Mineralogical and geochemical characteristics of coal from the Southeastern Qinshui Basin: Implications for the enrichment and economic value of Li and REY

Comprehensive assessment of the critical elements in coal is vital for understanding the geological processes affecting element enrichment allowing full utilization of coal in an economical and environmentally friendly manner. This study reports the latest data on the petrology, mineralogy, and coal geochemistry of the No. 15 coal seam in the southeastern Qinshui Basin. The enrichment mechanism of lithium (Li) and rare earth element and yttrium (REY) was analyzed. The result indicates that Li is significantly enriched (CC is 19.55) and mainly occurs in Ti-bearing minerals (e.g., clay minerals). REY mainly occurs in phosphate minerals, such as goyazite. The sedimentary provenance is the dominant factor influencing the mineralogical composition and elevated trace element concentrations of No.15 coal seam. Furthermore, hydrothermal fluids and marine environment also affected the mineral composition. After the high-temperature combustion process, the Li and REY have a higher enrichment ratio in the coal than that in the carbonaceous mudstone, parting the roof and floor samples. The REY contents of coal, roof and floor samples are higher than the marginal grade for industrial deposits. The evaluation results indicate the No. 15 coal seam has a potential to provide raw materials for the comprehensive processing and utilization of Li and REY.