Characterization of Mine Waste from a Former Pb-Zn Mining Site: Reactivity of Minerals During Sequential Extractions

An integrated mineralogical and chemical characterization approach was applied to different types of mine waste collected from the ancient Pb-Zn mining area of Plombieres. The combination of different methods to determine (pseudo-)total element concentrations, sequential extractions, and quantitative mineralogical analysis provided detailed information on the reactivity of minerals in the waste, as well as the associated metal(loid) release under different experimental conditions. Lithium borate (LiBO2) fusion was not suited to determine total metal(loid) concentrations in the investigated mine waste samples, due to the incomplete dissolution of the samples, and the volatilization of As and Cd during the fusion. Because some elements were below detection limit of X-ray fluorescence spectrometry (e.g., Cd), aqua regia digestion was useful to complement the chemical sample characterization, bearing in mind that only pseudo-total concentrations could be determined. Galena (PbS) and its alteration products, cerussite and anglesite (PbSO4), were the main lead minerals associated with the mining waste. Because of the high cerussite (PbCO3) content of the investigated samples (2-5 wt%), Pb not only shows the highest potential for recovery from the mining waste, but it also poses the highest environmental and human health risk. Zinc minerals showed a lower reactivity towards the BCR sequential extraction (sphalerite, ZnS) or were less abundant (willemite, Zn2SiO4). Quantitative XRD analysis allowed for better evaluation of the incomplete dissolution of some minerals, improving the interpretation of the sequential extraction results. [GRAPHICS] .