Cerium oxide is widely used in fine polishing processes, such as production of optical lenses, prisms, LCD panels and HDD glass substrates. More than 90% of rare earth elements used in Japan, including cerium, have been imported from China, and their prices have risen sharply. Therefore, reuse and/or recycling are urgently required. Our previous study of technologies for recovery of cerium-oxide abrasive particulates from used slurry revealed that freezing and thawing caused particulates to agglomerate and form aggregates that can be easily separated by sedimentation. In this study, various freezing conditions were examined to study the separation properties. It was found that aggregate formation could be monitored by measuring the slurry temperature during freezing. The slurry was completely frozen when its temperature reached that of the inside of the freezer or the temperature of the coolant. The completely frozen slurry separated entirely after thawing, but the slurry during latent heat removal did not. The aggregate size decreased with increase in the rate of freezing and can, therefore, also be controlled by adjusting the freezing conditions. The abrasive particles are probably discharged into the interfaces of the crystalline ice and concentrated in water region between ice crystals. The particles are then compressed by the ice crystals to form aggregates when the slurry is completely frozen at below the freezing temperature.