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.
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.
Sci Total Environ. 2021 Aug 25;784:147105. doi: 10.1016/j.scitotenv.2021.147105. Epub 2021 Apr 15.
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.
当中和矿产生的酸的矿物不足时，暴露在水和氧气中的矿山尾矿会产生酸性矿山排水（AMD）。硫化物氧化和碳酸盐溶解等矿物反应会导致矿山尾矿的物理、矿物和地球化学性质发生多种变化，这可能导致金属（如 As、Cu、Zn、Fe、S）释放到环境中。在一个已关闭超过 25 年的金矿选矿厂的尾矿储存设施（TSF）中，从两个垂直剖面采集了新鲜和氧化尾矿。氧化尾矿是通过新鲜尾矿在 20 多年的原位氧化形成的。采集的样品进行了以下分析：i）电感耦合等离子体原子发射光谱（ICP-AES）、X 射线荧光（XRF）和总 S/C 进行化学组成分析；ii）X 射线衍射（XRD）、矿物解离分析仪（MLA）、穆斯堡尔光谱和 Fe L 边 X 射线吸收近边光谱（XANES）进行矿物组成分析。矿物学上，新鲜尾矿含有超过 22wt%的碳酸盐和超过 10wt%的硫化物。相比之下，氧化尾矿主要由次生矿物如铁的氢氧化物和石膏组成。地球化学方面，新鲜尾矿在风化电池实验中表现出近中性行为，且如 As 等污染物的释放量可以忽略不计（<0.3mg/L）。这可以用次生铁的氢氧化物的形成来解释，已知其具有从浸出液中吸收几种污染物的能力。新鲜尾矿的长期氧化将导致类似于原位采集的高度氧化的尾矿。尽管由于潜在酸度而耗尽了硫化物，但氧化尾矿仍表现出酸性行为。地球化学行为受到次生矿物（如石膏和铁的氢氧化物的溶解）的反应性强烈控制。定量地说，氧化尾矿释放了 163mg/kg 的 Fe、约 12000mg/kg 的 S 和约 6mg/kg 的 Zn。
