Extraction Behaviour of Tris(2-methylbutyl) Phosphate with Fission Products and Heavy Metal Ions

ABSTRACT

Systematic screening of various symmetric trialkyl phosphates has led to the conclusion that tris(2-methylbutyl) phosphate (T2MBP), an organophosphate having branched amyl groups, can also be adopted as an alternate extractant to tri-n-butyl phosphate (TBP) for the selective extraction of U(VI) and Pu(IV) during the nuclear fuel reprocessing. In this context, a detailed study on the extraction efficiency of 1.1 M T2MBP/n-dodecane for the extraction of two important nuclear fuel elements, U(VI) and Pu(IV) has been carried out. The cross-current extraction study with U(VI), Pu(IV), and mixed U(VI)–Pu(IV) feed solutions has also been carried out to investigate the extraction and stripping behaviour of the respective metal ions by T2MBP. Results indicated that in contrast to TBP-based systems, there was no occurrence of third-phase formation during the extraction of tetravalent plutonium by T2MBP up to its threshold limit. In addition, its extraction behaviour with certain important fission product elements was also taken up as a part of the study. It has been observed that the extraction of trivalent lanthanides (La, Ce, Nd, Gd), Zr and Tc using T2MBP is marginally lower than is seen for TBP, indicating the possibility of achieving better decontamination factor during reprocessing.

KEYWORDS:

• Tri-n-butyl phosphate
• tris(2-methylbutyl) phosphate
• cross-current extraction
• uranium(VI)
• plutonium(IV)
• fission products