A suite of 72 samples of Illinois Basin coal was collected from 2015 to 2018, from 14 active coal mining and preparation operations in Illinois and Indiana. The goals of the study were to investigate the behavior of trace elements during coal preparation and provide current coal quality data for active mining operations in the Illinois Basin, which has become one of the most important suppliers of U.S. coal. Samples include raw coal, cleaned coal, and waste (refuse) coal. The efficiency of cleaning is shown by reduction of ash yield, increase in heating values, and a pronounced shift in the proportion of sulfur forms. In most raw coals, pyritic sulfur (Py S) exceeds organic sulfur (Org S; Org S/Py S ≤ 1.0), whereas in prepared coals, organic sulfur is the predominant sulfur form (Org S/Py S ≥ 1.0). In waste (refuse) coals, Org S/Py S is substantially reduced, or almost entirely in the pyritic form (Org S/Py S near zero). Trends in the distribution of inorganically-associated lithophile and chalcophile elements are shown, as well those for elements having mixed organic-inorganic associations and those that are primarily organic-hosted. Lithophile elements, including Li, Al, P, Ti, Sc, Rb, Y, Zr, Nb, Cs, Ba, the lanthanides, Hf, Th, and U, are partitioned into waste coals with corresponding reduction in cleaned coals. At the same time, chalcophile elements hosted by pyrite, such as As, Sb, Hg, and Pb, are also partitioned into waste coals. Rare earth elements (REEs), including Sc, Y, and the lanthanides, are enriched in waste coals at levels that approximate their content in the upper continental crust (UCC). Several other critical elements, defined as mineral commodities deemed critical to the economy and security of the United States, including V, Cr, As, Rb, Sb, and Cs, show enrichment in waste coals, that may facilitate their co-extraction with the REEs. Concentrations for elements of environmental concern in cleaned coals are similar to or below those for world average coals with the exception of Pb in coals from Illinois. Laser-ablation ICP-MS (LA-ICP-MS) for pyrite in a subset of 21 samples of raw and cleaned coal provided direct determinations of V, Cr, Mn, Co, Ni, Cu, Zn, As, Se, Mo, Ag, Cd, Sb, Au, Hg, Tl, Pb, and Bi. LA-ICP-MS was used together with bulk sample pyritic sulfur and trace element concentrations to estimate the elemental proportion of bulk Cu, As, Hg, and Pb in pyrite, indicating that Hg and Pb are hosted almost entirely by pyrite, whereas the proportion of Cu and As in pyrite accounts for about half of the bulk content. With growing interest in recovering critical elements from coal, partitioning of a large range of elements into waste coals presents a possible opportunity, but also a potential hazard, due to enrichment in harmful elements such as Hg, As, and Pb.

从 2015 年到 2018 年，从伊利诺伊州和印第安纳州的 14 个活跃的煤炭开采和准备作业中收集了 72 个伊利诺伊州盆地煤炭样本。该研究的目标是调查选煤过程中微量元素的行为，并为伊利诺伊盆地的活跃采矿作业提供当前的煤炭质量数据，伊利诺伊盆地已成为美国煤炭最重要的供应商之一。样品包括原煤、精煤和废（废）煤。灰分产量的减少、热值的增加以及硫形式比例的显着变化表明了清洁效率。在大多数原煤中，黄铁矿硫 (Py S) 超过有机硫 (Org S; Org S/Py S ≤ 1.0)，而在精制煤中，有机硫是主要的硫形式 (Org S/Py S ≥ 1.0)。在废（废）煤中，Org S/Py S 显着减少，或几乎完全呈黄铁矿形式（Org S/Py S 接近于零）。显示了无机结合的亲石元素和亲硫元素的分布趋势，以及具有混合有机-无机结合的元素和主要以有机为主体的元素的分布趋势。亲石元素，包括 Li、Al、P、Ti、Sc、Rb、Y、Zr、Nb、Cs、Ba、镧系元素、Hf、Th 和 U，被分配到废煤中，相应地减少了清洁煤。同时，黄铁矿中的 As、Sb、Hg 和 Pb 等亲硫元素也被分配到废煤中。稀土元素 (REE)，包括 Sc、Y 和镧系元素，在废煤中的含量接近于它们在上大陆地壳 (UCC) 中的含量。其他几个关键要素，被定义为对美国的经济和安全至关重要的矿物商品，包括 V、Cr、As、Rb、Sb 和 Cs，它们在废煤中富集，可能促进它们与稀土元素的共同提取。除了来自伊利诺伊州的煤中的铅外，清洁煤中环境问题元素的浓度与世界平均煤的浓度相似或低于这些元素。激光烧蚀 ICP-MS (LA-ICP-MS) 对 21 个原煤和精煤样品中的黄铁矿进行了直接测定，可直接测定 V、Cr、Mn、Co、Ni、Cu、Zn、As、Se、Mo、 Ag、Cd、Sb、Au、Hg、Tl、Pb 和 Bi。LA-ICP-MS 与大块样品黄铁矿硫和痕量元素浓度一起使用来估计黄铁矿中大块 Cu、As、Hg 和 Pb 的元素比例，表明 Hg 和 Pb 几乎完全由黄铁矿承载，而黄铁矿中Cu和As的比例约占总含量的一半。随着人们对从煤中回收关键元素的兴趣日益浓厚，将大量元素分配到废煤中既是可能的机会，也是潜在的危险，因为有害元素如 Hg、As 和 Pb 的富集。