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Spectrophotometric and calorimetric studies of Np(V) complexation with sulfate at 10–70°c

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Abstract

Sulfate, one of the inorganic constituents in the groundwater of nuclear waste repository, could affect the migration of radioactive materials by forming complexes. Spectrophotometric and microcalorimetric titrations were performed to identify the Np(V)/sulfate complex and determine the equilibrium constants and enthalpy of complexation at 10–70°C.

Results show that the complexation of Np(V) with sulfate is weak but slightly enhanced by the increase in temperature. The complexation is endothermic and becomes more endothermic with the increase in temperature. The enhanced complexation at elevated temperatures is due to the increasingly larger entropy of complexation that exceeds the increase in enthalpy, indicating that the complexation of Np(V) with sulfate is entropy-driven.

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Authors and Affiliations

  1. Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA

    L. Rao & G. Tian

  2. Pacific Northwest National Laboratory, Richland, WA, 99352, USA

    Y. Xia & J. I. Friese

Authors
  1. L. Rao
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  2. G. Tian
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  3. Y. Xia
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  4. J. I. Friese
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Correspondence to L. Rao.

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Rao, L., Tian, G., Xia, Y. et al. Spectrophotometric and calorimetric studies of Np(V) complexation with sulfate at 10–70°c. J Therm Anal Calorim 95, 409–413 (2009). https://doi.org/10.1007/s10973-008-9247-0

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  • DOI: https://doi.org/10.1007/s10973-008-9247-0

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