EXTRACTION STUDIES OF SELECTED ACTINIDE IONS FROM AQUEOUS SOLUTIONS WTTH 4.BENZOYL-24-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-THIONE AND TRI-n-OCTYLPHOSPHTNE OXIDE

The first measurements of distribution coefficients (K(d)) for Cm(III), Bk(III), Cf(III), Es(III), and Fm(III) between aqueous perchlorate solutions and solutions of 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione (BMPPT) and the synergist tri-n-octylphosphine oxide (TOPO) in toluene are reported. Curium-243, berkelium-250, californium-249, einsteinium-254, and fermium-253 were used in these studies. The K(d) for Am-241 was also measured and is in agreement with previously published results. Our new results show that the K(d)'s decrease gradually with increasing atomic number for the actinides with a dip at Cf. In general, the K(d)'s for these actinides are about about a factor of 10 greater than the K(d)'s for the homologous lanthanides at a pH of 2.9, a BMPPT concentration of 0.2 M, and a TOPO concentration of 0.04 M. The larger K(d)'s for the actinides are consistent with greater covalent bonding between the actinide metal ion and the sulfur bonding site in the ligand.