Relationships between trace elements and organic matter in coals

Qin, Shenjun; Lu, Qingfeng; Li, Yanheng; Wang, Jinxi; Zhao, Qiaojing; Gao, Kang

doi:10.1016/j.gexplo.2018.01.015

Cited by 34 publications

(23 citation statements)

References 123 publications

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“…Uranium shows primarily affinity to organic matter, probably in the formation of uranyl organic complexes or adsorbed coal matrix, and inorganic U should be mainly related to clay minerals. Strontium presents multiple modes of occurrence including carbonates (such as calcite), silicates (such as kaolinite), and exchangeable ion state that can also be considered as organic associated (Qin et al., 2018b; Yang, 2006). At last, Ag mainly exists in sulfide and silicate states, i.e.…”

Section: Resultsmentioning

confidence: 99%

Geochemistry of elements associated with Late Permian coal in the Zhongliangshan mine, Chongqing, Southwest China

Qin

Gao

et al. 2018

Energy Exploration & Exploitation

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The enrichment and geochemical significance of elements associated with Late Permian coals in Southwest China have always gained widespread interest in the field of coal geology. The present study focuses on the geochemical characterization of Late Permian coal in the Zhongliangshan mine. Twenty-three samples were collected from the K1a coal seam of the Zhongliangshan mine, and the major and trace elements in the coal were analyzed by using X-ray fluorescence spectroscopy (XRF) and inductively coupled plasma mass spectrometry. The composition of minerals in the Zhongliangshan coal, and the modes of occurrence of coal-associated elements, especially those with elevated contents, were studied through a combination of microscopic analyses, X-ray powder diffraction, and scanning electron microscope -energy dispersive X-ray spectrometer. The minerals in coal mainly consist of kaolinite, pyrite, calcite, and quartz, as well as small amount of gypsum and anatase. Compared with the average elemental concentrations in world coal, the Zhongliangshan coal is enriched in Cr, and slightly enriched in Li, U, Sr, V and Ag. Combining the correlation analysis and sequential chemical extraction experiments, it can be inferred that many trace elements in the Zhongliangshan coal have both inorganic and organic affinities. The elements Cr, Li, and V mainly occur in clay minerals, and also are related to organic matter in the coal. Uranium presents firstly in the organic and then silicate states. Strontium shows multiple modes of occurrence including carbonate, silicate, and exchangeable ion states, and Ag primarily occurs in sulfides followed by silicates. The terrigenous debris input from the Emeishan basalt is the major reason for the enrichment of above elements in the Zhongliangshan coal.

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Section: Resultsmentioning

confidence: 99%

Geochemistry of elements associated with Late Permian coal in the Zhongliangshan mine, Chongqing, Southwest China

Qin

Gao

et al. 2018

Energy Exploration & Exploitation

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“…Although no one has set the exact and affirmative cut-off grades of Rb in coals up to now, it was proposed that if the concentration of Rb is 5 times higher than that the average of world coal [3,58]. It is generally believed that Rb in coal has an inorganic affinity; it mainly occurs in illite and mixed-layer clays and can readily substitute for potassium [3,57,59,60]. Our study results showed that rubidium in the coal is clearly associated with K-rich clay minerals (i.e., illite + I/S; Figures 8 and 10-12).…”

Section: Rubidiummentioning

confidence: 99%

“…Up to now no one has set the exact and affirmative cut-off grades of W in coal. Many studies have indicated that organic matter in coals is the main carrier of W [4,10,57,60,63,64]. Moreover, some reports have shown that tungsten in coals can be associated with inorganic constituents, such as carbonate minerals [61] and quartz veins [1].…”

Section: Tungstenmentioning

confidence: 99%

Minerals and Enrichment of W, Rb, and Cs in Late Permian Coal from Meitian Mine, Meitian Coalfield, Southern China by Magmatic Hydrothermal Fluids

et al. 2018

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We report on the effects of magmatic hydrothermal fluids on the mineralogical and geochemical compositions of 12U and 12L Coals from the Meitian Mine in the Meitian Coalfield, southern China. The minerals in 12U Coal are predominantly chlorite, quartz, and calcite, while the minerals in 12L Coal consist mainly of illite, quartz, chlorite, kaolinite, and mixed-layer illite/smectite (I/S). The vesicle- and fracture-filling illite, chlorite, I/S, pyrite, and fluorite, cleat- and fracture-filling carbonate minerals (i.e., calcite, and dolomite), and cleat-filling tremolite, diopside, and talc have epigenetic hydrothermal origins. Tremolite, diopside, and talc were probably formed from the reaction between dolomite and Si-rich magmatic hydrothermal fluids. Elevated Pb–Zn–Sn–Cd assemblages are characteristic for the 12U Coal, while 12L Coal is enriched in W, Rb, Cs, Th, V, Zn, and Zr, most notably W, Rb, and Cs. REY (Rare Earth Elements and Yttrium) plots for almost all coals, partings and host rocks are similar, showing an M-type REY distribution, Gd-maximum, positive Y anomalies, and negative Ce anomalies, suggesting acid hydrothermal circulation in the coal-bearing strata. Rubidium and cesium in the coal is clearly associated with K-rich clay minerals (illite + I/S), and to a lesser extent with silicate minerals that were precipitated from hydrothermal solutions. W in the coals mainly occurs in the inorganic constituents of illite and pyrite, especially illite. Enrichment of W, Rb, and Cs in the coal and host rocks is genetically associated with magmatic hydrothermal fluids. Specifically, magmatic hydrothermal fluids of relatively high temperatures that are rich in volatile matter can extract abundant W, Rb, and Cs from granitic melts. The enrichment of these rare metals in the coal is mainly related to illitization. Our study results suggest that, for coal intruded by magmatic rocks, the type of hydrothermal alteration may greatly influence the enrichment of elements.

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“…However, regardless of their primary or newly-identified sources, the extraction of rare earth elements has always created environmental concerns. Radioactive elements are frequently seen in the same mineralization as rare earths due to the deformations occurring in soil matrix during geological formations [22][23][24][25][26]. The concentration of thorium dioxide and uranium dioxide in the conventional sources of rare earths can be as high as 20% and 16%, respectively [27].…”

Section: Introductionmentioning

confidence: 99%

Separation of Radionuclides from a Rare Earth-Containing Solution by Zeolite Adsorption

Talan

Huang

2020

Minerals

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The increasing industrial demand for rare earths requires new or alternative sources to be found. Within this context, there have been studies validating the technical feasibility of coal and coal byproducts as alternative sources for rare earth elements. Nonetheless, radioactive materials, such as thorium and uranium, are frequently seen in the rare earths’ mineralization, and causes environmental and health concerns. Consequently, there exists an urgent need to remove these radionuclides in order to produce high purity rare earths to diversify the supply chain, as well as maintain an environmentally-favorable extraction process for the surroundings. In this study, an experimental design was generated to examine the effect of zeolite particle size, feed solution pH, zeolite amount, and contact time of solid and aqueous phases on the removal of thorium and uranium from the solution. The best separation performance was achieved using 2.50 g of 12-µm zeolite sample at a pH value of 3 with a contact time of 2 h. Under these conditions, the adsorption recovery of rare earths, thorium, and uranium into the solid phase was found to be 20.43 wt%, 99.20 wt%, and 89.60 wt%, respectively. The Freundlich adsorption isotherm was determined to be the best-fit model, and the adsorption mechanism of rare earths and thorium was identified as multilayer physisorption. Further, the separation efficiency was assessed using the response surface methodology based on the development of a statistically significant model.

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Relationships between trace elements and organic matter in coals

Cited by 34 publications

References 123 publications

Geochemistry of elements associated with Late Permian coal in the Zhongliangshan mine, Chongqing, Southwest China

Geochemistry of elements associated with Late Permian coal in the Zhongliangshan mine, Chongqing, Southwest China

Minerals and Enrichment of W, Rb, and Cs in Late Permian Coal from Meitian Mine, Meitian Coalfield, Southern China by Magmatic Hydrothermal Fluids

Separation of Radionuclides from a Rare Earth-Containing Solution by Zeolite Adsorption

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