Current-Induced Membrane Discharge
Name
Andersen-2012-Current-induced membrane discharge.pdf
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Author(s)
Andersen, M. B.
van Soestbergen, M.
Mani, Ali
Bruus, Henrik
Biesheuvel, P. M.
Date Issued
September 2012
Journal
Physical Review Letters
Publisher
American Physical Society
Citation
Andersen, M. et al. “Current-Induced Membrane Discharge.” Physical Review Letters 109.10 (2012) © 2012 American Physical Society
Version
Final published version
Abstract
Possible mechanisms for overlimiting current (OLC) through aqueous ion-exchange membranes (exceeding diffusion limitation) have been debated for half a century. Flows consistent with electro-osmotic instability have recently been observed in microfluidic experiments, but the existing theory neglects chemical effects and remains to be quantitatively tested. Here, we show that charge regulation and water self-ionization can lead to OLC by “current-induced membrane discharge” (CIMD), even in the absence of fluid flow, in ion-exchange membranes much thicker than the local Debye screening length. Salt depletion leads to a large electric field resulting in a local pH shift within the membrane with the effect that the membrane discharges and loses its ion selectivity. Since salt co-ions, H[superscript +] ions, and OH[superscript -] ions contribute to OLC, CIMD interferes with electrodialysis (salt counterion removal) but could be exploited for current-assisted ion exchange and pH control. CIMD also suppresses the extended space charge that leads to electro-osmotic instability, so it should be reconsidered in both models and experiments on OLC.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
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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/PhysRevLett.109.108301
