Fábio Oliveira, Tobias Hertel, and Yiannis Pontikes from KU Leuven have published a new study on the transformation of bauxite residue (BR) into high-performance monoliths using an autoclaving technique inspired by the Bayer process, in the Journal of Sustainable Metallurgy (June 2025 issue).
The research showcases a simple yet effective valorisation route: 100% BR is alkali-activated with sodium silicate, pressed into dense cubes, and subjected to hydrothermal curing at 220 °C and 24 bar. The resulting autoclaved samples achieved a compressive strength of 31 MPa—six times higher than the non-autoclaved equivalent. Microstructural analysis revealed that hydrothermal treatment enhanced mineral reactivity, facilitated phase transformations (e.g. sodalite to cancrinite), and promoted the formation of Na–Si-rich gel phases that contributed to mechanical and chemical stability. Crucially, leaching tests showed a reduction in hazardous element release to levels below EU hazardous waste thresholds.
Reference:
Oliveira, F., Hertel, T., & Pontikes, Y. (2025). Autoclaved Bauxite Residue Monoliths: A Bayer Process-Inspired Valorization Route. Journal of Sustainable Metallurgy. https://doi.org/10.1007/s40940-025-00391-4
Acknowledgements:
This article was published as part of the thematic section “Honoring Diran Apelian's Leadership in Sustainable Metallurgy.”
