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Ganchenko GS, Alekseev MS, Moroz IA, Mareev SA, Shelistov VS, Demekhin EA. Electrokinetic and Electroconvective Effects in Ternary Electrolyte Near Ion-Selective Microsphere. MEMBRANES 2023; 13:membranes13050503. [PMID: 37233564 DOI: 10.3390/membranes13050503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 05/05/2023] [Accepted: 05/08/2023] [Indexed: 05/27/2023]
Abstract
The paper presents theoretical and experimental investigations of the behavior of an electrolyte solution with three types of ions near an ion-selective microparticle with electrokinetically and pressure-driven flow. A special experimental cell has been developed for the investigations. An anion-selective spherical particle composed of ion-exchange resin is fixed in the center of the cell. An enriched region with a high salt concentration appears at the anode side of the particle when an electric field is turned on, according to the nonequilibrium electrosmosis behavior. A similar region exists near a flat anion-selective membrane. However, the enriched region near the particle produces a concentration jet that spreads downstream akin to a wake behind an axisymmetrical body. The fluorescent cations of Rhodamine-6G dye are chosen as the third species in the experiments. The ions of Rhodamine-6G have a 10-fold lower diffusion coefficient than the ions of potassium while bearing the same valency. This paper shows that the concentration jet behavior is described accurately enough with the mathematical model of a far axisymmetric wake behind a body in a fluid flow. The third species also forms an enriched jet, but its distribution turns out to be more complex. The concentration of the third species increases in the jet with an increase in pressure gradient. The pressure-driven flow stabilizes the jet, yet electroconvection has been observed near the microparticle for sufficiently strong electric fields. The electrokinetic instability and the electroconvection partially destroy the concentration jet of salt and the third species. The conducted experiments show good qualitative agreement with the numerical simulations. The presented results could be used in future for implementing microdevices based on membrane technology for solving problems of detection and preconcentration, and thus simplifying chemical and medical analyses utilizing the superconcentration phenomenon. Such devices are called membrane sensors, and are actively being studied.
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Affiliation(s)
- Georgy S Ganchenko
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University under the Government of the Russian Federation, 53 Leningradsky Prospect str., Moscow 125167, Russia
| | - Maxim S Alekseev
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University under the Government of the Russian Federation, 53 Leningradsky Prospect str., Moscow 125167, Russia
- Membrane Institute, Kuban State University, 149 Stavropolskaya str., Krasnodar 350040, Russia
| | - Ilya A Moroz
- Membrane Institute, Kuban State University, 149 Stavropolskaya str., Krasnodar 350040, Russia
| | - Semyon A Mareev
- Membrane Institute, Kuban State University, 149 Stavropolskaya str., Krasnodar 350040, Russia
| | - Vladimir S Shelistov
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University under the Government of the Russian Federation, 53 Leningradsky Prospect str., Moscow 125167, Russia
| | - Evgeny A Demekhin
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University under the Government of the Russian Federation, 53 Leningradsky Prospect str., Moscow 125167, Russia
- Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, 1 Michurinsky Prospect, Moscow 119192, Russia
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Stockmeier F, Stüwe L, Kneppeck C, Musholt S, Albert K, Linkhorst J, Wessling M. On the interaction of electroconvection at a membrane interface with the bulk flow in a spacer-filled feed channel. J Memb Sci 2023. [DOI: 10.1016/j.memsci.2023.121589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2023]
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3
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The effects of reaction kinetics upon the instabilities in cathodic electrodeposition. Curr Opin Colloid Interface Sci 2022. [DOI: 10.1016/j.cocis.2022.101591] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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4
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Stockmeier F, Schatz M, Habermann M, Linkhorst J, Mani A, Wessling M. Direct 3D observation and unraveling of electroconvection phenomena during concentration polarization at ion-exchange membranes. J Memb Sci 2021. [DOI: 10.1016/j.memsci.2021.119846] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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5
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Schiffbauer J, Ganchenko G, Nikitin N, Alekseev M, Demekhin E. Novel electroosmotic micromixer configuration based on ion-selective microsphere. Electrophoresis 2021; 42:2511-2518. [PMID: 34553795 DOI: 10.1002/elps.202100040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Revised: 06/18/2021] [Accepted: 09/11/2021] [Indexed: 11/07/2022]
Abstract
In this paper, a micromixer of a new configuration is presented, consisting of a spherical chamber in the center of which an ion-selective microsphere is placed. Stratified liquid is introduced through the chamber via inlet and outlet holes under an external pressure gradient and an external electric field is directed in such a way that the resulting electroosmotic flow is directed against the pressure-driven flow, resulting in mixing. The investigation is carried out by direct numerical simulation on a super-computer. Optimal values of the applied electric field are determined to yield strong mixing. Above this optimal mixing regime, a number of instabilities and bifurcations are realized, which qualitatively coincide with those occurring during electrophoresis of an ion-selective microgranule. As shown by our calculation, these instabilities do not lead to an enhanced mixing. The resulting electroconvective vortices remain confined near the surface of the microgranule, and do not sufficiently perturb the stratified fluid flow further from the granule. On the other hand, another type of instability caused by the salt concentration gradient can generate sufficiently strong oscillations to enhance mixing. However, this only occurs when the external electric field is sufficiently high that the electroosmotic flow is comparable to the pressure-driven flow. This ultimately leads to creation of reverse flows of the liquid and cessation of the device operation. Thus, it was shown that the best mixing occurs in the absence of electrokinetic instability. Based on the data obtained, it is possible to select the necessary geometric characteristics of the micromixer to achieve the optimal mixing mode for a given set of liquids, which may be ten times more effective than passive mixers at the same flow rates. A comparison with the experimental data of the other authors confirms the effectiveness of this device and its other capabilities. Furthermore, the basic device design can be operated in other modes, for example, an electrohydrodynamic pump, a streaming current generator, or even a micro-reactor, depending on the system parameters and choice of an ion-selective granule.
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Affiliation(s)
- Jarrod Schiffbauer
- Department of Physical and Environmental Sciences, Colorado Mesa University, Grand Junction, CO, USA
| | - Georgy Ganchenko
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University, Krasnodar, Russia
| | - Nikolay Nikitin
- Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, Moscow, Russia
| | | | - Evgeny Demekhin
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University, Krasnodar, Russia.,Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, Moscow, Russia.,Department of Mathematics and Computer Science, Financial University, Krasnodar, Russia
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6
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Schiffbauer J, Demekhin E, Ganchenko G. Transitions and Instabilities in Imperfect Ion-Selective Membranes. Int J Mol Sci 2020; 21:ijms21186526. [PMID: 32906711 PMCID: PMC7554848 DOI: 10.3390/ijms21186526] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 08/31/2020] [Accepted: 09/02/2020] [Indexed: 11/16/2022] Open
Abstract
Numerical investigation of the underlimiting, limiting, and overlimiting current modes and their transitions in imperfect ion-selective membranes with fluid flow through permitted through the membrane is presented. The system is treated as a three layer composite system of electrolyte-porous membrane-electrolyte where the Nernst–Planck–Poisson–Stokes system of equations is used in the electrolyte, and the Darcy–Brinkman approach is employed in the nanoporous membrane. In order to resolve thin Debye and Darcy layers, quasi-spectral methods are applied using Chebyshev polynomials for their accumulation of zeros and, hence, best resolution in the layers. The boundary between underlimiting and overlimiting current regimes is subject of linear stability analysis, where the transition to overlimiting current is assumed due to the electrokinetic instability of the one-dimensional quiescent state. However, the well-developed overlimiting current is inherently a problem of nonlinear stability and is subject of the direct numerical simulation of the full system of equations. Both high and low fixed charge density membranes (low- and high concentration electrolyte solutions), acting respectively as (nearly) perfect or imperfect membranes, are considered. The perfect membrane is adequately described by a one-layer model while the imperfect membrane has a more sophisticated response. In particular, the direct transition from underlimiting to overlimiting currents, bypassing the limiting currents, is found to be possible for imperfect membranes (high-concentration electrolyte). The transition to the overlimiting currents for the low-concentration electrolyte solutions is monotonic, while for the high-concentration solutions it is oscillatory. Despite the fact that velocities in the porous membrane are much smaller than in the electrolyte region, it is further demonstrated that they can dramatically influence the nature and transition to the overlimiting regimes. A map of the bifurcations, transitions, and regimes is constructed in coordinates of the fixed membrane charge and the Darcy number.
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Affiliation(s)
- Jarrod Schiffbauer
- Department of Physical and Environmental Sciences, Colorado Mesa University, Grand Junction, CO 81501, USA;
| | - Evgeny Demekhin
- Department of Mathematics and Computer Science, Financial University, 350051 Krasnodar, Russia
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University, 350051 Krasnodar, Russia;
- Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, 119192 Moscow, Russia
- Correspondence:
| | - Georgy Ganchenko
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University, 350051 Krasnodar, Russia;
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7
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Liu W, Zhou Y, Shi P. Scaling laws of electroconvective flow with finite vortex height near permselective membranes. Phys Rev E 2020; 102:033102. [PMID: 33075936 DOI: 10.1103/physreve.102.033102] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Accepted: 08/14/2020] [Indexed: 06/11/2023]
Abstract
In a steady state, the linear scaling laws are confirmed between the intensity characteristics of electroconvective (EC) vortex (including the vortex height and electroosmotic slip velocity) and the applied voltage for the nonshear EC flow with finite vortex height near permselective membranes. This finding in the nonshear EC flow is different from the shear EC flow [Kwak et al., Phys. Rev. Lett. 110, 114501 (2013)10.1103/PhysRevLett.110.114501] and indicates that the local concentration gradient has a significant improvement in the analysis of slip velocity. Further, our study reveals that the EC vortex is mainly driven by the second peak effect of the Coulomb thrust in the extended space-charge layer, and the linear scaling law exhibited by the Coulomb thrust is an essential reason for the linear scaling laws of vortex intensity. The scaling laws proposed in this paper are supported by our direct numerical simulation data and previous experimental observations [Rubinstein et al., Phys. Rev. Lett. 101, 236101 (2008)10.1103/PhysRevLett.101.236101].
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Affiliation(s)
- Wei Liu
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, People's Republic of China
| | - Yueting Zhou
- School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai 200092, People's Republic of China
| | - Pengpeng Shi
- School of Civil Engineering & Institute of Mechanics and Technology, Xi'an University of Architecture and Technology, Xi'an 710055, Shaanxi, People's Republic of China
- State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center of NDT and Structural Integrity Evaluation, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, Shaanxi, People's Republic of China
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8
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Kang S, Kwak R. Pattern Formation of Three-Dimensional Electroconvection on a Charge Selective Surface. PHYSICAL REVIEW LETTERS 2020; 124:154502. [PMID: 32357025 DOI: 10.1103/physrevlett.124.154502] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 11/04/2019] [Accepted: 03/16/2020] [Indexed: 06/11/2023]
Abstract
When a charge selective surface consumes or transports only cations or anions in the electrolyte, biased ion rejection initiates hydrodynamic instability, resulting in vortical fluid motions called electroconvection. In this Letter, we describe the first laboratory observation of three-dimensional electroconvection on a charge selective surface. Combining experiment and scaling analysis, we successfully categorized three distinct patterns of 3D electroconvection according to [(Ra_{E})/(Re^{2}Sc)] [electric Rayleigh number (Ra_{E}), Reynolds number (Re), Schmidt number (Sc)] as (i) polygonal, (ii) transverse, or (iii) longitudinal rolls. If Re increases or Ra_{E} decreases, pure longitudinal rolls are presented. On the other hand, transverse rolls are formed between longitudinal rolls, and two rolls are transformed as polygonal one at higher Ra_{E} or lower Re. In this pattern selection scenario, Sc determines the critical electric Rayleigh number (Ra_{E}^{*}) for the onset of each roll, resulting in Ra_{E}^{*}∼Re^{2}Sc. We also verify that convective ion flux by electroconvection (represented by an electric Nusselt number Nu_{E}) is fitted to a power law, Nu_{E}∼[(Ra_{E}-Ra_{E}^{*})/(Re^{2}Sc)]^{α_{1}}Re^{α_{2}}Pe^{α_{3}} [Péclet number (Pe)], where each term represents the characteristics of electroconvection, shear flow, and ion transport.
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Affiliation(s)
- Soohyeon Kang
- 1Department of Mechanical Engineering, Hanyang University, Seoul 04763, Republic of Korea
| | - Rhokyun Kwak
- 1Department of Mechanical Engineering, Hanyang University, Seoul 04763, Republic of Korea
- 2Institute of Nano Science and Technology, Hanyang University, Seoul 04763, Republic of Korea
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9
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Park JS, Oh J, Kim SJ. Controllable pH Manipulations in Micro/Nanofluidic Device Using Nanoscale Electrokinetics. MICROMACHINES 2020; 11:E400. [PMID: 32290354 PMCID: PMC7231315 DOI: 10.3390/mi11040400] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Revised: 04/07/2020] [Accepted: 04/07/2020] [Indexed: 11/16/2022]
Abstract
Recently introduced nanoscale electrokinetic phenomenon called ion concentration polarization (ICP) has been suffered from serious pH changes to the sample fluid. A number of studies have focused on the origin of pH changes and strategies for regulating it. Instead of avoiding pH changes, in this work, we tried to demonstrate new ways to utilize this inevitable pH change. First, one can obtain a well-defined pH gradient in proton-received microchannel by applying a fixed electric current through a proton exchange membrane. Furthermore, one can tune the pH gradient on demand by adjusting the proton mass transportation (i.e., adjusting electric current). Secondly, we demonstrated that the occurrence of ICP can be examined by sensing a surrounding pH of electrolyte solution. When pH > threshold pH, patterned pH-responsive hydrogel inside a straight microchannel acted as a nanojunction to block the microchannel, while it did as a microjunction when pH < threshold pH. In case of forming a nanojunction, electrical current significantly dropped compared to the case of a microjunction. The strategies that presented in this work would be a basis for useful engineering applications such as a localized pH stimulation to biomolecules using tunable pH gradient generation and portable pH sensor with pH-sensitive hydrogel.
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Affiliation(s)
- Jae Suk Park
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Korea
- Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826, Korea
| | - Jeewhan Oh
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Korea
| | - Sung Jae Kim
- Department of Electrical and Computer Engineering, Seoul National University, Seoul 08826, Korea
- Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826, Korea
- Nano Systems Institute, Seoul National University, Seoul 08826, Korea
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10
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Electro-Kinetic Instability in a Laminar Boundary Layer Next to an Ion Exchange Membrane. Int J Mol Sci 2019; 20:ijms20102393. [PMID: 31091791 PMCID: PMC6566642 DOI: 10.3390/ijms20102393] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Revised: 04/17/2019] [Accepted: 04/28/2019] [Indexed: 02/03/2023] Open
Abstract
The electro-kinetic instability in a pressure driven shear flow near an ion exchange membrane is considered. The electrochemical system, through which an electrical potential drop is applied, consists in a polarization layer in contact with the membrane and a bulk. The numerical investigation contained two aspects: analysis of the instability modes and description of the Lagrangian transport of fluid and ions. Regarding the first aspect, the modes were analyzed as a function of the potential drop. The analysis revealed how the spatial distribution of forces controls the dynamics of vortex association and dissociation. In particular, the birth of a counter-clockwise vortex between two clockwise vortices, and the initiation of clusters constituting one or two envelopes wrapping a vortex group, were examined. In regards to the second aspect, the trajectories were computed with the fourth order Runge Kutta scheme for the time integration and with the biquadratric upstream scheme for the spatial and time interpolation of the fluid velocity and the ion flux. The results for the periodic mode showed two kinds of trajectories: the trochoidal motion and the longitudinal one coupled with a periodic transverse motion. For the aperiodic modes, other mechanisms appeared, such as ejection from the mixing layer, trapping by a growing vortex or merging vortices. The analysis of the local velocity field, the vortices’ shape, the spatial distribution of the forces and the ion flux components explained these trajectories.
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11
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Li G, Archer LA, Koch DL. Electroconvection in a Viscoelastic Electrolyte. PHYSICAL REVIEW LETTERS 2019; 122:124501. [PMID: 30978047 DOI: 10.1103/physrevlett.122.124501] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 12/31/2018] [Indexed: 06/09/2023]
Abstract
Direct numerical simulations of a liquid electrolyte with polymer additives demonstrate that viscoelasticity promotes an earlier transition from steady to unsteady electroconvective flow. Viscoelasticity also decreases the overlimiting current resulting from convection by up to 40%. Both of these effects would reduce the time-averaged spatial variability of ion flux suggesting that polymeric fluids may inhibit dendrite growth. Polymer relaxation near a surface destabilizes the flow structures and decreases the time duration of high current fluxes. This mechanism of polymer-induced flux reduction is general to wall bounded flows with transfer of mass, heat or momentum.
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Affiliation(s)
- Gaojin Li
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Lynden A Archer
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
| | - Donald L Koch
- Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14853, USA
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12
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Ganchenko GS, Kalaydin EN, Schiffbauer J, Demekhin EA. Modes of electrokinetic instability for imperfect electric membranes. Phys Rev E 2016; 94:063106. [PMID: 28085376 DOI: 10.1103/physreve.94.063106] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Indexed: 11/07/2022]
Abstract
The direct transition to overlimiting current bypassing the stage of limiting currents is considered for imperfect membranes. Instability of the quiescent steady-state one-dimensional solution, which is the result of a balance of diffusion and electromigration, is investigated on the basis of the full Nernst-Planck-Poisson-Stokes system and a simplified quasielectroneutral system. A three-layer geometry, electrolyte-porous membrane-electrolyte, is considered. The usual assumption of a constant electrochemical potential along the membrane surface is removed from consideration. The effect of bulk and surface effects on the instability and transition to the overlimiting currents is evaluated for a different membrane selectivity. It becomes clear that for sufficiently small fixed charge concentration (large ion concentration in the electrolyte), the monotonic instability is replaced by an oscillatory one. The dependence of instability on the membrane porosity is found to be weak.
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Affiliation(s)
- G S Ganchenko
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University, Krasnodar 350051, Russian Federation
| | - E N Kalaydin
- Department of Mathematics and Informatics, Financial University, Krasnodar 350051, Russian Federation
| | - J Schiffbauer
- University of Notre Dame, Notre Dame, Indiana 46556, USA
| | - E A Demekhin
- Laboratory of Micro- and Nanoscale Electro- and Hydrodynamics, Financial University, Krasnodar 350051, Russian Federation.,Department of Mathematics and Informatics, Financial University, Krasnodar 350051, Russian Federation.,Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, Moscow 119192, Russian Federation
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13
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Hlushkou D, Knust KN, Crooks RM, Tallarek U. Numerical simulation of electrochemical desalination. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:194001. [PMID: 27089841 DOI: 10.1088/0953-8984/28/19/194001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present an effective numerical approach to simulate electrochemically mediated desalination of seawater. This new membraneless, energy efficient desalination method relies on the oxidation of chloride ions, which generates an ion depletion zone and local electric field gradient near the junction of a microchannel branch to redirect sea salt into the brine stream, consequently producing desalted water. The proposed numerical model is based on resolution of the 3D coupled Navier-Stokes, Nernst-Planck, and Poisson equations at non-uniform spatial grids. The model is implemented as a parallel code and can be employed to simulate mass-charge transport coupled with surface or volume reactions in 3D systems showing an arbitrarily complex geometrical configuration.
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Affiliation(s)
- D Hlushkou
- Department of Chemistry, Philipps-Universität Marburg, Hans-Meerwein-Strasse 4, 35032 Marburg, Germany
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14
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Pham SV, Kwon H, Kim B, White JK, Lim G, Han J. Helical vortex formation in three-dimensional electrochemical systems with ion-selective membranes. Phys Rev E 2016; 93:033114. [PMID: 27078454 DOI: 10.1103/physreve.93.033114] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Indexed: 11/07/2022]
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.
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Affiliation(s)
- Sang V Pham
- Research Laboratory of Electronics, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Singapore-MIT Alliance for Research and Technology (SMART), Singapore 138602.,Department of Ship Engineering and Fluid Mechanics, Hanoi University of Science and Technology, No1 DaiCoViet, Hanoi, Vietnam
| | - Hyuckjin Kwon
- Research Laboratory of Electronics, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Pohang Universities of Science and Technology, Pohang, Gyeoungbuk 790784, Republic of Korea
| | - Bumjoo Kim
- Research Laboratory of Electronics, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jacob K White
- Research Laboratory of Electronics, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Geunbae Lim
- Pohang Universities of Science and Technology, Pohang, Gyeoungbuk 790784, Republic of Korea
| | - Jongyoon Han
- Research Laboratory of Electronics, Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.,Singapore-MIT Alliance for Research and Technology (SMART), Singapore 138602.,Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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15
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On the Dynamical Regimes of Pattern-Accelerated Electroconvection. Sci Rep 2016; 6:22505. [PMID: 26935925 PMCID: PMC4776150 DOI: 10.1038/srep22505] [Citation(s) in RCA: 78] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/15/2016] [Indexed: 11/21/2022] Open
Abstract
Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.
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16
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Demekhin EA, Amiroudine S, Ganchenko GS, Khasmatulina NY. Thermoelectroconvection near charge-selective surfaces. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:063006. [PMID: 26172791 DOI: 10.1103/physreve.91.063006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Indexed: 06/04/2023]
Abstract
A new kind of instability caused by Joule heating near charge-selective surfaces (permselective membranes, electrodes, or systems of micro- and nanochannels) is investigated theoretically using a model based on the Rubinstein-Zaltzman approach. A simple relation is derived for the marginal stability curves: Joule heating can either destabilize or stabilize the steady state, depending on the location of the space charge region relative to the gravity vector. For the destabilizing case, the short-wave Rubinstein-Zaltzman instability is replaced by a long-wave thermal instability. The physical mechanism of the thermal instability is found to be very different from Rayleigh-Bénard convection, and is based on a nonuniform distribution of the electrical conductivity in the electrolyte. The study is complemented by numerical investigations both of linear and nonlinear instabilities near a charge-selective surface. There is a good qualitative agreement with the analytics. A possible explanation of the discrepancy between the experimental data and our previous theoretical voltage-current characteristics is highlighted.
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Affiliation(s)
- E A Demekhin
- Laboratory of Electro-Hydrodynamics of Micro- and Nanoscales, Department of Mathematics and Computer Science, Financial University, Krasnodar, 350051, Russian Federation
- Laboratory of General Aeromechanics, Institute of Mechanics, Moscow State University, Moscow, 117192, Russian Federation
| | - S Amiroudine
- Université Bordeaux, I2M, UMR CNRS 5295, 16 Av. Pey-Berland, 33607 Pessac, France
| | - G S Ganchenko
- Department of Computational Mathematics and Computer Science, Kuban State University, Krasnodar, 350040, Russian Federation
| | - N Yu Khasmatulina
- Department of Mathematical Modelling, Kuban State University, Krasnodar, 350040, Russian Federation
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Karatay E, Druzgalski CL, Mani A. Simulation of chaotic electrokinetic transport: Performance of commercial software versus custom-built direct numerical simulation codes. J Colloid Interface Sci 2015; 446:67-76. [DOI: 10.1016/j.jcis.2014.12.081] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Revised: 12/20/2014] [Accepted: 12/23/2014] [Indexed: 11/30/2022]
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Green Y, Park S, Yossifon G. Bridging the gap between an isolated nanochannel and a communicating multipore heterogeneous membrane. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 91:011002. [PMID: 25679562 DOI: 10.1103/physreve.91.011002] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2014] [Indexed: 06/04/2023]
Abstract
To bridge the gap between single and isolated pore systems to multipore systems, such as membranes and electrodes, we studied an array of nanochannels with varying interchannel spacing that controlled the degree of channel communication. Instead of treating them as individual channels connected in parallel or an assembly like a homogeneous membrane, this study resolves the pore-pore interaction. We found that increased channel isolation leads to current intensification, whereas at high voltages electroconvective effects control the degree of communication via suppression of the diffusion layer growth.
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Affiliation(s)
- Yoav Green
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion-Israel Institute of Technology, Technion City 32000, Israel
| | - Sinwook Park
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion-Israel Institute of Technology, Technion City 32000, Israel
| | - Gilad Yossifon
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion-Israel Institute of Technology, Technion City 32000, Israel
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