Environmental Science Research Institute, School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Environmental Science Research Institute, School of Environmental Science and Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Sci Total Environ. 2019 Jun 10;668:32-39. doi: 10.1016/j.scitotenv.2019.02.289. Epub 2019 Feb 21.
Massive realgar tailings abandoned in mining areas in China have caused serious arsenic (As) pollution seeking for urgent disposal. Stabilization treatment is a feasible strategy, however, stabilization technologies for realgar tailings, that are Fe-deficient, Ca-rich and S-rich, have not been well developed to date. In this study, we conducted a pilot-scale stabilization treatment of realgar tailings via ferrous sulfate addition to evaluate the transformation of As during stabilization. We found that Si, As, Ca, and S were the predominant elements in the raw realgar tailings with a low content of Fe, and realgar (AsS) and pharmacolite (CaHAsO·2HO) were the main As-bearing minerals. After the ferrous sulfate treatment, the As leaching concentration of realgar tailings was successfully reduced from 135 mg/L to a level below the Chinese regulatory limit (2.5 mg/L). Based on the results of leaching tests, sequential extraction analysis, XRD, SEM-EDS, XPS, and thermodynamic modeling, we concluded that ferrous sulfate addition enhanced the transformation of Ca-As and S-As species to more stable Fe-As species, e.g., crystalline symplesite and amorphous Fe-As complex. Dissolution of pharmacolite was facilitated by H and SO derived from the hydrolysis and oxidation of ferrous sulfate, and oxidation of realgar could be promoted by reactive oxygen species (ROSs) from Fe(II) oxygenation. This study improved our understanding of As transformation pathways in realgar tailings during ferrous sulfate treatment, which could serve as an alternative scheme for realgar tailings stabilization.
大量的雄黄尾矿在中国矿区被遗弃，造成了严重的砷（As）污染，急需处理。稳定化处理是一种可行的策略，然而，对于贫铁、富钙和富硫的雄黄尾矿，至今尚未开发出成熟的稳定化技术。在这项研究中，我们通过添加硫酸亚铁对雄黄尾矿进行了中试规模的稳定化处理，以评估稳定化过程中砷的转化。我们发现，原雄黄尾矿中含有大量的 Si、As、Ca 和 S，Fe 含量较低，主要的砷矿物为雄黄（AsS）和磷钙铝石（CaHAsO·2HO）。经过硫酸亚铁处理后，雄黄尾矿中的砷浸出浓度从 135mg/L 成功降低到中国监管限值（2.5mg/L）以下。基于浸出试验、连续提取分析、XRD、SEM-EDS、XPS 和热力学模拟的结果，我们得出结论，硫酸亚铁的添加促进了 Ca-As 和 S-As 物种向更稳定的 Fe-As 物种的转化，如结晶砷铁矿和无定形 Fe-As 络合物。磷钙铝石的溶解是由硫酸亚铁水解和氧化产生的 H 和 SO 促进的，雄黄的氧化可以被 Fe(II)氧化产生的活性氧物种（ROSs）促进。本研究提高了我们对硫酸亚铁处理过程中雄黄尾矿中砷转化途径的认识，为雄黄尾矿的稳定化提供了一种替代方案。
