Treatment of radioactive wastes: An X-ray absorption spectroscopy study of the reaction of technetium with green rust

Immobilization and Limited Reoxidation of Technetium-99 by Fe(II)-Goethite

“…In that case, the initial Tc environment was consistent with Tc incorporated into the lattice of green rust and after the green rust was oxidized, the coordination environment was consistent with Tc substituted for Fe in goethite, because of mineral transformation from the green rust to goethite. The Tc-Fe distances in the oxidized products are very similar to those determined here, although the previously reported Tc-Fe coordination numbers for the oxidized green rust and goethite (Pepper et al 2003) are smaller than ours.…”

“…A similar local environment for Tc in iron oxides was observed previously in TcO 4 -reduced using green rust (Pepper et al 2003). In that case, the initial Tc environment was consistent with Tc incorporated into the lattice of green rust and after the green rust was oxidized, the coordination environment was consistent with Tc substituted for Fe in goethite, because of mineral transformation from the green rust to goethite.…”

“…Numerous waste forms have been proposed to accommodate and immobilize Tc, including cement/ grout (Lockrem 2005;Lukens et al 2005), glass , hydroceramics (Siemer 2002;Bao et al 2005), phosphate-bonded ceramics (Siemer 2002;Singh et al 2006), resins (Gu et al 2000), aqueous biphasic systems (ABS) (Rogers et al 1997), nanoporous tin(II/IV) phosphates (Wellman et al 2006), and other sorbent materials (Liang et al 1996;Wharton et al 2000;Mattigod et al 2003;Pepper et al 2003). While each of these waste forms has merit and may ultimately prove to be the best candidate, none has yet been demonstrated to immobilize Tc over the hundreds of thousands or millions of years desired to alleviate human and environmental risks.…”

Retention of99mTc at Ultra-trace Levels in Flowing Column Experiments – Insights into Bioreduction and Biomineralization for Remediation at Nuclear Facilities

“…The rate of Tc(VII) reduction by Fe(II) is dependent on Fe(II) speciation with Fe (II) sorbed to Fe(III) oxides and Fe(II)-bearing minerals magnetite, green rust and iron sulfides yielding greater 99 Tc(VII) reduction rates than siderite and vivianite (Bishop et al 2012;Burke et al 2010;Fredrickson et al 2004;Liu et al 2008;Livens et al 2004;Peretyazhko et al 2012;Pepper et al 2003) and with aqueous Fe(II) being the least effective 99 Tc (VII) reductant (Lloyd et al 2000;Zachara et al 2007). …”

Developments in Bioremediation of Soils and Sediments Polluted with Metals and Radionuclides. 3. Influence of Chemical Speciation and Bioavailability on Contaminants Immobilization/Mobilization Bio-processes

“…In addition, green rusts are a product of microbial degradation by dissimilatory iron reducing bacteria (Fredrickson et al 1998). Due to their highly reactive surfaces and reduction potentials, green rusts may have strong influences on the fate of environmental contaminants such as selenium (Myneni et al 1997;Johnson & Bullen 2003), chromium (Bond & Fendorf 2003;Lee & Batchelor 2003), uranium (O'Loughlin et al 2003) and technetium (Pepper et al 2003). In contrast, As(V) has shown not to be reduced in the presence of green rust (Randall et al 2001).…”