Change search
ReferencesLink to record
Permanent link

Direct link
Competitive ligand exchange on akaganéite surfaces enriches bulk chloride loadings
Umeå University, Faculty of Science and Technology, Department of Chemistry.
Umeå University, Faculty of Science and Technology, Department of Chemistry.
2012 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 376, no 1, 331-3 p.Article in journal (Refereed) Published
Abstract [en]

Akaganéite (β-FeOOH) is a nanosized iron oxyhydroxide mineral with a hollandite structure containing chloride ions in 0.4×0.4nm wide channels. Proton and chloride co-sorption into these channels induces variations in bulk O-H stretching vibrations, crystallographic lattice size, and thermal stability, as a result of hydrogen bond formation with chloride ions. In this work, we show that chloride ions bound to akaganéite surfaces can be dislodged into aqueous solutions by competitive adsorption of foreign ions and then transferred alongside co-sorbed protons into the akaganéite bulk. Fourier transform infrared and X-ray photoelectron spectroscopic measurements show that HClO(4), H(2)SO(4), and benzoic acid, and thereby, many other anions of various charge-to-size ratios can all effectively contribute to this phenomenon. This linked surface-bulk reactivity should be accounted for in mixed anion systems containing akaganéite-like materials.

Place, publisher, year, edition, pages
Elsevier, 2012. Vol. 376, no 1, 331-3 p.
National Category
Chemical Sciences
URN: urn:nbn:se:umu:diva-54395DOI: 10.1016/j.jcis.2012.03.006PubMedID: 22459024OAI: diva2:523680
Available from: 2012-04-25 Created: 2012-04-25 Last updated: 2013-05-13Bibliographically approved
In thesis
1. Surface and Bulk Reactivity of Iron Oxyhydroxides: A Molecular Perspective
Open this publication in new window or tab >>Surface and Bulk Reactivity of Iron Oxyhydroxides: A Molecular Perspective
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Iron oxyhydroxide (FeOOH) mineral plays an important role in a variety of atmospheric, terrestrial and technological settings. Molecular resolution of reactions involving these minerals is thereby required to develop a fundamental understanding of their contributions in processes taking place in the atmosphere, Earth’s upper crust as well as the hydrosphere. This study resolves interactions involving four different types of synthetic FeOOH particles with distinct and well-defined surfaces, namely lath- and rod-shaped lepidocrocite (γ), goethite (α) and akaganéite (β). The surface and bulk reactivities of these particles are controlled by their distinct structures. When exposed to ambient atmospheric or aqueous conditions their surfaces are populated with different types of (hydr)oxo functional groups acting as reaction centers. These sites consist of hydroxyl groups that can be singly- (≡FeOH, -OH), doubly- (≡Fe2OH, μ-OH), or triply-coordinated (≡Fe3OH, μ3-OH) with underlying Fe atoms. Moreover, these sites exhibit different types, densities, distributions, as well as hydrogen bonding patterns on different crystal planes for each mineral. Knowledge of the types and distributions of hydroxyl groups on minerals with different surface structures is fundamental for building a molecular-scale understanding of processes taking place at FeOOH particle surfaces.

In this thesis, Fourier transform infrared (FTIR) spectroscopy was used to resolve the interactions between (hydr)oxo groups of FeOOH particles with (in)organic acids, salts, water vapor as well as carbon dioxide. The focus on such compounds was justified by their importance in natural environments. This thesis is based on 9 articles and manuscripts that can be found in the appendices.

FTIR spectroscopic signatures of hydroxyl groups in the bulk of well crystallized FeOOH minerals were characterized for structural differences and thermal stabilities. Those of akaganéite were particularly resolved for the variable bond strength of bulk hydroxyls induced by the incorporation of HCl through nanostructured channels at the terminations of the particles. FTIR bands of hydroxyl groups at all particle surfaces were monitored for responses to thermal gradients and proton loadings, providing experimental validation to previous theoretical accounts on surface site reactivity. This site reactivity was resolved further in the fluoride (F-) and phosphate (PO43-) ions adsorption study to follow the site selectivity for ligand-exchange reactions. These efforts showed that singly-coordinated groups are the primary adsorption centers for ligands, doubly-coordinated groups can only be exchanged at substantially higher ligand loadings, while triply coordinated groups are largely resilient to any ligand-exchange reaction.

These findings helped consolidate fundamental knowledge that can be used in investigating sorption processes involving atmospherically and geochemically important gases. The latter parts of this thesis were therefore focused on water vapor and carbon dioxide interactions with these FeOOH particles. These efforts showed how surface structure and speciation affect sorption loadings and configurations, as well as how water diffused into and through the akaganéite bulk. Hydrogen bonding is one of the most important forms of interactions between gas phase and minerals. It plays a crucial role in the formation of thin water films and in stabilizing surface (bi)carbonate species. The affinity of surface hydroxyl groups for water and carbon dioxide is strongly dependent on their abilities to form hydrogen bonds. These are controlled by coordination number and site accessibility/steric constraints. In agreement with the aforementioned ligand-exchange studies, surfaces dominated by singly coordinated groups have stronger ability to accumulate water layers than the ones terminated by groups of larger coordination number. Collectively, these efforts consolidate further the concept for structure-controlled reactivities in iron oxyhydroxides, and pave the way for new studies along such lines.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2013. 83 p.
Iron oxyhydroxide, adsorption, water, carbon dioxide, FTIR, molecular resolution
National Category
Physical Chemistry Inorganic Chemistry Geosciences, Multidisciplinary
urn:nbn:se:umu:diva-70289 (URN)978-91-7459-669-4 (printed) (ISBN)
Public defence
2013-06-05, KBC-huset, KB3B1, Umeå Universitet, Umeå, 13:00 (English)
Available from: 2013-05-13 Created: 2013-05-13 Last updated: 2013-05-15Bibliographically approved

Open Access in DiVA

No full text

Other links

Publisher's full textPubMed

Search in DiVA

By author/editor
Song, XiaoweiBoily, Jean-François
By organisation
Department of Chemistry
In the same journal
Journal of Colloid and Interface Science
Chemical Sciences

Search outside of DiVA

GoogleGoogle Scholar
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Altmetric score

Total: 265 hits
ReferencesLink to record
Permanent link

Direct link