Chromatographic Separation of Cs in Simulated High-level Liquid Wastes

Spherical and elastic AWP-CaALG microcapsules (∼700 μm in diameter) were obtained and fine crystals of AWP were uniformly immobilized in alginate matrices. The uptake of Cs+, Rb+ and Ag+ in 2 M HNO3 for AWP-CaALG was examined by batch method. The uptake of Cs+ was fairly fast in the initial stage and the uptake equilibrium attained within 5 h. The decreasing order of Kd was Cs+ > Rb+ > Ag+, and the separation factors of Cs/Rb and Cs/Ag were estimated to be over 10, suggesting the selective separation of Cs+. The Kd,Cs value was almost constant over 103 cm3/g in the wide concentration range of HNO3 up to 5 M. The uptake (%) of Cs+ in simulated HLLW (SHLLW, 28 components solution, SW-11E, JAEA) was estimated to be 97%, and the distribution of Cs+ into AWP phase and Zr/Ru to alginate phase were observed by EDS analysis. The stepwise chromatographic separation of Cs+ in SHLLW was examined under different eluting conditions using the columns packed with AWP-CaALG xerogels. The stepwise elution conditions were as follows; (1) H2O→1 M HNO3→5 M HNO3→3 M NH4NO3→5 M NH4NO3 (25 °C), (2) H2O→3 M NH4NO3 (25 °C), (3) H2O→1 M NH4NO3→5 M NH4NO3 (25 °C), (4) H2O→1 M NH4NO3→5 M NH4NO3 (40 °C), (5) H2O→1 M NH4NO3→5 M NH4Cl (25 °C). Most effective separation of Cs+ was accomplished under the condition of (3); most of the Rb+ and Ag+ ions over 90% were eluted by 1 M NH4NO3, and Cs+ ions eluted by 5 M NH4NO3. The recovery ratio was estimated to be 73.4%. The AWP-CaALG xerogel column is thus effective for the selective separation and recovery of Cs+ from SHLLW.