Role of secondary minerals in the acid generating potential of weathered mine tailings: Crystal-chemistry characterization and closed mine site management involvement.

Autor: Elghali A; Geology and Sustainable Mining Department, Mohammed VI Polytechnic University, Lot 660, Hay Moulay Rachid, Ben Guerir 43150, Morocco; Université du Québec en Abitibi-Témiscamingue 445, boul. de l'Université, Rouyn-Noranda, Québec J9X 5E4, Canada., Benzaazoua M; Université du Québec en Abitibi-Témiscamingue 445, boul. de l'Université, Rouyn-Noranda, Québec J9X 5E4, Canada; Mining Environment and Circular Economy, Mohammed VI Polytechnic University, Lot 660, Hay Moulay Rachid, 43150, Ben Guerir, Morocco. Electronic address: Mostafa.benzaazoua@uqat.ca., Bouzahzah H; Université du Québec en Abitibi-Témiscamingue 445, boul. de l'Université, Rouyn-Noranda, Québec J9X 5E4, Canada; Université de Liège, Génie minéral, matériaux et environnement, Allée de la découverte, 13/A. Bât. B52/3 Sart-Tilman, 4000 Liège, Belgium., Abdelmoula M; Laboratoire de Chimie Physique et Microbiologie pour les Matériaux et l'Environnement, LCPME UMR 7564 CNRS-Université de Lorraine, 405 rue de Vandoeuvre, 54600 Villers-lès-Nancy, France., Dynes JJ; Canadian Light Source, 44 Innovation Boulevard, Saskatoon, SK S7N 2V3, Canada., Jamieson HE; Department of Geological Sciences and Geological Engineering, Queen's University, Kingston, ON K7L 3N6, Canada.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2021 Aug 25; Vol. 784, pp. 147105. Date of Electronic Publication: 2021 Apr 15.
DOI: 10.1016/j.scitotenv.2021.147105
Abstrakt: Mine tailings exposed to water and oxygen generate acid mine drainage (AMD) when the neutralizing minerals are insufficient to buffer the acid produced by sulfide oxidation. Mineral reactivity, such as sulfide oxidation and carbonate dissolution, leads to several changes within mine tailings in terms of their physical, mineralogical, and geochemical properties, which may lead to the release of metal(oid)s (e.g., As, Cu, Zn, Fe, S) into the environment. Fresh and oxidized tailings were sampled at two vertical profiles in a tailings storage facility (TSF). The TSF contains tailings from gold ore processing at a mine that has been closed for more than 25 years. Oxidized tailings have formed by in-situ oxidation of fresh tailings over more than 20 years. The collected samples were analyzed for: i) chemical composition by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence (XRF), and total S/C; and ii) mineralogical composition by X-ray diffraction (XRD), Mineral Liberation Analyzer (MLA), Mossbauer spectroscopy, and Fe L-edge X-ray absorption near-edge spectroscopy (XANES). Mineralogically, the fresh tailings included more than 22 wt% carbonates and more than 10 wt% sulfides. In contrast, the oxidized tailings were composed mainly of secondary minerals such as iron oxy-hydroxides and gypsum. Geochemically, the fresh tailings exhibited a circumneutral behavior during weathering cell experiments and contaminants such as As were negligibly released (<0.3 mg/L). The latter is explained by formation of secondary iron oxy-hydroxides, which are known for the capacity to uptake several contaminants from the leachate. Long term oxidation of fresh tailings will lead to highly oxidized tailings similar to those collected in situ. The oxidized tailings exhibited an acidic behavior despite sulfide depletion due to latent acidity. The geochemical behavior was strongly controlled by the reactivity of secondary minerals (e.g., dissolution of gypsum and iron oxy-hydroxides). Quantitatively, the oxidized tailings released 163 mg/kg Fe, around 12,000 mg/kg S, and around 6 mg/kg Zn.
Competing Interests: Declaration of competing interest The authors declare no conflict of interest.
(Copyright © 2021 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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