On the permselectivity of di- and mono-valent cations: Influence of applied current density and ionic species concentration

Dong, Ting; Yao, Jun; Wang, Yi; Luo, Tao; Han, Le

doi:10.1016/j.desal.2020.114521

Cited by 25 publications

(15 citation statements)

References 51 publications

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“…This effect is traditionally associated with the presence of the diffusion boundary layer, where decreasing transport of doubly charged ions is ascribed to its lower diffusivity in the solution. The authors of [48] investigated the Selemion CMV membrane permselectivity in the mixture of Na + /Mg 2+ and discovered that increasing the current density (below the limiting condition) resulted in decreased transport number of Mg 2+ and the permselectivity over Na + . The limiting permeability coefficient in the mixed Ca 2+ /H + solution equals 0.13, so the H + flux should exceed Ca 2+ one in 8 times.…”

Section: Heterogeneous Membranesmentioning

confidence: 99%

Permselectivity of Cation Exchange Membranes Modified by Polyaniline

Фалина

Loza

et al. 2021

Membranes

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This work discusses the applicability of polyaniline-modified cation exchange membranes for the separation of monovalent/divalent cations by electrodialysis. A novel method of membrane modification directly in the electrodialysis unit is used to prepare permselective membranes. Complex characterization of the membranes before and after modification allows revealing the influence of membrane matrix on the modification efficiency. The characterization of the membranes includes determination of the diffusion permeability, specific conductivity and current–voltage curves in HCl, NaCl and CaCl2 solutions, as well as transport-structural parameters of the extended three-wire model. The characterization results are used to predict the influence of the modification on membrane permselectivity. The competitive mass transfer of singly and doubly charged cations in the electrodialysis process is investigated in underlimiting and overlimiting currents. Electrodialysis desalination of a solution containing Na+/Ca2+ or H+/Ca2+ cations shows that the modification leads to an increase in membrane permselectivity to single-charged cations due to the repulsion of Ca2+ ions from the positively charged membrane surface. The permselectivity of the polyaniline-modified perfluorinated membrane to H+ in the mixture of H+/Ca2+ cations is observed in all current regimes.

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Section: Heterogeneous Membranesmentioning

confidence: 99%

Permselectivity of Cation Exchange Membranes Modified by Polyaniline

Фалина

Loza

et al. 2021

Membranes

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show abstract

“…where 𝑡 " # is the transport number of counter-ion 𝑖 in the membrane phase, 𝐶 " stands for the molarity of counter-ion 𝑖 (mol m -3 ) at the membrane surface on the desalination side, and 𝑧 " is the valence of the counter-ion. As is generally known, the transport selectivity of counter-ions measured in ED depends on the experimental conditions [10], which include but are not limited to the current density, the equivalence ratio of counter-ions in the solutions [43], the ionic strength of solutions, the mixing conditions (with or without flow) and the temperature. If one aims at characterizing the counter-ion transport selectivity of the membrane itself, it is necessary to choose carefully the experimental conditions to screen out the influence from other factors as much as possible.…”

Section: The Ionic Conductivity Experimental Approach For the Counter-ion Selectivity Determinationmentioning

confidence: 99%

Combining Manning's theory and the ionic conductivity experimental approach to characterize selectivity of cation exchange membranes

Luo

Zhong

et al. 2021

Journal of Membrane Science

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The transport selectivity of different cations through cation exchange membranes (CEMs) could be estimated with the partition coefficient (𝐾 ! " ) and the cation mobility ratio in the membrane (𝑢 # " 𝑢 # ! ⁄ ), which in turn can be related to corresponding membrane conductivity and dimensional swelling degree data [Journal of Membrane Science, 2020, 597, 117645]. This method has been validated in two hydrocarbon-based CEMs, and the obtained K + /Na + selectivity equals to the one obtained with conventional electrodialysis (ED) method. However, the K + /Na + selectivity of perfluorosulfonic acid (PFSA) membranes, and the bi-/monovalent cation (Mg 2+ /Na + ) selectivity of all three types of CEMs estimated with this ionic conductivity experimental approach deviate noticeably from corresponding values obtained with ED. In this work, it is proved that this deviation is mostly due to the simplification of cation activity coefficients in the membrane. Here, the cation activity coefficients in three types of CEMs are calculated according to Manning`s counter-ion condensation model. In this model, the Manning parameter (𝜉) characterizing the dimensionless linear charge density is determined by the

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Section:  the Selectivity Of Cem To Other Cations Over Nh4 + -N Decr...mentioning

confidence: 99%

“…(i) transport in the channel including the boundary layer [128], (ii) partition (adsorption) in the IEM, and (iii) transport through the IEM [129]. In the channel and boundary, the ion transport is affected by their diffusion coefficient [128]. In the partition step, the selectivity between different ions is affected by their hydration size, hydration energy, and concentration [129].…”

Section:  the Selectivity Of Cem To Other Cations Over Nh4 + -N Decr...mentioning

On the permselectivity of di- and mono-valent cations: Influence of applied current density and ionic species concentration

Cited by 25 publications

References 51 publications

Permselectivity of Cation Exchange Membranes Modified by Polyaniline

Permselectivity of Cation Exchange Membranes Modified by Polyaniline

Combining Manning's theory and the ionic conductivity experimental approach to characterize selectivity of cation exchange membranes

Electrodialysis (ED) based processes for resource recovery

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