Separation of water-alcohol mixtures using carbon nanotubes under an electric field

Carbon nanotubes (CNTs) are a promising candidate for separation membranes because of their ability to transport substances at very high flow rates. However, there is a tradeoff between achieving a high selectivity using small pore sizes and the reduction of water flux. Here, using molecular dynamic...

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Bibliographic Details
Published in:Physical chemistry chemical physics : PCCP 2019-07, Vol.21 (28), p.15431-15438
Main Authors: Winarto, Yamamoto, Eiji, Yasuoka, Kenji
Format: Article
Language:English
Subjects:
Carbon nanotubes
Electric fields
Filtration
Flow velocity
Graphene
Methanol
Molecular dynamics
Penetration
Selectivity
Separation
Water chemistry
Water purification
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Summary:Carbon nanotubes (CNTs) are a promising candidate for separation membranes because of their ability to transport substances at very high flow rates. However, there is a tradeoff between achieving a high selectivity using small pore sizes and the reduction of water flux. Here, using molecular dynamics simulations, we report that CNTs can effectively separate water-methanol mixtures under an electric field. Without an electric field and under piston pressure, both water and methanol flow through a CNT, resulting in no separation effect. In contrast, under an electric field and high piston pressure, CNTs allow selective water permeation while rejecting the permeation of methanol molecules. This separation effect is caused by the ordered structures of water molecules in the CNT. A high filtering effect is observed under the conditions of high methanol concentration in the solution or even with large-diameter CNTs up to 3.39 nm. As long as the ordered structure of water in the CNTs can be maintained, the strong filtering effect can be maintained. Under piston pressures and electric fields, CNTs with diameter up to 3.39 nm allow water to flow while rejecting methanol.
ISSN:1463-9076
1463-9084
DOI:10.1039/c9cp01799b