| abstract |
Aqueous suspensions of red mud are effectively removed from the Bayer process for making alumina by the addition to at least the first stage of the caustic recovery circuit of a flocculant selected from starch, homopolymers of acrylic acid or acrylates, co-polymers of acrylic acid or acrylates containing at least 80 molar percent acrylic acid or acrylate monomers and combinations thereof and subsequent addition to later, more dilute stages in the caustic recovery circuit of a copolymer containing from about 35 to 75 molar percent of acrylic acid or acrylate and from about 65 to 25 molar percent of acylamide monomers. |