Valence control of Ce(III) and mutual separation of Ce and Eu by solvent extraction

Fundamental investigations on preparation of Ce(IV) in nitric acid solutions were carried out in order to selective extraction of Ce(IV) as a first step the Am/lanthanide separation. Ce(III) is oxidized into Ce(IV) in the presence of oxidant, (NH4)2S2O8, and with a catalyst, AgNO3, in nitric acid solution. The yield of Ce(IV) decreased with increased HNO3 concentrations and (NH4)2S2O8 concentration up to 0.1M. The maximum yield of Ce(IV) was found in the 0.01M concentration of AgNO3. The sequence of effective extractants for the Ce extraction yields were Zr-DEHPA≥DEHPA>TBP. Oxidation of Ce(III) to Ce(IV) was performed below the 2M HNO3 and Ce(III)/Ce(IV) extracted with 1M DEHPA, Zr-1M DEHPA and 1M TBP in above the 5M HNO3. Finally, extracted Ce(III)/Ce(IV) in organic solvent was stripped with reductant H2O2/HNO3 solution. These results could be use in the development of mutual separation process of Am and lanthanide elements contained in the radioactive liquid waste solution