In Bayer process production of alumina, bauxite ore is digested in a high temperature, highly caustic solution. Remaining red mud residue, which does not digest, is left suspended in the resulting saturated sodium aluminate solution. This red mud residue must be removed prior to further processing of the saturated solution to ultimately precipitate a purified alumina trihydrate product. Red mud removal requires the use of flocculants effective in bridging and entrapping fine red mud solids to rapidly separate the solids from the saturated liquor. This separation process occurs via decantation and subsequently in multiple counter current washing stages to reclaim soluble alumina and soda.
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