Recovery of alkali and alumina from bauxite residue (red mud) and complete reuse of the treated residue

Bauxite residue is an alkaline solid waste produced during the extraction of alumina from bauxite, which causes serious environmental problems and safety risks. In this study, alkali and alumina were recovered from Bayer bauxite residue using a novel calcification-carbonisation process. This produced a nonhazardous and near-neutral residue (C-C residue), the properties of which facilitated its subsequent reuse. After the calcification-carbonisation treatment, 46.5% of the alumina was extracted and the Na2O content in the final residue (C-C residue) dropped to less than 0.3%. In addition, the feasibility of using CC residue in the production of cement and the preparation of soil was analysed. The results showed that the chemical composition of C-C residue is very close to that of Portland cement clinker, which allows the dosage of bauxite residue in cement production to be increased. A comparison of the C-C residue with a general soil showed that the former performed well for many soil parameters, such as alkalinity and salinity, and has great potential for application in soil preparation. Thus, the calcification-carbonisation method, combined with cement production or soil preparation, is a sustainable process for completely reusing Bayer bauxite residue and facilitating bauxite waste minimisation. (C) 2018 Published by Elsevier Ltd.