Extraction of thorium(IV) by a mixture of 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone and tri-n-octyl phosphine oxide

The extraction behavior of Th(IV) from dilute nitric as well as perchloric acid medium using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) and its mixture with tri-n-octyl phosphine oxide (TOPO) was investigated. The species of the type Th(X)(PMBP)3 x (HPMBP) and Th(X)(PMBP)3 x (TOPO) were extracted for the binary and ternary extraction systems, respectively, where X=NO3- or ClO4-. The presence of 1.25 x 10-5 M Th carrier in the aqueous phase resulted in the extracted species of the type of Th(PMBP)4 and Th(PMBP)4 x (TOPO), respectively. The extraction constant (log kex) for the binary species Th(PMBP)4 was found to be 6.89±0.01 while the overall extraction constant (log K) for the ternary species Th(PMBP)4 x (TOPO) was calculated to be 13.17±0.06. (author)