The Recovery of Rare Earth Metals from Bauxite Residues

Abstract

With the rising use of contemporary, environmentally friendly technology, there is an increase in the demand for crucial commodities like scandium and rare earth elements (REEs) and other valuable metals, which necessitates the use of innovative resources to secure supply. This thesis includes both pyrometallurgical and hydrometallurgical methods aiming decarbonizattion process for recovering valuable metals from bauxite residues, with the hydrogen plasma reduction and direct acid leaching serving as the primary approaches. The objectives of adopting these procedures are to provide alternative and/or creative techniques for the recovery of REEs and other valuable metals from materials like bauxite residue, which cannot be disposed of in an ecologically responsible manner following the Bayer chemical process, which extracts aluminum. As carbon smelting, which was previously used to recover REEs from BR, was inefficient due to using carbon as a reagent, hydrogen is now being investigated as a replacement. Hydrogen plasma reduction recovers about 99,9% of iron as crude metallic iron, which can be separated from slag that contains aluminum and silicon. In order to recover valuable metals like scandium and aluminum, the slag is treated or leached by acids. Bauxite residue is also subjected to direct acid leaching (hydrometallurgy) in order to extract rare earth elements such as yttrium, scandium. To obtain more effective and optimum outcomes, the pyrometallurgy and hydrometallurgy combination of the two techniques was also investigated. Effective characterisation techniques for examining the results of hydrogen plasma reduction and direct acid leaching studies for their mineralogical, chemical (macro component), and micro impurity investigations were described. The goal of extracting Fe, Al, Ti, and Si was accomplished since the data clearly indicate their presence and provide proof that they are vital for a sustainable future and all facets of human existence.