Study on the clarification of a red mud slurry during flocculation

One of the important steps in the Bayer process is the solid-liquid separation by which the particulate materials are removed from the feed slurry. One of the ultimate goals of the alumina industry is to obtain a perfect overflow clarity. In this study, the parameters that can influence the clarity of the overflow liquor resulting from the flocculation of the red mud slurry are systematically evaluated. Several laboratory tests are done by combining commercial synthetic flocculants and new polymers. By varying the concentration of polymer solutions, the quantity and the sequence of introduction of polymeric materials, extremely low levels of turbidity were found in the overflow liquor. This represents a definite step towards the objective of reaching a perfectly clear overflow liquor right at the decanter stage.