β Scribed by Zhongsheng Li; Colin R. Ward; Lila W. Gurba
No coin nor oath required. For personal study only.
Electron microprobe study of individual macerals in low-rank coals of Permian to Tertiary age from Australia, New Zealand, Indonesia and Thailand has shown that measurable proportions of inorganic elements are consistently found in organic components, especially the vitrinite macerals, in which no minerals or mineral inclusions are visible under the microscope. The vitrinites of such coals have been found to contain up to around 0.5% Al, 1.5% Ca, 0.1% Mg, 0.7% Fe and 0.2% Ti. The Al occurs without measurable proportions of Si, and hence does not represent sub-micron clay minerals within the maceral components. Inertinite macerals in the coals, such as fusinite, typically contain lesser proportions of these elements, and often have no more than background (b 0.05%) concentration levels. Except where soluble minerals such as carbonates are also present, the proportion of Ca, Al and Fe indicated from microprobe analysis in the macerals, especially in the vitrinites, is very close to the mobile proportion of the same elements indicated in previous studies from selective leaching techniques. This suggests that the elements occur as an inherent part of the organic structure in the macerals, possibly as a combination of exchangeable ions, carboxylates, chelates and other organometallic compounds; they may also be held by physical absorption and adsorption mechanisms, or may possibly represent inorganic nanoparticles. The proportions of Al, Ca and Fe in the vitrinites of the samples studied decrease with coal rank. Although there are exceptions, these and other non-mineral inorganic elements (Mg, Ti) are also not usually detected by the microprobe in higher rank coals (above 75% carbon in vitrinite or around 0.6% vitrinite reflectance). Their absence is probably a consequence of expulsion from the maceral structures during the progressive aromatization associated with rank advance, by processes such as dehydration, decarboxylation and dehydroxylation.
π SIMILAR VOLUMES
Correlations resulting from ash level determinations and X-ray fluorescence data performed on lignite ash samples taken from the Cdmpulung coal field, Rumania, were determined. The existence of linear relationships between the concentrations of each analysed element: Si, Al, Ca, Fe, S, Mg, Na and K
Acidic functional groups in five low-rank coals from various parts of the world have been determined by aqueous ion exchange and non-aqueous titration procedures. The total acidity found by titration was, in general, significantly higher than that obtained by ion exchange at pH 13 for all the coals.