Rare earth and radioactive elements in some coals from the Sofia, Svoge and Pernik Basins, Bulgaria

doi:10.1016/0166-5162(93)90028-9

International Journal of Coal Geology

Volume 22, Issues 3–4, July 1993, Pages 237-246

https://doi.org/10.1016/0166-5162(93)90028-9 Get rights and content

Abstract

Coal samples from three Bulgarian basins were investigated for their rare earth and radioactive element concentrations. The samples ranged in rank from lignite to anthracite. All the samples contained La, Ce, Sm, Eu, Tb, Yb, Th and U. Lu occurs in sub-bituminous coal samples from the Pernik Basin and in a lignite sample from the Sofia Basin. The concentrations of most elements are lower than or close to data reported in the literature from other coal basins or the Clarke values determined by Yudovich et al. (1985). The elements Tb and Lu are exceptions to this, together with Th in the Svoge Basin anthracites.

The lowest concentrations of most elements are found in lignite samples from the Sofia Basin; the highest concentrations occur in anthracite samples from the Svoge Basin. In this study the Sofia and Svoge coals display inorganic affinities for the elements. Sub-bituminous coal samples from the Pernik Basin, however, show a more widespread organic affinity for the elements. The trace elements were also grouped in geochemical associations by cluster analysis. In the lignite samples from the Sofia Basin and the sub-bituminous coal from the Pernik Basin, this grouping is almost identical. U, Tb and Yb are grouped in an association; the other elements are grouped separately. Ce, Th and Sm correlate well in a separate association. The anthracites from the Svoge Basin display two associations: one including U, Th and Sm, and the other composed of the remaining elements, which correlate well with one another and with the coal ash.

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Concluding comments: Iodine in coal appears to largely be associated with organic matter. The REY group in this paper is referred to as the 14 lanthanide elements (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) and Y. Following several decades of research (e.g., Goldschmidt and Peters, 1933; Finkelman and Brown Jr., 1991; Kortenski and Bakardjiev, 1993; Van der Flier-Keller, 1993; Seredin, 1996; Eskenazy, 1987, 1999; Hower et al., 1999, and among others), coal has been universally recognized as an important raw source for REY recovery Hedin et al., 2020; Seredin and Dai, 2012; Blissett et al., 2014; Franus et al., 2015; Hower et al., 2016; Taggart et al., 2016; Sutcu et al., 2021), which has attracted substantial attention due to the wide applications of REY (Pecht et al., 2012), relative changes in supply and demand in the world market (Kronholm et al., 2013; Mayfield and Lewis, 2013; Home, 2020), and elevated concentrations of REY in coal and coal combustion productions that are readily extractable for utilization (Seredin and Dai, 2012; Dai and Finkelman, 2018). Based on the data of REY in many coal deposits worldwide, Seredin and Dai (2012) comprehensively reviewed the genetic types of REY enrichment in coal and proposed evaluation methods for coal and coal ashes as a REY raw source material.
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2016, International Journal of Coal Geology
Citation Excerpt :
In 2015, the U.S. Department of Energy's (DOE) National Energy Technology Laboratory (NETL) selected 10 projects to receive funding for research in support of their program on recovery of rare earth elements from coal and coal byproducts; the selected research projects were focused on the development of cost-effective and environmentally benign approaches for the recovery of rare earth elements from U.S. domestic coal and coal byproducts (http://www.netl.doe.gov/; Release date, December 02, 2015). Rare earth elements and yttrium have been widely used for many years as geochemical indicators (Bau et al., 2014) of the sedimentary environment and post-depositional history of coal deposits because of their coherent behavior during different geochemical processes and their predictable patterns of fractionation (Eskenazy, 1987a, 1987b; Kortenski and Bakardjiev, 1993; Van der Flier-Keller, 1993; Hower et al., 1999, 2015a, 2015b; Schatzel and Stewart, 2003; Qi et al., 2007; Seredin, 1996, 1998, 2005; Seredin and Finkelman, 2008; Seredin and Dai, 2012; Dai et al., 2015b), such as anomalies of La, Ce, Eu, Gd, and Y, and the enrichment or depletion of light-, medium-, and heavy-REY. The smoothness of a normalized (to Upper Continental Crust, UCC; Post-Archean Australian Shale, PAAS, or North American Shale Composite, NASC) REY distribution pattern provides a simple but reliable basis for testing the quality of REY chemical analyses of coal and other sedimentary rocks.
Coal deposits have attracted much attention in recent years as promising alternative raw sources for rare earth elements and yttrium (REY), not only because the REY concentrations in many coals or coal ashes are equal to or higher than those found in conventional types of REY ores but also because of the world-wide demand for REY in recent years has been greater than supply. In addition to anomalies of enrichment or depletion of light-, medium-, and heavy-REY in coal deposits (normalized to Upper Continental Crust, Post-Archean Australian Shale, or North American Shale Composite), anomalies of redox-sensitive Ce and Eu, and, in some cases, of non-redox-sensitive La, Gd, and Y, could be used as geochemical indicators of the sediment-source region, sedimentary environment, tectonic evolution, and post-depositional history of coal deposits. Factors controlling REY anomalies in coal deposits include the geochemistry of terrigenous source rocks, ingress of hydrothermal fluids, influence of marine environments, percolating natural waters, volcanic ashes, and sedimentary environments of peat formation. Additionally, the smoothness of a normalized REY distribution pattern provides a simple but reliable basis for testing the quality of REY chemical analyses for coal and other sedimentary rocks.
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Additional geological processes, such as groundwater alteration/leaching through localized faults, basement rocks or partings, and hydrothermal fluids generated by magmatic intrusions, can also modify REE concentrations (Dai et al., 2011a; Ren et al., 1999). The dominant processes leading to REE concentrations in particular coal-bearing sequences, however, need further clarification, although there have been many studies on the REE geochemistry of coals from different countries, coal-bearing basins or individual coal mines, relating to abundances, distribution and origin (Birk and White, 1991; Dai et al., 2006, 2008; Eskenazy, 1987, 1999; Hower et al., 1999; Kortenski and Bakardjiev, 1993; Pollock et al., 2000; Seredin, 1996; Seredin and Shpirt, 1995). The Zhuji coal mine is a new mine still under development.
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The black shale and coal Clarkes presented here provide an important scientific base for many geochemical comparisons and issues.
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2008, International Journal of Coal Geology
Twenty-six samples including roof, bottom and coal plies of a marine influenced coal bed were collected from the Antaibao mining district, Shanxi, China. The rare earth elements (REEs) were determined in solids and organic solvent extracts. The distribution pattern showed three distinct patterns: shale-like, LREE-rich and HREE-rich. This is attributed to the variable microenvironment of peat-forming swamp, the degree of marine influences and different REE sources. REEs in the coal are mainly controlled by detrital minerals but also affected by seawater. The chondrite-normalized REE patterns of the organic solvent extracts are distinctly different from those of corresponding original coal samples, which show a negative Eu anomaly, a depletion of middle REEs and an enrichment of HREEs. The LREEs in coal extracts are likely adsorbed by hydrogen-containing functional groups, and HREEs are likely bonded to carbon atoms.

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Rare earth and radioactive elements in some coals from the Sofia, Svoge and Pernik Basins, Bulgaria

Abstract

Int. J. Coal Geol.

Int. J. Coal Geol.

Int. J. Coal Geol.

Statistics and Data Analysis in Geology

Rare-earth elements in some coal basins of Bulgaria

Geol. Balcanika