GEOC 120 |
| Ferrihydrite, Fe5HO8 • 4H2O, is a metastable, poorly crystalline iron oxide and serves as a precursor of more crystalline iron oxides such as goethite. Recently, high concentrations of arsenic in groundwater around the world have generated interest in the mechanisms controlling the geochemical cycling of arsenic. Although it is known that arsenic can be released by desorption from and reductive dissolution of iron oxides, the mechanisms of arsenic adsorption and release are not well understood. Coprecipitated and adsorbed samples were prepared by adding arsenate before or after particle formation. These samples and undoped ferrihydrite were characterized by transmission electron microscopy and X-ray diffraction. Reactivity was quantitatively compared by monitoring the rate of reductive dissolution by hydroquinone. The empirical rate orders and temperature dependence of the reactivity were determined. The coprecipitated arsenic sample was more reactive than the undoped ferrihydrite. The adsorbed arsenic samples were less reactive than the undoped ferrihydrite. |
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The Structure and Reactivity of Nanoparticles in the Environment
1:30 PM-4:00 PM, Wednesday, 13 September 2006 Moscone Center -- Room 262, Oral
Division of Geochemistry |