Scaling resistance by fluoro-treatments: the importance of wetting states

Liu, L., Charlton, L., Song, Y. , Li, T., Li, X., Yin, H. and He, T. (2022) Scaling resistance by fluoro-treatments: the importance of wetting states. Journal of Materials Chemistry A, 10(6), pp. 3058-3068. (doi: 10.1039/D1TA07695G)

[img] Text
263407.pdf - Accepted Version

[img] Text
263407Suppl.pdf - Supplemental Material



Membrane distillation is a thermally driven separation process using hydrophobic, porous membranes. Among various problems faced by membrane distillation, scaling remains an unresolved challenge in treating streams of high salinity. Development of superhydrophobic membranes has been a central approach to address this, with CF4 plasma treatment or fluorochemical modification commonly used. However, contradictory observations often occur where some membranes are scaling resistant, but others are not. For the first time, we examine this issue by systematic comparison of the impacts of commonly used fluoro-treatments on scaling resistance. A state-of-the-art surface patterned micro-pillared poly (vinylidene fluoride) membrane (MP-PVDF) was used and both CF4 plasma and fluorosilane reagents were utilized to enhance membrane hydrophobicity. The resulting membranes CF4-MP-PVDF (by CF4 plasma) and FAS-MP-PVDF (via fluorosilane) were systematically characterized and their anti-scaling performance was evaluated using a supersaturated CaSO4 solution. Although both modified membranes showed an increased water contact angle, reduced sliding angle and surface energy, CF4-MP-PVDF demonstrated better scaling resistance than FAS-MP-PVDF. Conventional thermodynamic nucleation models dictate similar nucleation energy barriers for both, in discrepancy to experimental observations. Instead, the wetting states and hydraulic surface slippage were identified as the determinant factors. The CF4-MP-PVDF in a suspended-wetting state with slippage resisted scaling robustly, while FAS-MP-PVDF in an unstable transition state and pristine MP-PVDF in a pinned state were suspectable to scaling. These results unravel, for the first time, the fundamental mechanism behind the differences in scaling resistance by CF4 plasma treatment and fluorosilane surface modification.

Item Type:Articles
Additional Information:The research was partially supported by National Natural Science Foundation of China (No. 21978315, 52011530031, 21764011), Royal Society Newton Advanced Fellowship (No. NA170113) EPSRC SoftMech (EP/N014642/1), and CAS International Collaboration (No. GJHZ2080). We also thank the frame work research consortium BRICS for financial support (RFBR No. 18-58- 80031, NSFC No. 51861145313, DST IPN/7864, NRT No.116020, CNPq/BRICS-STI-2-442229/2017–8).
Glasgow Author(s) Enlighten ID:Charlton, Ms Laura and He, Mr Tao and Yin, Professor Huabing and Song, Dr Yanqing
Authors: Liu, L., Charlton, L., Song, Y., Li, T., Li, X., Yin, H., and He, T.
College/School:College of Science and Engineering > School of Engineering
College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:Journal of Materials Chemistry A
Publisher:Royal Society of Chemistry
ISSN (Online):2050-7496
Published Online:07 January 2022
Copyright Holders:Copyright © 2022 Royal Society of Chemistry
First Published:First published in Journal of Materials Chemistry A 10(6): 3058-3068
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher

University Staff: Request a correction | Enlighten Editors: Update this record

Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
300180Nanotechnology for clean water: High throughput, In-situ analysis of biofouling in membrane separation processesHuabing YinThe Royal Society (ROYSOC)NA170113ENG - Biomedical Engineering
172141EPSRC Centre for Multiscale soft tissue mechanics with application to heart & cancerRaymond OgdenEngineering and Physical Sciences Research Council (EPSRC)EP/N014642/1M&S - Mathematics