Influence of NpO₂⁺ and UO₂²⁺ Cation-Cation Complex on Np(Ⅴ) Extraction by 30%TBP-Kerosene

The influence of cation-cation complex between Np(Ⅴ) and U(Ⅵ) on the extraction behavior of Np(Ⅴ) in 30%TBP-kerosene has been researched by spectrophotometry and liquid scintillation. The results show that Np(Ⅴ)-U(Ⅵ) cation-cation complex can be extracted into TBP organic phase directly and the distribution ratio is several times higher than Np(Ⅴ).The distribution ratio of Np(Ⅴ)-U(Ⅵ) cation-cation increases with the increasing of U concentration within 0.12-0.60 mol/L. The distribution ratio of Np(Ⅴ)-U(Ⅵ) cation-cation decreases as the U concentration reaches 0.72 mol/L because of the effect of U saturation degree in organic phase. At room temperature, when the concentration of U(Ⅵ) and HNO₃ of solution are 0.6 mol/L and 3 mol/L respectively and the phase ratio (o/a) is 2∶1, the total distribution ratio of Np(Ⅴ) can reaches about 0.1 after 1 min extraction and almost 9% Np is extracted into TBP organic phase. The distribution ratio of Np(Ⅴ)-U(Ⅵ) cation-cation complex increases with the increase of HNO₃ concentration. The contacting time of two phase has no influence on the extraction of Np(Ⅴ)-U(Ⅵ) cation-cation complex.