期刊
JOURNAL OF ENVIRONMENTAL RADIOACTIVITY
卷 74, 期 1-3, 页码 211-219出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.jenvrad.2004.01.012
关键词
technetium; uranium; neptunium; sulfides; spectroscopy
Technetium, uranium and neptunium may all occur in the environment in more than one oxidation state (IV or VII, IV or VI and IV or V respectively). The surface of mackinawite, the first-formed iron sulfide: phase in anoxic conditions, can promote redox changes so a series of laboratory experiments were carried out to explore the interactions of Tc, U and Np with this mineral. The products of reaction were characterised using X-ray absorption spectroscopy. Technetium, added as TcO4-, is reduced to oxidation state IV and forms a TcS2-like species. On oxidation of the mackinawite in air to form goethite, Tc remains in oxidation state IV but in an oxide, rather than a sulfide environment. At low concentrations, uranium forms uranyl surface complexes on oxidised regions of the-mackinawite surface but at higher concentrations, the uranium promotes surface oxidation and forms a mixed oxidation state oxide phase. Neptunium is reduced to oxidation IV and forms a surface complex with surface sulfide ions. The remainder of the Np coordination sphere is filled with water molecules or hydroxide ions. (C) 2004 Elsevier Ltd. All rights reserved.
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