Synergistic extraction of radionuclides from fuel debris with a［C₂mim］［Tf₂N］–based extractant

Water contamination with radionuclides has been found to occur during the processing of fuel debris by the submersion method. In this study, we have investigated the collective removal of radionuclides by the solvent extraction method with the ultimate goal of developing a process for treating such contaminated water. Co（II）, Ni （II）, Sr （II）, Zr （IV）, Mo（VI）, Cs （I）, and Nd（III）, which are assumed to be present in the fuel debris, are chosen as the target species for the solvent extraction process. Octyl （phenyl）–N,N–diisobutylcarbamoylmethylphosphine oxide（CMPO）–tributyl phosphate （TBP）–［C₂mim］［Tf₂N］, which serves as the extractant, exhibits a strong ability to extract Co（II）, Ni （II）, Sr （II）, and Nd（III）at a NaCl concentration of 2.0 mol/dm³, whereas it exhibits high extraction ability towards Co（II）, Ni （II）, Sr （II）, Zr （IV）, Cs （I）, and Nd（III）at a H₃BO₄ concentration of 0.1 mol/dm³. This extractant also quickly extracts the radionuclides, allowing extraction equilibrium to be reached within 3 min in the cases of Co（II）, Ni （II）, Sr （II）, Zr （IV）, Cs （I）, and Nd（III）. The results of the present study suggest that the radionuclides present in contaminated water can be extracted with high efficiency using CMPO–TBP–［C₂mim］［Tf₂N］as the extractant.