School of Computing, Engineering & Digital Technologies, Teesside University, United Kingdom.
Department of Environment, Land, and Infrastructure Engineering, Politecnico di Torino, Italy.
J Contam Hydrol. 2023 Feb;253:104126. doi: 10.1016/j.jconhyd.2022.104126. Epub 2022 Dec 23.
Nanoremediation is a new groundwater remediation technology in which nanoparticles (NPs) are injected into the sub-surface to promote in-situ degradation of aquifer contaminants. Although nanoremediation is an effective process to eliminate contaminants in-situ, its success relies on sufficiently mobile NPs that can reach the contaminated zones and remain there to facilitate chemical degradation of contaminants. Therefore, understanding the main parameters that control the mobility and retention of NPs in saturated porous media is a key component of designing a successful nanoremediation process. This work presents the outcome of a pore-scale study of nZVI NP (zero-valent iron) transport in sandy porous media using the non-destructive 3D imaging technique, X-ray computed micro-tomography (X-ray micro-CT). We investigate the effect of grain size (fine, coarse, carbonate and mixed sand) and composition (carbonate vs sand grains) on the mobility and retention of NPs in sand columns. To achieve this, we used four columns packed with grains of different sizes and compositions. The main contribution of this work is, therefore, to understand the effect of NP injection on the structural and geometric properties of sandy porous media and to identify the main pore-scale mechanisms controlling NP transport and entrapment. Our experiment shows that the pore geometries change because of NP injection. Pore clogging is evidenced through pore size and throat size distribution displaying a shift to the left with a noticeable reduction in pore connectivity in all the columns. The porosity and permeability of the columns studied display significant reduction as result of the NP injection.
纳米修复是一种新的地下水修复技术，其中纳米颗粒（NPs）被注入地下以促进含水层污染物的原位降解。尽管纳米修复是一种有效消除原位污染物的方法，但它的成功依赖于足够移动的 NPs，这些 NPs 可以到达污染区域并留在那里，以促进污染物的化学降解。因此，了解控制纳米颗粒在饱和多孔介质中迁移和保留的主要参数是设计成功纳米修复过程的关键组成部分。这项工作展示了使用非破坏性的 3D 成像技术——X 射线计算微断层扫描（X 射线微 CT）对 nZVI NP（零价铁）在沙质多孔介质中传输的孔隙尺度研究的结果。我们研究了粒度（细、粗、碳酸盐和混合沙）和组成（碳酸盐与沙粒）对沙柱中 NPs 迁移和保留的影响。为了实现这一目标，我们使用了四个填充不同大小和组成颗粒的柱子。因此，这项工作的主要贡献是了解 NP 注入对沙质多孔介质结构和几何性质的影响，并确定控制 NP 传输和捕获的主要孔隙尺度机制。我们的实验表明，NP 注入会导致孔隙几何形状发生变化。通过孔径和喉道尺寸分布向左偏移，可以明显看出所有柱子中的孔隙连通性降低，从而证明了孔隙堵塞。由于 NP 注入，研究中柱子的孔隙率和渗透率显示出显著降低。
