Unlocking scandium from red mud: A critical review of challenges, opportunities, and recovery methods

Abstract

Red mud, the fine iron-rich residue generated during the processing of bauxite using the Bayer process, is a highly alkaline hazardous waste with significant environmental implications. While it is predominantly stored in landfills, only a small fraction is repurposed, such as in construction materials. Notably, red mud contains elevated concentrations of Scandium, a critical mineral with growing industrial demand. Over the past few decades, numerous methods have been investigated for scandium recovery from red mud. However, no commercial processes have yet been implemented at scale. This review critically examines these methods, emphasizing the influence of iron on scandium recovery. It concludes by outlining three promising scandium recovery approaches: (i) reduction roasting followed by acid baking and water leaching of the slag, (ii) acid-baking combined with ball-mill assisted water leaching, and (iii) two-stage acid-baking and water leaching.