Experimental observation of phenomena developing on ion-exchange systems during current-voltage curve measurement

Belloň, Tomáš; Polezhaev, Petr; Vobecká, Lucie; Svoboda, Miloš; Slouka, Zdeněk

doi:10.1016/j.memsci.2018.11.037

Cited by 44 publications

(36 citation statements)

References 46 publications

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“…Figure 5 shows the CVCs calculated for the GD and PD regimes. All CVCs have a linear initial part (denoted by 1 in Figure 5a), a sloping plateau (2 in Figure 5a), and an overlimiting current (3,4 in Figure 5a), which qualitatively corresponds to the existing experimental [5,7,9,13] and theoretical [16,19,31] studies about the CVCs of membrane systems. Note that the limiting current density of the calculated CVCs, determined by the point of intersection of the tangents drawn to the initial part and to the sloping plateau of the curve is close to i lim , calculated using Leveque's Equation (28) (values differ by less than 2%) [47]:…”

Section: Parameters Used In Computationssupporting

confidence: 78%

“…Electromembrane systems are described by a nonlinear current-voltage curve (CVC), owing largely to the phenomena of concentration polarization, current-induced convection, and water dissociation [5,6]. For dilute electrolyte solutions considered in this article, the main mechanism of overlimiting transfer is electroconvection, as shown by experimental [7][8][9][10][11][12][13] and theoretical studies [14][15][16][17][18][19]. It is customary to distinguish three modes on the CVC of membrane system ( Figure 3):…”

Section: Introductionmentioning

confidence: 99%

“…The existence of the extended SCR at the electrolyte solution/membrane interface, which is much larger than the region of the equilibrium EDL when a sufficiently high voltage is applied, was first shown by I. Rubinstein and L. Shtilman on the basis of a numerical solution of the Nernst-Planck and Poisson equations for the potential of the electric field [25]. depleted region [7][8][9][10][11][12][13][14][15][16][17][18][19]. Electroconvection is the entrainment of liquid molecules by ions that form a space charge at the ion-selective surface under the influence of the electric force [24].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Potentiodynamic and Galvanodynamic Regimes of Mass Transfer in Flow-Through Electrodialysis Membrane Systems: Numerical Simulation of Electroconvection and Current-Voltage Curve

Uzdenova

Уртенов

2020

Membranes

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Electromembrane devices are usually operated in two electrical regimes: potentiodynamic (PD), when a potential drop in the system is set, and galvanodynamic (GD), when the current density is set. This article theoretically investigates the current-voltage curves (CVCs) of flow-through electrodialysis membrane systems calculated in the PD and GD regimes and compares the parameters of the electroconvective vortex layer for these regimes. The study is based on numerical modelling using a basic model of overlimiting transfer enhanced by electroconvection with a modification of the boundary conditions. The Dankwerts’ boundary condition is used for the ion concentration at the inlet boundary of the membrane channel. The Dankwerts’ condition allows one to increase the accuracy of the numerical implementation of the boundary condition at the channel inlet. On the CVCs calculated for PD and DG regimes, four main current modes can be distinguished: underlimiting, limiting, overlimiting, and chaotic overlimiting. The effect of the electric field regime is manifested in overlimiting current modes, when a significant electroconvection vortex layer develops in the channel.

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Section: Parameters Used In Computationssupporting

confidence: 78%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Potentiodynamic and Galvanodynamic Regimes of Mass Transfer in Flow-Through Electrodialysis Membrane Systems: Numerical Simulation of Electroconvection and Current-Voltage Curve

Uzdenova

Уртенов

2020

Membranes

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“…The solutions in the tanks were replaced with fresh ones before each experimental run. The measurements of the pH were carried out in tank (5) and in flow pass cell with pH combination electrode (10) using pH-meter Expert 001 (Econix-Expert, Ltd., Moscow, Russia) (11); in this way, the pH difference between the inlet and outlet DC solutions was determined. The electrodialysis cell (1) design (in particular, the special input and output devices of the solution) provide a laminar flow of the solution in the intermembrane space [63] (see Supplementary Material).…”

Section: Voltammetry and Chronopotentiometrymentioning

confidence: 99%

“…In the course of electrodialysis of dilute solutions, the surface properties of ion-exchange membranes (IEM) significantly affect the performance of the separation process. In particular, the membrane surface parameters have a strong impact on the development of the effects coupled with concentration polarization: first of all, on the intensity of electroconvection (EC) and generation of H + and OHions occurring at the membrane/solution interface [5][6][7][8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

How Electrical Heterogeneity Parameters of Ion-Exchange Membrane Surface Affect the Mass Transfer and Water Splitting Rate in Electrodialysis

Zyryanova

Mareev

Gil

et al. 2020

IJMS

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Electrodialysis (ED) has been demonstrated as an effective membrane method for desalination, concentration, and separation. Electroconvection (EC) is a phenomenon which can essentially increase the mass transfer rate and reduce the undesirable water splitting effect. Efforts by a number of researchers are ongoing to create conditions for developing EC, in particular, through the formation of electrical heterogeneity on the membrane surface. We attempt, for the first time, to optimize the parameters of surface electrical heterogeneity for ion-exchange membranes used in a laboratory ED cell. Thirteen different patterns on the surface of two Neosepta anion-exchange membranes, AMX and AMX-Sb, were tested. Low-conductive fluoropolymer spots were formed on the membrane surface using the electrospinning technique. Spots in the form of squares, rectangles, and circles with different sizes and distances between them were applied. We found that the spots’ shape did not have a visible effect. The best effect, i.e., the maximum mass transfer rate and the minimum water splitting rate, was found when the spots’ size was close to that of the diffusion layer thickness, δ (about 250 μm in the experimental conditions), and the distance between the spots was slightly larger than δ, such that the fraction of the screened surface was about 20%.

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Electric‐field‐enhanced selective separation of products of an enzymatic reaction in a membrane micro‐contactor

Romanov

Slouka

Přibyl

2020

Biotech & Bioengineering

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Processes employed in separations of products of enzyme reactions are often driven by diffusion, and their efficiency can be limited. Here, we exploit the effect of a direct current (DC) electric field that intensifies mass transfer through a semipermeable membrane for fast, continuous, and selective separation of electrically charged molecules. Specifically, we separate low‐molecular‐weight reaction products (phenylacetic acid, 6‐aminopenicillanic acid) from the original reaction mixture containing a free enzyme (penicillin acylase). The developed microfluidic dialysis‐membrane contactor allows a stable counter‐current arrangement of the retentate and permeates liquid streams on which DC electric field is perpendicularly applied. The applied electric field significantly accelerates the transport of electrically charged products through the semipermeable membrane yielding high separation efficiencies at short residence times. The residence time of 5 min is sufficient to reach 100% separation yield in the electric field. The same residence time provides only a 50% yield in the diffusion‐controlled experiments. We experimentally demonstrated that a combined microreactor–microextractor with a recycle of the soluble penicillin acylase can continuously produce both the reaction products at high concentrations. The developed membrane‐contactor is a versatile platform allowing to tune its characteristics, such as selectivity given by the membrane, or the type of the retentate phase, for a specific application.

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Experimental observation of phenomena developing on ion-exchange systems during current-voltage curve measurement

Cited by 44 publications

References 46 publications

Potentiodynamic and Galvanodynamic Regimes of Mass Transfer in Flow-Through Electrodialysis Membrane Systems: Numerical Simulation of Electroconvection and Current-Voltage Curve

Potentiodynamic and Galvanodynamic Regimes of Mass Transfer in Flow-Through Electrodialysis Membrane Systems: Numerical Simulation of Electroconvection and Current-Voltage Curve

How Electrical Heterogeneity Parameters of Ion-Exchange Membrane Surface Affect the Mass Transfer and Water Splitting Rate in Electrodialysis

Electric‐field‐enhanced selective separation of products of an enzymatic reaction in a membrane micro‐contactor

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