Sugarcane bagasse and iron ore tailings thermochemical conversion towards sustainable iron recovery with biogenic carbon and hydrogen production

The recovery of valuable chemical elements from industrial waste is essential for production processes' economic and environmental sustainability. The interaction between the iron ore tailings and sugarcane bagasse, both wastes, has the potential to provide a secondary iron source for future iron and steelmaking processes. This study evaluated the use of volatiles from sugarcane bagasse (SCB) and iron ore tailings (IOT) to the synergistic promotion of carbon deposition, H₂ production and conversion of weak magnetic iron oxides in strong magnetic iron phases. The experiments were carried out at 400, 600, 800, and 1000 °C with different SCB/IOT ratios under an N₂ atmosphere. In all tests, SCB and IOT were heated simultaneously in separate beds to prevent direct contact between the materials. The combination of 600 °C and higher SCB/IOT ratio resulted in a product with 96.7% magnetite, 98% magnetic fraction recovery, and 3.5% deposited carbon. The use of lower SCB/IOT ratio provided an increase in H₂ production. Regardless of the mass ratio, heating the IOT and SCB simultaneously up to 1000 °C led to significant mineralogical transformations, reaching reduced phases such as wüstite, fayalite and metallic iron, which impaired magnetic separation efficiency. The results indicate an alternative for recovering iron from IOT using biomass waste as a renewable reducing agent for the steel industry.