Extraction of neptunium(IV) by a mixture of 3-phenyl-4-acetyl-5-isoxazolone and tri-n-octyl phosphine oxide

The extraction behaviour of Np(IV) by 3-phenyl-4-acetyl-5-isoxazolone (HPAI) was investigated from nitric acid medium in the presence of tri-n-octyl phosphine oxide (TOPO). Speciation studies, carried out by the slope analysis method, yielded binary species of the type Np(PAI)4 when only HPAI was used as the extractant and ternary and quaternary species of the type Np(PAI)4·TOPO and Np(PAI)3·(NO3)·TOPO, respectively when both HPAI and TOPO were used together as the extractants. The two-phase extraction constant for the binary species (log k ex) was calculated to be 8.44±0.05 while those for the ternary and quaternary species were found to be 12.84±0.22 and 11.26±0.07, respectively.