| As a solid waste associated with coal mining,coal gangue not only retains the mineralogical properties of rocks,but also contains chemical major elements,trace elements and organic matter.Huainan mine gangue is used in large quantities to fill and reclaim coal mining subsidence areas,but heavy metals released from the filled coal gangue under the action of rainwater leaching will pollute the surrounding soil.Therefore,the release characteristics of heavy metals in coal gangue and their migration and accumulation in the environment need in-depth study.This paper selects the coal gangue in the reclamation area of Xinzhuangzi Mine,the physical and chemical properties of the collected gangue were analysed,such as lithological characteristics,mineral content characteristics,microstructure characteristics,chemical composition characteristics,conducts static immersion experiments and dynamic leaching experiments,studies the characteristics of heavy metal element release from coal gangue under different influence factors,and predicts the release rules of heavy metal elements during dynamic leaching through time series gray model fitting.On the basis of dynamic leaching and sorption experiments,the migration and accumulation of heavy metals released from coal gangue in soil were simulated and verified by soil column leaching experiments,and the following conclusions were drawn:(1)The lithology of the coal gangue in the study area is mainly sandstone rock,and the constituent minerals of coal gangue are mainly quartz and kaolinite,in addition,there are a small amount of muscovite,illite,potassium feldspar,etc.According to SEM-EDS analysis,gangue has cracks and pores on its surface,poor structural stability,and is easily broken under the influence of external factors such as weathering and rainfall,thus releasing internal materials.The gangue in the study area belongs to high silicon aluminum type gangue,and the variation range of major elements in different parts of gangue is small,and the correlation between elements is significant(2)Static leaching experiments show that the p H value of the leaching solution,the liquid-solid ratio,the particle size of the coal gangue,the frequency of disturbance and leaching time during the leaching process will affect the precipitation rate and concentration of heavy metals in the gangue.Dynamic leaching experiments showed that the release concentration of heavy metals in the gangue fluctuated with time,with the release rate being faster in the early and middle stages and levelling off in the later stages.The heavy metal precipitation concentration was predicted to decrease exponentially with drenching time by fitting a grey prediction model;The concentration of heavy metals in leaching solution collected at different depths of gangue column increased with the increase of depth.(3)The single heavy metal adsorption experiment and the multi-metal coexistence adsorption experiment show that the soil in the landfill area has a strong adsorption capacity for heavy metals,and the maximum adsorption capacity of single metal is much larger than that of multi-metal coexistence.The adsorption capacity of each heavy metal is shown as Cu=Pb>Zn>Cd>Ni;Under the condition of expanding the concentration multiple of heavy metals released from coal gangue,the migration of heavy metals in soil during 20 years of rainfall was simulated.The results showed that the simulation results were consistent with the results of soil column leaching experiment.Cu,Pb,Cd only accumulated in 0~2cm soil layer,and Zn and Ni could migrate to 5 cm depth;Simulation of heavy metal transport over 500 years indicates large transport distances for Cu,Pb and Cd is still less than 10 cm,and Zn and Ni can migrate to 60 cm.The results revealed the precipitation of different heavy metals under different conditions,as well as the migration and accumulation of different heavy metals in soil,providing a theoretical basis and reference for the filling of coal gangue in the coal mining subsidence area and its potential environmental impact.Figure[39] Table[26] Reference[92]... |
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