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Adsorption of Trimethyl Phosphate on Maghemite, Hematite and Goethite Nanoparticles
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Department of Materials Chemistry, The Ångstrom Laboratory, Uppsala University.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Department of Engineering Sciences, The Ångstrom Laboratory, Uppsala University.
2011 (English)In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 115, no 32, 8948-8959 p.Article in journal (Refereed) Published
Abstract [en]

Adsorption of trimethyl phosphate (TMP) on well-characterized hematite, maghemite and goethite nanoparticles was studied by in situ DRIFT spectroscopy as a model system for adsorption of organophosphorous (OP) compounds on iron minerals. The iron minerals were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), specific surface area and pore size distribution. The minerals were found to consist of stoichimetrically and morphologically well-defined maghemite, hematite and goethite nanoparticles. Analysis of in situ diffuse reflectance Fourier transform (DRIFT) spectroscopy show that TMP bonds mainly to Lewis acid Fe sites through the O phosphoryl atom (-P=O-Fe) on hematite and maghemite. On goethite most TMP molecules bond to Brønstedt acid surface OH groups and form hydrogen bonded surface complexes. The vibrational mode analysis and uptake kinetics suggest two main reasons for the observed trend of reactivity towards TMP (hematite > maghemite > goethite): (i) Larger number of accessible Lewis acid adsorption sites on hematite, (ii) stronger interaction between the Lewis acid Fe sites and the phosphoryl O atom on TMP for hematite and maghemite compared to goethite with concomitant formation of surface coordinated TMP and dimethyl phosphate intermediates. As a result, on the oxides a surface oxidation pathways dominates during the initial adsorption, which results in the formation of surface methoxy and formate. In contrast, on goethite a slower hydrolysis pathway is identified which eventually yields phosphoric acid. The observed trends of the reactivity and analysis of the corresponding surface structure and particle morphology suggest an intimate relation between the surface chemistry of exposed crystal facets on the iron minerals. These results are important to understand OP surface chemistry on iron minerals.

Place, publisher, year, edition, pages
American Chemical Society , 2011. Vol. 115, no 32, 8948-8959 p.
Keyword [en]
Trimethyl phosphate, hematite, maghemite, goethite, nanoparticles, adsorption
National Category
Physical Chemistry
Identifiers
URN: urn:nbn:se:umu:diva-45372DOI: 10.1021/jp201065wPubMedID: 21711003OAI: oai:DiVA.org:umu-45372DiVA: diva2:429333
Note
Publication Date (Web): June 28, 2011Available from: 2011-07-04 Created: 2011-07-04 Last updated: 2017-12-11Bibliographically approved
In thesis
1. Surface reactions of Organophosphorus compounds on Iron Oxides
Open this publication in new window or tab >>Surface reactions of Organophosphorus compounds on Iron Oxides
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2012. 99 p.
National Category
Chemical Sciences
Identifiers
urn:nbn:se:umu:diva-53958 (URN)978-91-7459-409-6 (ISBN)
Public defence
2012-04-27, KBC-huset, Lilla hörsalen, KB3A9, Umeå universitet, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2012-04-13 Created: 2012-04-10 Last updated: 2012-04-23Bibliographically approved

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