Ionization behavior of nanoporous polyamide membranes
© 2020 National Academy of Sciences. All rights reserved. Escalating global water scarcity necessitates high-performance desalination membranes, for which fundamental understanding of structure–property–performance relationships is required. In this study, we comprehensively assess the ionization be...
| Main Authors: | , , , , , , |
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| Format: | Article |
| Language: | English |
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Proceedings of the National Academy of Sciences
2021
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| Online Access: | https://hdl.handle.net/1721.1/133409 |
| _version_ | 1811085091227566080 |
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| author | Ritt, Cody L Werber, Jay R Wang, Mengyi Yang, Zhongyue Zhao, Yumeng Kulik, Heather J Elimelech, Menachem |
| author_facet | Ritt, Cody L Werber, Jay R Wang, Mengyi Yang, Zhongyue Zhao, Yumeng Kulik, Heather J Elimelech, Menachem |
| author_sort | Ritt, Cody L |
| collection | MIT |
| description | © 2020 National Academy of Sciences. All rights reserved. Escalating global water scarcity necessitates high-performance desalination membranes, for which fundamental understanding of structure–property–performance relationships is required. In this study, we comprehensively assess the ionization behavior of nanoporous polyamide selective layers in state-of-the-art nanofiltration (NF) membranes. In these films, residual carboxylic acids and amines influence permeability and selectivity by imparting hydrophilicity and ionizable moieties that can exclude coions. We utilize layered interfacial polymerization to prepare physically and chemically similar selective layers of controlled thickness. We then demonstrate location-dependent ionization of carboxyl groups in NF polyamide films. Specifically, only surface carboxyl groups ionize under neutral pH, whereas interior carboxyl ionization requires pH >9. Conversely, amine ionization behaves invariably across the film. First-principles simulations reveal that the low permittivity of nanoconfined water drives the anomalous carboxyl ionization behavior. Furthermore, we report that interior carboxyl ionization could improve the water–salt permselectivity of NF membranes over fourfold, suggesting that interior charge density could be an important tool to enhance the selectivity of polyamide membranes. Our findings highlight the influence of nanoconfinement on membrane transport properties and provide enhanced fundamental understanding of ionization that could enable novel membrane design. |
| first_indexed | 2024-09-23T13:02:45Z |
| format | Article |
| id | mit-1721.1/133409 |
| institution | Massachusetts Institute of Technology |
| language | English |
| last_indexed | 2024-09-23T13:02:45Z |
| publishDate | 2021 |
| publisher | Proceedings of the National Academy of Sciences |
| record_format | dspace |
| spelling | mit-1721.1/1334092021-10-28T03:57:32Z Ionization behavior of nanoporous polyamide membranes Ritt, Cody L Werber, Jay R Wang, Mengyi Yang, Zhongyue Zhao, Yumeng Kulik, Heather J Elimelech, Menachem © 2020 National Academy of Sciences. All rights reserved. Escalating global water scarcity necessitates high-performance desalination membranes, for which fundamental understanding of structure–property–performance relationships is required. In this study, we comprehensively assess the ionization behavior of nanoporous polyamide selective layers in state-of-the-art nanofiltration (NF) membranes. In these films, residual carboxylic acids and amines influence permeability and selectivity by imparting hydrophilicity and ionizable moieties that can exclude coions. We utilize layered interfacial polymerization to prepare physically and chemically similar selective layers of controlled thickness. We then demonstrate location-dependent ionization of carboxyl groups in NF polyamide films. Specifically, only surface carboxyl groups ionize under neutral pH, whereas interior carboxyl ionization requires pH >9. Conversely, amine ionization behaves invariably across the film. First-principles simulations reveal that the low permittivity of nanoconfined water drives the anomalous carboxyl ionization behavior. Furthermore, we report that interior carboxyl ionization could improve the water–salt permselectivity of NF membranes over fourfold, suggesting that interior charge density could be an important tool to enhance the selectivity of polyamide membranes. Our findings highlight the influence of nanoconfinement on membrane transport properties and provide enhanced fundamental understanding of ionization that could enable novel membrane design. 2021-10-27T19:52:42Z 2021-10-27T19:52:42Z 2020 2021-06-11T16:41:22Z Article http://purl.org/eprint/type/JournalArticle https://hdl.handle.net/1721.1/133409 en 10.1073/pnas.2008421117 Proceedings of the National Academy of Sciences of the United States of America Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use. application/pdf Proceedings of the National Academy of Sciences PNAS |
| spellingShingle | Ritt, Cody L Werber, Jay R Wang, Mengyi Yang, Zhongyue Zhao, Yumeng Kulik, Heather J Elimelech, Menachem Ionization behavior of nanoporous polyamide membranes |
| title | Ionization behavior of nanoporous polyamide membranes |
| title_full | Ionization behavior of nanoporous polyamide membranes |
| title_fullStr | Ionization behavior of nanoporous polyamide membranes |
| title_full_unstemmed | Ionization behavior of nanoporous polyamide membranes |
| title_short | Ionization behavior of nanoporous polyamide membranes |
| title_sort | ionization behavior of nanoporous polyamide membranes |
| url | https://hdl.handle.net/1721.1/133409 |
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