Metallurgical process for valuable elements recovery from red mud—A review

Red mud, namely bauxite residue or red sludge, is a potential valued solid waste produced from the alumina extraction process with substantial reserve of over 2.7 billion tonnes worldwide. Taking into account the rise in iron ore price and scarcity of rare earth supply worldwide, recovering aluminum, iron, sodium and other valuable elements from red mud is significant in the disposal of problems associated with these solid wastes. The current application status and composition characteristics of red mud are first introduced. Metallurgical processes for aluminum, sodium, iron, titanium, vanadium, scandium and other valuable elements recovery from red mud are investigated in detail by subsequent sections. Some mechanisms and performance of solvent extraction involved in the extraction or stripping process are also reviewed in this paper. The result suggests that much work still needs to be done for the improvement of leaching and extraction selectivity as well as efficiency, and also for the development of a green recovery process with environmental benignity, low energy requirements and cost.