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Diffusivity of Mono- and Divalent Salts and Water in Polyelectrolyte Desalination Membranes

Cite this: J. Phys. Chem. B 2018, 122, 33, 8098–8110
Publication Date (Web):August 14, 2018
Copyright © 2018 American Chemical Society

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    Abstract Image

    The dynamics of ions and solvent molecules in polyelectrolyte desalination membranes is key to water purification technologies in which selective transport of the different components is desired. Recent experimental and our computational results have shown that nontrivial mechanisms underlie the transport properties of salt ions and water in charged polymer membranes. Explicitly, in polymer electrolytes, we found a reversal in the salt concentration dependence of the mobilities of Na+, Cl salt ions and water molecules when compared with aqueous solutions. Motivated by such results, in this study, we have used atomistic molecular dynamics simulations to probe whether the mechanisms deduced in our earlier work apply to other salt systems and to mixtures of salts. Specifically, we report results for the ion diffusivities in aqueous KCl, MgCl2, and a 1:1 mixture of NaCl and MgCl2 salt solutions at different concentrations (ranging from 0.06 to 1 M) and investigate, at the molecular level, the mechanisms underlying the behaviors of salt and water transport properties. Our results show that diffusion of salt ions and water in charged polymer membranes are in general influenced by their association with polymer charge groups and ion pairing effects. Divalent ions are more strongly coupled with the polymeric ionic groups than monovalent salt ions and exhibit diffusivity trends that are distinct relative to monovalent salts. Further, we demonstrate that the mobilities of water molecules are influenced by coordination of water with polymer charge groups and their ion pairing tendencies and also exhibit distinct trends in monovalent and divalent salt solutions.

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    The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.jpcb.8b05979.

    • Mean square displacement of K+, Na+, and Cl ions; the number of condensed, paired, and free of K+ and Na+ ions; local dielectric constant of water molecules as a function of distance from sulfur for polymer backbone at 0.04 and 1 M MgCl2 concentration; cluster distribution of water molecules in polymer electrolyte membrane; discussion of the results for diffusion coefficients of Mg2+, Na+, and Cl ions in the 1:1 mixture of NaCl and MgCl2, and the impact salt concentration on diffusion of sulfur atoms of polymer backbone (PDF)

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    Cited By

    This article is cited by 11 publications.

    1. Thomas G. Mason, Benny D. Freeman, Ekaterina I. Izgorodina. Influencing Molecular Dynamics Simulations of Ion-Exchange Membranes by Considering Comonomer Propagation. Macromolecules 2023, 56 (3) , 1263-1277.
    2. Michael Beckinghausen, Andrew J. Spakowitz. Interplay of Polymer Structure, Solvent Ordering, and Charge Fluctuations in Polyelectrolyte Solution Thermodynamics. Macromolecules 2023, 56 (1) , 136-152.
    3. Weiguang Zhu, Yanming Zhang, Junhua Shen, Yunfeng Shi, Mingxin Li, Jie Lian. Large-Area Uniaxial-Oriented Growth of Free-Standing Thin Films at the Liquid–Air Interface with Millimeter-Sized Grains. ACS Nano 2022, 16 (8) , 11802-11814.
    4. Changyong Zhang, Jinxing Ma, Lei Wu, Jingyi Sun, Li Wang, Tianyu Li, T. David Waite. Flow Electrode Capacitive Deionization (FCDI): Recent Developments, Environmental Applications, and Future Perspectives. Environmental Science & Technology 2021, 55 (8) , 4243-4267.
    5. Junjun Ma, Jinxing Ma, Changyong Zhang, Jingke Song, Richard N. Collins, T. David Waite. Water Recovery Rate in Short-Circuited Closed-Cycle Operation of Flow-Electrode Capacitive Deionization (FCDI). Environmental Science & Technology 2019, 53 (23) , 13859-13867.
    6. Ritwick Kali, Scott T. Milner. Simulations predict water uptake and transport in nanostructured ion exchange membranes. Journal of Membrane Science 2023, 687 , 122060.
    7. Akhilesh Paspureddi, Zidan Zhang, Venkat Ganesan, Mukul M. Sharma, Lynn E. Katz. Mechanism of monovalent and divalent ion mobility in Nafion membrane: An atomistic simulation study. The Journal of Chemical Physics 2023, 158 (21)
    8. David Kitto, Jovan Kamcev. Manning condensation in ion exchange membranes: A review on ion partitioning and diffusion models. Journal of Polymer Science 2022, 60 (21) , 2929-2973.
    9. Fatemeh Aghili, Ali Asghar Ghoreyshi, Bart Van der Bruggen, Ahmad Rahimpour. A highly permeable UiO-66-NH2/polyethyleneimine thin-film nanocomposite membrane for recovery of valuable metal ions from brackish water. Process Safety and Environmental Protection 2021, 151 , 244-256.
    10. Shuwen Yue, Athanassios Z. Panagiotopoulos. Dynamic properties of aqueous electrolyte solutions from non-polarisable, polarisable, and scaled-charge models. Molecular Physics 2019, 117 (23-24) , 3538-3549.
    11. Dipak Aryal, Venkat Ganesan. Impact of cross-linking of polymers on transport of salt and water in polyelectrolyte membranes: A mesoscopic simulation study. The Journal of Chemical Physics 2018, 149 (22)

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