A Review of Laboratory Methods for Metal Recovery from Red Mud: Extraction Strategies and Technological Insights

Abstract

Red mud, a solid waste byproduct from alumina production via the Bayer process, represents a potentially valuable secondary resource. The global scientific community is increasingly focused on developing environmentally friendly and economically viable technologies for red mud recycling. This review summarizes findings from 162 scientific publications, with emphasis on studies related to the extraction of valuable elements such as iron (Fe), aluminum (Al), sodium (Na), and titanium (Ti). Reported concentrations of key oxides in red mud vary significantly depending on bauxite composition and processing route, with Fe₂O₃ ranging from 7–70 wt.%, Al₂O₃ from 2–33 wt.%, TiO₂ from 2.5–22 wt.%, and Na₂O up to 12.5 wt.%. Maximum extraction efficiencies achieved under laboratory conditions reached 97.5% for iron, 89.7% for aluminum, 96.4% for sodium, and 97% for titanium.

The analysis highlights the predominance of laboratory-scale studies, with limited transition to industrial applications. Integrated processing schemes—such as reduction smelting, magnetic separation, and leaching with mineral (HCl, H₂SO₄, HNO₃) and organic (H₂C₂O₄) acids—are identified as particularly promising. Emerging methods involving microwave, ultrasonic, and plasma-assisted treatments are also discussed. However, economic feasibility remains a major uncertainty. This review proposes a structured overview of current extraction technologies and outlines criteria for processes that balance environmental, energy, and cost considerations. Additionally, the article presents laboratory results on combined extraction schemes and explores the use of red mud in mold separation coatings.