Magnetite Oxidation in Aqueous Systems

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Virginia Tech

Magnetite, an iron oxide, is a possible candidate for in situ remediation of contaminated groundwater systems due to its oxidation/reduction potential for reduction of contaminants such as carbon tetrachloride. Little characterization and analysis has been done to describe the kinetics of magnetite transformation during oxidation. This work focuses on monitoring the concentrations of magnetite and one of its oxidation transformation products, maghemite, by the use of UV-Vis-NIR spectroscopy. As oxidation proceeded at a constant specific temperature, the concentration of magnetite decreases, which was indicated by a decrease in absorption in the NIR-region of the spectrum. As magnetite concentrations decreased, the concentration of maghemite increased, which was indicated by an increase in absorption in the UV-region. The temperature at which the suspensions of magnetite and maghemite were measured was of great importance for complete understanding of the magnetite transformation as seen by UV-Vis-NIR spectroscopy analysis. Higher measurement temperatures produced higher absorptivities of FeII-FeIII electron hopping transitions, while decreasing the absorptivity of FeIII-FeIII in the NIR and UV-regions respectively. Lower temperatures produced the opposite effects on the iron oxides' transitions. Higher temperature increased the rate of oxidation.

spectroscopy, UV-Vis-NIR, Oxidation, magnetite, maghemite, transition