Title page for ETD etd-07252007-104027


Type of Document Dissertation
Author Luxton, Todd Peter
Author's Email Address tluxton@vt.edu
URN etd-07252007-104027
Title Oxyanion Adsorption by Iron and Ruthenium Oxides: A macroscopic, Spectroscopic, and Kinetic Investigation
Degree PhD
Department Crop and Soil Environmental Sciences
Advisory Committee
Advisor Name Title
Eick, Matthew J. Committee Chair
Hochella, Michael F. Jr. Committee Member
Scheckel, Kirk Committee Member
Zelazny, Lucian W. Committee Member
Keywords
  • Solid/Solution Interface
  • Adsorption
  • Arsenic
  • Chromium
  • Spectroscopy
  • Pressure-
Date of Defense 2007-07-18
Availability unrestricted
Abstract
The adsorption and desorption behavior of trace element contaminants was evaluated

solids-goethite and ruthenium oxide. The importance of anion displacement as a mechanism

responsible for arsenic release from iron oxides was investigated on goethite. The adsorption

and polymerization of silicate on goethite was examined as a function of surface concentration

determine the influence of adsorbed silicate monomers and polymers on arsenite adsorption

desorption. A kinetic model was employed to describe arsenite adsorption and desorption

absence and presence of silicate. The potential environmental impacts of the research

discussed. Hydrous and crystalline ruthenium oxides were extensively characterized

traditional colloidal surface characterization techniques, dissolution experiments, and macro-

spectroscopic experiments. The two ruthenium oxide phases exhibited large specific

areas, a high density of reactive surface functional groups and the presence of multiple

oxidation states in both solids. Enhanced dissolution of hydrous ruthenium oxide occurred

presence of oxalate and ascorbate. While enhanced dissolution of the crystalline phase

only in the presence of oxalate at pH 3. Results from the dissolution experiments were

develop possible mechanisms for the oxalate and ascorbate promoted dissolution of ruthenium

oxides. Macroscopic adsorption studies of arsenate adsorption on both ruthenium oxides

examined over a broad pH (3-10) and initial solution concentration range (0.01 to

Results from the adsorption studies indicate arsenate forms a stable surface complex with

ruthenium oxide phases. Extended x-ray absorption fine structure spectroscopy and Pressurejump

relaxation studies indicates arsenate is specifically adsorbed the ruthenium oxide

Chromate adsorption on ruthenium oxides was investigated as a function of pH and

chromate solution concentration. Macroscopic adsorption studies and zeta

measurements suggest chromate forms an inner-sphere surface complex with both oxide

X-ray absorption near edge spectroscopy data indicates chromate (Cr(VI)) is reduced

chromium (Cr(III)) on the ruthenium oxide surface. Modeling of the first Cr shell indicated

two oxygen backscattering distances similar to the Cr-O atomic distances reported for

coordinated to Cr(VI) and Cr(III) providing additional evidence for Cr(VI) reduction.

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