PubMed · 3776645
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K Bibow, B Salbu. 1986. Trace elements in Norwegian diets.. https://doi.org/10.1111/j.1600-0773.1986.tb02716.x
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A superoxochromium(III) ion, CraqOO2+, abstracts the hydrogen atom from the hydroxylic group of a substituted, cationic phenol (ArOH), kCrOO = 1.24 M-1 s-1 in acidic aqueous solution at 25 degrees C. The reaction has a large kinetic isotope effect, kArOH/kArOD approximately 12 and produces ArO., which also reacts with CraqOO2+ in a rapid second step, kArO = 1.26 x 10(4) M-1 s-1. The final oxidation product is an o-quinone, which was identified by its behavior on a cation-exchange resin, UV-visible spectrum, and reaction with iodide ions. This work has extended to three the types of element-hydrogen bonds that react with CraqOO2+ about 10(2) times more slowly than with CraqO2+. The mechanistic implications of these findings are discussed.
A method has been developed for removing chromium from alkaline high-level radioactive tank waste. Removing chromium from these wastes is critical in reducing the volume of waste requiring expensive immobilization and deep geologic disposition. The method developed is based on the oxidation of insoluble chromium(III) compounds to soluble chromate using ferrate. This method could be generally applicable to removing chromium from chromium-contaminated solids, when coupled with a subsequent reduction of the separated chromate back to chromium(III). The tests conducted with a simulated Hanford tank sludge indicate that the chromium removal with ferrate is more efficient at 5 M NaOH than at 3 M NaOH. Chromium removal increases with increasing Fe(VI)/Cr(II) molar ratio, but the chromium removal tends to level out for Fe(VI)/ Cr(III) greaterthan 10. Increasingtemperature leadsto better chromium removal, but higher temperatures also led to more rapid ferrate decomposition. Tests with radioactive Hanford tank waste generally confirmed the simulant results. In all cases examined, ferrate enhanced the chromium removal, with a typical removal of around 60-70% of the total chromium present in the washed sludge solids. The ferrate leachate solutions did not contain significant concentrations of transuranic elements, so these solutions could be disposed as low-activity waste.
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