Reduction of Np(VI) and Pu(VI) by organic chelating agents
- Argonne National Lab., IL (United States)
The reduction of NpO{sub 2}{sup 2+} and PuO{sub 2}{sup 2+} by oxalate, citrate, and ethylenediaminetetraacetic acid (EDTA) was investigated in low ionic strength media and brines. This was done to help establish the stability of the An(VI) oxidation state depended on the pH nd relative strength of the various oxidation state-specific complexes. At low ionic strength and pH 6, NpO{sub 2}{sup 2+} was rapidly reduced to form NpO{sub 2}{sup +} organic complexes. At longer times, Np(IV) organic complexes were observed in the presence of citrate. PuO{sub 2}{sup 2+} was predominantly reduced to Pu{sup 4+}, resulting in the formation of organic complexes or polymeric/hydrolytic precipitates. The relative rates of reduction to the An(V) complex were EDTA > citrate > oxalate. Subsequent reduction to An(IV) complexes, however, occurred in the following order: citrate > EDTA > oxalate because of the stability of the An(VI)-EDTA complex. The presence of organic complexants led to the rapid reduction of NpO{sub 2}{sup 2+} and PuO{sub 2}{sup 2+} in G-Seep brine at pHs 5 and 7. At pHs 8 and 10 in ERDA-6 brine, carbonate and hydrolytic complexes predominated and slowed down or prevented the reduction of An(VI) by the organics present.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States); Argonne National Lab., IL (United States)
- Sponsoring Organization:
- USDOE Office of Environmental Restoration and Waste Management, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000; W-31109-ENG-38
- OSTI ID:
- 658224
- Report Number(s):
- SAND--97-2845C; CONF-971090--; ON: DE98005702; BR: EW3155010
- Country of Publication:
- United States
- Language:
- English
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