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  • Perspective
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A multiscale perspective for understanding transport mechanisms in desalination and ion-selective membranes

Nature Water volume 4, pages 120–137 (2026)Cite this article

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Abstract

Membranes with nanometre- and subnanometre-scale pores play a vital role in aqueous separations across applications ranging from desalination and wastewater reuse to resource recovery and green hydrogen production. Despite their widespread use, the molecular-level mechanisms that govern water and solute transport in these membranes remain inadequately understood. In this Perspective, we examine advances in membrane and nanochannel transport across macroscopic, microscopic and molecular scales to establish a unified mechanistic framework. We begin by analysing current macroscopic models, highlighting their simplifying assumptions and inherent limitations. We then explore insights from nano- and ångström-scale fluidic studies, revealing unconventional transport phenomena that are not captured by classical continuum theories. Next, we describe how molecular simulations offer atomistic resolution of transport processes, providing mechanistic insight into how water and ions traverse the dynamic, heterogeneous porous networks of real-world, state-of-the-art polymer membranes. Finally, we discuss how to integrate these molecular, microscopic and macroscopic scales to advance theoretical understanding and inform the rational design of next-generation membranes. We conclude by identifying key knowledge gaps and outlining emerging opportunities to bridge scales through advanced characterization techniques and multiscale modelling.

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Fig. 1: Selective separation membranes for various applications in the water and energy sectors.
Fig. 2: Macroscopic transport phenomena and models.
Fig. 3: Unconventional phenomena under extreme confinement in nanofluidic systems.
Fig. 4: MD simulations reveal transport mechanisms in membranes.
Fig. 5: Bridging the gap between macroscopic transport models and molecular-level mechanisms.

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Acknowledgements

This Perspective is based on discussions from the ‘Interdisciplinary Perspectives on Transport Mechanisms in Membranes and Nanopores’ workshop held at the Rice Global Paris Center on 17–18 March 2025. We gratefully acknowledge support from the Rice WaTER Institute and the Rice Center for Membrane Excellence (RiCeME) at Rice University, which provided funding to attend the symposium.

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Authors and Affiliations

  1. Department of Civil and Environmental Engineering, Rice University, Houston, TX, USA

    Hanqing Fan, Bezawit A. Getachew, Qilin Li & Menachem Elimelech

  2. Rice Center for Membrane Excellence, Rice University, Houston, TX, USA

    Hanqing Fan, Bezawit A. Getachew, Qilin Li & Menachem Elimelech

  3. Department of Chemical and Environmental Engineering, Yale University, New Haven, CT, USA

    Makenna Parkinson

  4. Laboratory of Advanced Separations, Ecole Polytechnique Fédérale de Lausanne, Sion, Switzerland

    Kumar Varoon Agrawal

  5. Institut Européen des Membranes, Adaptive Supramolecular Nanosystems Group, ENSCM-CNRS, UMR5635, University of Montpellier, Montpellier, France

    Mihail Barboiu

  6. Laboratoire de Physique de l’Ecole Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, Paris, France

    Lydéric Bocquet

  7. Department of Chemical and Biomolecular Engineering, Rice University, Houston, TX, USA

    Qilin Li & Menachem Elimelech

  8. Rice WaTER Institute, Rice University, Houston, TX, USA

    Qilin Li & Menachem Elimelech

  9. Department of Mechanical Engineering, University of Wisconsin-Madison, Madison, WI, USA

    Ying Li

  10. Department of Civil and Environmental Engineering, Vanderbilt University, Nashville, TN, USA

    Shihong Lin

  11. Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA

    Shihong Lin

  12. Pritzker School of Molecular Engineering, University of Chicago, Chicago, IL, USA

    Chong Liu

  13. Materials Science Division, Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, Livermore, CA, USA

    Aleksandr Noy

  14. School of Natural Sciences, University of California Merced, Merced, CA, USA

    Aleksandr Noy

  15. Department of Physics and Astronomy, School of Natural Sciences, The University of Manchester, Manchester, UK

    Boya Radha

  16. National Graphene Institute, The University of Manchester, Manchester, UK

    Boya Radha

  17. Photon Science Institute, The University of Manchester, Manchester, UK

    Boya Radha

  18. Forschungszentrum Jülich GmbH, JCNS-1/ICS-1: Neutron Scattering and Soft Matter, Jülich, Germany

    Dietmar Schwahn

  19. Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) – UMR 6226, Rennes, France

    Anthony Szymczyk

Authors
  1. Hanqing Fan
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  2. Makenna Parkinson
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  3. Kumar Varoon Agrawal
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  15. Menachem Elimelech
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Contributions

All authors contributed to the discussions, drafting and analysis of the Perspective. M.E. and H.F. edited the final version of the manuscript. M.P. and H.F. prepared the illustrations.

Corresponding author

Correspondence to Menachem Elimelech.

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Nature Water thanks Kecheng Guan, Wooyoung Shim and Liping Wen for their contribution to the peer review of this work.

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Fan, H., Parkinson, M., Agrawal, K.V. et al. A multiscale perspective for understanding transport mechanisms in desalination and ion-selective membranes. Nat Water 4, 120–137 (2026). https://doi.org/10.1038/s44221-026-00585-1

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