Influence of CationCation Complexation Between NpO⁺₂ and UO²⁺₂ on Redox Potential of Np(Ⅵ)/Np(Ⅴ)

The formation of cation-cation complex between Np(Ⅴ) and U(Ⅵ) in the aqueous solution of nitric acid has been studied by spectrophotometry. The influence of U(Ⅵ) concentration on the redox potential of Np(Ⅵ)/Np(Ⅴ) couple in nitric acid media has been also researched. The results show that the presence of U(Ⅵ) influences the redox potential of Np(Ⅵ)/Np(Ⅴ) couple. With an increase in the U(Ⅵ) concentration, the redox potential of Np(Ⅵ)/Np(Ⅴ) is increased and the redox reaction becomes irreversible. It is also found that the redox potential can be reduced by increasing the HNO₃ concentration.