STUDY OF ISOTACHOPHORETIC SEPARATION BEHAVIOR OF METAL-CATIONS BY MEANS OF PARTICLE-INDUCED X-RAY-EMISSION .4. SEPARATION OF METAL-IONS IN A NONRADIOACTIVE MODEL SOLUTION OF A HIGH-LEVEL LIQUID WASTE

The isotachophoretic separation behaviour of metal ions in a model soluition of a high-level liquid waste (HLLW) was investigated by means of the isotachophoresis-particle-induced X-ray emission (ITP-PIXE) method for the purpose of fractionation of useful elements contained in the HLLW. The leading electrolyte used was 20 mM ammonia solution buffered by acetic acid (pH 4.8), in which a complex-forming agent (10 mM alpha-hydroxyisobutyric acid) was contained. The migration order of the cationic components was (Rb+, Cs+), NH4+, Ba2+, Sr2+, Na+, Mn2+, Fe2+, (Cr2+, Rh2+, Cd2+), Ni2+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+ and Y3+, where the ions in parentheses could not be separated from each other. The separation efficiency of rare earth elements was 178 nmol/C and it was decreased to 96 nmol/C when NaNO3 coexisted as the matrix. Part of the Fe3+, ZrIVO2+, MoVIO42- and platinum group elements formed a cationic colloidal zone. Although the cationic recovery was 100% for most of the components, a substantial part of Fe, TeVIO3, ZrIVO, Ru, Rh and Pd did not migrate, suggesting the formation of non-ionic hydrolysis species. Although ITP was not suitable for their analysis, platinum group metals in the HLLW might be partitioned efficiently as non-ionic components.