GEOCHEMICAL DISTRIBUTION OF METALLIC ELEMENTS IN THE MINERAL MATTER OF BRAZILIAN COALS

This work is a study of metals' geochemical speciation for Co, Cu, Pb, Ni, Cr, Mn and Fe, in the mineral matter of coal samples from Souther n Brazilian coals. The main purpose is to evaluate the potential mobil ity of these metals in aquatic and atmospheric environments, affected by coal activities. Two methods of five-step sequential extractions we re used (Tessier and Meguellati), following different leaching orders. A comparative study was done with the data from the two sequential sc hemes which has shown that the Tessier scheme presented, in general, b etter accuracy. Results obtained from both schemes, however, suggested that the leaching order of extractions influenced the reproducibility of metals' geochemical distributions in the mineral matter of the Lea o coal. Cr and Mn presented the least and greatest mobilities, respect ively, while Pb, Co, Ni, Fe and Cu have shown intermediate mobilities. Coal tailings with different sulphur contents, on which only the Tess ier scheme was applied, presented Ni, Cu, Pb and Fe associated to the oxidizable fraction, Mn to the carbonate and reducible, and Cr and Ni to the aluminosilicate fraction. Tailing samples with less sulphur con tents have shown better precision in data quality.