XANES Spectroscopic Characterization of Selected Elements in Deep-Cleaned Fractions of Kentucky No. 9 Coal

Abstract

The mode of occurrence of various elements in Kentucky No. 9 coal has been examined by XAFS spectroscopic characterization of the elements in float and tailings fractions generated by different flotation tests and chemical leaching methods on the finely ground coal. PIXE spectroscopy was used to determine the elemental concentrations in the same fractions. In this investigation, the elements examined include the lithophile elements, K, Ca, Ti, V, Cr, and Mn, and the predominantly chalcophile elements, Fe and As. The lithophile elements, except for K, exist in two distinct forms: an organically associated form that contributes as much as 50% of the occurrence of Ti, V, and Cr in the coal and a mineralogical form consisting of either illite (K, Ti, V, Cr) or calcite (Ca, Mn). In contrast, the two chalcophile elements examined are associated almost exclusively with pyrite and its oxidation products. Evidence is presented for arsenic as arsenate being incorporated in the major pyrite oxidation product, jarosite. There is a useful synergy in such studies because the more fractions examined with XAFS spectroscopy the better the mode of occurrence is determined, and conversely, the better the mode of occurrence is determined, the better the behavior of elements in flotation and leaching tests can be explained.