Current-Induced Membrane Discharge
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...
| Main Authors: | , , , , |
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| Other Authors: | |
| Format: | Article |
| Language: | en_US |
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American Physical Society
2012
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| Online Access: | http://hdl.handle.net/1721.1/74073 |
| _version_ | 1826217575937212416 |
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| author | Andersen, M. B. van Soestbergen, M. Mani, Ali Bruus, Henrik Biesheuvel, P. M. |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Andersen, M. B. van Soestbergen, M. Mani, Ali Bruus, Henrik Biesheuvel, P. M. |
| author_sort | Andersen, M. B. |
| collection | MIT |
| description | 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. |
| first_indexed | 2024-09-23T17:05:52Z |
| format | Article |
| id | mit-1721.1/74073 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T17:05:52Z |
| publishDate | 2012 |
| publisher | American Physical Society |
| record_format | dspace |
| spelling | mit-1721.1/740732022-10-03T10:22:01Z Current-Induced Membrane Discharge Andersen, M. B. van Soestbergen, M. Mani, Ali Bruus, Henrik Biesheuvel, P. M. Massachusetts Institute of Technology. Department of Chemical Engineering Biesheuvel, P. M. 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. 2012-10-18T14:52:13Z 2012-10-18T14:52:13Z 2012-09 2012-02 Article http://purl.org/eprint/type/JournalArticle 0031-9007 1079-7114 http://hdl.handle.net/1721.1/74073 Andersen, M. et al. “Current-Induced Membrane Discharge.” Physical Review Letters 109.10 (2012) © 2012 American Physical Society en_US http://dx.doi.org/10.1103/PhysRevLett.109.108301 Physical Review Letters 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. application/pdf American Physical Society APS |
| spellingShingle | Andersen, M. B. van Soestbergen, M. Mani, Ali Bruus, Henrik Biesheuvel, P. M. Current-Induced Membrane Discharge |
| title | Current-Induced Membrane Discharge |
| title_full | Current-Induced Membrane Discharge |
| title_fullStr | Current-Induced Membrane Discharge |
| title_full_unstemmed | Current-Induced Membrane Discharge |
| title_short | Current-Induced Membrane Discharge |
| title_sort | current induced membrane discharge |
| url | http://hdl.handle.net/1721.1/74073 |
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