.org/10.1103/PhysRevE.84.061504
