Coal gangue (CG) is a major by-product of coal mining and preparation, which is generated in large volumes and poses persistent environmental and land-use challenges. Despite its potential as a secondary mineral resource, existing studies remain largely descriptive and lack an integrated framework linking geological controls, mineralogical composition, geochemical evolution, and utilization performance. This review proposes a unified Geo-Mineralogical-Geochemical-Environmental-Utilization (GMGEU) framework to systematically evaluate coal gangue from a coal preparation and resource utilization perspective. CG is predominantly composed of SiO2 (40–70 wt.%) and Al2O3 (15–35 wt.%), with mineral assemblages dominated by quartz, kaolinite, and illite. These minerals control key transformation processes, including sulfide oxidation, aluminosilicate hydrolysis, and thermal activation processes such as metakaolin formation. It directly influences both contaminant release behavior and material reactivity. The analysis shows that environmental risks, such as acid mine drainage and trace metal leaching, are intrinsically linked to utilization performance in applications including cementitious materials, geopolymers, and ceramics. Current global utilization rates remain below 40%, highlighting significant scope for improved resource recovery. In addition, rare earth element concentrations (50–500 mg/kg) indicate potential for value-added extraction under optimized processing conditions. This review provides a mechanistic and quantitative basis for process-oriented evaluation and risk-informed utilization of coal gangue, supporting its transformation from a mining by-product into a functional resource within coal preparation and utilization systems.
Juan et al. (Tue,) studied this question.