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Adsorption Isotherm and Aggregate Properties of Fluorosurfactants on Alumina Measured by 19F NMR
KTH, Tidigare Institutioner                               , Kemi.
KTH, Tidigare Institutioner                               , Kemi.ORCID-id: 0000-0002-0231-3970
KTH, Tidigare Institutioner                               , Kemi.
KTH, Tidigare Institutioner                               , Kemi.
2002 (Engelska)Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 18, nr 21, s. 8096-8101Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The adsorption and self-assembly of ammonium perfluorooctanoate (APFO) at surfaces of porous alumina immersed in solution at pH similar to 4 have been studied using F-19 NMR. From the intensity of the APFO NMR signals, the amount of adsorbed surfactant, and thereby the adsorption isotherm, was determined. The adsorption isotherm indicates that APFO forms bilayers on alumina. This result is supported by finding the CF3 signal of adsorbed APFO shifted upfield compared to the signal in aqueous solution with an amount that corresponds to a change from aqueous to fluorocarbon environment. Additionally, faster transverse relaxation of the fluorine nuclei adjacent to the head group compared to that of the CF3 group adds a further argument for the formation of a bilayer. The exchange pattern of surfactants between the adsorbed layer and the aqueous bulk was studied through the CF3 group F-19 signals and their time-averaged behavior. Inside the pores of the alumina particles, the exchange time was found to be fast (much less than1 ms) between adsorbed and dissolved APFO. The presented NMR method to determine the adsorption isotherm could be a powerful new tool when studying systems of mixed surfactants, since the adsorbed amount of chemically different surfactants and their formation in aggregates would become separately quantifiable. The method is readily applicable to any NMR nuclei and thereby to many adsorption problems.

Ort, förlag, år, upplaga, sidor
2002. Vol. 18, nr 21, s. 8096-8101
Nyckelord [en]
Adsorption; Aggregates; Alumina; Ammonium compounds; Dissolution; Fluorocarbons; Isotherms; Nuclear magnetic resonance; pH effects; Porous materials; Self assembly; Solutions
Nationell ämneskategori
Kemi
Identifikatorer
URN: urn:nbn:se:kth:diva-5686DOI: 10.1021/la026014vISI: 000178589700050Scopus ID: 2-s2.0-0037109683OAI: oai:DiVA.org:kth-5686DiVA, id: diva2:10133
Anmärkning
QC 20100826Tillgänglig från: 2006-05-10 Skapad: 2006-05-10 Senast uppdaterad: 2020-03-10Bibliografiskt granskad
Ingår i avhandling
1. Molecular Association Studied by NMR Spectroscopy
Öppna denna publikation i ny flik eller fönster >>Molecular Association Studied by NMR Spectroscopy
2006 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This Thesis presents studies of molecular association in aqueous solution and at the liquid/solid interface. The investigated molecular systems range from self-aggregating surfactants to hydration water in contact with micelles or individual molecules. In most studies, combinations of various NMR methods were applied. These vary from simple chemical shift and intensity measurements to more elaborate self-diffusion and intermolecular cross-relaxation experiments.

Non-ideal mixed micelles of fluorinated and hydrogenated surfactants were studied by an experimental procedure that allows an analysis in terms of micellar structure, using a minimal number of initial assumptions. Quantitative conclusions about micro-phase separation within mixed micelles were obtained within the framework of the regular solution theory. Additionally, NMR was introduced and developed as a powerful method for studying adsorption of surfactants at solid interfaces. Adsorption isotherms for pure and mixed surfactant systems and non-ideal mixing behavior of fluorinated and hydrogenated surfactants at solid surfaces were quantified. Fluorosurfactant-protein association was investigated using the methods described.

Intermolecular cross-relaxation rates between solute and solvent molecules were recorded at several different magnetic fields. The results reveal strong frequency dependence for both small molecules and micelles. This finding demonstrates that intermolecular cross-relaxation is not solely controlled by fast local motions, but also by long-range translational dynamics. Data analysis in terms of recently developed relaxation models provides information about the hydrophobic hydration and micellar structure.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH, 2006. s. 52
Serie
Trita-FYK ; 0602
Nyckelord
NMR, spin relaxation, self-diffusion, intermolecular cross-relaxation, chemical shift, fluorinated surfactants, hydrogenated surfactant, micelle, non-ideal mixing, adsorption, hydration, surfactant-protein association
Nationell ämneskategori
Fysikalisk kemi
Identifikatorer
urn:nbn:se:kth:diva-3947 (URN)91-7178-345 8 (ISBN)
Disputation
2006-05-19, F3, Lindstedtsv. 26, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20100914Tillgänglig från: 2006-05-10 Skapad: 2006-05-10 Senast uppdaterad: 2010-09-14Bibliografiskt granskad

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