Mineralogical Assessment of the Solid Phase Obtained on Leaching of Brazilian Red Mud

摘要

The main residue generated during the Bayer Process is the red mud or bauxite residue. In 2015, the quantity of red mud stored around the world reached 4 billion tonnes. The composition of the red mud varies according to the bauxite used in the alumina extraction process. The main components of the residue are iron, aluminum, silicon and titanium. Besides that, the red mud is the major source of scandium, which is considered a critically important metal. Hydrometallurgical processing is the main route used for scandium extraction from red mud. However, the effect of acid reaction in the red mud is not studied in-depth. For this reason, the goal of this work is the mineral assessment of the solid phase obtained on leaching of Brazilian red mud. Thermodynamic simulations were carried out using FactSage 7.2 software to predict which phases can be formed during the leaching. The software is not explored for hydrometallurgical reactions in the literature. The Brazilian sample was leached by sulfuric acid 20%. The solid/liquid ratio was 1/10 and samples were analyzed in different time reactions at 25 °C. Results showed that the mineral phases obtained were in agreement with the thermodynamic simulation calculated using FactSage software. Also, the software has demonstrated to be an important tool for leaching studies.