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微米尺度方铅矿在不同介质中铅的释放行为及矿物相变特征

Release Behavior of Lead and Mineral Transformation Characteristics of Micro-Scale Galena in Different Media

  • 摘要: 方铅矿作为主要铅矿石,其风化行为直接影响重金属Pb在环境中的迁移与归趋。风化环境的差异及时间均会影响方铅矿风化产物,已有研究多聚焦于单因子短期实验及电化学和搅动实验,忽视了长时间跨度和常规实验条件下的方铅矿风化行为。为此,本文以微米级方铅矿为研究对象,根据物相图特征和矿区环境特点,设置pH、伴生矿物(黄铁矿)、氧化剂(氯化铁)和有机酸(乙酸、柠檬酸和腐植酸)实验组以及纯水对照组,通过为期一年的常温静置实验,结合电感耦合等离子体质谱(ICP-MS)和X射线衍射(XRD)分析,探究不同介质环境对方铅矿中Pb2+释放行为及矿物相变的影响。结果表明:氯化铁的加入可显著增加方铅矿中Pb2+释放,乙酸和柠檬酸能促进Pb2+释放,低pH会有利于Pb2+释放,黄铁矿和腐植酸则显著抑制了Pb2+释放;矿物相在黄铁矿组和氯化铁组中发生了显著变化,分别形成了晶型完好的次生矿物铅矾和氯铅矿。由于氯铅矿的溶度积远高于方铅矿和铅矾,故其Pb元素更容易进入溶液。与前人研究不同的是黄铁矿组,并没有因为方铅矿-黄铁矿的电偶相互作用促进方铅矿溶解,本实验在该组观察到大量的铅矾生成,其在方铅矿表面沉积,起到了钝化作用,从而抑制了Pb2+释放。本研究揭示了长时间不同介质下方铅矿的静置溶解特点,弥补了搅动实验对矿物钝化现象认识的不足,为矿区污染防控及修复策略提供了科学依据。

     

    Abstract: The weathering behavior of galena, as the main lead ore, directly affects the migration and fate of heavy metal Pb in the environment. Weathering environment and time both affect the weathering products of galena. Previous studies have mostly focused on single-factor, short-term, electrochemical and stir experiments, neglecting galena weathering behavior under long-term and conventional experimental conditions. Therefore, through a one-year room-temperature static experiment combined with inductively coupled plasma-mass spectrometry (ICP-MS) and X-ray diffraction (XRD) analysis, the influence of different media on the release behavior of Pb2+ in galena and the mineral phase transformation was explored. According to the characteristics of phase diagram and mining area environment of galena, experimental groups for pH, associated mineral (pyrite), oxidant (ferric chloride), and organic acids (acetic acid, citric acid, and humic acid) as well as a pure water control group were set up. The results showed that: ferric chloride addition significantly increased Pb2+ release from galena; acetic acid and citric acid promoted Pb2+ release; low pH was conducive to Pb2+ release; pyrite and humic acid significantly inhibited Pb2+ release. Mineral phases changed significantly in the pyrite and ferric chloride groups, yielding well-crystallized secondary minerals—anglesite and cotunnite, respectively. Because the solubility product (Ksp) of cotunnite is much higher than that of galena and anglesite, the Pb element in cotunnite is more likely to enter the solution. Unlike previous studies, the pyrite group did not promote galena dissolution through the galena-pyrite galvanic interaction. In this group, a large amount of anglesite was formed and deposited on the surface of galena, acting as a passivation layer that inhibited the release of Pb2+. This study reveals the static dissolution of galena in different media over a long period, addressing the shortcomings of stir experiments in recognizing the mineral passivation phenomenon. It provides a scientific basis for pollution prevention, control, and remediation strategies in mining areas. The BRIEF REPORT is available for this paper at http://www.ykcs.ac.cn/en/article/doi/10.15898/j.ykcs.202504170095.

     

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