Assessing the Reactive Surface Area of Phlogopite during Acid Dissolution: An Atomic Force Microscopy, X-ray Photoelectron Spectroscopy, and Low Energy Electron Diffraction Study

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dc.contributor.authorRufe, Ericen
dc.contributor.committeechairHochella, Michael F. Jr.en
dc.contributor.committeememberRimstidt, J. Donalden
dc.contributor.committeememberBodnar, Robert J.en
dc.contributor.departmentGeological Sciencesen
dc.date.accessioned2014-03-14T20:34:03Zen
dc.date.adate2001-05-11en
dc.date.available2014-03-14T20:34:03Zen
dc.date.issued2000-01-14en
dc.date.rdate2004-05-11en
dc.date.sdate2001-04-23en
dc.description.abstractThe behavior during dissolution of edge and basal surfaces of the mica phlogopite were examined using in situ atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) in an attempt to characterize the reactive surface area during dissolution. Mica minerals are the ideal material for this study because they offer a high degree of structural anisotropy. Therefore surfaces with different structures are easily identified. Dissolution is shown to proceed preferentially by removal of material from {hk0} edges. Dissolution rates were calculated by measuring the volume of material removed from etch pits, and normalizing to either the "reactive" surface area of {hk0} edges exposed at pit walls, or to a total "BET-equivalent" surface area. Rates normalized to total surface area are in the range of dissolution rates reported in the literature. Edge surface normalized rates are about 100 times faster. Long-term in situ AFM observations of phlogopite dissolution reveal that exposed (001) surfaces also display a distinct reactivity, though it operates on a different time scale. The top layer is shown to expand between 39 and 63 hours in contact with pH 2 HCl solution. Subsequent LEED analysis shows that the (001) surface becomes amorphous upon reacting with pH 2 HCl. Compositional characterization of the phlogopite after reaction shows that for pitted phlogopite surfaces, dissolution is characterized by leaching of octahedral cations and polymerization of the silica-enriched residual layer. No chemical changes or polymerization are observed for freshly cleaved unpitted phlogopite after reaction with pH 2 HCl for 24 hours. This suggests a gallery access mechanism is facilitated by edge attack, and is only significant on exposed (001) surfaces after a certain amount of dissolution by edge attack.en
dc.description.degreeMaster of Scienceen
dc.identifier.otheretd-04232001-165507en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-04232001-165507/en
dc.identifier.urihttp://hdl.handle.net/10919/31837en
dc.publisherVirginia Techen
dc.relation.haspartRUFEpdf.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectphlogopiteen
dc.subjectLEEDen
dc.subjectreactive surface areaen
dc.subjectXPSen
dc.subjectAFMen
dc.titleAssessing the Reactive Surface Area of Phlogopite during Acid Dissolution: An Atomic Force Microscopy, X-ray Photoelectron Spectroscopy, and Low Energy Electron Diffraction Studyen
dc.typeThesisen
thesis.degree.disciplineGeological Sciencesen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.levelmastersen
thesis.degree.nameMaster of Scienceen

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