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首页> 外文期刊>Soils and foundations >Hydraulic performance and chemical compatibility of a powdered Na-bentonite geosynthetic clay liner permeated with mine drainage
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Hydraulic performance and chemical compatibility of a powdered Na-bentonite geosynthetic clay liner permeated with mine drainage

机译：矿用排水弥散的钠基膨润土土工合成粉衬砌的水力性能和化学相容性

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摘要

The hydraulic and chemical compatibility of a geosynthetic clay liner (GCL), containing powdered Na-bentonite, was evaluated against artificial acid rock drainage (ARD) in terms of the swell index, hydraulic conductivity and heavy metal retention. Six artificial ARDs with an approximate pH of 3 and different metal concentrations (electrical conductivity, EC, ranging between 75 and 1000 mS/m; ionic strength ranging between 8 and 400 mM) were used in the experiments. The results of free swelling tests showed that high metal concentrations (EC higher than 70 mS/m) negatively impact the swell volume by lowering it. The hydraulic conductivity of the GCL permeated with distilled water was 1.2 x 10(-11) m/s, falling in the range of 7.9 x 10(-12) to 1.1 x 10(-11) m/s when prehydrated with distilled water and permeated with ARDs. The ion exchange and metal precipitation appeared to be the main mechanisms controlling the metal attenuation on the bentonite. The ion exchange mechanism starts with the release of Na from the bentonite and the sorption of the bi-and tri-metals present in the ARDs onto the bentonite. After the depletion of Na, the ion exchange reaction proceeds with the desorption of Ca and Mg from the bentonite and the sorption of cations present in the ARDs onto the bentonite layers. The depletion of Na from the bentonite and the subsequent release of Ca and Mg correlate to the sudden drop in pH and a gradual increase or equilibration of the hydraulic conductivity. It is possible to say that, after this point, hydraulic and chemical equilibrium is reached. From the overall results, the tested GCL showed acceptably low hydraulic conductivity and the potential to attenuate heavy metals present in ARDs. (C) 2019 Production and hosting by Elsevier B.V.
机译：评估了粉状钠膨润土的土工合成粘土衬里（GCL）的水硬性和化学相容性，相对于人工酸性岩石排泄物（ARD）的溶胀指数，水力传导率和重金属保持力。实验中使用了六种人工ARD，其pH值约为3，金属浓度不同（电导率，EC介于75和1000 mS / m之间;离子强度介于8和400 mM之间）。自由溶胀试验的结果表明，高金属浓度（EC高于70 mS / m）通​​过降低溶胀体积产生负面影响。用蒸馏水预浸的GCL的水力传导率是1.2 x 10（-11）m / s，当用蒸馏水预水合时，其水力传导率在7.9 x 10（-12）到1.1 x 10（-11）m / s的范围内并充满了ARD。离子交换和金属沉淀似乎是控制膨润土上金属衰减的主要机理。离子交换机制始于从膨润土中释放Na以及将ARDs中存在的双金属和三金属吸附到膨润土上。消耗完钠后，离子交换反应会继续进行，使钙和镁从膨润土中脱附，并使ARDs中存在的阳离子吸附到膨润土层上。膨润土中Na的减少以及随后Ca和Mg的释放与pH值的突然下降以及水力传导率的逐渐增加或平衡有关。可以说，在此之后达到了水力和化学平衡。从总体结果来看，测试的GCL显示出可接受的低水力传导率，并且具有衰减ARDs中重金属的潜力。 （C）2019由Elsevier B.V.制作和主持

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