The synergistic recovery of aluminum, lithium and gallium from fly ash using physical enrichment followed by an alkali fusion-organic acid leaching method

Enrichment and leaching of aluminum (Al), lithium (Li) and gallium (Ga) from coal fly ash is an important step in the recovery of critical elements, which determines the dissolution of critical elements in the aqueous phase and influences subsequent extraction efficiency. In this work, synergistic recovery of Al, Li and Ga was investigated by a combination of physical enrichment and Na 2 CO 3 fusion-citric acid leaching processes. The results show that fly ash from different regions of Pingwei Power Plant in China, designated as FA-PA and FA-PB respectively, exhibits high consistency in chemical composition and mineralogy. Both batches exhibited enrichment of Al, Li, and Ga in particles < 45 μm in diameter. Calcination at 870 °C for 90 min with Na 2 CO 3 effectively activated Al, Li, and Ga in both samples. However, the optimal leaching conditions for Al, Li, and Ga differed slightly between the two batches. FA-PA achieved maximum leaching rates of 97.1%, 98.9%, and 80.4% for Al, Li, and Ga respectively, while FA-PB exhibited leaching rates exceeding 90% for all three elements under optimal conditions. The sodium carbonate fusion combined with citric acid leaching employed in this study effectively disrupted the silicate-aluminate glass of fly ash and activated the reactive substances within the minerals, enabling the release of Al, Li, and Ga into solution. This study provides theoretical support for the synergistic recovery of Al, Li and Ga from coal fly ash.