An integrated process for the recovery of aluminum and iron from bauxite residue coupled with CO2 sequestration via low-temperature roasting and carbonation

Bauxite residue, a highly alkaline by-product of alumina production, poses significant environmental challenges worldwide. This study presents an integrated process for the comprehensive treatment of bauxite residue, coupling the recovery of valuable metals (Al and Fe) with CO 2 sequestration. The process involves low-temperature roasting of bauxite residue with ammonium bisulfate, followed by water leaching, sequential recovery of Al and Fe from the leaching solution, and carbonation of the leaching residue. Under optimized roasting conditions (ammonium bisulfate dosage of 1.8 times the theoretical amount, 400 °C, 90 min) and leaching conditions (95 °C, liquid−solid ratio of 3 mL/g, 60 min), extraction efficiencies of 95.9% for Al and 98.6% for Fe were achieved. Aluminum was selectively recovered from the leaching solution as ammonium alum via crystallization. After recrystallization under optimized conditions, the recrystallization efficiency reached 89.3% with an Fe impurity content as low as 0.068 wt%. Iron was subsequently precipitated as an Fe-rich product (42.06 wt% Fe) with > 99.99% efficiency. The leaching residue was carbonated using (NH 4 ) 2 CO 3 , achieving a carbonation efficiency of 96.28% and a CO 2 sequestration capacity of 100.61 kg per 1000 kg of bauxite residue. This process also effectively removed sodium (from 6.31 wt% in the original bauxite residue to 0.09 wt% in the carbonated slag), rendering the slag suitable for construction materials or soil improvement. The recovered sulfates can be recycled as a roasting agent for the subsequent bauxite residue treatment. This integrated approach offers a promising circular economy strategy for the sustainable management of bauxite residue, combining valuable metal recovery with effective CO 2 sequestration.