Extraction of Aluminum and Lithium from Fly Ash via Alkali Roasting-Acid Leaching

Fly ash (FA) represents a promising secondary resource for the recovery of critical metals, particularly aluminum and lithium. This study proposes a combined process of NaOH roasting followed by hydrochloric acid leaching for efficiently extract aluminum and lithium from FA. The effects of key operational parameters on the leaching efficiencies of both metals were systematically investigated Under the optimized conditions (roasting at 700 °C with a FA/NaOH mass ratio of 1:1.1, followed by leaching at 90 °C with a liquid-to-solid ratio of 10:1), the leaching efficiencies reached 90.79% for aluminum and 80.72% for lithium. The underlying extraction mechanism was elucidated through thermodynamic calculations and comprehensive characterization of the roasting products and leached residues. The analysis revealed that the alkali roasting process effectively destroys the stable aluminosilicate matrix, facilitating the subsequent selective dissolution of aluminum and lithium. This work provides an effective strategy for recovering aluminum and lithium and a potential pathway for the sustainable and high-value utilization of FA.