Distribution and Migration of Trace Elements during Flotation in Ge-Rich Low-Rank Coal from Wulantuga Coal Mine, Inner Mongolia, China

The high-Ge low-rank coal in Wulantuga Coal Mine, Inner Mongolia, China, has a high utilization value due to its enrichment of critical element Ge. However, it is also enriched with toxic elements such as Be, F, As, and Hg; therefore, the coal should be cleaned before use. In this study, the flotation experiment, X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier transform infrared (FTIR) analysis, and the release experiment for the high-Ge low-rank coal from Wulantuga were carried out, and the results are as follows. (1) The total mineral content of the feed coal is higher than that of the cleaned coal and tailing, and the content of the functional group -OH is also increased, indicating that the moisture in the cleaned coal is increased after flotation. (2) Argillation occurred and some minerals (dihydrate gypsum and kaolinite) and elements were released into the water during flotation, so the ash yield and the percentage of TiO2, Al2O3, Fe2O3, MgO, and CaO of the cleaned coal and tailing are lower than those of feed coal. (3) The concentrations of elements Li, Be, F, Mn, Zn, Sr, Hg, Tl, and Pb of the cleaned coal are higher than those of tailing, indicating that these elements are more likely to occur in organic matter or fine-grained mineral embedded in organics, but the concentration of other elements such as Ge, As, Sb, and W in the cleaned coal is lower than that of tailing, suggesting that these elements are weakly associated with organics or occur in minerals. (4) After flotation, trace elements Be, Cs, Ti, Ge, Sb, and W enriched in the feed coal were removed in large quantities, while F, As, and Hg were difficult to remove; therefore, other preparation methods should be tried. (5) The release experiment showed that the release rate of chalcophile and siderophile elements and rare earth elements and yttrium (REY) is relatively higher. In addition to those of Be, Ga, Sr, and Cs, the release rate of most elements is relatively low.