Carbonate-Alkaline Leaching of Yttrium from Sr–Y Carbonates for 90Sr–90Y Separation

The carbonate-alkaline leaching technique for the separation of the 90Sr–90Y pair in nuclear waste processing was studied. The influence of potassium carbonate concentration, alkali metal cation, temperature, and stirring speed on the yttrium extraction was examined using stable isotopes of strontium and yttrium in the carbonate form. The highest degree of yttrium extraction (99.9 %) was achieved under the following optimum conditions: 2 M K2CO3 solution, 70°C, stirring speed 500 rpm, liquid-to-solid ratio 20 mL/g, Sr : Y weight ratio 10 : 1, and leaching time 2 h. Under these conditions, the leaching process is primarily diffusion-controlled, as evidenced by the strong dependence of the extraction efficiency on the stirring speed and the apparent activation energy of 13.9 kJ mol–1.