Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, SE-971 87, Luleå, Sweden.
Department of Environment and Mineral Resources, Greenland Institute of Natural Resources, 3900, Nuuk, Greenland.
Environ Sci Pollut Res Int. 2017 Sep;24(25):20372-20389. doi: 10.1007/s11356-017-9650-9. Epub 2017 Jul 13.
Sealing layers made of two alkaline paper mill by-products, fly ash and green liquor dregs, were placed on top of 50-year-old sulfide-containing tailings as a full-scale remediation approach. The performance and effectiveness of the sealing layers with high water content for an oxygen barrier and low hydraulic conductivity for a sealing layer in preventing the formation of acid rock drainage were evaluated 5 years after the remediation. The leaching behavior of the covered tailings was studied using batch leaching tests (L/S ratio 10 L/kg). The leaching results revealed that, in general, the dregs- and ash-covered tailings released relatively lower concentrations of many elements contained in acid rock drainage compared to those from the uncovered tailings. A change in the chemical composition and mineralogical state of the tailings was observed for the tailings beneath the covers. The increase in pH caused by the alkaline materials promoted metal precipitation. Geochemical modeling using PHREEQC confirmed most of the geochemical changes of the covered tailings. Both the ash and dregs showed potential to function as sealing materials in terms of their geochemical properties. However, mobilization of Zn and Ni from the lower part of the dregs-covered tailings was observed. The same phenomenon was observed for the lower part of the ash-covered tailings. Ash showed advantages over dregs as a cover material; based on geochemical studies, the ash immobilized more elements than the dregs did. Lysimeters were installed below the sealing layers, and infiltrating water chemistry and hydrology were studied to monitor the amount and quality of the leachate percolating through.
采用两种碱性造纸厂副产品——粉煤灰和绿液渣——作为密封层，覆盖在 50 年历史的含硫化物尾矿之上，这是一种大规模修复方法。修复 5 年后，评估了高含水率的密封层作为氧屏障和低水力传导率的密封层，以防止形成酸性矿山排水。采用间歇浸出试验（浸出液/固体比为 10 L/kg）研究了覆盖尾矿的浸出行为。浸出结果表明，一般来说，与未覆盖的尾矿相比，渣和灰覆盖的尾矿释放出的酸性矿山排水中所含许多元素的浓度相对较低。在覆盖层下的尾矿中观察到尾矿的化学成分和矿物状态发生了变化。碱性材料引起的 pH 值升高促进了金属沉淀。使用 PHREEQC 进行地球化学模拟证实了覆盖尾矿的大部分地球化学变化。粉煤灰和渣都具有作为密封材料的地球化学性质潜力。然而，在渣覆盖的尾矿下部观察到 Zn 和 Ni 的迁移。在灰覆盖的尾矿下部也观察到了同样的现象。灰作为覆盖材料比渣具有优势；根据地球化学研究，灰固定的元素比渣多。在密封层下方安装了渗滤计，研究了渗入水的化学和水文学特性，以监测通过渗滤的浸出液的数量和质量。
