How is red mud separated from sodium aluminate solution?

In the Bayer process, the separation of insoluble red mud from the sodium aluminate solution occurs during the clarification step. This process involves several stages to remove impurities of varying sizes:1

• Sand Traps: The mixture first passes through crude cyclones known as sand traps to remove coarse materials, such as beach sand.1
• Raking Thickeners: Finer residues are settled in raking thickeners. Synthetic flocculants are added to this stage to assist in the settling process.1
• Cloth Filters: Any remaining solids found in the thickener overflow are removed using cloth filters.1

Once separated, these residues are washed, combined, and discarded. The resulting clarified solution is then cooled in heat exchangers before proceeding to the precipitation stage.1