Extraction of plutonium from acidic media using various phosphine oxides

Extraction, loading and stripping studies of Pu(IV) have been carried out using three phosphine oxides namely CyanexR -923 (cyn-923), CyanexR -925 (cyn-925) and TOPO in dodecane from nitric acid medium. All the three phosphine oxides have shown very high extraction of Pu. The order of extraction for Pu by these compounds is cyn-923 > TOPO ∼ cyn-925. Loading of Pu (∼30.0 mg/l) in 3.0M HNO3 was carried out using 5% solution of each of the phosphine oxides in dodecane. It was found that even at an organic to aqueous phase ratio of 1:10, the loading of Pu is >96%. From the loaded organic phase, Pu could be almost quantitatively stripped using 0.1 or 0.5M oxalic acid. The extraction of Pu(IV) with cyn-925 has also been carried out from HCl, HNO3 or HClO4 (0.5 to 9.1M). The species extracted into the cyn-925/dodecane phase from 3.0M HNO3 or HCl media was found to be Pu(L)4 x 2 cyn-925 where L = NO3- or Cl-. Similar species were observed to be formed when dodecane was replaced by xylene, chlorobenzene or o-dichlorobenzene. (author)