Alkali recovery from bauxite residue via ferric sulfate dealkalization and convert dealkalization residue into a secondary iron resource

The most effective means to promote the sustainability of the circular economy is to recycle waste from various sources, such as industry and commerce. This study aimed to investigate alkali recovery from bauxite residue and the potential of iron recovery from dealkalized bauxite residue via the ferric sulfate dealkalization method. Under constant solid–liquid ratio and temperature conditions, the optimal dealkalization rate reaches 99.17% whren bauxite residue, FeSO₄, and H₂O₂ in a proportion of 2:3:2. After undergoing 4 dealkalization cycles,, the Na⁺concentration in the supernatant reached 1800 mg L⁻¹, and the alkaline recovery rate increased to 90% with the addition of 5 g L⁻¹ CaO. Compared to acid leaching, this dealkalization method demonstrated superior long-term effectiveness in regulating alkalinity. The formation of Fe(OH)₃ facilitated cementation the bauxite residue particles and considerably improved filtration performance through adsorption, bridging, and cross-linking mechanisms. Furthermore, the iron content of the dealkalized BR increased from 46.97% to 76.24%, meeting the China Standard for production grade iron ores (V grade). Approximately 8 tons of bauxite residue were estimated to be consumed, resulting in the generation of 4.64 tons of CaSO₄. Thus, this sustainable method offers complete reutilization of bauxite residue, contributing to waste minimization efforts.