The distribution of Rare Earth elements (REE) in coal-derived fly ashes can have distinctive patterns when fly ashes are produced from different coals within or between basins, such as the Pennsylvanian Class F fly ashes from the Illinois and Central Appalachian basins. Both the Fire Clay coal and a blend of a number of eastern Kentucky coals show strong Gd peaks and an H-type distribution in the Upper Continental Crust-corrected plots. The Fire Clay coal-derived ash has a higher heavy REE concentration than the blended coal-derived ash. The Illinois Basin-derived fly as has an overall lower REE concentration than the latter ashes. Class C fly ash derived from Powder River Basin coals has, with the exception of an Eu peak, a flatter distribution of REE and an overall L-type or indistinct H- versus L-type distribution. The signatures of the REE in fly ashes may be useful in predicting their behavior in the extraction of the REE; simple extrapolations from the basic concentrations and the predicted extraction percentages for ashes from different basins are not necessarily indicative of the actual distribution of the extracted REE.

Beneficiated fly ash from the combustion of Central Appalachian high volatile bituminous coals was extracted with HNO3 in a pilot-scale processing plant. Several major oxides (notably CaO and SO3, but also including Fe2O3, MgO, K2O, and P2O5) and minor elements (Mn, As, Sr, Ba, and Pb) are depleted in the post-HNO3extraction spent ash. The total lanthanides, Y, and Sc concentration is reduced by about 20% in the spent ash, with Gd showing the greatest decrease. Along with Gd, Nd and Dy are also well differentiated between the feed and spent ashes, with La and Sm showing minimal partitioning. The Gd decrease is correlated with the depletion of Fe2O3. The heavy rare earth elements (REE heavier than Eu) and Y are disproportionately concentrated in the HNO3-leachate compared to the light REE. For the ashes studied, Sc did not partition between the feed and spent ashes. Pozzolanicity tests show that the compressive strength and strength activity indices of the spent ash + ordinary Portland cement (OPC) mixes are comparable to 100% OPC, indicating that the spent ashes produced in the pilot-scale runs have the potential to be sold as a Class F fly ash. Ultimately, the beneficiated ash chemistry influences the chemistry of the post-HNO3-extraction spent ash and the HNO3-leachate. A 500-ppm-REE fly ash will presumably be a more economically favorable feedstock than an ash with a significantly lesser concentration.

This study examined rare earth element (REE) trends for Illinois Basin coal-sourced fly ashes, with the goal of understanding the elemental composition and resource potential for various fly ash fractions. Illinois Basin coals have a high volatile C through A bituminous rank with a moderate ash content (slightly>12% ash (dry basis)), about 3% sulfur, and, in general, lower concentrations of hazardous and other trace elements than many Central Appalachian coals. Fly ash from the combustion of Illinois Basin coals tends to have a high Fe2O3 content owing to the amount of pyrite in the feed coals. The rare earth element (REE) concentrations in Illinois Basin coal sourced fly ashes are less than that for fly ashes from the combustion of Central Appalachian coals. The Upper continental crust-corrected fly ashes show an H-type enrichment, a positive EuN/EuN*, and, in some cases, a sharp Gd peak. For comparison, a suite of fly ashes from the combustion of a blend of eastern Kentucky coals had an H-type enrichment, a positive Eu-N/Eu-N*, but only a minimal Gd peak. In contrast, fly ash from the combustion of the Fire Clay coal, a REE-rich coal, had a negative Eu-N/Eu-N* and a sharp Gd peak. These results highlight the importance of feed coal composition on trace element contents of respective combustion fly ash fractions and also the unique REE enrichment patterns of the Illinois Basin fly ashes relative to the better studied fly ashes of eastern Kentucky and Central Appalachia.

The Pennsylvania Anthracite Fields are in a complex tectonic and metamorphic terrain, historically hosting one of the largest concentrations of coal mining in the USA. Anthracite mining now largely consists of the surface mining of the pillars remaining from the prime years of underground mining. The geochemical study of the sized coal products and the refuse (largely rock) from three preparation plants (breakers) demonstrates that Principal components analysis (PCA) of select major oxide, minor element, and rare earth elements illustrates some differentiation among the products from the individual plants. The rock samples, with abundant quartz and metamorphic Al-Si minerals and with a lower ash-basis REE concentration than the coals, were distinctly separated from the coal samples on the PCA plots. Plots of Gd-N/Gd-N* vs. Eu-N/Eu-N* and Ce-N/Ce-N* vs. Eu-N/Eu-N* showed differentiation between the individual suites of coals showed that the refuse samples had distinct REE distributions compared to the associated coals. Several minor and trace elements show enrichments in the coal samples. Lithium, with concentrations of up to 314 ppm on an ash basis, is among the most promising of the critical elements, exceeding the enrichment of the REY and Sc.