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Competition between Hydration Shell and Ordered Water Chain Induces Thickness-Dependent Desalination Performance in Carbon Nanotube Membrane
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Chengyuan Wang
Membranes, Volume: 13, Issue: 5, Start page: 525
Swansea University Author:
Chengyuan Wang
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DOI (Published version): 10.3390/membranes13050525
Abstract
Exploring new reverse osmosis (RO) membranes that break the permeability-selectivitytrade-off rule is the ultimate goal in seawater desalination. Both nanoporous monolayer graphene(NPG) and carbon nanotube (CNT) channels have been proposed to be promising candidates forthis purpose. From the perspec...
| Published in: | Membranes |
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| ISSN: | 2077-0375 |
| Published: |
MDPI AG
2023
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| Online Access: |
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| URI: | https://cronfa.swan.ac.uk/Record/cronfa65153 |
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| Abstract: |
Exploring new reverse osmosis (RO) membranes that break the permeability-selectivitytrade-off rule is the ultimate goal in seawater desalination. Both nanoporous monolayer graphene(NPG) and carbon nanotube (CNT) channels have been proposed to be promising candidates forthis purpose. From the perspective of membrane thickness, both NPG and CNT can be classifiedinto the same category, as NPG is equivalent to the thinnest CNT. While NPG has the advantage ofa high water flux rate and CNT is excellent at salt rejection performance, a transition is expectedin practical devices when the channel thickness increases from NPG to infinite-sized CNTs. Byemploying molecular dynamics (MD) simulations, we find that as the thickness of CNT increases,the water flux diminishes but the ion rejection rate increases. These transitions lead to optimaldesalination performance around the cross-over size. Further molecular analysis reveals that thisthickness effect originates from the formation of two hydration shells and their competition withthe ordered water chain structure. With the increase in CNT thickness, the competition-dominatedion path through CNT is further narrowed. Once above this cross-over size, the highly confinedion path remains unchanged. Thus, the number of reduced water molecules also tends to stabilize,which explains the saturation of the salt rejection rate with the increasing CNT thickness. Our resultsoffer insights into the molecular mechanisms of the thickness-dependent desalination performancein a one-dimensional nanochannel, which can provide useful guidance for the future design andoptimization of new desalination membranes |
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| Keywords: |
thickness effect; carbon nanotube; nanoporous monolayer graphene; ion dehydration; desalination performance |
| College: |
Faculty of Science and Engineering |
| Funders: |
This work is supported by the National Natural Science Foundation of China (Grant No. 12102151, 12072134, and 12102422) and the Postdoctoral Science Foundation of Jiangsu Province (Grant No. 2021K113B). |
| Issue: |
5 |
| Start Page: |
525 |