Technospheric Mining of Rare Earth Elements and Refractory Metals from Bauxite Residue

For moving towards a sustainable future and building the circular economy, there is a push towards waste valorization. Bauxite residue is the by-product of the Bayar process for alumina production. It contains considerable amounts of rare earth elements (REEs) and refractory metals, some of which are considered critical materials and initiatives have begun to mine them from secondary sources, such as landfilled industrial process residues. Here, we develop a novel pyro-hydrometallurgical process called acid-baking water-leaching to extract REEs and refractory metals from bauxite residue. In this process, bauxite residue is mixed with concentrated sulfuric acid, baked at 200-400 degrees C, and leached in water at ambient conditions. Compared with conventional hydrometallurgical processes, the developed process offers the advantages of less acid consumption, less wastewater generation, and fast kinetics. Work is currently underway to develop this promising technique as the first step of a potential near-zero-waste integrated process for the sustainable valorization of bauxite residue.