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Explorations of combined nonsolvent and thermally induced phase separation (N-TIPS) method for fabricating novel PVDF hollow fiber membranes using mixed diluents

Explorations of combined nonsolvent and thermally induced phase separation (N-TIPS) method for fabricating novel PVDF hollow fiber membranes using mixed diluents
Explorations of combined nonsolvent and thermally induced phase separation (N-TIPS) method for fabricating novel PVDF hollow fiber membranes using mixed diluents

The combination of nonsolvent and thermally induced phase separation (N-TIPS) method has shown promising ability in harvesting the features from the nonsolvent induced phase separation (NIPS) and thermally induced phase separation (TIPS) processes for developing membranes with a tailorable surface pore structure. However, previous approaches have been subjected to either the formation of macrovoids or dense layer due to the dominant NIPS effect, or required sophisticated instruments and operation skills. In this work, a facile attempt was carried out to fabricate novel polyvinylidene fluoride (PVDF) hollow fiber membranes with tunable surface pore structure while maintaining the narrow pore size distribution and mechanical strength. A modified N-TIPS method was developed by using mixed diluents: dimethyl phthalate (DMP) as a water-immiscible poor solvent for TIPS process, and triethyl phosphate (TEP) as a water-miscible neutral solvent to bridge the TIPS and NIPS processes. To further control the membrane formation especially near the membrane surface, an amphiphilic additive Pluronic F127 was also added as a potential pore-former and surface hydrophilicity modifier. PVDF hollow fiber membranes with a highly porous structure and a narrow pore size distribution were successfully synthesized by using TEP and Pluronic F127 in the N-TIPS process. The mechanism of N-TIPS process was thoroughly discussed. The water permeability of the membrane increased significantly from 389 ± 30–922 ± 36 L m–2 h–1 bar–1, with overall porosity improved from 50 ± 2.2–69 ± 2.9%, and a mean pore size of ~ 0.18 µm. The membranes produced by N-TIPS method also exhibited a good tensile strength ranging from 5.6 ± 0.1–6.5 ± 0.2 MPa, showing a great potential for a broad range of water applications after further modifications. Besides, the formation of piezoelectric β-phase crystals of the PVDF membrane was observed when the mixed diluent was used, which sheds light on the possible applications of resultant membranes in electrochemical separation process.

Combined nonsolvent and thermally induced phase separation, Hollow fiber membrane, Pluronic F127, Polyvinylidene fluoride
0376-7388
210-222
Zhao, Jie
3be79b67-2e5f-4fc1-a6db-539f6a04aece
Chong, Jeng Yi
2f9ead94-86f2-4e20-9e67-75f10759555b
Shi, Lei
b092e01b-e66b-48d8-becf-15618b5e5425
Wang, Rong
1f58a88c-01ff-4941-857a-427ee8c8aa62
Zhao, Jie
3be79b67-2e5f-4fc1-a6db-539f6a04aece
Chong, Jeng Yi
2f9ead94-86f2-4e20-9e67-75f10759555b
Shi, Lei
b092e01b-e66b-48d8-becf-15618b5e5425
Wang, Rong
1f58a88c-01ff-4941-857a-427ee8c8aa62

Zhao, Jie, Chong, Jeng Yi, Shi, Lei and Wang, Rong (2019) Explorations of combined nonsolvent and thermally induced phase separation (N-TIPS) method for fabricating novel PVDF hollow fiber membranes using mixed diluents. Journal of Membrane Science, 572, 210-222. (doi:10.1016/j.memsci.2018.11.015).

Record type: Article

Abstract

The combination of nonsolvent and thermally induced phase separation (N-TIPS) method has shown promising ability in harvesting the features from the nonsolvent induced phase separation (NIPS) and thermally induced phase separation (TIPS) processes for developing membranes with a tailorable surface pore structure. However, previous approaches have been subjected to either the formation of macrovoids or dense layer due to the dominant NIPS effect, or required sophisticated instruments and operation skills. In this work, a facile attempt was carried out to fabricate novel polyvinylidene fluoride (PVDF) hollow fiber membranes with tunable surface pore structure while maintaining the narrow pore size distribution and mechanical strength. A modified N-TIPS method was developed by using mixed diluents: dimethyl phthalate (DMP) as a water-immiscible poor solvent for TIPS process, and triethyl phosphate (TEP) as a water-miscible neutral solvent to bridge the TIPS and NIPS processes. To further control the membrane formation especially near the membrane surface, an amphiphilic additive Pluronic F127 was also added as a potential pore-former and surface hydrophilicity modifier. PVDF hollow fiber membranes with a highly porous structure and a narrow pore size distribution were successfully synthesized by using TEP and Pluronic F127 in the N-TIPS process. The mechanism of N-TIPS process was thoroughly discussed. The water permeability of the membrane increased significantly from 389 ± 30–922 ± 36 L m–2 h–1 bar–1, with overall porosity improved from 50 ± 2.2–69 ± 2.9%, and a mean pore size of ~ 0.18 µm. The membranes produced by N-TIPS method also exhibited a good tensile strength ranging from 5.6 ± 0.1–6.5 ± 0.2 MPa, showing a great potential for a broad range of water applications after further modifications. Besides, the formation of piezoelectric β-phase crystals of the PVDF membrane was observed when the mixed diluent was used, which sheds light on the possible applications of resultant membranes in electrochemical separation process.

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More information

Published date: 15 February 2019
Additional Information: Funding Information: We acknowledge funding support from the Singapore Economic Development Board to the Singapore Membrane Technology Centre. Special thanks are due to Dr. Loh Chun Heng, Dr. Shanshan Zhao, Dr. Chang Liu and Dr. Yuqing Lin for their valuable suggestions and help. Publisher Copyright: © 2018 Elsevier B.V.
Keywords: Combined nonsolvent and thermally induced phase separation, Hollow fiber membrane, Pluronic F127, Polyvinylidene fluoride

Identifiers

Local EPrints ID: 486376
URI: http://eprints.soton.ac.uk/id/eprint/486376
ISSN: 0376-7388
PURE UUID: 3d5c86ce-232f-4160-a042-b8bc85c5e66e
ORCID for Jeng Yi Chong: ORCID iD orcid.org/0000-0002-0593-6313

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Date deposited: 18 Jan 2024 19:26
Last modified: 06 Jun 2024 02:20

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Contributors

Author: Jie Zhao
Author: Jeng Yi Chong ORCID iD
Author: Lei Shi
Author: Rong Wang

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