School of Resource and Environment Engineering, Anhui University, Hefei 230601, China.
National Engineering Laboratory of the Coal Mine Ecological Environment Protection, Huainan 232001, China.
Int J Environ Res Public Health. 2023 Jan 19;20(3):1887. doi: 10.3390/ijerph20031887.
Coal, being one of the major energy sources for power generation, contains several critical trace elements. There is a growing scarcity and expense of these critical elements as a result of the increased demand and limitation of mining sources. To explore the geochemical characteristics of the rare-metal, rare-dispersed (scattered), and rare-earth elements (TREs) in coal, 25 coal seam samples of the Shanxi Formation in the Huainan coalfield were collected. The major element oxides, minerals, and TREs were analyzed by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the coal of the Shanxi Formation had ultra-low moisture and low ash yield and was medium-high-volatility with low sulfur content and high calorific value. Concerning minerals, the coal was mainly composed of kaolinite, illite, quartz, calcite, dolomite, and pyrite. Compared with Chinese coal and world hard coal, rare-metal element Li and rare-dispersed element Se were enriched, whereas Ga and Ta were only slightly enriched. The average content of REYs was 51.34 μg/g, which is lower than the average content of REYs in Chinese coal. It has the enrichment characteristics of light REYs. In the vertical direction, the content of most TREs was higher in the roof and floor of the coal seam and the parting, indicating that the sedimentary microenvironment plays an important role in controlling the migration and enrichment of elements. The experimental results of sequential chemical extraction and correlation analysis showed that the TREs in the Shanxi Formation coal mainly exist in a residual and carbonate bound state, and occur in clay minerals and carbonate minerals. The enrichment of Se may be due to its high organic form ratio. The C-value, B content, (Sr)/(Ba), and REY geochemical parameters indicated that the Shanxi Formation Coal seam was developed in a transitional, semi-saline, deltaic sedimentary environment. With their development affected by seawater, REYs in coal are greatly supplied by terrigenous clastics. The complex sedimentary environment is an important reason for the varying occurrence states of TREs in the Shanxi Formation coals.
煤炭是发电的主要能源之一，其中含有多种关键微量元素。由于需求增加和采矿资源的限制，这些关键元素日益稀缺且价格昂贵。为了研究稀有金属、稀散（分散）和稀土元素（TREs）在煤炭中的地球化学特征，采集了淮南煤田山西组 25 个煤层样品。采用 X 射线荧光光谱（XRF）、X 射线衍射（XRD）和电感耦合等离子体质谱（ICP-MS）分析了主要元素氧化物、矿物和 TREs。结果表明，山西组煤具有超低水分和低灰分产率，中高挥发分，低硫分和高热值。在矿物方面，煤主要由高岭石、伊利石、石英、方解石、白云石和黄铁矿组成。与中国煤和世界硬煤相比，稀有金属元素 Li 和稀散元素 Se 富集，而 Ga 和 Ta 仅略有富集。REY 的平均含量为 51.34μg/g，低于中国煤中 REY 的平均含量。它具有轻 REY 富集的特征。在垂向上，大多数 TRE 的含量在煤层的顶底板和分层面较高，表明沉积微环境对元素的迁移和富集起着重要作用。顺序化学提取实验结果和相关分析表明，山西组煤中 TREs 主要以残余态和碳酸盐结合态存在，赋存于粘土矿物和碳酸盐矿物中。Se 的富集可能是由于其高有机形态比。C 值、B 含量、(Sr)/(Ba)和 REY 地球化学参数表明，山西组煤层发育于过渡、半咸水、三角洲沉积环境。受海水影响，煤中 REY 主要由陆源碎屑提供。复杂的沉积环境是山西组煤中 TREs 赋存状态变化的重要原因。
