Coal mining in Santa Catarina, Sout

Coal mining in Santa Catarina, South Brazil, impacted the environment by means of a large number of coal waste piles emplaced over the old mine sites and the adjacent areas of the Criciúma, Urussanga, and Siderópolis. Poor disposal of coal cleaning rejects represents significant environmental concerns due to their potential influence on soils and river sediments, as well as on the surface and groundwater in the surroundings of these zones. In this research advanced analytical techniques were performed to provide an improved understanding of the complex processes related with sulfide-rich coal waste oxidation, spontaneous combustion, sequences of mineral formation, and the transport mechanisms of hazardous elements by neoformed soluble nanominerals and ultrafine particles. The results showed the presence of massive amorphous Si–Al–Fe–Ti–Zr (oxy-) hydroxides and Fe-hydr/oxides with goethite and hematite with various degrees of crystallinity, containing hazardous elements, such as Cr, Hf, Hg, Mo, Ni, Se, Pb, Th, U, Zr, and others. Several of the neoformed nanominerals found in the burned coal rejects are the same as those commonly associated with coal mine drainage, in which oxidation of sulfides plays an important role to environment and human health. This is the first Brazilian coal spontaneous combustion research.