Overlimiting Current and Shock Electrodialysis in Porous Media
| Autor: | Sven Schlumpberger, Boris Zaltzman, Ali Mani, Daosheng Deng, Martin Z. Bazant, E. Victoria Dydek, Ji-Hyung Han |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
Chemical Physics (physics.chem-ph)
Materials science Condensed Matter - Mesoscale and Nanoscale Physics Diffusion Limiting current Fluid Dynamics (physics.flu-dyn) FOS: Physical sciences Physics - Fluid Dynamics Surfaces and Interfaces Electrodialysis Condensed Matter Physics Electrochemistry chemistry.chemical_compound Chemical engineering chemistry Physics - Chemical Physics Nafion Mesoscale and Nanoscale Physics (cond-mat.mes-hall) General Materials Science Current (fluid) Porous medium Spectroscopy Frit |
| DOI: | 10.48550/arxiv.1310.5719 |
| Popis: | Most electrochemical processes, such as electrodialysis, are limited by diffusion, but in porous media, surface conduction and electro-osmotic flow also contribute to ionic fluxes. In this paper, we report experimental evidence for surface-driven over-limiting current (faster than diffusion) and deionization shocks (propagating salt removal) in a porous medium. The apparatus consists of a silica glass frit (1 mm thick with 500 nm mean pore size) in an aqueous electrolyte (CuSO$_4$ or AgNO$_3$) passing ionic current from a reservoir to a cation-selective membrane (Nafion). The current-voltage relation of the whole system is consistent with a proposed theory based on the electro-osmotic flow mechanism over a broad range of reservoir salt concentrations (0.1 mM - 1.0 M), after accounting for (Cu) electrode polarization and pH-regulated silica charge. Above the limiting current, deionized water ($\approx 10 \mu$ $M$) can be continuously extracted from the frit, which implies the existence of a stable shock propagating against the flow, bordering a depleted region that extends more than 0.5mm across the outlet. The results suggest the feasibility of "shock electrodialysis" as a new approach to water desalination and other electrochemical separations. Comment: 39 pages, 9 figs |
| Databáze: | OpenAIRE |
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