The oxidation of various sulfides in mining wastes and rock outcrops commonly leads to environmental problems, which therefore make the oxidation of sulfides one of the most concerned epigenetic processes. The oxidation mechanism has been well understood and successfully stimulated biological metallurgical technologies. Meanwhile, several secondary minerals derived microbial oxidation of sulfides have attracted numerous experimental studies on synthesis, environmental applications. Actually, the secondary minerals in mining environments include various mineral phases with different Eh-pH stability, and record natural evolution paths. We studied the iron-rich hardpan covered on oxidized tailings of a Cu-Au mine, which contain large amounts of metals and metalloids (e.g. As, Cd, Co, Cu, Fe, In, Mn, Mo, Th, U, Y, and Zn). We further experimentally investigated the microbial oxidation of pyrite, chalcopyrite, arsenopyrite, molybdenite, and sphalerite, and the secondary minerals were characterized. The thermodynamic transformation from schwertmannite, jarosite, to goethite and finally to hematite can be clearly disclosed, as well as similar reactive transformations in nature including other minerals depending on the mineral assemblage of tailings or rocks, e.g., gypsum, scorodite, powellite, and so on. The mineral transformation is closely related to environmental changes, such as temperature, pH, redox conditions, and the presence of microbes. Accompanying with the formation of secondary minerals, various heavy metals can be either adsorbed by iron (oxy) hydroxides (e.g. ferrihydrite and goethite) or coprecipitated into iron sulfates (e.g. schwertmannite and jarosite), whereas others will form secondary minerals (e.g. scorodite, cafarsite, and arsenolite). Therefore, the formation, transformation and decomposition are crucial for heavy metal contaminations in mining areas. The secondary minerals and related transformations in a depth profile of a tailing dam were characterized and their environmental consequences were discussed.<br/>

Secondary minerals derived microbial oxidation sulfides

2019 Spring National Meeting

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