New ion exchanger with porous silica as a supporting material and diphosphonic acid as a functional chelating group has been developed for the effective removal of transition metals and actinide ions from radioactive liquid wastes ranging from neutral to very acidic conditions. Thermal treatment of metal (Co, Cs or U) loaded resin was accomplished to enhance the safety and stability of final product during transportation and disposal. In this paper, characteristics of metal-loaded resins before and after three different thermal treatment conditions were compared to see the effectiveness of heat conditioning. The heat-treated resins maintained its original powder form even if some volume reduction effect could be achieved, which needs additive materials to convert the powder waste into a monolithic final waste form.