Optimization in Granulation Conditions for Adsorbent of Extraction Chromatography

Japan Atomic Energy Agency has been working on development of extraction chromatography technology for recovery of trivalent minor actinides (MA(III): Am, Cm) from high-level radioactive waste generated in reprocessing of spent fuel. The technology utilizes porous silica particles with about 50μm diameter for support of adsorbents. The particles are coated by styrene-divinylbenzene copolymer, and an extractant for MA recovery is impregnated into the polymer. Pressure drop of the packed column depends on characteristics of the particle (diameter, uniformity and pore size). Large pressure drop of the column is not favorable for safety assessment of the technology although a certain level of the pressure drop is indispensable for excellent separation performance. In this study, we applied a granulation technique using a spray dryer that is widely used in industry, and conducted experiments to find the optimal specifications for silica support particles and conditions for the granulation operation. A basic characterization of the adsorbent prepared from the produced particles was carried out by an adsorption test of simulated high level liquid waste. As a result, it was first found that the uniformity of particle size could be improved by suppressing pulsation during supply of the feed slurry to the spray dryer. Next, by adjusting the viscosity of the feed slurry, it was possible to suppress the generation of particles with undesirable shapes such as hollow particles and depressed particles. It was also confirmed that these particles had a lower pressure drop than conventionally used particles.