Trivalent f-Element Intra-group Separation by Solvent Extraction with CMPO-complexant System

Abstract

For trivalent actinide and lanthanide separation, the solvent extraction system which employs neutral bifunctional extractant n-octyl(phenyl)-N, N-diisobutylcarbamoylmethylphosphine oxide (CMPO) and aminopolyacetic acid was investigated. The system is based on CMPO-tri-n-butylphosphate (TBP) mixed solvent and diethylenetriaminepentaacetic acid (DTPA)-sodium nitrate solution. The separation is achieved by complexing trivalent actinide preferentially with DTPA in aqueous phase and extracting lanthanide into organic phase. Mutual separation between light lanthanide, Am and Cm was mainly governed by complex formation with DTPA. The acidity is most affecting parameter for partitioning and its increase results in decrease of distribution ratio. For selective stripping of trivalent actinide from 0.2 _M CMPO—1.0 _M TBP in n-dodecane at room temperature, 0.05 _M DTPA and 2–4 _M sodium nitrate solution (pH 2) is useful. From the observed distribution behavior, a basic flow sheet which is composed of four steps was proposed. In batchwise experiments with radioactive nuclides, separation factor of larger than 13 and 27 for Ce/Am and Cm/Eu, respectively, were obtained and the applicability of the system was indicated.

KEYWORDS:

• solvent extraction
• separation process
• americium
• curium
• lanthanides
• CMPO
• DTPA
• sodium nitrate
• TBP
• pH value