The term "waste alumina" here refers to alumina materials and alumina-containing products that have lost their original functionality, or although not completely lost their utility value, have been discarded during the production and use processes in metallurgy, chemical industry, refractories, ceramics, and catalysis. After collection, classification, and processing, they can be recycled as alumina resources for reuse in smelting, refractory production, or other recycling applications.