Speciation and separation of fission product rhodium

The rhodium speciation in nitric acid has been identified, primarily by the use of 103Rh Nuclear Magnetic Resonance Spectroscopy. The results have indicated that the rhodium species in stored high level waste (HLW) will range from the hexaaquo ion, {Rh(H20)6}3+-to complexes of the general formula {Rh(H20)6-n(NO2)nl(3-n)+, depending on the nitrite ion concentration. The solvent extraction of these complexes by dinonylnaphthalene sulphonic acid and various organo-phosphine sulphides has been investigated, and an integrated scheme for recovering rhodium from HLW is proposed.