Comparison of physical properties between treated and untreated bauxite residue mud

Dry stacking is an improved method of storing bauxite residue mud, a by-product of the Bayer process in the alumina industry. Stacking has the potential to increase the density and stability of the residue deposit, reducing the costs associated with the construction of impoundment areas. Minimizing the land area exposed to the residue mud also reduces the possibility of groundwater contamination. The stored residue is alkaline and carries the potential for environmental impacts over the long term. Carbonation is being evaluated at Alcoa World Alumina Australia's (Alcoa's) Kwinana Refinery in Western Australia, as a means of neutralizing residue alkalinity. This paper details the physical characteristics exhibited by bauxite residue following treatment with carbonation and/or the addition of bitterns. The impact of residue carbonation and bitterns addition on the initial drainage and drying behavior of bauxite residues was evaluated. The long term consolidation properties of the residues and the impact of these chemical treatments on the overall stability of the deposit was also determined.