浸泡淋滤作用下煤矸石重金属元素的释放规律及特征研究

为探究天然煤矸石在雨水浸泡淋滤作用下重金属元素的释放规律及特征，通过扫描电镜(SEM)对天然煤矸石进行表征以观察其淋滤前后的微观形貌，借助X射线衍射(XRD)技术测定煤矸石淋滤前后的矿物成分组成及变化情况.结合模拟降水连续静态浸泡与动态淋滤试验，考察在不同固液比、粒径、pH、土壤介质条件下煤矸石中重金属元素的释放规律与特性.结果表明：(1)淋滤后的煤矸石表面凹凸结构较多，淋滤前后煤矸石中各矿物相含量差异较小.(2)As、Mn的浸出浓度均较高，最大释放率大小表现为As>Cd>Cu≈Ni>Mn>Cr>Zn>Pb. As的累积释放对周边土壤环境以及地下水产生不利影响的风险较高.(3)连续动态淋滤试验在pH为3时，Mn、Cu、Zn、Ni的累积释放量明显较高，As、Cr在中性条件下的累积释放量高于在酸性条件下.引入土壤介质这一因素后，Cr、As的累积释放量均明显减少，这两种重金属元素均呈现出在土壤中积累的状态.研究显示：对于相同煤矸石堆存量，降雨量越大，重金属的释放总量越高，固液比为1∶20时，As释放量最高可达2.822μg/L;Cr、As呈现出在土壤中积累...

Research on Release Law and Characteristics of Heavy Metals in Coal Gangue under Soaking and Leaching

In order to explore the release law and characteristics of heavy metals in natural coal gangue under the rainwater soaking and leaching, scanning electron microscope (SEM) was used to observe the microscopic morphology of natural coal gangue and X-ray diffraction (XRD) was used to determine the mineral composition and changes before and after leaching. The release law and characteristics of heavy metals in coal gangue were investigated by continuous static soaking and dynamic leaching tests with simulated precipitation under different solid-liquid ratio, particle size, pH and soil medium conditions. The results show that: (1) SEM and XRD analysis results reveal that the surface of natural coal gangue has a layered structure with high smoothness, and after leaching, the surface of coal gangue presents more concave-convex structures. There is small change in the content of each mineral phase, therefore the coal gangue has high stability during natural rainfall leaching process. (2) The simulated continuous static soaking test shows that the leaching content of As and Mn is higher, and the release rates are ranked as As>Cd>Cu≈Ni>Mn>Cr>Zn>Pb. Among them, the cumulative release of As poses a higher risk of adverse effects on the surrounding soil environment and groundwater, and the leaching of Cu has two stages: rapid release and stable release. Zn, Pb, and Cd belong to the late-stage release elements; Cr and As belong to indirect release elements; Mn belongs to fast release elements; and Ni belongs to slow release elements. (3) The continuous dynamic leaching test shows that the cumulative release of Mn, Cu, Zn and Ni is significantly higher at pH 3.0, and the cumulative release of As and Cr under neutral conditions is higher than that under acidic conditions. After the introduction of the soil medium, the cumulative release of Cr and As decreased significantly, indicating that both heavy metals are adsorbed the soil. The research shows that for the same stack of coal gangue, the release of heavy metals is higher with high rainfall. The maximum release of As can reach 2.822 μg/L at a solid-liquid ratio of 1∶20. Because Cr and As are accumulated in the soil, after leaching of the coal gangue, Cr and As pose potential risk of polluting the soil, and the impact on surrounding groundwater should also be considered.