Research on the Recovery and High-Value Utilization Pathways of Valuable Elements from Coal Gangue: A Review

As the largest solid waste generated by the coal industry, massive stockpiling of coal gangue not only encroaches on land resources but also poses severe ecological and environmental risks. However, coal gangue is rich in recoverable elements: bulk constituents such as aluminum (Al) and iron (Fe), the matrix component silicon (Si), and supply-critical elements such as lithium (Li), gallium (Ga), and rare earth elements (REEs). Although silicon (Si) is the dominant matrix component, it is recovered mainly as a byproduct during the extraction of these metals. Coal gangue holds significant potential as an “urban mine” for resource recovery. In light of this, this paper first elucidates the mineralogical characteristics and physicochemical properties of coal gangue, and reviews pretreatment activation processes such as mechanical and roasting activation aimed at enhancing reactivity. Secondly, it focuses on mainstream technological routes for valuable element extraction, separation and purification, and the high-value utilization of tailings. On this basis, the challenges faced by existing technologies in terms of energy consumption, costs, and secondary pollution are thoroughly analyzed, and future development directions in this field are outlined. Focusing primarily on Chinese coal gangue and targeting Al, Fe, Li, Ga and REEs (with silicon treated as the matrix component and recovered mainly as a byproduct), this review covers the literature published up to July 2026 identified through Web of Science and Scopus. This review aims to provide a scientific reference for establishing a “green extraction–high-value utilization” industrial chain for coal gangue, thereby promoting the green and low-carbon transformation of the coal industry.