Distributions of Trace Elements and Their Relationships With Heavy Minerals in Some Chinese Low-Rank Coals

To better understand the properties of low rank coals, especially the correlation information between the trace elements (TEs) and minerals, four typical low-rank coals in China, namely Xiaolongtan (XLT), Shenbei (SB), Huolinhe (HLH), and Shengli (SL) were quantitatively studied for their mineralogical characteristics and TEs distributions, to provide a basis for proposing methods to remove impurities from low-rank coal and reduce environmental pollution. Results show that light mineral fractions (LMFs, rho < 2.89 g/cm(3)) are more than 90% (wt.%) in the four low-rank coals with clay minerals dominating in composition. Minerals in the heavy mineral fractions (HMFs, rho > 2.89 g/cm(3)) vary from coal to coal. Rare heavy mineral particles including zircon, sphalerite, and gypsum are observed in HMFs from four low-rank coals. Minerals are the major carriers of the TEs, and different kinds of minerals carry different kinds of TEs. TEs such as Cu, Zn, Tl, As, Cd, Sn, Ni, Sb, Pb have an affinity to occur in pyrite; Gd, Sr, Ba, Eu, and Bi are associated with barite; Cr, Mo are abundant in Fe-bearing carbonate.