Microscale electrodialysis: Concentration profiling and vortex visualization

Kwak, Rhokyun; Guan, Guofeng; Peng, Weng Kung; Han, Jongyoon

doi:10.1016/j.desal.2012.07.017

Cited by 176 publications

(147 citation statements)

References 35 publications

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“…The ability to control ion transport through a nanoporous membrane or nanochannel via an external electric field has been utilized for significant engineering applications, such as electrodesalination, [1][2][3][4] concentrating biomolecules, 5-9 separation, 10,11 fluid pumping and switching, 12 nanofluidic diodes, and ionic field effect transistors. [13][14][15][16][17] Elucidating the fundamentals of ion transportation also remains an active research area because various related phenomena are not fully understood yet.…”

Section: Introductionmentioning

confidence: 99%

Capillarity ion concentration polarization for spontaneous biomolecular preconcentration mechanism

Lee

Son

et al. 2016

Biomicrofluidics

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Ionic hydrogel-based ion concentration polarization devices have been demonstrated as platforms to study nanoscale ion transport and to develop engineering applications, such as protein preconcentration and ionic diodes/transistors. Using a microfluidic system composed of a perm-selective hydrogel, we demonstrated a micro/nanofluidic device for the preconcentration of biological samples using a new class of ion concentration polarization mechanism called "capillarity ion concentration polarization" (CICP). Instead of an external electrical voltage source, the capillary force of the perm-selective hydrogel spontaneously generated an ion depletion zone in a microfluidic channel by selectively absorbing counter-ions in a sample solution. We demonstrated a reasonable preconcentration factor ($100-fold/min) using the CICP device. Although the efficiency was lower than that of conventional electrokinetic ICP operation due to the absence of a drift ion migration, this mechanism was free from the undesirable instability caused by a local amplified electric field inside the ion depletion zone so that the mechanism should be suitable especially for an application where the contents were electrically sensitive. Therefore, this simple system would provide a point-of-care diagnostic device for which the sample volume is limited and a simplified sample handling is demanded. V C 2016 AIP Publishing LLC. [http://dx

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Section: Introductionmentioning

confidence: 99%

Capillarity ion concentration polarization for spontaneous biomolecular preconcentration mechanism

Lee

Son

et al. 2016

Biomicrofluidics

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“…Integrating (18) in the electroneutral part of EBL and keeping the leading order terms, we conclude that…”

Section: Driving Factors Of Hydrodynamic Instability In Cpmentioning

confidence: 99%

“…This type of balance is a common element of the theory of EDL, [29]. Integrating (18) and applying the boundary conditions (22), (26) we compute the electric field and electric potential as functions of the control parameters C(x, t), Φ(x, t), J and k.…”

Section: Driving Factors Of Hydrodynamic Instability In Cpmentioning

confidence: 99%

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Driving factors of electro-convective instability in concentration polarization

2016

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Ionic current in a binary electrolyte passing through a charge-selective interface (electrode, ion exchange membrane, micro-nano-channel junction) is a basic element of many electrochemical engineering and micro-fluidic processes, such as electrodeposition, electrodialysis and protein preconcentration. Such current passage is diffusion-limited in the sense that it induces a decrease of electrolyte concentration towards the interface (concentration polarization) whose expression is the saturation of current upon increasing voltage at some value -the limiting current. Upon a further increase of voltage, this saturation is followed by a relatively rapid current increase -over-limiting conductance regime. It is commonly accepted that in open systems over-limiting conductance is mediated by a micro-scale vortical flow which spontaneously develops as a result of electro-convective instability of quiescent concentration polarization near the limiting current. Electro-convection is a flow driven by the electric force acting either upon the space charge of the interfacial electric double layer (electro-osmosis) or the residual space charge of the quasi-electroneutral bulk (bulk electroconvection). There are two types of electro-osmosis, the equilibrium and the non-equilibrium one, the former relating to the action of the tangential electric field upon the space charge of the electric double layer, and the latter pertaining to the similar action upon the extended space charge which forms next to the electric double layer near the limiting current. For a perfectly charge-selective interface, concentration polarization under the equilibrium electro-osmotic slip condition is stable, and so it is with respect to bulk electro-convection, as opposed to non-equilibrium electro-osmosis which may cause instability. For this reason until recently, the electro-convective instability in concentration polarization was attributed to this latter mechanism. Lately, it was shown that imperfect charge-selectivity of the interface makes equilibrium instability possible, driven by either equilibrium electro-osmosis or bulk electro-convection, or both. In this paper we identify and analyze the major surface and bulk factors affecting the electro-convective instability. These factors, some known previously under the names of diffusio-osmosis, electro-osmosis or bulk electroconvection, and some newly identified in this paper, are manifestations of the electric force and pressure gradient, balanced by the viscous force acting in various locations in solution. The contribution of these factors to hydrodynamic stability in concentration polarization is analyzed for a varying perm-selectivity of the interface.

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“…In essence, this limit upon the rate of ion removal occurs as ion diffusion towards the membrane surface becomes insufficient to replenish the concentration of salt at membranesolution interfaces. The physics observed in this regime of operation is complex and analysed in detail in literature [8,9].…”

Section: 2mentioning

confidence: 99%

Hybrid electrodialysis reverse osmosis system design and its optimization for treatment of highly saline brines

McGovern

Zubair

Lienhard

2014

IDA Journal of Desalination and Water Reuse

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Abstract:The demand is rising for desalination technologies to treat highly saline brines arising from hydraulic fracturing processes and inland desalination. Interest is growing in the use of electrical desalination technologies for this application. The hybridization of electrodialysis (ED) with reverse osmosis (RO) allows high salinities (beyond the range of RO alone) to be reached while avoiding the operation of ED with a low conductivity diluate stream. Such hybrid systems have been experimentally investigated for concentrates from brackish and seawater desalination. However, progress is required in the modelling and optimization of hybrid systems at higher concentrations. A novel hybrid arrangement of counterflow ED systems with reverse osmosis is presented to concentrate a saline feed at 120 ppt. The system is considered from the perspective of efficiency, membrane productivity and the levelised cost of water, with emphasis on the optimisation of current density. In contrast to brackish ED systems, membrane resistances are found to dominate diluate and concentrate resistances at high salinity. The current density found to minimise LCW (levelised cost of water) is significantly greater than the current density found to maximise efficiency, indicating the high current capital cost of ED per unit membrane area and poor membrane transport properties relative to RO. Finally, performance at high recoveries is found to be limited by high stream-to-stream concentration differences, increasing water transport via osmosis, decreasing efficiency and increasing the LCW.

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Microscale electrodialysis: Concentration profiling and vortex visualization

Cited by 176 publications

References 35 publications

Capillarity ion concentration polarization for spontaneous biomolecular preconcentration mechanism

Capillarity ion concentration polarization for spontaneous biomolecular preconcentration mechanism

Driving factors of electro-convective instability in concentration polarization

Hybrid electrodialysis reverse osmosis system design and its optimization for treatment of highly saline brines

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