Electro-osmotic instability of concentration enrichment in curved geometries for an aqueous electrolyte

Bingrui Xu, Zhibo Gu, Wei Liu, Peng Huo, Yueting Zhou, S. M. Rubinstein, M. Z. Bazant, B. Zaltzman, I. Rubinstein, Daosheng Deng

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

We report that an electro-osmotic instability of concentration enrichment in curved geometries for an aqueous electrolyte, as opposed to the well-known one, is initiated exclusively at the enriched interface (anode), rather than at the depleted one (cathode). For this instability, the limitation of an unrealistically high material Peclet number in planar geometry is eliminated by the strong electric field arising from the line charge singularity. In a model setup of concentric circular electrodes, we show by stability analysis, numerical simulation, and experimental visualization that instability occurs at the inner anode, below a critical radius of curvature. The stability criterion is also formulated in terms of a critical electric field and extended to arbitrary (two-dimensional) geometries by conformal mapping. This discovery suggests that transport may be enhanced in processes limited by salt enrichment, such as reverse osmosis, by triggering this instability with needlelike electrodes.

Original languageEnglish
Article number091701
JournalPhysical Review Fluids
Volume5
Issue number9
DOIs
StatePublished - 9 Sep 2020

ASJC Scopus subject areas

  • Computational Mechanics
  • Modeling and Simulation
  • Fluid Flow and Transfer Processes

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