Lepidocrocite was the most abundant oxidized product for pH i 10 after 5 days, but was not observed at pH of 4 or 7. Solid phase characterization showed that magnetite was the only oxidized crystalline phase for the first 6 h regardless of initial pH. Analysis was performed with Sigmaplot 11.0. Aqueous fraction of Tc was measured at 0.4% at pH i 7 within 6 h, whereas ≥ 97% of Tc was removed from solutions at pH i of 4 and 10 within 24 h. Statistical comparisons were made using two-tailed Students t test for comparison of two datasets and ANOVA for comparison of multiple dataset using the Bonferroni as a post hoc test. Tc reduction was the fastest at pH i 7 and slowest at pH i 10 (Tc reduction rate pH i 7 > 4 > 10). We investigated the oxidative transformation of Fe 0 and reductive removal of TcO 4 - in 0.1 M Na 2SO 4 as a function of initial pH (i.e., pH i 4, 7, and 10) under aerobic conditions up to 30 days. The impact of sulfate on the kinetics of oxidation and reduction capacity of Fe 0 in the presence of Tc has not been examined. Elemental iron Fe 0 is a promising reductant for removal of radioactive technetium-99 (Tc) from complex aqueous waste streams that contain sulfate, halides, and other inorganic anions generated during processing of legacy radioactive waste.
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