Review: research progress on the resource utilization and high-value conversion of fly ash—turning waste into wealth

Fly ash (FA), a bulk solid waste generated from coal-fired power plants, holds significant potential for resource utilization and value-added applications, serving as a critical enabler for advancing global carbon peak and carbon neutrality objectives alongside sustainable development goals. The physicochemical properties of FA and its rich content of valuable components endow it with significant potential for resource recovery and high-value utilization. However, the massive stockpiling of FA occupies substantial land resources and causes environmental contamination through the leaching of heavy metals. This paper systematically reviews the physicochemical properties and hazards of the subject matter, while also providing a comprehensive overview of recent advancements in both resource utilization and deep processing applications. FA, characterized by its cost-effectiveness, high strength, and superior stability, is extensively utilized in the construction materials sector. Owing to its unique compositional structure and physicochemical properties, it also finds broad applications in environmental protection and energy storage materials. In contrast to existing reviews, this article focuses on two critical issues in the resource utilization of FA: the loss of valuable elements and the environmental threats posed by the extensive consumption of chemical agents and generation of secondary waste liquids during deep processing. Consequently, future research should advance FA reuse toward environmentally friendly, low-cost, and high-efficiency approaches, enabling “wealth creation from waste” and fostering green sustainable development.