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Structure-motion-performance relationship of flux-enhanced reverse osmosis (RO) membranes composed of aromatic polyamide thin films.
Environ Sci Technol 2001; 35(21):4334-40ES

Abstract

The present paper explores the role of dimethyl sulfoxide (DMSO) used as an additive to modify the morphological as well as the molecular nature of aromatic polyamide during the formation of thin-film-composite (TFC) membranes. In addition, it elucidates the mechanism of enhancing the reverse osmosis (RO) permeation of the resulting membranes in proportion to the addition of DMSO. Morphological studies by atomic force microscopy (AFM) observed that as the concentration of DMSO increased, the surface roughness and the surface area of the aromatic polyamide TFC membranes became higher and larger, compared to FT-30 membrane for which DMSO was not added during interfacial reaction. Such morphological changes were brought about from fluctuating interface through reducing the immiscibility between aqueous/organic phases by DMSO and provided more opportunities to have contact with water molecules on the surface, participating in the enhancement of the water permeability. Chemical composition studies by X-ray photoelectron spectroscopy (XPS) revealed that there was a considerable increase of the cross-linked amide linkages relative to the linear pendant carboxylic acid groups in the TFC membranes of more DMSO addition. The increase of such amide linkages as hydrogen bonding sites facilitated the diffusion of water molecules through the thin films and played a favorable role in elevating water flux without considerable loss of salt rejection. Relaxation and motion analyses by 1H solid-state nuclear magnetic resonance (NMR) spectroscopy also confirmed the XPS revelation on the basis of measurements of the spin-lattice relaxation time in the rotating frame, T1rho, and determination of the correlation time, tau(c), for the aromatic polyamides forming thin films. The trend of longer tau(c)'s with the increase of DMSO concentration reflected the thin-film aromatic polyamides of less locally mobile chains, accompanied by the higher degree of cross-linking and, hence, the greater number of amide groups. The combined results of AFM, XPS, and solid-state NMR provided a robust explanation for the mechanism of flux enhancement of the aromatic polyamide TFC membranes with the addition of DMSO, which would contribute to not only a fundamental understanding of the process but also an advanced designing of the so-called "tailor-fit" TFC membranes.

Authors+Show Affiliations

Hyperstructured Organic Materials Research Center, and School of Materials Science and Engineering, Seoul National University, Kwanak-ku, Korea. sykwak-p@gong.snu.ac.krNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

11718351

Citation

Kwak, S Y., et al. "Structure-motion-performance Relationship of Flux-enhanced Reverse Osmosis (RO) Membranes Composed of Aromatic Polyamide Thin Films." Environmental Science & Technology, vol. 35, no. 21, 2001, pp. 4334-40.
Kwak SY, Jung SG, Kim SH. Structure-motion-performance relationship of flux-enhanced reverse osmosis (RO) membranes composed of aromatic polyamide thin films. Environ Sci Technol. 2001;35(21):4334-40.
Kwak, S. Y., Jung, S. G., & Kim, S. H. (2001). Structure-motion-performance relationship of flux-enhanced reverse osmosis (RO) membranes composed of aromatic polyamide thin films. Environmental Science & Technology, 35(21), pp. 4334-40.
Kwak SY, Jung SG, Kim SH. Structure-motion-performance Relationship of Flux-enhanced Reverse Osmosis (RO) Membranes Composed of Aromatic Polyamide Thin Films. Environ Sci Technol. 2001 Nov 1;35(21):4334-40. PubMed PMID: 11718351.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Structure-motion-performance relationship of flux-enhanced reverse osmosis (RO) membranes composed of aromatic polyamide thin films. AU - Kwak,S Y, AU - Jung,S G, AU - Kim,S H, PY - 2001/11/23/pubmed PY - 2002/4/19/medline PY - 2001/11/23/entrez SP - 4334 EP - 40 JF - Environmental science & technology JO - Environ. Sci. Technol. VL - 35 IS - 21 N2 - The present paper explores the role of dimethyl sulfoxide (DMSO) used as an additive to modify the morphological as well as the molecular nature of aromatic polyamide during the formation of thin-film-composite (TFC) membranes. In addition, it elucidates the mechanism of enhancing the reverse osmosis (RO) permeation of the resulting membranes in proportion to the addition of DMSO. Morphological studies by atomic force microscopy (AFM) observed that as the concentration of DMSO increased, the surface roughness and the surface area of the aromatic polyamide TFC membranes became higher and larger, compared to FT-30 membrane for which DMSO was not added during interfacial reaction. Such morphological changes were brought about from fluctuating interface through reducing the immiscibility between aqueous/organic phases by DMSO and provided more opportunities to have contact with water molecules on the surface, participating in the enhancement of the water permeability. Chemical composition studies by X-ray photoelectron spectroscopy (XPS) revealed that there was a considerable increase of the cross-linked amide linkages relative to the linear pendant carboxylic acid groups in the TFC membranes of more DMSO addition. The increase of such amide linkages as hydrogen bonding sites facilitated the diffusion of water molecules through the thin films and played a favorable role in elevating water flux without considerable loss of salt rejection. Relaxation and motion analyses by 1H solid-state nuclear magnetic resonance (NMR) spectroscopy also confirmed the XPS revelation on the basis of measurements of the spin-lattice relaxation time in the rotating frame, T1rho, and determination of the correlation time, tau(c), for the aromatic polyamides forming thin films. The trend of longer tau(c)'s with the increase of DMSO concentration reflected the thin-film aromatic polyamides of less locally mobile chains, accompanied by the higher degree of cross-linking and, hence, the greater number of amide groups. The combined results of AFM, XPS, and solid-state NMR provided a robust explanation for the mechanism of flux enhancement of the aromatic polyamide TFC membranes with the addition of DMSO, which would contribute to not only a fundamental understanding of the process but also an advanced designing of the so-called "tailor-fit" TFC membranes. SN - 0013-936X UR - https://www.unboundmedicine.com/medline/citation/11718351/Structure_motion_performance_relationship_of_flux_enhanced_reverse_osmosis__RO__membranes_composed_of_aromatic_polyamide_thin_films_ L2 - https://dx.doi.org/10.1021/es010630g DB - PRIME DP - Unbound Medicine ER -