Impact of network heterogeneity on electrokinetic transport in porous media

Alizadeh, Shima; Bazant, Martin Z.; Mani, Ali

doi:10.1016/j.jcis.2019.06.023

Cited by 35 publications

(40 citation statements)

References 62 publications

(158 reference statements)

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“…In fact, there are surely electro‐convective vortices at the pore scale, 13,14,28 as well as regions of strong salt depletion and double layer overlap, leading to violation of the assumptions of linear electrokinetic response 16 and local electroneutrality 29 . The distribution of pore size in the porous media may lead to eddy dispersion, even for linear electrokinetics, 30 and electrokinetic dispersion in a porous network has been shown to strongly enhance over‐limiting current and deionization, both experimentally 7 and theoretically 31 . Such effects would presumably need to be captured in future models.…”

Section: Comparison With Experimental Datamentioning

confidence: 99%

Deionization shocks in crossflow

et al. 2021

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Shock electrodialysis is a recently developed electrochemical water treatment method that shows promise for water deionization and ionic separations. Although simple models and scaling laws have been proposed, a predictive theory has not yet emerged to fit experimental data and enable system design. Here, we extend and analyze existing “leaky membrane” models for the canonical case of a steady shock in crossflow, as in recent experimental prototypes. Two‐dimensional numerical solutions are compared with analytical boundary‐layer approximations and experimental data. The boundary‐layer theory accurately reproduces the simulation results for desalination, and both models predict the data collapse of the desalination factor with dimensionless current, scaled to the incoming convective flux of cations. The numerical simulation also predicts the water recovery increase with current. Nevertheless, neither approach can quantitatively fit the transition from normal to over‐limiting current, which suggests gaps in our understanding of extreme electrokinetic phenomena in porous media.

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Section: Comparison With Experimental Datamentioning

confidence: 99%

Deionization shocks in crossflow

et al. 2021

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“…More importantly, we find that the structure of flow field can be described in terms of the "electro-osmotic coupling coefficient," a nondimensional parameter measuring the relative strength of electro-osmotic velocity to total mean velocity and which is tunable experimentally. Finally, recent work on coupled nonlinear electrokinetics in random pore network also demonstrate similar vortical flow structures and their interactions with deionization shock waves [61]. In this article, we neglect nonlinear effects and instead provide a clear physical explanation for the formation of vortical structures.…”

Section: Introductionmentioning

confidence: 85%

Vortices of electro-osmotic flow in heterogeneous porous media

et al. 2020

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Traditional models of electrokinetic transport in porous media are based on homogenized material properties, which neglect any macroscopic effects of microscopic fluctuations. This perspective is taken not only for convenience but also motivated by the expectation of irrotational electro-osmotic flow, proportional to the electric field, for uniformly charged surfaces (or constant ζ potential) in the limit of thin double layers. Here, we show that the inherent heterogeneity of porous media generally leads to macroscopic vortex patterns, which have important implications for convective transport and mixing. These vortical flows originate due to competition between pressure-driven and electroosmotic flows, and their sizes are characterized by the correlation length of heterogeneity in permeability or surface charge. The appearance of vortices is controlled by a single dimensionless control parameter, defined as the ratio of a typical electro-osmotic velocity to the total mean velocity.

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“…This is contradictory to our present observation [13] and it may come due to the complex geometry of cellulose and interaction of particles with it. In the random (or natural) pore network, various convective flow such as recirculation can be included in the analysis [20][21][22][23]. Thus, one need further investigations for the exact fundamentals in paper-based device.…”

Section: Experimental Demonstration Of Spontaneous Separationmentioning

confidence: 99%

Spontaneous diffusiophoretic separation in paper-based microfluidic device

Lee

Kim

2020

Micro and Nano Syst Lett

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Microfluidic paper-based analytical devices (μPADs) for separating particles have been playing a key role for point-ofcare diagnostics in the area of remote settings. While splendid separation methods using μPADs have been explosively developed, they still require external devices inducing external field. In this work, the spontaneous separation method in μPADs was suggested by leveraging convective flow (the imbibition of paper and nanoporous medium) and diffusiophoresis by ion exchange medium. Especially, the paper's fast imbibition was utilized as driving particles at the first stage, which results in fast overall processing in contrast to the spontaneous separation method of microfluidic chip integrated with only ion exchange medium. Therefore, our novel spontaneous selective preconcentration method based on μPADs would have key potential to be used in portable point-of-care devices in remote settings.

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Impact of network heterogeneity on electrokinetic transport in porous media

Cited by 35 publications

References 62 publications

Deionization shocks in crossflow

Deionization shocks in crossflow

Vortices of electro-osmotic flow in heterogeneous porous media

Spontaneous diffusiophoretic separation in paper-based microfluidic device

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