Recovery of valuable elements from coal fly ash: A review

Coal fly ash is a solid waste produced during the combustion of coal in power plants, which occupies a vast area of land, entails high maintenance costs, and poses ecological and environmental risks. Nevertheless, coal fly ash contains abundant valuable elements, giving it potential utilization value. Considering the increasing depletion of native mineral resources worldwide and the restricted availability of rare earth elements, the recovery of valuable elements from coal fly ash is of great significance in addressing the issues of large-scale solid waste disposal and resource scarcity. This paper comprehensively summarizes the composition, content, distribution, and forms of various elements in coal fly ash, providing a scientific basis for subsequent recovery and utilization. It focuses on the methods and latest advancement in the recovery of valuable elements (such as Al, Si, Fe, Li, Ga and several rare earth elements) from coal fly ash, including physical beneficiation, hydrometallurgy, pyrometallurgy, and other novel processes. The effectiveness, benefits, and drawbacks of existing extraction methods are evaluated based on energy consumption, recovery efficiency, environmental consequences, and the future development direction of sustainable utilization of coal fly ash is discussed. The proposal of new technologies for the comprehensive, environmentally friendly, and low-energy consumption recovery of valuable elements from coal fly ash is aimed at promoting the comprehensive utilization of bulk solid waste and green economic development.