Overlimiting Current in a Microchannel

Dydek, E. Victoria; Zaltzman, Boris; Rubinstein, Isaak; Deng, Daosheng; Mani, Ali; Bazant, Martin Z.

doi:10.1103/physrevlett.107.118301

Cited by 246 publications

(444 citation statements)

References 32 publications

Supporting

Mentioning

409

Contrasting

Order By: Relevance

“…In order to limit excessive grid refinement near membrane surfaces, the equations were solved with a dimensionless Debye length, λ = 10 −3 , far larger than a physically realistic value (i.e., ∼10 −4 ). Other studies [6,7,[15][16][17][18] employ similar dimensionless Debye length values, and as shown below, the simulation results are clearly qualitatively similar to the realistic phenomenon observed in the experiment.…”

Section: -2supporting

confidence: 78%

“…In the overlimiting regime, wider channels sustain parallel helical vortices, a surprising result first observed in 3D simulation and then verified experimentally. The 3D simulation was performed using our customized Poisson-Nernst-Planck-Navier-Stokes solver, and the initial experiments were performed using our microscale electrical desalination system designed specifically for observing ion transport processes in detail [17]. Below we describe a comprehensive experimental and numerical characterization of a device exhibiting this recently discovered 3D electrokinetic instability.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes

et al. 2016

View full text Add to dashboard Cite

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.

show abstract

Section: -2supporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes

et al. 2016

View full text Add to dashboard Cite

show abstract

“…The overlimiting conductance found in this model is approximately three times larger than the conductance found in Ref. [26], where diffusion and advection in the diffuse double layers is neglected. In the limit of negligible surface charge the numerical results agree with our previous analytical model [8] for the overlimiting current due to an extended spacecharge region.…”

Section: Introductioncontrasting

confidence: 58%

Concentration polarization, surface currents, and bulk advection in a microchannel

Nielsen

Bruus

2014

Phys. Rev. E

View full text Add to dashboard Cite

We present a comprehensive analysis of salt transport and overlimiting currents in a microchannel during concentration polarization. We have carried out full numerical simulations of the coupled Poisson-Nernst-Planck-Stokes problem governing the transport and rationalized the behaviour of the system. A remarkable outcome of the investigations is the discovery of strong couplings between bulk advection and the surface current; without a surface current, bulk advection is strongly suppressed. The numerical simulations are supplemented by analytical models valid in the long channel limit as well as in the limit of negligible surface charge. By including the effects of diffusion and advection in the diffuse part of the electric double layers, we extend a recently published analytical model of overlimiting current due to surface conduction.

show abstract

“…Sketch of a charged cylindrical pore subjected to water flow, electrical current, and salt flux between a high-salinity (left) and low-salinity (right) reservoir. and diffusion dominate, although nonequilibrium structures, such as "salt fingers" extending along the pore surfaces, can arise in microchannels, if electro-osmotic convection dominates [41,44,45,48]. Here, we neglect such effects and focus on deriving the consequences of local (but not global) quasiequilibrium.…”

Section: Introductionmentioning

confidence: 99%

Analysis of electrolyte transport through charged nanopores

et al. 2016

View full text Add to dashboard Cite

We revisit the classical problem of flow of electrolyte solutions through charged capillary nanopores or nanotubes as described by the capillary pore model (also called "space charge" theory). This theory assumes very long and thin pores and uses a one-dimensional flux-force formalism which relates fluxes (electrical current, salt flux, and fluid velocity) and driving forces (difference in electric potential, salt concentration, and pressure). We analyze the general case with overlapping electric double layers in the pore and a nonzero axial salt concentration gradient. The 3×3 matrix relating these quantities exhibits Onsager symmetry and we report a significant new simplification for the diagonal element relating axial salt flux to the gradient in chemical potential. We prove that Onsager symmetry is preserved under changes of variables, which we illustrate by transformation to a different flux-force matrix given by Gross and Osterle [J. Chem. Phys. 49, 228 (1968)]. The capillary pore model is well suited to describe the nonlinear response of charged membranes or nanofluidic devices for electrokinetic energy conversion and water desalination, as long as the transverse ion profiles remain in local quasiequilibrium. As an example, we evaluate electrical power production from a salt concentration difference by reverse electrodialysis, using an efficiency versus power diagram. We show that since the capillary pore model allows for axial gradients in salt concentration, partial loops in current, salt flux, or fluid flow can develop in the pore. Predictions for macroscopic transport properties using a reduced model, where the potential and concentration are assumed to be invariant with radial coordinate ("uniform potential" or "fine capillary pore" model), are close to results of the full model.

show abstract

Overlimiting Current in a Microchannel

Cited by 246 publications

References 32 publications

Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes

Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes

Concentration polarization, surface currents, and bulk advection in a microchannel

Analysis of electrolyte transport through charged nanopores

Contact Info

Product

Resources

About