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 evaluatedsolids-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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