Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes
Name
PhysRevE.93.033114.pdf
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1.28 MB
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Checksum (MD5)
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Author(s)
Pham, Sang V.
Kwon, Hyuckjin
Kim, Bumjoo
White, Jacob K.
Lim, Geunbae
Han, Jongyoon
Date Issued
March 2016
Journal
Physical Review E
Publisher
American Physical Society
Citation
Pham, Sang V., Hyuckjin Kwon, Bumjoo Kim, Jacob K. White, Geunbae Lim, and Jongyoon Han. "Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes." Phys. Rev. E 93, 033114 (March 2016). © 2016 American Physical Society
Version
Final published version
Abstract
The rate of electric-field-driven transport across ion-selective membranes can exceed the limit predicted by Nernst (the limiting current), and encouraging this “overlimiting” phenomenon can improve efficiency in many electrochemical systems. Overlimiting behavior is the result of electroconvectively induced vortex formation near membrane surfaces, a conclusion supported so far by two-dimensional (2D) theory and numerical simulation, as well as experiments. In this paper we show that the third dimension plays a critical role in overlimiting behavior. In particular, the vortex pattern in shear flow through wider channels is helical rather than planar, a surprising result first observed in three-dimensional (3D) simulation and then verified experimentally. We present a complete experimental and numerical characterization of a device exhibiting this recently discovered 3D electrokinetic instability, and show that the number of parallel helical vortices is a jump-discontinuous function of width, as is the overlimiting current and overlimiting conductance. In addition, we show that overlimiting occurs at lower fields in wider channels, because the associated helical vortices are more readily triggered than the planar vortices associated with narrow channels (effective 2D systems). These unexpected width dependencies arise in realistic electrochemical desalination systems, and have important ramifications for design optimization.
MIT Department
Massachusetts Institute of Technology. Department of Biological Engineering
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science
Massachusetts Institute of Technology. Research Laboratory of Electronics
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DOI of Published Version
https://doi.org/10.1103/PhysRevE.93.033114
