Micro-to nano-scale characterisation of polyamide structures of the SW30HR RO membrane using advanced electron microscopy and stain tracers

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Title: Micro-to nano-scale characterisation of polyamide structures of the SW30HR RO membrane using advanced electron microscopy and stain tracers
Authors: Klosowski, MM
McGilvery, CM
Li, Y
Abellan, P
Ramasse, Q
Cabral, JT
Livingston, AG
Porter, AE
Item Type: Journal Article
Abstract: The development of new reverse osmosis (RO) membranes with enhanced performance would benefit from a detailed knowledge of the membrane structures which participate in the filtration process. Here, we examined the hierarchical structures of the polyamide (PA) active layer of the SW30HR RO membrane. Scanning electron microscopy combined with focused ion beam milling (FIB-SEM) was used to obtain the 3-D reconstructions of membrane morphology with 5 nm cross-sectional resolution (comparable with the resolution of low magnification TEM imaging in 2D) and 30 nm slice thickness. The complex folding of the PA layer was examined in 3 dimensions, enabling the quantification of key structural properties of the PA layer, including the local thickness, volume, surface area and their derivatives. The PA layer was found to exhibit a much higher and convoluted surface area than that estimated via atomic force microscopy (AFM). Cross-sectional scanning transmission electron microscopy (STEM) was used to observe the distribution of a tracer stain under various conditions. The behaviour of stain in dry and wet PA indicated that the permeation pathways have a dynamic nature and are activated by water. High resolution STEM imaging of the stained PA nano-films revealed the presence of <1 nm pore-like structures with a size compatible with free volume estimations by positron annihilation lifetime spectroscopy (PALS). This study presents a comprehensive map of the active PA layer across different length scales (from micro- to sub-nanometre) and mechanistic insight into their role in the permeation process.
Issue Date: 31-Jul-2016
Date of Acceptance: 30-Jul-2016
URI: http://hdl.handle.net/10044/1/42766
DOI: http://dx.doi.org/10.1016/j.memsci.2016.07.063
ISSN: 1873-3123
Publisher: Elsevier
Start Page: 465
End Page: 476
Journal / Book Title: Journal of Membrane Science
Volume: 520
Copyright Statement: © 2016, Elsevier Ltd. All rights reserved. This manuscript is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International http://creativecommons.org/licenses/by-nc-nd/4.0/
Sponsor/Funder: BP International Limited
Funder's Grant Number: Order No. 75195/ICAM10 (IC)
Keywords: Science & Technology
Technology
Physical Sciences
Engineering, Chemical
Polymer Science
Engineering
RO membrane
Characterisation
FIB-SEM
STEM
Permeation
REVERSE-OSMOSIS MEMBRANES
FILM COMPOSITE MEMBRANES
WASTE-WATER RECLAMATION
ATOMIC-FORCE MICROSCOPY
SEAWATER DESALINATION
INTERFACIAL POLYMERIZATION
NANOFILTRATION MEMBRANES
NANOCOMPOSITE MEMBRANES
ACTIVE LAYERS
NF MEMBRANES
Chemical Engineering
03 Chemical Sciences
09 Engineering
Publication Status: Accepted
Appears in Collections:Faculty of Engineering
Mechanical Engineering
Materials
Chemical Engineering
Faculty of Natural Sciences



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