Interaction of aqueous Se(IV)/Se(VI) with FeSe/FeSe2: implication to Se redox process.
Since reductive precipitation is considered as the most effective way to immobilize (79)Se, interaction of aqueous Se(IV)/Se(VI) with Fe(II)-bearing minerals has received extensive attention. In contrast to the thermodynamic calculations, as well as the prevalence of iron selenide phases observed in soil, sediments and ore deposits, most laboratory experiments have found that Se(0) was the reaction product. In this study, the interaction of Se(IV)/Se(VI) with FeSe/FeSe2 were investigated. The results demonstrate that FeSe and FeSe2 can be oxidized to Se(0) by Se(IV) with relatively fast kinetics, while reaction between Se(VI) and FeSe/FeSe2 only occurs under limited conditions (i.e. in the presence of high ferrous content and higher pH) with much slower kinetics, and there is no evident reaction in most case. Therefore, reduction of Se(IV) by Fe(II)-bearing minerals, in particular by natural occurring minerals, is envisioned to produce Se(0) at the early stage of experiments, rather than FeSe or FeSe2. Due to the formation of bulk Se(0) and its low solubility, the Fe-Se-O-H2O system will maintain redox disequilibrium in laboratory time-scale. This study also reveals that iron selenides, like iron sulfides, have strong reactivity toward Fe(3+). The findings in this study give insight into possible controls on Se redox process.
Beijing National Laboratory for Molecular Sciences, Radiochemistry and Radiation Chemistry Key Laboratory for Fundamental Science, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
Mingliang
M
Kang
Bin
B
Ma
Fabrizio
F
Bardelli
Fanrong
F
Chen
Chunli
C
Liu
Zhong
Z
Zheng
Shijun
S
Wu
Laurent
L
Charlet
D000327:Adsorption; D005296:Ferrous Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D018036:Selenium Compounds / Q000737:chemistry*; D056928:X-Ray Absorption Spectroscopy
D005296:Ferrous Compounds; D018036:Selenium Compounds