Characterization and Oxidation of Chromium(III) by Sodium Hypochlorite in Alkaline Solutions
Chromium exists in nuclear waste sludges and is a problematic element in the vitrification process of high-level nuclear wastes. It is therefore necessary to treat the waste sludges to remove chromium prior to vitrification, by caustic leaching or oxidation of Cr(III) to Cr(VI). The objective of this study is to investigate the effect of oligomerization of Cr(III) on its oxidation by hypochlorite in alkaline solutions. Monomeric, dimeric and trimeric Cr(III) species in solution were separated by ion exchange. The kinetics of the oxidation of the separated species by hypochlorite in alkaline solutions was studied by UV/Vis absorption spectroscopy, and compared with the oxidation by hydrogen peroxide previously studied. Results indicate that hypochlorite can oxidize Cr(III) to Cr(VI) in alkaline solutions, but the rate of oxidation by hypochlorite is slower than that by hydrogen peroxide at the same alkalinity and concentrations of oxidants. The rate of oxidation of Cr(III) by both oxidants decreases as the concentration of sodium hydroxide is increased, but the oxidation by hypochlorite seems less affected by the degree of oligomerization of Cr(III) than that by peroxide. Compared with the oxidation by hydrogen peroxide where the major reaction pathway has an inverse order with respect to CNaOH, the oxidation by hypochlorite has a significant reaction pathway independent of [OH?].
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 890111
- Report Number(s):
- PNNL-SA-51355; 8891; TRN: US0604524
- Journal Information:
- Inorganica Chimica Acta, 359(10):3237-3242, Journal Name: Inorganica Chimica Acta, 359(10):3237-3242
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION SPECTROSCOPY
ACID NEUTRALIZING CAPACITY
CHROMIUM
HYDROGEN PEROXIDE
ION EXCHANGE
KINETICS
LEACHING
OXIDATION
OXIDIZERS
RADIOACTIVE WASTES
SLUDGES
SODIUM
SODIUM HYDROXIDES
VITRIFICATION
WASTES
Environmental Molecular Sciences Laboratory