Biodesulphurising high sulphur content tailings from coal mining in Brazil

Brazilian coal is characterized by its low calorific value, high ash and sulphur (S) contents, which requires beneficiation processes that increase costs and reduce its competitiveness compared to other energy sources. The processing of such coal generates a huge amount of residues rich on sulphide minerals, which disposal leads to the generation of Acid Mine Drainage (AMD) that need to be treated. The reason for processing such residue is to produce low sulphur content coal for energy generation purpose, which have to be lower than 1% of sulphur. Therefore, this technical contribution aims at bio-assisted digesting the iron sulphide minerals, pyrite in particular, producing iron sulphate bearing leachates. The bioleaching tests is being accomplished using a consortium of natural autotrophic microorganisms in a VAT-heap leaching reaction system, where the tailing is flooded with the leaching solution bearing the aforementioned microorganisms. According to the results, out of the in-progress bioleaching test, the iron is being progressively extracted, and so does the tailing desulphurised, which means that this process is prone to be enhanced as the operation parameters are being optimised. Finally, the leachate being produced is a potential raw material for producing iron oxyhydroxides, such goethite and maghemite, with high industrial added values.