Electric mass transport of sodium chloride through cation-exchange membrane MK-40 in dilute sodium chloride solutions: A rotating membrane disk study

Заболоцкий, В. И.; Sharafan, M. V.; Шельдешов, Н. В.; Lovtsov, E. G.

doi:10.1134/s1023193508020018

Cited by 16 publications

(7 citation statements)

References 10 publications

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“…Simultaneously with recording the voltammetric characteristics of the tested membranes, we measured the transport numbers by the Hittorf method. The procedure of experiments with RMD is described in detail elsewhere [6,[18][19][20]. The studies were carried out in a sodium chloride solution with the concentration of 0.01 M at 25°С.…”

Section: Methodsmentioning

confidence: 99%

“…Then, according to Eqs. (8) and (12), for SCR, we obtain β close to 1 and the effective rate constant of water dissociation becomes equal to the corresponding rate constant for the slow deprotonation of ternary amino groups (18) According to [13], we assume that the rate constant of the rate determining stage k 2 depends on the elec tric field strength (19) where k 20 is the rate constant for Е = 0. Then, with allowance made for Eq.…”

Section: н о H Ohmentioning

confidence: 99%

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Transfer of electrolyte ions and water dissociation in anion-exchange membranes under intense current conditions

et al. 2012

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Polarization characteristics of electromembrane systems (EMS) based on the Russian commer cial heterogeneous membranes MA 40 and MA 41, the anion exchange heterogeneous membrane AMH (Mega, Czech Republic), and the modified membrane MA 40M are studied by the method of rotating mem brane disk in dilute sodium chloride solutions. The effective transport numbers of ions are found; the partial voltammetric characteristics (VAC) with respect to chloride and hydroxyl ions are measured; the limiting cur rent densities are calculated as a function of the membrane disk rotation rate. In terms of the theory of the overlimiting state of EMS, based on experimental VAC and the dependences of the effective transport num bers on the current density, the following internal parameters of systems under study are calculated: the space charge and electric field strength distribution over the diffusion layer and the membrane. It is shown that water dissociation can be virtually completely eliminated by substituting chemically stable quaternary ammo nium groups inert with respect to water dissociation in the surface layer of a heterogeneous anion exchange membrane MA 40 for the active ternary and secondary functional amino groups. The maximum electric field strength values at the membrane/solution interface, which were found in the framework of the theory of over limiting state, turned out to be close for all anion exchange membranes studied, namely, (7-9) × 10 6 V/cm. This suggests that it is the nature of ionogenic groups in the surface layer rather than the field effect that plays the decisive role in the membrane ability to accelerate the water dissociation reaction. It is proved experimen tally that in highly intense current modes of the electrodialysis process, the thermal hydrolysis of quaternary ammonium bases occurs in strongly basic MA 41 and AMH membranes by the Hofmann reaction to form ternary amino groups catalytically active in water dissociation reaction. Based on the concept on the catalytic mechanism of water dissociation, the fraction of ternary amino groups formed by thermal hydrolysis in the surface layer (the space charge region) of monopolar anion exchange membranes MA 41 and AMH is assessed quantitatively as 0.7 and 6.5%, respectively.

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Section: Methodsmentioning

confidence: 99%

Section: н о H Ohmentioning

confidence: 99%

Transfer of electrolyte ions and water dissociation in anion-exchange membranes under intense current conditions

et al. 2012

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“…The limiting current values calculated using Equation ( 17) are also much larger than the experimentally observed values. 17), 2-calculated using Equation (19) for BM-a-10, 3-calculated using Equation (19) for BM-a-30, 4-experimental data for BM-a-10, 5-experimental data for BM-a-30, 6calculation using the modified Levich's equation [86].…”

Section: The Nature Of the Limiting Current On Bilayer Membranementioning

confidence: 99%

“…Dependence of the limiting current density on the diffusion boundary layer thickness. 1-calculated using Equation (17), 2-calculated using Equation(19) for BM-a-10, 3-calculated using Equation(19) for BM-a-30, 4-experimental data for BM-a-10, 5-experimental data for BM-a-30, 6-calculation using the modified Levich's equation[86].…”

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Water Splitting and Transport of Ions in Electromembrane System with Bilayer Ion-Exchange Membrane

et al. 2020

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Bilayer ion-exchange membranes are mainly used for separating single and multiply charged ions. It is well known that in membranes in which the layers have different charges of the ionogenic groups of the matrix, the limiting current decreases, and the water splitting reaction accelerates in comparison with monolayer (isotropic) ion-exchange membranes. We study samples of bilayer ion-exchange membranes with very thin cation-exchange layers deposited on an anion-exchange membrane-substrate in this work. It was revealed that in bilayer membranes, the limiting current’s value is determined by the properties of a thin surface film (modifying layer). A linear regularity of the dependence of the non-equilibrium effective rate constant of the water-splitting reaction on the resistance of the bipolar region, which is valid for both bilayer and bipolar membranes, has been revealed. It is shown that the introduction of the catalyst significantly reduces the water-splitting voltage, but reduces the selectivity of the membrane. It is possible to regulate the fluxes of salt ions and water splitting products (hydrogen and hydroxyl ions) by changing the current density. Such an ability makes it possible to conduct a controlled process of desalting electrolytes with simultaneous pH adjustment.

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“…(2). We obtain the equation for the current density carried across the membrane by hydrogen and hydroxyl ions formed in the dissociation of water molecules in the space charge region (11) After taking the logarithm of this equation, we obtain The experimental data necessary for the model cal culations of rate constants and other parameters of the reaction of water molecule dissociation in the space charge region, particularly, voltammetric characteris tics (VAC) and the effective transfer numbers for ions, were obtained in our earlier study [23] carried out by means of a setup with a RMD (rotating membrane disk) according to the procedure described in detail in [24]. The rotation rate of the membrane disk varied from 100 to 500 rpm.…”

Section: Theorymentioning

confidence: 99%

The dissociation rate of water molecules in systems with cation- and anion-exchange membranes

2012

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Within the framework of the mathematical model of Nernst-Planck-Poisson, an attempt is undertaken to theoretically describe the electrodiffusion of ions in the system diffusion layer/monopolar ion exchange membrane, which is accompanied by dissociation of water molecules. The formulas for estimating the current density transferred through a monopolar membrane by hydrogen or hydroxyl ions formed in dis sociation of water in the space charge region are derived. The rate constants and other parameters of disso ciation of water molecules in the space charge region of monopolar membranes under conditions of stabili zation of the diffusion layer thickness are calculated. Their comparative analysis with the similar characteris tics of bipolar membranes is carried out. For the phosphoric acid heterogeneous membrane MK 41 in which the polarization conditions in the current density range under study are not so severe and the reaction layer is not being depleted as in the bipolar membrane MB 3 (contains the same phosphoric acid groups), it is shown that only single charged phosphoric acid groups are involved in the water dissociation reaction. For MK 41, the calculated constants of the heterolytic reaction of water molecule dissociation are lower than for the het erogeneous membrane MA 40 containing ternary and quaternary amino groups. It is confirmed that the nature of ionogenic groups in membranes is a factor that determines the rate of water dissociation in systems with ion exchange membranes.

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Electric mass transport of sodium chloride through cation-exchange membrane MK-40 in dilute sodium chloride solutions: A rotating membrane disk study

Cited by 16 publications

References 10 publications

Transfer of electrolyte ions and water dissociation in anion-exchange membranes under intense current conditions

Transfer of electrolyte ions and water dissociation in anion-exchange membranes under intense current conditions

Water Splitting and Transport of Ions in Electromembrane System with Bilayer Ion-Exchange Membrane

The dissociation rate of water molecules in systems with cation- and anion-exchange membranes

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