Research status and progress of high-value utilization of coal gangue solid waste

Coal gangue, a solid waste generated during coal mining and washing processes, poses significant environmental risks when left to accumulate naturally.Prolonged accumulation not only occupies land and causes soil erosion but also increases hazards like spontaneous combustion and explosions. Moreover, its heavy metal content contributes to soil and groundwater contamination. Statistics show China's annual coal gangue production exceeds 700 million tons, with cumulative stockpiles surpassing 6 billion tons.Consequently, effective management and utilization of coal gangue have become critical challenges for the coal industry. Current applications primarily include road construction using waste rock, mine backfilling, and producing low-performance building materials like bricks and tiles. These rough applications fail to make full use of the rich chemical components and rare elements of coal gangue, such as SiO₂, Al₂O₃, Fe₂O₃, K₂O, MgO, CaO, Na₂O, Ni, B, Be, Ti and Ga. With China's sustainable development strategy, the industry is shifting toward green, high-value utilization. Innovative approaches include: extracting alumina and silica gel through acid leaching; developing geopolymer materials with 1.5 times the strength of traditional cement via alkali-activated processes; synthesizing zeolite molecular sieves for wastewater treatment and gas adsorption using thermal activation technology; and optimizing formulations to produce high-performance ceramics or microbial-modified soil conditioners that regulate pH levels and supplement trace elements. From the perspective of coal gangue mineral composition, this study systematically discusses the current status of high-value utilization of coal gangue as raw material, including chemical product extraction, synthetic geopolymer production, and preparation of ceramics, zeolite molecular sieves, and soil amendments. It analyzes the main challenges in coal gangue application and the development trends of multi-component cascade utilization models, aiming to provide insights and references for related research on coal gangue and the high-value utilization of solid waste.