Identity of Fluoride and Phosphate-Binding Sites at FeOOH Surfaces
Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Iron oxyhydroxides are of widespread occurrence in nature and play essential roles in both environmental as well as industrial processes. Due to their high reactivity, these minerals can act as sinks and/or transformation centers for a variety of inorganic and organic ions. These reactions are often mediated by various surface hydroxyl groups that are in turn singly-, doubly- or triply-coordinated with respect to underlying Fe atoms. In an effort to follow the reactivity of these different groups, attenuated total reflectance (ATR) - Fourier transform infrared (FTIR) spectroscopy was used to monitor adsorption reactions of on iron oxyhydroxide minerals.
This work was specifically focused on synthetic submicron-sized lepidocrocite and goethite particles reacted to aqueous solutions of sodium fluoride and sodium phosphate. Langmuir-Freundlich adsorption isotherms were calibrated on adsorption data at various pH values to provide independent clues to the maximum sorption density achieved by these ions. When compared to theoretical site densities, these values suggested that although singly-coordinated groups are by far the more reactive groups on all surfaces, doubly-coordinated groups could be substituted by fluoride ions. FTIR measurements of dry mineral samples equilibrated with fluoride and phosphate confirmed these findings and also showed that triply-coordinated groups cannot be exchanged.
: goethite, lepidocrocite, FTIR, surface, adsorption, isotherm, modeling
Place, publisher, year, edition, pages
2012. , 37 p.
IdentifiersURN: urn:nbn:se:umu:diva-56738OAI: oai:DiVA.org:umu-56738DiVA: diva2:537205
Master’s program in Chemistry
UppsokPhysics, Chemistry, Mathematics