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PreprintCC BYChemRxiv

Elucidating permselectivity mechanisms in polyamide membranes through controlled chlorination and hydrolysis

  • Mohammad Allouzi1,2,3,4
  • Sasha R. Neefe3,4,5,2
  • Nathanael S. Schwindt5,2
  • Austin Herbel5,2
  • Thomas Brooks6,2
  • Erin E. Dunphy5,2
  • Devin L. Shaffer7,8
  • Michael R. Shirts5,2
  • Michael F. Toney5,2,6,9
  • Anthony P. Straub1,2,3,4,6
9 affiliations
  1. 1Department of Civil, Environmental and Architectural Engineering
  2. 2University of Colorado Boulder
  3. 3Department of Mechanical and Process Engineering
  4. 4ETH Zürich
  5. 5Department of Chemical and Biological Engineering
  6. 6Materials Science and Engineering Program
  7. 7Department of Civil and Environmental Engineering
  8. 8University of Houston
  9. 9Renewable and Sustainable Energy Institute
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Abstract

Polyamide membranes are widely used in freshwater production because of their high water permeance and water–salt selectivity, but emerging applications require tunable permselectivity. We investigate the structure–property–performance relationships governing membrane behavior by modifying permselectivity through sequential chlorination and alkaline treatment. Chemical, structural, and transport properties are examined using X-ray characterization, free-energy barrier analysis, and molecular dynamics simulations. We find chlorine–alkaline modification more than doubles water permeance through hydrolysis, which enhances swelling, increases water–membrane interactions, and promotes water transport. Despite the resulting looser structure, the hydrolyzed membrane maintains water–salt selectivity because of entropic barriers to salt transport, likely caused by the presence of bulky chlorine groups on the aromatic rings. These findings identify distinct mechanisms by which chemical modification alters water and salt transport, challenge the prevailing view that swelling is detrimental to selectivity, and provide new design insights for tuning polyamide membrane performance.

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Cite

BibTeXRIS
BibTeX
@misc{allouzi2026elucidating,
  title = {{Elucidating permselectivity mechanisms in polyamide membranes through controlled chlorination and hydrolysis}},
  author = {Mohammad Allouzi and Sasha R. Neefe and Nathanael S. Schwindt and Austin Herbel and Thomas Brooks and Erin E. Dunphy and Devin L. Shaffer and Michael R. Shirts and Michael F. Toney and Anthony P. Straub},
  howpublished = {ChemRxiv},
  year = {2026},
  month = oct,
  doi = {10.26434/chemrxiv.15010980/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010980/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Elucidating permselectivity mechanisms in polyamide membranes through controlled chlorination and hydrolysis
AU  - Mohammad Allouzi
AU  - Sasha R. Neefe
AU  - Nathanael S. Schwindt
AU  - Austin Herbel
AU  - Thomas Brooks
AU  - Erin E. Dunphy
AU  - Devin L. Shaffer
AU  - Michael R. Shirts
AU  - Michael F. Toney
AU  - Anthony P. Straub
PY  - 2026
DA  - 2026/10/23
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15010980/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010980/v1
AB  - Polyamide membranes are widely used in freshwater production because of their high water permeance and water–salt selectivity, but emerging applications require tunable permselectivity. We investigate the structure–property–performance relationships governing membrane behavior by modifying permselectivity through sequential chlorination and alkaline treatment. Chemical, structural, and transport properties are examined using X-ray characterization, free-energy barrier analysis, and molecular dynamics simulations. We find chlorine–alkaline modification more than doubles water permeance through hydrolysis, which enhances swelling, increases water–membrane interactions, and promotes water transport. Despite the resulting looser structure, the hydrolyzed membrane maintains water–salt selectivity because of entropic barriers to salt transport, likely caused by the presence of bulky chlorine groups on the aromatic rings. These findings identify distinct mechanisms by which chemical modification alters water and salt transport, challenge the prevailing view that swelling is detrimental to selectivity, and provide new design insights for tuning polyamide membrane performance.
ER  -