6. Bauxite Residue/Red Mud

The chapter on bauxite residue (red mud) comprehensively reviews all aspects of bauxite residue from separation, management and disposal through to the ever-increasing use of the Material. Mud washing and the optimum recovery of soda and alumina values is presented. Dewatering options, filtration theory is described in detail and the benefits that can be achieved using various filter types. The management and storage of bauxite residue is then reviewed from a historical perspective together with the trends and changes in disposal methods. Topics covered include sea water neutralisation, costs of disposal, dry mud stacking, filtration and as well as recent developments in the remediation of closed bauxite residue areas. Some current best practices in Europe and Australia are discussed with a detailed review of mud farming methods and rehabilitation trials that have been carried out at Aughinish Alumina in Ireland. Alcoa’s vision for more sustainable management of bauxite residue in their Australian operations is described together with a historical overview of best practices covering their move into thickened slurry disposal, solar drying through to filtration. The mineralogy and chemical composition data for bauxite residue are discussed prior to discussing possible uses. The very wide spectrum of uses is reviewed from laboratory studies that have been undertaken through to current significant industrial uses. Areas covered include use of bauxite residue in cement, iron and steel extraction, materials recovery (particularly rare earths), landfill capping, heavy metal and phosphate removal, manufacture of construction products, heat storage medium, and fire retardants. Some of the recent extensive work programmes being undertaken under EU HORIZON 2020 funding are also reviewed.