Studies on Stripping of Actinides, and Some Fission and Corrosion Products from Loaded TRPO by N,N,N′,N′-Tetramethyl Diglycolamide

Abstract

In order to strip transuranic elements (TRU) from loaded 30% trialkylphosphine oxide (TRPO) / kerosene, N,N,N′,N′-tetramethyl diglycolamide (TMDGA), was synthesized. The distribution behaviors of metal ions between TMDGA/HNO3 and 30%TRPO/kerosene were investigated. D values of An(III, IV), Ln(III), Mo(VI), Pd(II), and Tc(VII) show a trend of first upward and then downward with increasing acidity, which is attributed to the common-ion effect and the competition extraction of HNO3. TMDGA could enhanced the stripping strongly for Pu(III, IV), Am(III), Ln(III), Y(III), and Zr(IV), weakly for Np(IV) and Np(VI), slightly for U(VI), Np(V), Mo(VI), Tc(VII), Pd(II), Ru(III), and Fe(III). TMDGA should be used in <0.3 mol/L HNO3 media to ensure the co-stripping of TRU. Multi-stage cascade stripping experiments were carried out using diluted nitric acid with 0.2 mol/L TMDGA as stripping agent. The results of the five-stage countercurrent stripping show that >99.9% Am(III), Pu(IV), and Nd(III) could be stripped from loaded TRPO. However, 6.3% Np(IV) remained in the organic phase, probably because of the interference of residual Mo(VI) in TRPO. The residual Np(IV) could be completely removed by the mixed solution of 0.1 mol/L TMDGA and 0.1 mol/L oxalic acid.