Desalination-of water by vapor-phase transport through hydrophobic nanopores
We propose a new approach to desalination of water whereby a pressure difference across a vapor-trapping nanopore induces selective transport of water by isothermal evaporation and condensation across the pore. Transport of water through a nanopore with saline water on one side and pure water on the...
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| Format: | Article |
| Language: | en_US |
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American Institute of Physics (AIP)
2013
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| Online Access: | http://hdl.handle.net/1721.1/78853 https://orcid.org/0000-0003-0588-9286 |
| _version_ | 1826214375924432896 |
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| author | Lee, Jongho Karnik, Rohit |
| author2 | Massachusetts Institute of Technology. Department of Mechanical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Mechanical Engineering Lee, Jongho Karnik, Rohit |
| author_sort | Lee, Jongho |
| collection | MIT |
| description | We propose a new approach to desalination of water whereby a pressure difference across a vapor-trapping nanopore induces selective transport of water by isothermal evaporation and condensation across the pore. Transport of water through a nanopore with saline water on one side and pure water on the other side under a pressure difference was theoretically analyzed under the rarefied gas assumption using a probabilistic framework that accounts for diffuse scattering from the pore walls as well as reflection from the menisci. The analysis revealed that in addition to salinity, temperature, and pressure difference, the nanopore aspect ratio and the probability of condensation of a water molecule incident on a meniscus from the vapor phase, known as the condensation coefficient, are key determinants of flux. The effect of condensation coefficient on mass flux becomes critical when the aspect ratio is small. However, the mass flux becomes independent of the condensation coefficient as the pore aspect ratio increases, converging to the Knudsen flux for long nanopores. For design of a nanopore membrane that can trap vapor, a minimum aspect ratio is derived for which coalescence of the two interfaces on either side of the nanopore remains energetically unfavorable. Based on this design criterion, the analysis suggests that mass flux in the range of 20–70 g/m[superscript 2] s may be feasible if the system is operated at temperatures in the range of 30–50 °C. The proposed approach further decouples transport properties from material properties of the membrane, which opens the possibility of engineering membranes with appropriate materials that may lead to reverse osmosis membranes with improved flux, better selectivity, and high chlorine resistance. |
| first_indexed | 2024-09-23T16:04:25Z |
| format | Article |
| id | mit-1721.1/78853 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T16:04:25Z |
| publishDate | 2013 |
| publisher | American Institute of Physics (AIP) |
| record_format | dspace |
| spelling | mit-1721.1/788532022-10-02T06:08:34Z Desalination-of water by vapor-phase transport through hydrophobic nanopores Lee, Jongho Karnik, Rohit Massachusetts Institute of Technology. Department of Mechanical Engineering Lee, Jongho Karnik, Rohit We propose a new approach to desalination of water whereby a pressure difference across a vapor-trapping nanopore induces selective transport of water by isothermal evaporation and condensation across the pore. Transport of water through a nanopore with saline water on one side and pure water on the other side under a pressure difference was theoretically analyzed under the rarefied gas assumption using a probabilistic framework that accounts for diffuse scattering from the pore walls as well as reflection from the menisci. The analysis revealed that in addition to salinity, temperature, and pressure difference, the nanopore aspect ratio and the probability of condensation of a water molecule incident on a meniscus from the vapor phase, known as the condensation coefficient, are key determinants of flux. The effect of condensation coefficient on mass flux becomes critical when the aspect ratio is small. However, the mass flux becomes independent of the condensation coefficient as the pore aspect ratio increases, converging to the Knudsen flux for long nanopores. For design of a nanopore membrane that can trap vapor, a minimum aspect ratio is derived for which coalescence of the two interfaces on either side of the nanopore remains energetically unfavorable. Based on this design criterion, the analysis suggests that mass flux in the range of 20–70 g/m[superscript 2] s may be feasible if the system is operated at temperatures in the range of 30–50 °C. The proposed approach further decouples transport properties from material properties of the membrane, which opens the possibility of engineering membranes with appropriate materials that may lead to reverse osmosis membranes with improved flux, better selectivity, and high chlorine resistance. 2013-05-09T19:23:00Z 2013-05-09T19:23:00Z 2010-08 2009-08 Article http://purl.org/eprint/type/JournalArticle 0021-8979 1089-7550 http://hdl.handle.net/1721.1/78853 Lee, Jongho, and Rohit Karnik. “Desalination of Water by Vapor-phase Transport through Hydrophobic Nanopores.” Journal of Applied Physics 108.4 (2010): 044315. ©2010 American Institute of Physics https://orcid.org/0000-0003-0588-9286 en_US http://dx.doi.org/10.1063/1.3419751 Journal of Applied Physics 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 American Institute of Physics (AIP) MIT web domain |
| spellingShingle | Lee, Jongho Karnik, Rohit Desalination-of water by vapor-phase transport through hydrophobic nanopores |
| title | Desalination-of water by vapor-phase transport through hydrophobic nanopores |
| title_full | Desalination-of water by vapor-phase transport through hydrophobic nanopores |
| title_fullStr | Desalination-of water by vapor-phase transport through hydrophobic nanopores |
| title_full_unstemmed | Desalination-of water by vapor-phase transport through hydrophobic nanopores |
| title_short | Desalination-of water by vapor-phase transport through hydrophobic nanopores |
| title_sort | desalination of water by vapor phase transport through hydrophobic nanopores |
| url | http://hdl.handle.net/1721.1/78853 https://orcid.org/0000-0003-0588-9286 |
| work_keys_str_mv | AT leejongho desalinationofwaterbyvaporphasetransportthroughhydrophobicnanopores AT karnikrohit desalinationofwaterbyvaporphasetransportthroughhydrophobicnanopores |