Search Results (270)

Coal serves as the primary energy source for China, with production anticipated to reach 4.76 billion tons in 2024. However, the mining process generates a significant amount of gangue, with approximately 800 million tons produced in 2023 alone. Currently, China faces substantial gangue stockpiles, characterized by a low comprehensive utilization rate that fails to meet the country’s ecological and environmental protection requirements. The environmental challenges posed by the treatment and disposal of gangue are becoming increasingly severe. This review employs bibliometric analysis and theoretical perspectives to examine the latest advancements in gangue utilization, specifically focusing on the application of computational chemistry to elucidate the structural features and interaction mechanisms of coal gangue, and to collate how these insights have been leveraged in the literature to inform its potential utilization routes. The aim is to promote the effective resource utilization of this material, and key topics discussed include evaluating the risks of spontaneous combustion associated with gangue, understanding the mechanisms governing heavy metal migration, and modifying coal byproducts to enhance both economic viability and environmental sustainability. The case studies presented in this article offer valuable insights into the gangue conversion process, contributing to the development of more efficient and eco-friendly methods. By proposing a theoretical framework, this review will support ongoing initiatives aimed at the sustainable management and utilization of coal gangue, emphasizing the critical need for continued research and development in this vital area. This review uniquely combines bibliometric analysis with computational chemistry to identify new trends and gaps in coal waste utilization, providing a roadmap for future research. Full article

This study investigates the impact of two comminution technologies—Vertical Shaft Impactors (VSI) and High-Pressure Grinding Rolls (HPGR)—on gold flotation performance, using ore samples from the Ballarat Gold Mine, Australia. The motivation stems from the growing need to improve energy efficiency and flotation recovery in mineral processing, particularly under increasing economic and environmental constraints. Despite the widespread use of HPGR and VSI in the industry, limited comparative studies have explored their effects on downstream flotation behavior. Laboratory-scale experiments were conducted across particle size fractions (300–600 µm) using two collector types—Potassium Amyl Xanthate (PAX) and DSP002 (a proprietary dithiophosphate collector) to assess differences in flotation recovery, concentrate grade, and specific energy consumption. The results reveal that HPGR produces more fines and micro-cracks, enhancing liberation but also increasing gangue entrainment and energy demand. Conversely, VSI produces coarser, cubical particles with fewer slimes, achieving higher flotation grades and recoveries at lower energy input. VSI at 600 µm demonstrated the highest flotation efficiency (4241) with only 9.79 kWh/t energy input. These findings support the development of hybrid or tailored comminution strategies for improved flotation selectivity and sustainable processing. Full article

Coal gangue, a major by-product of coal mining, poses significant environmental challenges due to its large-scale accumulation, land occupation, and potential for air and water pollution. This manuscript presents a comprehensive overview of continuous chamber gangue storage technology as a sustainable mining solution for coal mines. The principles of this approach emphasize minimizing disturbance to overlying strata, enabling uninterrupted mining operations, and reducing both production costs and environmental risks. By storing the surface or underground gangue in continuous chambers, the proposed method ensures the roof stability, maximizes the waste storage, and prevents the interaction between mining and waste management processes. Detailed storage sequences and excavation methods are discussed, including continuous and jump-back excavation strategies tailored to varying roof conditions. The process flows for both underground and ground-based chamber storage are described, highlighting the integration of gangue crushing, paste preparation, and pipeline transport for efficient underground storage. In a case study with annual storage of 500,000 t gangue, the annual economic benefit reached CNY 1,111,425,000. This technology not only addresses the urgent need for sustainable coal gangue management, but also aligns with the goals of resource conservation, ecological protection, and the advancement of green mining practices in the coal industry. Full article

To address the limitations of traditional hardened concrete road surfaces in coal mine tunnels, which are prone to damage and entail high maintenance costs, this study proposes using modular concrete blocks composed of fly ash and coal gangue as an alternative to conventional materials. These blocks offer advantages including ease of construction and rapid, straightforward maintenance, while also facilitating the reuse of substantial quantities of solid waste, thereby mitigating resource wastage and environmental pollution. Initially, the mineral composition of the raw materials was analyzed, confirming that although the physical and chemical properties of Liangshui Well coal gangue are slightly inferior to those of natural crushed stone, they still meet the criteria for use as concrete aggregate. For concrete blocks incorporating 20% fly ash, the steam curing process was optimized with a recommended static curing period of 16–24 h, a temperature ramp-up rate of 20 °C/h, and a constant temperature of 50 °C maintained for 24 h to ensure optimal performance. Orthogonal experimental analysis revealed that fly ash content exerted the greatest influence on the compressive strength of concrete, followed by the additional water content, whereas the aggregate particle size had a comparatively minor effect. The optimal mix proportion was identified as 20% fly ash content, a maximum aggregate size of 20 mm, and an additional water content of 70%. Performance testing indicated that the fabricated blocks exhibited a compressive strength of 32.1 MPa and a tensile strength of 2.93 MPa, with strong resistance to hydrolysis and sulfate attack, rendering them suitable for deployment in weakly alkaline underground environments. Considering the site-specific conditions of the Liangshuijing coal mine, ANSYS 2020 was employed to simulate and analyze the mechanical behavior of the blocks under varying loads, thicknesses, and dynamic conditions. The findings suggest that hexagonal coal gangue blocks with a side length of 20 cm and a thickness of 16 cm meet the structural requirements of most underground mine tunnels, offering a reference model for cost-effective paving and efficient roadway maintenance in coal mines. Full article

Anthropogenic revegetation allows effective and timely soil development in mine restoration areas. The evaluation of soil quality is one of the most important criteria for measuring reclamation effectiveness, providing scientific reference for the subsequent management of ecological restoration projects. The aim of this research was to further investigate the influence of revegetation on mine-reclaimed soils in a semi-arid region. Thus, a coal-gangue dump within the afforestation chronosequence of 1 and 19 years in Shanxi Province, China, was selected as the study area. We assessed the physicochemical properties and nutrient stock of topsoils under four revegetation species, i.e., Pinus tabuliformis (PT), Medicago sativa (MS), Styphnolobium japonicum (SJ), and Robinia pseudoacacia ‘Idaho’ (RP). A two-way ANOVA revealed that reclamation age significantly affected SOC, TN, EC, moisture, and BD (p < 0.05), while the interaction effects of revegetation type and age were also significant for TN and moisture. In addition, SOC and TN stocks at 0–30 cm topsoil at the RP site performed the best among 19-year reclaimed sites, with an accumulation of 62.09 t ha⁻¹ and 4.23 t ha⁻¹, respectively. After one year of restoration, the MS site showed the highest level of SOC and TN accumulation, which increased by 186.8% and 88.5%, respectively, compared to bare soil in the 0–30 cm interval, but exhibited declining stocks during the 19-year restoration, possibly due to species invasion and water stress. In addition, an integrated soil quality index (ISQI) and the partial least squares structural equation model (PLS-SEM) were used to estimate comprehensive soil quality along with the interrelationship among influencing factors. The reclaimed sites with an ISQI value > 0 were 19-RP (3.906) and 19-SJ (0.165). In conclusion, the restoration effect of the PR site after 19 years of remediation was the most pronounced, with soil quality approaching that of the undisturbed site, especially in terms of soil carbon and nitrogen accumulation. These findings clearly revealed the soil dynamics after afforestation, further providing a scientific basis for choosing mining reclamation species in the semi-arid regions. Full article

Specific computational methods, such as machine learning algorithms, can assist mining professionals in quickly and consistently identifying and addressing classification issues related to mineralized horizons, as well as uncovering key variables that impact predictive outcomes, many of which were previously difficult to observe. The integration of numerical and categorical variables, which are part of a dataset for defining ore grades, is part of the daily routine of professionals who obtain the data and manipulate the various phases of analysis in a mining project. Several supervised and unsupervised machine learning methods and applications integrate a wide variety of algorithms that aim at the efficient recognition of patterns and similarities and the ability to make accurate and assertive decisions. The objective of this study is the classification of gold ore or gangue through supervised machine learning methods using numerical variables represented by grade and categorical variables obtained through drillholes descriptions. Four groups of variables were selected with different variable configurations. The application of classification algorithms to different groups of variables aimed to observe the variables of importance and the impact of each one on the classification, in addition to testing the best algorithm in terms of accuracy and precision. The datasets were subjected to training, validation, and testing using the decision tree, random forest, Adaboost, XGBoost, and logistic regression methods. The evaluation was randomly divided into training (60%) and testing (40%) with 10-fold cross-validation. The results revealed that the XGBoost algorithm obtained the best performance, with an accuracy of 0.96 for scenario C1. In the SHAP analysis, the variable As was prominent in the predictions, mainly in scenarios C1 and C3. The arsenic class (Class_As), present mainly in scenario C4, had a significant positive weight in the classification. In the Receiver Operating Characteristic (ROC) and Area Under the Curve (AUC) curves, the results showed that XGBoost/scenario C1 obtained the highest AUC of 0.985, indicating that the algorithm had the best performance in ore/gangue classification of the sample set. The logistic regression algorithm together with AdaBoost had the worst performance, also varying between scenarios. Full article

Coal gangue, a primary byproduct of coal mining, causes significant environmental harm due to its improper utilization. This research proposes integrating microalgae with coal gangue-derived ecological products to improve soil conditions in ecologically vulnerable coal-mining regions. A field-scale experiment at the Jintong Coal Mine tested soils amended with varying proportions of a coal gangue ecological matrix (0%, 10%, 30%, and 50%), with and without microalgae inoculation. The results demonstrated that coal gangue addition caused undesirable soil pH decreases (11.30~42.20%) while increasing total dissolved solids (506.88~524.93%) and organic matter (8.51~46.81%). These effects were mitigated by the presence of microalgae. Microalgae play a role in regulating soil nutrient profiles, enhancing enzymatic activities, and modulating the microbial community structure. For example, they restored catalase activity under the stress imposed by coal gangue and stimulated urease activity at higher coal gangue proportions. Plant growth trials revealed that adding 30% coal gangue or combining coal gangue with microalgae significantly promoted the growth of Medicago sativa L. In summary, coupling the coal gangue ecological matrix with microalgae effectively enhances soil quality. Maintaining the coal gangue addition at 30% or less in conjunction with microalgae application represents an optimal approach for soil improvement in mining areas. Full article

This study characterises low-grade copper ore tailings from a conventional flotation circuit to evaluate their feasibility for further processing. A suite of advanced analytical techniques, such as X-ray fluorescence (XRF), inductively coupled plasma (ICP), X-ray diffraction (XRD), and the quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN), was employed to assess the elemental, chemical, and mineralogical composition of the tailings. Chalcopyrite was identified as the dominant copper-bearing mineral phase, predominantly locked within iron oxides and silicate gangue minerals. The QEMSCAN results showed that chalcopyrite was only partially liberated, which highlights the complex mineral intergrowths that hinder efficient recovery. Based on the mineralogical characteristics, the applicability of various processing techniques, including conventional froth flotation, advanced flotation methods [including Hydrofloat^TM, Jameson, and the Reflux Flotation Cell (RFC)], magnetic separation, and gravity separation, was evaluated. Overall, this study indicates that incorporating HydroFloat™, the Jameson Cell, and the RFC into the flotation circuit could greatly improve copper recovery from tailings. This study also identified rare earth elements (REEs) as potential by-products of copper recovery, so it is an additional opportunity for resource recovery. This paper contributes to sustainable mining practices and resource optimization by highlighting the characteristics and recovery of valuable minerals from tailings. Full article

Coal gangue is a fine-grained mineral with nutrient content, which can be used as a potential soil amendment. Nevertheless, current research on using coal gangue to improve soil water and support plant growth is still insufficient. In this study, coal gangue powder (CGP) was added to aeolian sandy soil. We compared the soil hydraulic properties and plant growth of original aeolian sandy soil (CK) and different CGP application rates (10% and 20%). The results indicated that the application of CGP transformed the soil texture from sandy to loamy, significantly reduced soil bulk density and saturated hydraulic conductivity (Ks) values, altered the soil water characteristic curve, enhanced soil water-holding capacity, and increased plant-available water. Compared with the CK group, the emergence rate of alfalfa seeds increased from approximately 50% to over 70% after CGP application. During the growth process, CGP application significantly elevated the net photosynthetic rate, transpiration rate, and stomatal conductance of alfalfa leaves. Rapid fluorescence kinetics monitoring of leaves demonstrated that alfalfa treated with CGP had a higher efficiency in light energy utilization. However, the photosynthetic capacity of leaves did not improve as the CGP application rate increased from 10% to 20%, suggesting that excessive CGP addition did not continuously benefit plant gas exchange. In conclusion, CGP application can improve the soil hydraulic properties of aeolian sandy soil and support plant growth and development, which is conducive to reducing the accumulated amount of coal gangue, alleviating plant water stress, and promoting ecological restoration in arid mining areas. We recommend a 10% addition of coal gangue powder as the optimal amount for similar soils. Full article

To improve the reliability of the shearer output shaft in coal seams with gangue, taking the MG400/951-WD shearer model as the research object, a test system for the physical and mechanical properties of coal seam samples containing gangue was established. Based on the coal breaking theory, the impact load of the spiral drum in a coal seam with gangue was simulated. Combined with rigid-flexible coupling virtual prototype technology, a rigid-flexible coupling virtual prototype model of a shearer with an output shaft as the modal neutral file was established. The output shaft is a typical symmetrical part, and it is of great significance to analyze it by using dynamic theory and mechanical reliability theory. The shearer system modal, the stress distribution of output shaft, and vibration characteristics were obtained by dynamic simulation. Based on resonance failure criterion and combined with a neural network, the output shaft stress reliability, vibration reliability, amplitude reliability, and reliability sensitivity were analyzed under relevant failure modes. The state function of the output shaft reliability optimization design was established, and the structural evolution algorithm obtained the optimal design variables. The results show that the maximum stress of the output shaft is reduced by 14.06%, the natural frequency of the output shaft is increased, the amplitude of the output shaft is reduced by 31.13%, and the reliability of the output shaft is improved. The combination of rigid-flexible coupling virtual prototype technology, reliability sensitivity design theory considering correlated failure modes, and structural evolution algorithm provides a more reliable analysis method for the reliability analysis and design of mechanical equipment transmission mechanisms, which can enhance the reliability of the shearer’s cutting unit and improve safety in fully mechanized coal mining faces. The proposed methodology demonstrates broad applicability in the reliability analysis of critical components for mining machinery, exhibiting universal adaptability across various operational scenarios. Full article

In this paper, a gangue grouting filling technology in goafs is proposed based on the dual requirements of not affecting the average production of tens of millions of tons of coal from mines and achieving the large-scale underground disposal of coal gangue, and the technology’s principle and critical technical issues are elucidated. This article explores practical problems, such as how coal gangue forms slurry, how the long-distance pipeline transportation of coal gangue slurry can be realized, and how coal gangue slurry intervenes in the gaps of collapsed rocks in goafs through laboratory experiments and large-scale experiments. Finally, the feasibility of this technology was verified through on-site underground industrial experiments to explore a technically and economically feasible avenue for the underground filling of coal gangue in tens of millions of tons of coal from mines in western China. Full article

The gangue mixed in raw coal has small feature differences from coal, in order to solve the existing gangue recognition, methods generally have slow detection speed and are difficult to deploy at the edge end of the problem, a lightweight gangue target detection algorithm is proposed to enhance the research for the field of coal mining. Firstly, a lightweight EfficientViT module is the backbone of the network; secondly is the introduction of the DRBNCSPELAN4 module, which can better capture target information at different scales; finally, the lightweight shared convolutional detection head Detect_LSCD is reconstructed in order to further reduce the model size and improve the detection speed for coal and gangue. The experimental results indicate that in the model compared with the original algorithm, mAP@50–95 is improved by 1.2%, model weight size, the number of parameters, and floating point operations are reduced by 52.34%, 55.35%, and 50.35%, respectively, and inference speed is accelerated by 20.87% on a Raspberry Pi 4B device. In the field of coal gangue sorting, the algorithm not only has high-precision, real-time detection performance, but also achieves significant results in the lightweight model, making it more suitable for deployment on edge equipment to meet the requirements of controlling the robotic arm sorting gangue. Full article

Coal mining and washing processes generate substantial amounts of coal gangue, posing significant environmental challenges. Coal gangue as a solid waste is rich in SiO₂ and Al₂O₃, with the SiO₂/Al₂O₃ molar ratio closely aligned with the ideal composition of 4A molecular sieves. In this study, through a synergistic pretreatment process involving low-temperature oxidation and hydrochloric acid leaching, the Fe₂O₃ content in coal gangue was reduced from 7.8 wt% to 1.1 wt%, markedly enhancing raw material purity. The alkali fusion–hydrothermal synthesis parameters were optimized via orthogonal experiments—calcination (750 °C, 2 h), aging (60 °C, 2 h), and crystallization (95 °C, 6 h) to maintain cubic symmetry, yielding highly crystalline 4A zeolite. Characterization via XRD, calcium ion adsorption capacity, SEM, and FTIR elucidated the regulatory mechanism of calcination on kaolinite phase transformation and the critical role of alkali fusion in activating silicon–aluminum component release. The as-synthesized zeolite exhibited a cubic morphology, high crystallinity, and sharp diffraction peaks consistent with the 4A zeolite phase. The pH of the zero point charge (pH_ZPC) of the 4A molecular sieve is 6.13. The 4A molecular sieve has symmetry-driven adsorption sites, and the adsorption of Cu²⁺ follows a monolayer adsorption mechanism (Langmuir model, R² = 0.997) with an average standard enthalpy change of 38.96 ± 4.47 kJ/mol and entropy change of 0.1277 ± 0.0148 kJ/mol, adhering to pseudo-second-order kinetics (R² = 0.999). The adsorption process can be divided into two stages. This study provides theoretical and technical insights into the high-value utilization of coal gangue. Full article

The increasing demand for sustainable mining practices has driven the development of environmentally friendly reagents for mineral processing. This study investigates vitamin E sodium succinate (VE_SS), a novel bio-based collector, for its potential in hematite flotation. The performance of VE_SS was benchmarked against sodium oleate (NaOL), a widely used conventional collector in mineral processing. To assess the flotation performance of VE_SS, micro-flotation experiments were conducted using hematite, sourced from a mine, and silica, a common associated gangue mineral. These tests were complemented by comprehensive surface characterizations, including contact angle measurements, zeta potential analysis, Fourier-transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS), to investigate the adsorption mechanisms of VE_SS in comparison to NaOL. The results demonstrate that VE_SS effectively enhances hematite recovery, achieving levels comparable to NaOL. Furthermore, VE_SS exhibited reduced sensitivity to pH, addressing a key limitation of NaOL, which performs well in neutral to alkaline conditions but shows significantly lower recovery under acidic pH. These findings highlight the potential of VE_SS as a bio-based alternative to conventional collectors, contributing to the advancement of more sustainable mineral processing practices. Full article

Coal gangue (CG) has become a critical environmental challenge in China, with nearly one billion tons produced annually. To address this challenge while simultaneously supplementing soil resources during mine ecological restoration, a novel process is proposed to convert CG into CG-based artificial soil (CGAS) using a microbial treatment method. This study examined the effects of local microbial agents (LMAs), commercial microbial agents (CMAs), and fly ash (FA) on key soil properties of CGAS, such as organic matter (OM) content, humic acid (HA) content, and water-holding capacity. Additionally, the mechanisms underlying aggregate formation in CGAS were investigated. The results showed that the synergistic effect of LMAs and FA significantly enhanced the essential quality properties of CGAS. In particular, the HA content increased by 2.06 times compared with untreated CG, the proportion of water-stable macroaggregates increased to 11.46%, and the bulk density decreased by 39.71%, achieving an optimal level of 1.30 g/cm³. Analysis of phase compositions, surface functional group characterization, and microstructural examination indicated that organic binders such as HA, inorganic binders such as calcium carbonate and gypsum, and the bonding effect of spherical particles of FA played significant roles in forming a stable and healthy soil structure in CGAS. Full article