Coupled solute transport through a polymer-enhanced bentonite
Coupled solute transport through a polymer-enhanced bentonite
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DOI：
10.1016/j.sandf.2022.101235
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发表时间：
2022-12
影响因子：
3.7
通讯作者：
Shan Tong;K. Sample-Lord
中科院分区：
文献类型：
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作者：
Shan Tong;K. Sample-Lord
用于地质环境防护屏障的聚合物增强膨润土，如膨润土-丙烯酸复合材料（BPC），即使暴露于腐蚀性废物溶液中，通常也具有较低的水导率（例如，k< 10 - 10m/s）。然而，对增强膨润土的扩散和膜行为特性以及对耦合污染物通过屏障的相关影响的了解仍然有限。在本研究中，测量了聚合物含量为3.2%（按质量计，简称BPC-3.2）的BPC的水导率(k)、有效扩散系数（D*）和膜效率（ω）。试验用氯化钾（KCl）溶液进行，浓度从稀释（2.5 mM）到侵蚀（400 mM）不等。随着浓度的增加，D*增加了3倍，ω减少了2个数量级，k保持在较低的水平（1.2 × 10−11 ~ 2.9 × 10−11m/s）。将实验结果与现有的耦合溶质输运模型进行配对，以评估膜行为和扩散对通过土工合成粘土衬里（GCL）和覆盖在衰减层上的GCL的预测总溶质通量的意义。预测的质量通量以扩散通量为主，扩散通量大于平流通量1 ~ 2个数量级。膜的行为使通过GCL的预测总溶质通量降低了5.8%至61%。结果表明，耦合溶质迁移在膨润土屏障的长期性能中起着重要作用，并促进了对BPC中污染物迁移的理解。
Polymer-enhanced bentonites for geoenvironmental containment barriers, such as bentonite-polyacrylic-acid composite (BPC), generally have low hydraulic conductivity (e.g.,k< 10−10m/s) even when exposed to aggressive waste solutions. However, understanding of diffusion and membrane behavior properties of enhanced bentonites and associated impacts on coupled contaminant transport through the barrier remains limited. In this study, hydraulic conductivity (k), effective diffusion coefficients (D*), and membrane efficiencies (ω) were measured for BPC with 3.2 % polymer content (by mass; referred to as BPC-3.2). Tests were performed with potassium chloride (KCl) solutions ranging from dilute (2.5 mM) to aggressive (400 mM) concentrations. As concentration increased,D*increased by a factor of three, ω decreased by two orders of magnitude, andkremained relatively low (1.2 × 10−11to 2.9 × 10−11m/s). The experimental results were paired with an existing coupled solute transport model to evaluate the significance of membrane behavior and diffusion on predicted total solute flux through a geosynthetic clay liner (GCL) and a GCL overlying an attenuation layer. The predicted mass flux was diffusion dominated, with the diffusive flux greater than the advective flux by one to two orders of magnitude. Membrane behavior reduced predicted total solute flux through the GCL by 5.8 to 61 %. The results demonstrate the role of coupled solute transport in the long-term performance of bentonite barriers, and advance understanding of contaminant transport in BPC.