Current-Induced Membrane Discharge

Mathias Bækbo Andersen, M. van Soestbergen, A. Mani, Henrik Bruus, P. M. Biesheuvel, M. Z. Bazant

    Research output: Contribution to journalJournal articleResearchpeer-review

    279 Downloads (Pure)

    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+ ions, and OH- 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 electroosmotic instability, so it should be reconsidered in both models and experiments on OLC.
    Original languageEnglish
    JournalPhysical Review Letters
    Volume109
    Issue number10
    Pages (from-to)Paper 108301
    Number of pages5
    ISSN0031-9007
    DOIs
    Publication statusPublished - 2012

    Bibliographical note

    © 2012 American Physical Society

    Fingerprint Dive into the research topics of 'Current-Induced Membrane Discharge'. Together they form a unique fingerprint.

    Cite this