Recovery of the Glass Abrasive Particulates from Used Slurry by Freezing and Thawing

概要

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Cerium oxide abrasive is widely used in fine polishing processes, such as fabrication of lenses, prisms, liquid crystal panels, and glass substrates for hard disks. More than 90 percent of rare-earth metals, including cerium, have been imported from China, but because of China's recent resource strategy, their price has risen dramatically. Reuse and recycling are, therefore, urgently required. Recovery technologies of cerium oxide abrasive particulates from used abrasive slurry were examined. The particles in used slurry were too small for separation by natural sedimentation. We have discovered that secondary particles were formed by freezing and thawing the slurry, and that the sediment and supernatant liquid were easily separated. This technique requires only a freezer, and does not employ flocculants or other chemicals. Freezing and thawing separation is an effective method of recovering the abrasive particulates in used slurry.