Acid removal rate of trace elements and its organic-inorganic affinity in coal
    |&mdash|in a case of the Late Paleozoic coal seam 5 from Weibei

The trace element contents of 5﹟coal samples from Weibei before and after acid treatment has been compared. The result shows that 44 trace elements in the coal seam, according to acid removal rate which is quantitative to characterize element affinity, can be divided into 5 categories. There is a very clear distribution in the periodic table of elements. Type I is most easily acid removed and is located mainly at IA and IIA in the periodic table of elements. They belong to s area according to their electronic configurations. Type II is easier to acid removal. Type III is less prone to acid removal, which is situated at IIIB, VB, VIB and VIIIB. It belongs to d area and left part of f area in the periodic table of elements. Type IV is difficult to be removed by acid, which is situated at IVA and VA. It belongs to p area and f central area in the periodic table elements. Type V is most difficult for acid removal and is located at IIB, IIIB and IVB. It belongs to the first half of d area, ds area and right part of f area in the periodic table of elements. The acid removal rate of trace elements in coal, along the direction of vertical, horizontal and diagonal in the periodic table of elements, has some correlations. Type II trace elements can not be determined in the periodic table of elements temporarily because of its small number and scatteration in this study.