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Technetium Behavior in Sulfide and Ferrous Iron Solutions

Published online by Cambridge University Press:  21 February 2011

Suk Y. Lee  and
Ernest A. Bondietti
Suk Y. Lee
Affiliation:
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
Ernest A. Bondietti
Affiliation:
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, USA
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Abstract

Pertechnetate oxyanion (99TcO4−), a potentially mobile species in leachate from a breached radioactive waste repository, was removed from a brine solution by precipitation with sulfide, iron, and ferrous sulfide at environmental pH's. Maghemite (γ-Fe23 ) and goethite (α-FeOOH) were the dominant minerals in the precipitate obtained from the TcO4−)-ferrous iron reaction. The observation of small particle size and poor crystallinity of the minerals formed in the presence of Tc suggested that the Tc was incorporated into the mineral structure after reduction to a lower valence state. Amorphous ferrous sulfide, an initial phase precipitating in the TcOÝ-ferrous iron-sulfide reaction, was transformed to goethite and hematite (α-Fe2O3 ) on aging. The black precipitate obtained from the TcOÝ-sulfide reaction was poorly crystallized technetium sulfide (Tc2S7 ) which was insoluble in both acid and alkaline solution in the absence of strong oxidants. The results suggested that ferrous- and/or sulfide-bearing groundwaters and minerals in host rocks or backfill barriers could reduce the mobility of Tc through the formation of less-soluble Tc-bearing iron and/or sulfide minerals.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 15: Symposium D – Scientific Basis for Nuclear Waste Management VI , 1982 , 315
Copyright
Copyright © Materials Research Society 1983

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References

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