Livens Francis R, Jones Mark J, Hynes Amanda J, Charnock John M, Mosselmans J Fred W, Hennig Christoph, Steele Helen, Collison David, Vaughan David J, Pattrick Richard A D, Reed Wendy A, Moyes Lesley N
Centre for Radiochemistry Research, Department of Chemistry, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
J Environ Radioact. 2004;74(1-3):211-9. doi: 10.1016/j.jenvrad.2004.01.012.
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 TcS(2)-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.
锝、铀和镎在环境中都可能以不止一种氧化态存在（分别为IV或VII、IV或VI以及IV或V）。在缺氧条件下首先形成的硫化铁相——硫铁矿的表面可促进氧化还原变化，因此开展了一系列实验室实验来探究锝、铀和镎与这种矿物的相互作用。使用X射线吸收光谱对反应产物进行了表征。以高锝酸根离子（TcO4(-)）形式添加的锝被还原至氧化态IV，并形成类似硫化锝（TcS(2)）的物种。当硫铁矿在空气中氧化形成针铁矿时，锝仍处于氧化态IV，但处于氧化物而非硫化物环境中。在低浓度下，铀在硫铁矿表面的氧化区域形成铀酰表面络合物，但在高浓度下，铀会促进表面氧化并形成混合氧化态的氧化物相。镎被还原至氧化态IV，并与表面硫离子形成表面络合物。镎配位球的其余部分由水分子或氢氧根离子填充。
