Geochemistry and pH control of seepage from Ni-Cu rich mine tailings at Selebi Phikwe, Botswana.

摘要: Acid mine drainage from tailings at Selebi Phikwe, eastern Botswana, has been investigated using a combination of total decomposition, sequential extraction, X-ray diffraction, Mossbauer spectroscopy, and SEM analyses solid phase samples, water analyses, isotopic geochemical modeling. The principal ferric phases in the seepage stream sediments are jarosite goethite, which incorporate Ni Cu. spectroscopy (MS) indicated exclusively 3+ oxidation state iron with typical features hydroxides/sulfates. A fraction dissolved sulfate is also sequestered gypsum precipitates further downstream. Significant portions Fe, Ni, Cu transported suspension. Values pH decreased downstream due to H+ generated by precipitation jarosite. δ2H δ18O indicate evaporation pore before seepage. δ34S(SO4) consistent sulfides, but sample face affected dissolution gypsum. No minerals were detected attenuation processes seem be adsorption co-precipitation Higher contents compared spite much higher concentrations. Based on speciation calculations, undersaturated respect all seems processes. Direct modeling was able reproduce trends, thus confirming as pH-controlling process.