A critical review on the ecological restoration utilization and prevention and control of heavy metal pollution of coal gangue

Coal gangue is a major industrial solid waste in China, which occupies a large amount of land and causes a serious ecological issues, such as geological disaster and environmental pollution. The extensive accumulation of coal gangue poses a significant constraint on the sustainable development of the coal industry. Therefore, it is urgent to find large-scale disposal methods for coal gangue. The ecological restoration utilization of coal gangue is an effective way to achieve large-scale disposal. The paper presents a comprehensive overview of the constituents and minerals in coal gangue, as well as the ecological restoration utilization technologies employed for the material. The release risk of heavy metals during the ecological restoration utilization processes, and prevention and control of heavy metal pollution are also discussed. Furthermore, some valuable recommendations for ensuring the safe utilization of coal gangue in ecological restoration are proposed. Coal gangue is comprised of sand and clay minerals, containing abundant N, P, K, organic matter, and other nutrients that serve as essential material foundation for ecological restoration utilization of coal gangue. Coal gangue can be utilized for ecological restoration utilization through backfill ditches and create land while also serving as a soil-functional planting substrate. However, the presence of high levels of heavy metals and sulfur in certain coal gangue samples presents a potential environmental risk associated with the release of heavy metals, thereby impeding the ecological restoration utilization of coal gangue. The use of techniques such as microbial technology, oxidation inhibition technology, and immobilization technology of heavy metals can effectively control the release of heavy metals in coal gangue. The environmental behavior of heavy metals during the process of ecological restoration utilization of coal gangue, which contains high levels of heavy metals and sulfur, should be further investigated to ensure its ecological restoration utilization. Integrated technologies encompassing physical, chemical, and microbial approaches need to be employed, inhibiting acid production and the release of heavy metals to achieve ecological restoration safe utilization of coal gangue. In addition, the monitoring of potential ecological and environmental risks of heavy metals in the ecological restoration process of coal gangue should be strengthened, ultimately achieving ecological restoration safe utilization of coal gangue.