The Geochemical Behaviour of Mine Tailings from the Touiref Pb-Zn District in Tunisia in Weathering Cells Leaching Tests

Flotation tailings associated with the extraction of Pb and Zn in the Touiref mining district, Tunisia, contain galena, sphalerite, pyrite, and marcasite in a carbonate gangue. The geochemical behaviour of oxidized and unoxidised tailings were consistent with their mineralogical and chemical characteristics. The leaching proceeded under neutral to slightly alkaline condition (pH 7.3–8.5), and positive Eh (250–470 mV). The concentrations of sulfate and Ca released during the leaching tests were associated with the neutralization of acidity by carbonates and the dissolution of gypsum initially present in the tailings. The iron precipitated, but significant amounts of Zn (5–3,300 μg/L), Cd (3–18 μg/L), and Pb (28–83 μg/L) were released during leaching, with the latter two exceeding international environmental norms (5 μg/L for Cd and 10 μg/L for Pb).