Red mud as a source of scandium: A review

The residue produced during the extraction of aluminum from bauxite ore via the Bayer process is known as red mud (RM), with 0.5–2.5 t of RM generated for each ton of alumina produced. Due to its highly alkaline nature (pH = 10.0–12.5), RM poses significant environmental threats and requires large storage areas. To address this environmental concern and develop sustainable way to utilize RM, extensive research has been conducted in fields such as soil remediation, metal recovery, steel production, catalytic reactions, cheap adsorbents for pollutant removal, ceramics, brick production, and pigment and slag additives for paint production. While early studies on metal recovery from RM focused on the recovery of metals such as Fe and Al, recent years have seen an increase in research on Sc recovery from RM, as RM is now recognized as an important source for Sc. This review examines in detail methods such as direct acid leaching, bioleaching, acid baking, and water leaching used for Sc recovery from RM. Additionally, data on the recovery of not only Sc but also other metals from RM are presented.