Characteristic, hazard and iron recovery technology of red mud - A critical review

Red mud (RM) is the major waste material with strong alkaline discharged which is during the alumina extraction process. The global stock of RM has exceeded 4 billion tons and its disposal as a solid waste has always been a thorny environmental problem. However, RM is widely considered to be a potential resource due to its high content of valuable metal components such as iron. High-iron RM is rich in iron and can potentially become a valuable resource if the iron can be extracted effectively. It is of great research value and profound significance to recover iron from high-iron RM. This paper systematically reviews the iron recovery methods for resource utilization of high-iron RM, and divides the technology of iron recovery from high-iron RM into three aspects: physical separation method, pyrometallurgy method (reduction smelting and reduction roasting) and hydrometallurgy method (acid leaching). The basic principles and effect of iron extraction of the above technologies are summarized respectively, and the advantages and disadvantages of different technologies are compared. It is pointed out that the feasibility and economic cost are the main factor restricting the industrial application of these technologies. Therefore, it is of great significance to overcome various problems and difficulties, and develop innovative processes and technologies, which can realize the recycling and utilization of iron in high-iron RM and realize the reduction of RM emission at the same time.