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Report No.

Reduction behavior of uranium in the presence of citric acid

Suzuki, Yoshinori; Nankawa, Takuya ; Yoshida, Takahiro*; Ozaki, Takuo; Onuki, Toshihiko; Francis, A. J.; Tsushima, Satoru*; Enokida, Yoichi*; Yamamoto, Ichiro*

We examined the reduction behavior of UO$$_{2}$$$$^{2+}$$ in citrate media at pH 2.0-7.0 by column electrodes. At pH 2.0, UO$$_{2}$$$$^{2+}$$ was reduced to U(IV) through a one-step reduction process, while it was reduced to U(IV) through a two-step reduction process at pH 3.0-5.0. The reduction potential of UO$$_{2}$$$$^{2+}$$ shifted to lower values with an increase in pH from 2.0 to 7.0. At pH 6.0 and 7.0, UO$$_{2}$$$$^{2+}$$ was not reduced to U(IV) completely at the electrode potential above -0.8 V. Ultraviolet-visible spectroscopy and speciation calculation of UO$$_{2}$$$$^{2+}$$ in citrate media indicated that uranium existed as a mainly UO$$_{2}$$$$^{2+}$$ at pH 2-3, and a predominant species at pH 3-5 was [(UO$$_{2}$$)$$_{2}$$Cit$$_{2}$$]$$^{2-}$$. At pH 5-7, polymeric complexes were present. These findings suggest that the reduction of UO$$_{2}$$$$^{2+}$$ is more difficult by polymerization of UO$$_{2}$$$$^{2+}$$ with citric acid at higher pHs.



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Category:Chemistry, Inorganic & Nuclear



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