Search Results (5)

To provide a comprehensive insight into the enrichment mechanism of gallium and indium in No. 9 coals, eighteen samples were collected from Anjialing mine, Ningwu Coalfield, Shanxi Province for coal petrological, mineralogical and geochemical analyses. The results suggested that Ga and In enrichment mainly hosted in the top horizons, with average concentration coefficients of 8.99 and 2.73 respectively, compared with the rest of horizons (2.46 for Ga and 1.69 for In). Source apportionment indicated that Ga and In were mainly derived from bauxite of Benxi Formation in Yinshan Oldland, while In could originate from felsic magmatic rocks in Yinshan Oldland as well. In addition, weak oxidation condition, medium to intensive weathering, transgression and input of terrestrial higher plants had positive effects on Ga and In enrichment. With the rapid expansion of emerging electronics manufacturing, Ga and In, of which potential risks on human health were neglected previously, were recently considered as hazardous elements. Therefore, this paper also discussed the potential pathways that these elements threatened human health. We suggested that potential risks on environment and human health caused by Ga and In enrichment in coals and coal-related products should be taken into account besides their economic value. Full article

Superhigh organic sulfur(SHOS) coals have currently attracted great attention due to their typical depositional environments and formation history as well as their great negative impact on the ecosystem. This study investigated the geochemistry of the No. 11coalof the Late Carboniferous Taiyuan Formation from the Sangshuping coalmine, Hancheng miningarea, Weibei coalfield, Shaanxi, North China. The No. 11 coal is a high-sulfur coal with a large proportion of organic sulfur content (3.7 to 5.5%, avg. 4.4%) and belongs to typical SHOS coal. The high sulfur content in the Sangshuping coal mine has been mainly caused by the combined influences of seawater and hydrothermal fluids. The SHOS in No. 11 coal was formed in the Fe-poor and S-rich high-marine influenced occlusive environment. During the late coalification stage, a high proportion of pyritic sulfur was formed due to sufficient Fe supply from the Fe–S-rich epigenetic hydrothermal fluids. The No. 11 SHOS coal is enriched in Li–Ga–Zr–Hf and Se–Mo–Cr–V–As–Pb element assemblages. The sediment provenance of the Sangshuping coal mine is predominantly felsic–intermediate rocks from both the Yinshan and Qinling Oldland. However, the elevated concentrations of critical elements (Li, Ga, Zr, and Hf) in the No. 11 coal are primarily inherited from the Yinshan Oldland. The enrichment of the Se–Mo–Cr–V–As–Pb assemblage in No. 11 coal can be ascribed to the influence of both seawater and epigenetic hydrothermal activity. Full article

Coal as the source of critical elements has attracted much attention and the enrichment mechanisms are of significant importance. This paper has an opportunity to investigate the mineralogical and geochemical characteristics of the Permian and Jurassic bituminous coals and associated non-coals from two underground coal mines in the Shanbei Coalfield (Northeast Ordos basin), Shaanxi Province, North China, based on the analysis of X-ray diffraction (XRD), inductively coupled plasma atomic-emission spectrometry (ICP-AES/MS), and scanning electron microscopy-energy-dispersive X-ray spectroscopy (SEM-EDS). The Jurassic and Permian coals have similar chemical features excluding ash yield, which is significantly higher in the Permian coals. Major mineral matters in the Jurassic coals are quartz, kaolinite, and calcite. By contrast, mineral assemblages of the Permian coals are dominated by kaolinite; and apatite occurring in the middle section’s partings. The Jurassic coals are only enriched in B, whereas the Permian coals are enriched in some trace elements (e.g., Nb, Ta, Th, and REY). Boron has a mixed inorganic and organic association which may be absorbed by organic matter from fluid (or groundwater) or inherited from coal-forming plants. Additionally, climatic variation also plays an important role. As for the Permian coals, kaolinite and apatite as the major carriers of elevated elements; the former were derived from the sedimentary source region (the Yinshan Oldland and the Benxi formation) and later precipitated from Ca-, and P-rich solutions. We deduced that those elevated elements may be controlled by the source rock and diagenetic fluid input. The findings of this work offered new data to figure out the mechanism of trace element enrichment of coal in the Ordos basin. Full article

This paper reports the mineral compositions and geochemical characteristics of the No. 5⁻² high-sulfur coal (Taiyuan Formation) from Dongpo Mine, Weibei Coalfield, Shaanxi, Northern China via transmitted and reflected light microscopy, scanning electron microscope equipped with an energy-dispersive X-ray spectrometer (SEM-EDS), X-ray diffraction (XRD), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray fluorescence spectrometry (XRF). We also confirmed the input of intermediate-felsic volcanic ashes into the Taiyuan Formation coals in Dongpo Mine, Weibei Coalfield. The results show that Dongpo coals are enriched in Ga and Li compared to the average values for world hard coals, and they are depleted in Al₂O₃ compared to Chinese coals. The coal low temperature ash contains kaolinite, illite, quartz, calcite, pyrite, and to a lesser extent, chlorite, plagioclase, dolomite, ankerite, and apatite. The concentration anomalies of Ga and Li in No. 5⁻² high-sulfur coal were not caused by the Benxi Formation Bauxite, but by the influence of multiple geological factors. The Middle Proterozoic moyite from the Yinshan Oldland led to the slightly higher Ga and Li contents of the No. 5⁻² coal than those in world hard coals. Input of synchronization volcanic ash, injection of hydrothermal fluids during the syngenetic or early diagenetic stages and influence of seawater further contributed to the Ga and Li enrichment of the No. 5⁻² coal. Full article

Fifteen samples of No. 4 coal from the Yongdingzhuang Mine in Datong Coalfield were tested for their elemental compositions, modes of occurrence, and mineralogical compositions, using X-ray powder diffraction, X-ray fluorescence spectrometry, inductively coupled plasma mass spectrometry, and scanning electron microscopy equipped with an energy-dispersive X-ray spectrometer. The samples have low sulfur content (0.63%). The major minerals are kaolinite and quartz, followed by pyrite and anatase. Compared with averages for the Chinese coals, the percentages of SiO₂ (15.11%), TiO₂ (0.7%), and Al₂O₃ (10.39%) are much higher. In No. 4 coals, Li (62.81 μg/g), Be (6.94 μg/g), Zr (235 μg/g), Ga (17.04 μg/g), F (165.53 μg/g), Tl (1.93 μg/g), and Hg (0.34 μg/g) are some potentially valuable and toxic trace elements with higher concentrations than Chinese coals and World hard coals. Lithium and F mainly have kaolinite associations. With the exception of kaolinite, Li, and F also partly occur in anatase, gorceixite and goyazite. Beryllium largely occurs in anatase; gallium is mainly associated with kaolinite and to a lesser extent, with gorceixite and goyazite; zirconium is associated with kaolinite, gorceixite and goyazite; and thallium and Hg occur in in pyrite. Potentially valuable elements (including Al, Li, Ga, and Zr) might be recovered as value-added byproducts from coal ash. Toxic elements (e.g., Be, F, Tl, and Hg) might have potential adverse effects to the environment and human health during coal processing. In addition, the distribution patterns of rare earth elements and yttrium (REY) indicate that the REY in No. 4 coals originated from the granite of Yinshan Oldland, and natural waters or hydrothermal solutions that may circulate in coal basins. Full article