scholarly journals Mass Transfer Phenomena during Electrodialysis of Multivalent Ions: Chemical Equilibria and Overlimiting Currents

2018 ◽  
Vol 8 (9) ◽  
pp. 1566 ◽  
Author(s):  
Manuel Martí-Calatayud ◽  
Montserrat García-Gabaldón ◽  
Valentín Pérez-Herranz
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Membrane Surface ◽  
Industrial Effluents ◽  
Water Dissociation ◽  
Chemical Equilibria ◽  
Multivalent Ions ◽  
Current Voltage ◽  
Weak Electrolytes ◽  
New Applications

Electrodialysis is utilized for the deionization of saline streams, usually formed by strong electrolytes. Recently, interest in new applications involving the transport of weak electrolytes through ion-exchange membranes has increased. Clear examples of such applications are the recovery of valuable metal ions from industrial effluents, such as electronic wastes or mining industries. Weak electrolytes give rise to a variety of ions with different valence, charge sign and transport properties. Moreover, development of concentration polarization under the application of an electric field promotes changes in the chemical equilibrium, thus making more complex understanding of mass transfer phenomena in such systems. This investigation presents a set of experiments conducted with salts of multivalent metals with the aim to provide better understanding on the involved mass transfer phenomena. Chronopotentiometric experiments and current-voltage characteristics confirm that shifts in chemical equilibria can take place simultaneous to the activation of overlimiting mass transfer mechanisms, that is, electroconvection and water dissociation. Electroconvection has been proven to affect the type of precipitates formed at the membrane surface thus suppressing the simultaneous dissociation of water. For some electrolytes, shifts in the chemical equilibria forced by an imposed electric field generate new charge carriers at specific current regimes, thus reducing the system resistance.

A perturbation solution to the problem of Wien dissociation in weak electrolytes

1978 ◽  
Vol 359 (1698) ◽  
pp. 303-317 ◽  
Keyword(s):  
Differential Equation ◽  
Electric Field ◽  
Applied Electric Field ◽  
Pair Distribution Function ◽  
Infinite System ◽  
Perturbation Technique ◽  
Relative Increase ◽  
Ion Pair ◽  
Legendre Transform ◽  
Weak Electrolytes

The problem of Wien dissociation of a weak electrolyte in the presence of a uniform applied electric field, X , is analysed by using a perturbation technique. The partial differential equation for the ion-pair distribution function is first reduced to an infinite system of ordinary differential equations by taking the Legendre transform . Explicit expressions for the relative increase in the dissociation constant, K ( X )/ K (0), due to the applied electric field, are calculated to second order in the expansion parameter 2 βq , where β is proportional to X and q is the Bjerrum association distance. Further, by induction, the m th term of this expansion is derived. The infinite series obtained in this way for K ( X )/ K (0) is convergent for all values of βq , and when summed, agrees with a formula in terms of an ordinary Bessel function of order one, given by onasager (1934) whose derivation has been published in full.

scholarly journals Temperature and Velocity Effects on Mass and Momentum Transport in Spacer-Filled Channels for Reverse Electrodialysis: A Numerical Study

Energies ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 2028 ◽  
Author(s):  
Zohreh Jalili ◽  
Jon Pharoah ◽  
Odne Stokke Burheim ◽  
Kristian Einarsrud
Keyword(s):  
Mass Transfer ◽  
Pressure Drop ◽  
Concentration Polarization ◽  
Numerical Study ◽  
Membrane Surface ◽  
Lower Pressure ◽  
Low Flow ◽  
Fluid Temperature ◽  
Reverse Electrodialysis ◽  
Flow Velocities

Concentration polarization is one of the main challenges of membrane-based processes such as power generation by reverse electrodialysis. Spacers in the compartments can enhance mass transfer by reducing concentration polarization. Active spacers increase the available membrane surface area, thus avoiding the shadow effect introduced by inactive spacers. Optimizing the spacer-filled channels is crucial for improving mass transfer while maintaining reasonable pressure losses. The main objective of this work was to develop a numerical model based upon the Navier–Stokes and Nernst–Planck equations in OpenFOAM, for detailed investigation of mass transfer efficiency and pressure drop. The model is utilized in different spacer-filled geometries for varying Reynolds numbers, spacer conductivity and fluid temperature. Triangular corrugations are found to be the optimum geometry, particularly at low flow velocities. Cylindrical corrugations are better at high flow velocities due to lower pressure drop. Enhanced mass transfer and lower pressure drop by elevating temperature is demonstrated.

Anomalous change of carrier transport property of ferroelectric Hf0.5Zr0.5O2 thin films in the first poling treatment

2022 ◽  
Author(s):  
Yukinori Morita ◽  
Hiroyuki OTA ◽  
Shinji MIGITA
Keyword(s):  
Thin Films ◽  
Electric Field ◽  
Transport Property ◽  
Carrier Transport ◽  
Current Flow ◽  
Discontinuity Point ◽  
Voltage Sweep ◽  
Current Voltage ◽  
Carrier Transport Property ◽  
Carrier Transport Properties

Abstract Carrier transport properties of ferroelectric Hf0.5Zr0.5O2 (HZO) thin films have been investigated on metal-ferroelectric-metal (MFM) capacitor in the first current flow of ferroelectric poling treatment. In current–voltage (I–V) measurement of MFM capacitor, a kink or discontinuity point of derivative in I–V characteristic appears, and after the cyclic voltage sweep this kink disappears. This phenomenon is different from the ferroelectric instabilities after several thousand or million voltage cycle applies reported as the wake-up and fatigue. From the analysis using Poole-Frenkel plot of I–V characteristics, it is suggested that irreversible trap generation by electric field apply occurs in poling treatment.

scholarly journals Analysis of Pole-Ascending–Descending Action by Insects Subjected to High Voltage Electric Fields

Insects ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 187 ◽  
Author(s):  
Yoshinori Matsuda ◽  
Yoshihiro Takikawa ◽  
Koji Kakutani ◽  
Teruo Nonomura ◽  
Hideyoshi Toyoda
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Negative Charge ◽  
Sitophilus Oryzae ◽  
Experimental System ◽  
Insect Behavior ◽  
Free Electrons ◽  
Current Voltage ◽  
Direct Current Voltage ◽  
Oppositely Charged

The present study was conducted to establish an electrostatic-based experimental system to enable new investigations of insect behavior. The instrument consists of an insulated conducting copper ring (ICR) linked to a direct current voltage generator to supply a negative charge to an ICR and a grounded aluminum pole (AP) passed vertically through the center of the horizontal ICR. An electric field was formed between the ICR and the AP. Rice weevil (Sitophilus oryzae) was selected as a model insect due to its habit of climbing erect poles. The electric field produced a force that could be imposed on the insect. In fact, the negative electricity (free electrons) was forced out of the insect to polarize its body positively. Eventually, the insect was attracted to the oppositely charged ICR. The force became weaker on the lower regions of the pole; the insects sensed the weaker force with their antennae, quickly stopped climbing, and retraced their steps. These behaviors led to a pole-ascending–descending action by the insect, which was highly reproducible and precisely corresponded to the changed expansion of the electric field. Other pole-climbing insects including the cigarette beetle (Lasioderma serricorne), which was shown to adopt the same behavior.

ELECTRIC FIELD-ASSISTED RELAXATION OF THE CHARGE DENSITY WAVES IN K0.3MoO3

2007 ◽  
Vol 21 (27) ◽  
pp. 1863-1867 ◽  
Author(s):  
SONG YUE
Keyword(s):  
Electric Field ◽  
Charge Density ◽  
Charge Density Waves ◽  
Voltage Characteristic ◽  
Metastable States ◽  
Threshold Field ◽  
Density Waves ◽  
Current Voltage Characteristic ◽  
Current Voltage ◽  
Ohmic Conductivity

The evolution of the current-voltage characteristic in K 0.3 MoO 3 was observed intuitively with the presence of current cycling. No variation of the ohmic conductivity was distinguished, while the threshold field for the charge density waves depinning exhibited distinct enhancement with the current cycling. These results were attributed to the electric field-assisted metastable states' relaxation of the charge density waves.

Neutralization of a spray of electrically charged droplets by a corona discharge

2016 ◽  
Vol 801 ◽  
pp. 130-149 ◽  
Author(s):  
F. J. Higuera
Keyword(s):  
Electric Field ◽  
Corona Discharge ◽  
Opposite Polarity ◽  
Forced Flow ◽  
Lagrangian Description ◽  
Charged Droplets ◽  
Corona Current ◽  
Current Voltage ◽  
Eulerian Descriptions ◽  
Electrically Charged

The neutralization of a dilute spray of electrically charged droplets by ions of the opposite polarity generated by a corona discharge at a wire ring is analysed numerically. A Lagrangian description of the spray and Eulerian descriptions of the gas and the ions are used to deal with this two-way coupled problem. A model of the corona consisting of a line of charge and a distribution of ion sources is proposed. In the configuration that is analysed, neutralization usually begins at the shroud of the spray and extends to inner regions when the corona current increases. The number density of droplets is large at the shroud due to neutralized droplets that are no longer pushed by the electric field. These droplets can be dragged towards a collector surface by a weak forced flow that overcomes the ionic wind due to the force of the ions on the gas. The fraction of the spray charge that is neutralized increases with the corona current, but the value of this current required for full neutralization is several times larger than the inlet electric current of the spray owing to loss of ions to the boundaries of the system. The electric field induced by the charge of the droplets opposes the field due to the voltage applied between the wire ring and the extractor through which the droplets are injected, and thus reduces the threshold voltage of the corona and significantly affects its current–voltage characteristic, which may become multivalued. In turn, the electric field due to the applied voltage and the space charge of the ions affects the shape of the spray and the velocity of the droplets.

Mass Transfer During Fluid Sphere Dissolution in an Alternating Electric Field

Volume 3 ◽  
2004 ◽  
Author(s):  
Tov Elperin ◽  
Andrew Fominykh ◽  
Zakhar Orenbakh
Keyword(s):  
Mass Transfer ◽  
Electric Field ◽  
Applied Electric Field ◽  
Fluid Motion ◽  
Analytical Form ◽  
Internal Resistance ◽  
Creeping Flow ◽  
Fluid Sphere ◽  
Droplet Deformation ◽  
Alternating Electric Field

In this study we considered mass transfer in a binary system comprising a stationary fluid dielectric sphere embedded into an immiscible dielectric liquid under the influence of an alternating electric field. Fluid sphere is assumed to be solvent-saturated so that an internal resistance to mass transfer can be neglected. Mass flux is directed from a fluid sphere to a host medium, and the applied electric field causes a creeping flow around the sphere. Droplet deformation under the influence of the electric field is neglected. The problem is solved in the approximations of a thin concentration boundary layer and finite dilution of a solute in the solvent. The thermodynamic parameters of a system are assumed constant. The nonlinear partial parabolic differential equation of convective diffusion is solved by means of a generalized similarity transformation, and the solution is obtained in a closed analytical form for all frequencies of the applied electric field. The rates of mass transfer are calculated for both directions of fluid motion — from the poles to equator and from the equator to the poles. Numerical calculations show essential (by a factor of 2–3) enhancement of the rate of mass transfer in water droplet–benzonitrile and droplet of carbontetrachloride–glycerol systems under the influence of electric field for a stagnant droplet. The asymptotics of the obtained solutions are discussed.

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