THE SYNTHESIS AND ACTINIDE AND LANTHANIDE COMPLEXATION OF“ SOFT” DONOR LIGANDS: COMPARISON BETWEEN 4-BENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-THIONE ( HBMPPT) AND 4-THIOBENZOYL-2,4-DIHYDRO-5-METHYL-2-PHENYL-3H-PYRAZOL-3-ONE ( HTBMPP) WITH TRI-n-OCTYLPHOSPHINE OXIDE (TOPO) SYNERGIST FOR Am( III) AND Eu( III) EXTRACTION

Abstract

ABSTRACT A comparison study between two “ soft” donor ligand isomers, 4-benzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-thione ( HBMPPT) and 4-thiobenzoyl-2,4-dihydro-5-methyl-2-phenyl-3H-pyrazol-3-one ( HTBMPP), both with tri-n-octylphosphine oxide ( TOPO) synergist in toluene, is reported for the extraction of Am( III) and Eu(UI). The more stable ligand, HBMPPT, gave no detectable extraction, but when HBMPPT and TOPO were combined, substantial extraction occurred with selectivity for Am( UI) over Eu( III) in three acid systems HC1, HCIO4, and HNO3. A maximum separation factor ( SF = DAm/ DEu) of 125 was obtained at pH 3.0 for the HBMPPT/ TOPO/ HCIO4 system. The other less stable ligand isomer, HTBMPP, did extract Am( m) to a small extent but combination with TOPO greatly enhanced the extraction. A maximum SF of 15 at pH 3.0 was observed for the HTBMPP/ TOPO/ HCIO4 system. Comparison of HBMPPT/ TOPO among the acids studied indicated different extraction mechanisms in the linear region in each system f...