Electrokinetic phenomena of the second kind and their applications

Dukhin, S. S.

doi:10.1016/0001-8686(91)80022-c

Cited by 307 publications

(326 citation statements)

References 4 publications

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“…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: 80%

“…In the ICP-desalination system, transport of ions is governed by the Nernst-Planck equations (1) and (2); electric potential field is related to the ion concentrations via the Poisson equations (3) and (4), and the fluid motion is governed by the Navier-Stokes equations (5) and (6). These equations are given in the dimensionless form as follows:…”

Section: Mathematical Model and Numerical Methodsmentioning

confidence: 99%

“…A curious and important characteristic of the current-voltage (I-V) relation in ion-exchange membranes is the presence of overlimiting current; at sufficiently high bias voltages, the rate of cross-membrane transport can exceed the so-called limiting current, posed by considering only diffusion and drift of ions. Several mechanisms have been suggested as the cause for overlimiting including water dissociation [1], gravitational convection [3][4][5], and electroconvection [6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

“…Electroconvection near ion-exchange membrane surfaces was first studied by Dukhin [6]. Later, Rubinstein and Zaltzman developed an electroconvection theory by assuming nonequilibrium electro-osmotic slip on ion-exchange membrane surfaces.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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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.

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Section: -2supporting

confidence: 80%

Section: Mathematical Model and Numerical Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

et al. 2016

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“…These are the quasiequilibrium regime [9,10] and the nonequilibrium EO [2,8,11]. While both regimes result from the action of a tangential electric field upon the space charge of the EDL, the first relates to the charge of quasiequilibrium EDL, whereas the second relates to the extended space charge of nonequilibrium EDL.…”

mentioning

confidence: 99%

Direct Observation of a Nonequilibrium Electro-Osmotic Instability

et al. 2008

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We present a visualization of the predicted instability in ionic conduction from a binary electrolyte into a charge selective solid. This instability develops when a voltage greater than critical is applied to a thin layer of copper sulfate flanked by a copper anode and a cation selective membrane. The current-voltage dependence exhibits a saturation at the limiting current. With a further increase of voltage, the current increases, marking the transition to the overlimiting conductance. This transition is mediated by the appearing vortical flow that increases with the applied voltage. DOI: 10.1103/PhysRevLett.101.236101 PACS numbers: 82.45.Gj, 47.20.Ma, 82.40.Ck Microscale fluid flows commonly arise when a dc current passes through the diffusion layers (DL) of binary ionic solutions adjacent to charge selective solids, such as electrodes [1], ion exchange granules [2] or membranes [3], and arrays of nanochannels [4]. Under conditions of extreme diffusion limitation (concentration polarization (CP) near the limiting current [5]), these flows provide an additional ionic transport mechanism. This mechanism is essential for the operation of nanofluidic preconcentrators [4] and overlimiting electrodialysis [6,7]. On short length scales and in the absence of free interfaces, these flows are not driven by gravity or surface tension. Instead, they are driven by the electric force acting upon the space charge of the nanometers-thick interfacial electric double layer (EDL). Slip-like fluid flow induced by this force is known as electro-osmosis (EO).There are two regimes of EO that correspond to the different states of the EDL and are controlled by the nonequilibrium voltage drop (overvoltage) across it [8]. These are the quasiequilibrium regime [9,10] and the nonequilibrium EO [2,8,11]. While both regimes result from the action of a tangential electric field upon the space charge of the EDL, the first relates to the charge of quasiequilibrium EDL, whereas the second relates to the extended space charge of nonequilibrium EDL. The nonequilibrium EDL develops in the course of CP near the limiting current.According to a recent theory [8], a novel critical instability of quiescent ionic conduction related to the extended charge EO stands behind the overlimiting conductance through a planar ion exchange membrane. During 1D conduction through a planar layer, an electrolyte concentration gradient forms. The related electric force does not impair the mechanical equilibrium in the system, which remains stable as long as the EDL retains its quasiequilibrium structure. As voltage increases, the system moves away from quasiequilibrium, and an extended space charge develops in the EDL. EO slip related to this extended space charge renders the quiescent conduction unstable [8]. This instability of 1D ionic conduction is reminiscent of instabilities in 1D thermal conduction, such as the RayleighBenard and Marangoni instabilities. While reports of the underlying extended space charge EO [2] and possibly its related flow patterns [1] ...

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Dispersive phenomena in electromigration separation methods

Gaš

Kenndler

2000

Electrophoresis

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A review on dispersive effects and on peak broadening in electromigration separation methods (capillary electrophoresis and electrochromatography) is presented, mainly covering papers published between the beginning of 1997 and the beginning of 2000. Most attention is drawn to work dealing with nonlinear effects that cause anomalous electromigration dispersion in electrolyte systems with two or multiple coions. Further, topics cover the comparison of electroosmotic and pressure-driven modes in electrochromatography, dispersive effects due to nonhomogeneous velocity fields in packed electrochromatography columns, to nonuniform electroosmotic flow, to sorption of analytes (mainly proteins) at the column wall or the stationary phase, and due to the influence of the nonideal column geometry like coiling or irregularities in shape.

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Electrokinetic phenomena of the second kind and their applications

Cited by 307 publications

References 4 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

Direct Observation of a Nonequilibrium Electro-Osmotic Instability

Dispersive phenomena in electromigration separation methods

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