The production of coal gangue, a by-product of coal mining and washing, is rapidly increasing due to growing energy consumption. As the accumulated coal gangue has not been appropriately utilized, this has resulted in a squander of resources, waste disposal problems, and environmental pollution issues. However, coal gangue, a form of solid waste, exhibits various potential applications in the field of recycling. Currently, the processing capacity and utilization rate of coal gangue are insufficient to meet the demands of global low-carbon environmental protection. As such, this paper provides a detailed overview of the physical and chemical properties of coal gangue and its resource utilization methods in the environmental field, particularly in soil remediation, soil reclamation, the preparation of adsorbents for heavy metals, dyes, and CO₂, and as catalysts for organic degradation and catalytic cracking. This review highlights the significance of coal gangue classification according to its properties for the comprehensive utilization of gangue. Additionally, we briefly introduce and discuss suggestions for future directions of research and development in this area. Nevertheless, with regard to the environmental impact of secondary pollution and the efficiency of coal gangue utilization, there remain numerous obstacles that hinder future research. This review is expected to provide significant insights into the development of coal gangue utilization strategies, potentially facilitating the efficient and practical large-scale management of solid waste.

Alkaline fusion is a pivotal process influencing the cost of synthesizing zeolite from coal gangue. This study examined the effects of alkaline fusion temperature (X ₁), treatment duration (X ₂) and the NaOH/coal gangue weight ratio (X ₃) on the composition and properties of the products, as well as their adsorption capacities for Cd²⁺ (q _e,Cd) and Pb²⁺ (q _e,Pb). Response surface methodology (RSM) was employed to analyze the interactions among these factors, and the adsorption mechanisms for Cd²⁺ and Pb²⁺ were investigated using X-ray diffraction, scanning electron microscopy-EDS, Fourier transform infrared, X-ray photoelectron spectroscopy, and N₂ adsorption-desorption techniques. The results reveal that (1) under optimized conditions-X ₁ of approximately 800 °C, X ₂ of around 2.8 h and X ₃ of 1.2-the maximum q _e,Cd and q _e,Pb for the synthesized NaX zeolite can reach 181.3 and 419.9 mg/g, respectively. (2) The RSM models indicate that increasing the X ₃ value can lower the required X ₁. For q _e,Cd and q _e,Pb of 150 and 350 mg/g, respectively, with X ₂ fixed at 2 h, increasing X ₃ from 0.976 to 1.134 and from 0.900 to 1.289 enables a reduction in X ₁ from 800 to 600 °C. (3) NaX zeolite primarily adsorbs Cd²⁺ and Pb²⁺ through ion exchange, allowing these ions to enter the zeolite's cage structure. Pb²⁺ can also precipitate as hydrocerussite (Pb₃(CO₃)₂(OH)₂) within the zeolite channels, while Cd²⁺ has a more significant impact on the [SiO₄] and [AlO₄] tetrahedra. (4) The synthesized NaX zeolite effectively reduces the exchangeable Cd content in contaminated soil from 3.51 to below 1.5 mg/kg. The remediation performance of the NaX zeolite for Cd and Pb in water and soil can be further enhanced by optimizing its Si/Al ratio and pore structure.

The surface subsidence caused by the coal seam mining seriously affects the ecology of the mining area. Compared with the single-coal seam mining, the mechanism of the overburden fracture and crack propagation caused by multi-coal seams mining is more complex, which has not been fully understood. Taking the 22,108 and 42,108 working faces of Buertai Coal Mine as a research object, the discrete element method is used to simulate the migration and failure characteristics of overlying strata, and the propogation of cracks in the process of multi-coal seams mining is also been investigated. So many cracks develop in the soft strata overlying the coal seam, and they cross each other and form a complex fracture system. The hard layer produces staggered cracks with a large size, mainly high-angle longitudinal cracks. The surface subsidence curve of the single coal seam mining shows a wide and slow “bowl” type, and the surface subsidence curve of the double coal seams mining show a “funnel” type with only one inflection point. The overburden structure disturbance caused by the previous coal seam and rock cracking—settlement have great influence on the mining of the latter coal seam. The research results are basically consistent with the field data comparison, which could provide a reference for the related research and engineering practice of shallow-buried double coal seam mining.

As coal resources are gradually being extracted at depth, the overlying strata movement behavior and stress environment become complex and violent, leading to the frequent triggering of strong dynamic hazards. To promote the productivity and effectiveness of mining activities, this paper investigated the evolution characteristics of overburden structure and stress in deep mining by using theoretical analysis, on-site monitoring, and numerical simulation. Based on key strata theory, key layers were determined, and how their movement states have a controlling effect on surface subsidence was analyzed. The evolution process of the overburden spatial structure in deep mining was revealed, which was consistent with the “O-X” type structure. The surrounding rock stress at the working face has gone through three stages, violent change, slow increase, and fluctuant increase, and strong strata behaviors appear because of the fracture and collapse of key layers. The goaf will have a significant effect on the structure, stress, and deformation of the overlying rock, which results in a larger deformation of the surrounding rock within the vicinity. The narrow coal pillar fails to maintain the stability of the overburden structure when the stress exceeds the bearing capacity. The deformation law of the surrounding rock at the roadway was studied, concluding that the existence of the goaf leads to a further increase in deformation.

The remote sensing ecological index (RSEI) has been widely used in the rapid monitoring and evaluation of the regional ecological environment; however, the research on the main factors that cause changes in RSEI and the impact of human activities in the mining area on RSEI is not often explored. To this end, this paper selected the Landsat (TM/OLI) series of remote sensing images from 1986 to 2022; extracted the four important indicators of the normalized difference vegetation index (NDVI), the wetness component of the tasseled cap transformation (WET), normalized difference built-up and soil index (NDBSI), and land surface temperature (LST); calculated the remote sensing ecological index (RSEI) based on the principal component analysis method; monitored and evaluated the ecological environment changes in the Shendong Mining Area for a period of 36 years; and analyzed the driving forces that cause these ecological environment changes. The results show the following: (1) The ecological status of the study area has shown an overall upward trend during the 1986–2022 period. (2) From 1986 to 2022, the area of RSEI with a grade of 0.4–0.6 increased by 1142.74 km², that with a grade of 0.6–0.8 increased by 124.09 km², and that with a grade of 0.8–1.0 increased by 0.73 km². (3) In the past 36 years, the proportion of RSEI with a positive grade difference was 97.52%, and the proportion of regions with a negative grade difference was 6.20%. (4) Rainfall is the main factor that causes changes in the regional ecological environment. By analyzing the main driving factors of ecological environment change and the relationship between human activities and RSEI, reference can be provided for the formulation of environmental protection policies and environmental planning in mining areas.

Coal mining subsidence leads to reductions in soil fertility. In order to improve soil physical and chemical properties and to promote vegetation restoration, a nitrogen-fixing bacterium named S1 was isolated from the coal mining subsidence area in the Shendong mining area, and a zeolite-immobilized nitrogen-fixing bacterium was studied to improve the soil in the subsidence area. The results show that the immobilized nitrogen-fixing bacteria can significantly improve the ammonium nitrogen and nitrate nitrogen of soil by 50 times and 0.6 times, respectively, at 20 days, and it can also improve organic matter. In pot experiments, it was found that immobilized microorganisms can improve germination rate, plant height and the dry and fresh weight of maize. The results of the above soil culture tests and pot experiments were then compared and analyzed. It was found that plants made obvious use of soil ammonium nitrogen and nitrate nitrogen, and planting the plants was conducive to increases in soil organic matter.