Impacts of Si on Se(IV) immobilization on ferrihydrite; An in situ ATR-IR spectroscopic study

Francisco, P. C. M.; Tachi, Yukio

ACS Earth and Space Chemistry (Internet), 4(12), p.2366 - 2377, 2020/12

https://doi.org/10.1021/acsearthspacechem.0c00243

Interaction of Fe and Si under anoxic and reducing conditions; Structural characteristics of ferrous silicate co-precipitates

Francisco, P. C. M.; Mitsui, Seiichiro; Ishidera, Takamitsu; Tachi, Yukio; Doi, Reisuke; Shiwaku, Hideaki

Geochimica et Cosmochimica Acta, 270, p.1 - 20, 2020/02

https://doi.org/10.1016/j.gca.2019.11.009

Se(-II) immobilization in Fe(II)-(hydro)oxides; Coprecipitation and post-transformation behavior

Francisco, P. C. M.; Ishidera, Takamitsu; Tachi, Yukio

no journal, , 

Selenide [Se(-II)] retention and mobilization in anoxic, iron-rich environments; Impacts of iron phase precipitation and transformation

Francisco, P. C. M.; Matsumura, Daiju; Kikuchi, Ryosuke*; Ishidera, Takamitsu; Tachi, Yukio

no journal, , 

Se(-II, IV) interactions with Fe(II) species and phases under anoxic and reducing conditions

Francisco, P. C. M.; Kikuchi, Ryosuke*; Matsumura, Daiju; Shiwaku, Hideaki; Ishidera, Takamitsu; Tachi, Yukio

no journal, , 

Selenium reactions in ferrous and sulfide-rich environments; Effects of sulfide speciation

Francisco, P. C. M.; Ishidera, Takamitsu; Shiwaku, Hideaki; Kikuchi, Ryosuke*; Tachi, Yukio

no journal, , 

Se immobilization in pyrite by reaction with Fe(II) and polysulfides; Impacts of aging conditions

Francisco, P. C. M.; Shiwaku, Hideaki; Ishidera, Takamitsu; Tachi, Yukio

no journal, , 

The long-lived fission product Se-79 is a significant contributor to predicted radioactivity in geological repositories long after their closure. One possible retardation in repositories is by incorporation into Fe-sulfides like pyrite (FeS2). In this study, we clarify the role of polysulfides in the incorporation of Se into pyrite. Polysulfides are intermediate-oxidation sulfide species that are likely produced by diagenetic and microbial processes in repository host rocks. The present results show that reaction of Se(-II) with polysulfides resulted in the initial formation of elemental selenium. Aging at anoxic conditions led to the incorporation of Se into pyrite. These results highlight the role of polysulfides in retaining Se. We also investigate the effects of aging in air to determine the effects of changes in the redox conditions. The results show that oxidation did not affect Se retention.