Electrochemical and spectrophotometric investigations of neptunium in alkaline media
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A.V. Gelis
The results of electrochemical and spectrophotometric studies of neptunium in concentrated alkali ([OH-]tot=0.9 to 6.5 M) and mixed hydroxo-carbonate solutions are reported. Using cyclic voltammetry, we have demonstrated reversibility of the Np(VI)/(V) couple and quasi-reversibility of the Np(VII)/(VI) couple in basic solutions ([OH-]tot above 1.0 M), implying nearly constant coordination geometries for the predominant Np(V), Np(VI) and Np(VII) species in such media. For the first time, formation of Np(IV) hydroxide in alkaline solutions has been demonstrated using voltammetric methods. The formal redox potential of the Np(VI)/(V) couple in 1 M NaOH was determined to be 0.106±0.001 V/N.H.E. This value is different in NaOH and LiOH media, which we have interpreted to indicate a specific interaction between the lithium cation and a Np anionic species. At [CO32-]tot greater than 0.1 M in 1.8 M NaOH, the Np(VI)/(V) couple was found to be quasi-reversible while the Np(VII)/(VI) couple was irreversible. Formal redox potentials for Np in several alkaline solutions have been evaluated. These results are discussed in comparison with previously reported information.
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Articles in the same Issue
- Separation of 248Cm from a 252Cf neutron source for production of Cm targets
- Investigation of separation/purification methodologies for the determination of 232U and 236Pu in solution of spent nuclear fuels by α-spectrometry
- Thermodynamics of dioxoneptunium(V) complexation by dicarboxylic acids
- Electrochemical and spectrophotometric investigations of neptunium in alkaline media
- Synergistic extraction of U(VI) with mixtures of 2-ethyl hexyl phosphonic acid-mono-2-ethyl hexyl ester (PC-88A) and TBP, TOPO or Cyanex 923
- Determination of fictive binary data for uranium(IV) nitrate: preliminary results
- The preparation and decomposition of methylhydrazine oxalate and its application as cleaning extractant
- Sorption behavior and coordination state of Eu(III) and Cm(III) in hydrochloric acid-methanol mixture/cation exchange resin system studied by time-resolved laser-induced fluorescence spectroscopy
- Detection of radioactive hot particles in environmental samples using a Marinelli-beaker measuring geometry
